ATCA Journal | Q2 2013

SUMMER 2013 | VOLUME 55, NO. 2

Balancing Safety and Efficiency of Airport Operations under

Lightning Threats Plus • NASA’s ATM Technology Demonstration -1 • The FAA ATO’s System Operations Security Office

www.atca.org

Summer 2013 | Vol. 55, No. 2 Published for:

Contents

Air Traffic Control Association 1101 King Street, Suite 300 Alexandria, VA 22314 703-299-2430 703-299-2437 Fax info@atca.org www.atca.org Published by:

140 Broadway, 46th Floor New York, NY 10005 Toll-free phone: 866-953-2189 Toll-free fax: 877-565-8557 www.lesterpublications.com President, Jeff Lester Vice-President & Publisher, Sean Davis

Feature 16 Balancing Safety and Efficiency of Airport Operations under Lightning Threats

A look inside the ramp closure decision-making process

EDITORIAL Editorial Director, Jill Harris Managing Editor, Kristy Rydz

DESIGN & LAYOUT Art Director, Myles O’Reilly Senior Graphic Designer, John Lyttle Graphic Designer, Gayl Punzalan Graphic Designer, Jessica Landry

Articles 9 Spotlight On: The FAA Air Traffic Organization’s System Operations Security Office

The organization responsible for protecting the U.S. air domain

ADVERTISING

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FAA Employs New Model in Benefits Calculation

Connie Lester | 866-953-2185 Walter Lytwyn | 866-953-2196 Joelle Portis | 425-652-1563

27

NASA’s ATM Technology Demonstration-1

DISTRIBUTION

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Jennifer Holmes | 866-953-2189

© 2013 Air Traffic Control Association, Inc. All rights reserved. The contents of this publication may not be reproduced by any means, in whole or in part, without the prior written consent of the ATCA. Disclaimer: The opinions expressed by the authors of the editorial articles contained in this publication are those of the respective authors and do not necessarily represent the opinion of the ATCA. Printed in Canada. Please recycle where facilities exist.

Cover images by hernan4429 & / Jeff Bough Photos.com Top photo by Clint Spencer / Photos.com

Outlining the 2013 update to the NextGen Implementation Plan

Moving NextGen Arrival Concepts from the laboratory to the operational NAS

Operations of Gas Turbine Engines in an Environment Contaminated with Volcanic Ash Reprinted with permission from the September 2012 issue of the Journal of Turbomachinery

Departments 3 From the President 5 From the Editor’s Desk 7 Member Benefits & Application

13 From the Archives Directory of Member 59 Organizations

60

Index to Advertisers

The Journal of Air Traffic Control

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New in 2013: #TechCenterTuesday and Half-Day Thursday Dozens of Exhibitors: FAA, Industry, Universities, & more!

Committed Participation: FAA, DoD, DoT, & NASA May 21, 2013 Resorts Hotel • Atlantic City, New Jersey

www.atca.org/techsymposium

m

Welcome to

Atlantic City

FROM THE PRESIDENT

By Peter F. Dumont President & CEO, ATCA

We look forward to seeing you at the ATCA Technical Symposium The ATCA Technical Symposium in Atlantic City is almost upon us. We are very excited that this year’s panel and speaker line-up will feature the FAA, NASA, and U.S. Department of Defense. We will also hear keynotes from a select few top-level government executives.

As you know, the sequester and the Continuing Resolution are putting severe restrictions on government travel. We are fortunate to have co-located our main events with the government agencies – the Tech Symposium takes place in Atlantic City, just a few miles away from the William J. Hughes Technical Center.

The availability of the FAA shuttle flights will also facilitate headquarters participation. But we felt that maybe this year, that wasn’t enough.

The decision to cancel our annual ATCA Scholarship Spring Golf Outing was difficult because it supports the ATCA Scholarship Fund. But let’s face it – when we go to an ATCA conference, we are going for education, the ability to have multiple high-level meetings in a short period of time,

and networking. In a word, we go there to work – not play. This is something that is getting lost in translation lately when I speak to our elected officials. Slowly but surely, they are recognizing and comprehending the benefit of industry-government interaction. After all, we are not replicating the GSA model of waste. We are perpetuating the model of a beneficial exchange of ideas, opportunities, solutions, and capabilities.

To help facilitate that interaction, we have expanded our programming and replaced the golf tournament this year with two sessions in the Technical Center auditorium on Tuesday, May 21. We will bus a maximum of 250 attendees in the morning and 250 attendees in the afternoon to the Tech Center.

While there, the attendees will view government exhibits, meet with managers, and attend presentations on the valuable work the Tech Center is conducting. We will provide lunch at Resorts Hotel after the morning session and before the afternoon session.

Wednesday, we will resume pro-

gramming and host it – along with the exhibition of dozens of companies – at Resorts Hotel.

This means you, as a participant, need to sign up as soon as possible to ensure you are slotted for your preferred session. There are also security procedures that will require some information in a timely manner from all participants. If, for any one session at the Tech Center, more than 250 people sign up, we will employ a first-come, first-served priority to attending.

In the current landscape, ATCA is working hard to make our programming more valuable than ever before, rather than scale back what is offered. This format for the Technical Symposium will provide attendees with more faceto-face interaction and new focuses in panel sessions. I look forward to seeing you in Atlantic City.

Peter Dumont, President and CEO, ATCA

Photographer: Tatiana Sayig / Photos.com

The Journal of Air Traffic Control

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“Our National Airspace System is built on redundancy. When funds and personnel are cut, layers of redundancy are eliminated, and layers of safety are slowly reduced…Let me be clear – making our national airspace the world’s safest and most efficient is the top priority for air traffic controllers and we will do everything in our power to maintain it moving forward.” NATCA President Paul Rinaldi

TELL CONGRESS ThAT SEquESTRATION wILL hAvE A dETRImENTAL EFFECT ON OuR NATIONAL AIRSPACE SySTEm. NATIONAL AIR TRAFFIC CONTROLLERS ASSOCIATION, AFL-CIO

NATCA.ORG

from the Editor’s desk

ATCA

Air Traffic Control Association

Summer 2013 | Vol. 55, No. 2 Air Traffic Control Association 1101 King Street, Suite 300 Alexandria, VA 22314 703-299-2430 703-299-2437 Fax info@atca.org Air Traffic Control Association www.atca.org

ATCA

Formed in 1956 as a non-profit, professional membership association, ATCA represents the interests of all professionals in the air traffic control industry. Dedicated to the advancement of professionalism and technology of air traffic control, ATCA has grown to represent several thousand individuals and organizations managing and providing ATC services and equipment around the world.

Editor-in-Chief: Steve Carver Publisher: Lester Publications, LLC

Officers and Board of Directors Chairman: James H. Washington, B3 Solutions Chairman-Elect: Neil Planzer, The Boeing Company President & CEO: Peter F. Dumont, Air Traffic Control Association Treasurer, Director-At-Large: Rachel Jackson, ASRC Research & Technology Solutions Secretary, East Area Director: Jeff Griffith, Washington Consulting Group Northeast Area Director: Mike Headley, Apptis South Central Area Director: William Cotton Southeast Area Director: Robert Coulson, Harris Corporation North Central Area Director: Jim Crook, Retired, US Air Force Western Area Director: Mike Lewis, Jeppesen Canada, Caribbean, Central and South America, Mexico Area Director: John Crichton, NAV CANADA Europe, Africa, Middle East Area Director: Steve James Pacific, Asia, Australia Area Director: Bob Gardiner, ACMAT Consultants Directors-At-Large: Allison Patrick, SRA International, Inc. Charlie Keegan, Raytheon Sandra Samuel, Lockheed Martin

By Steve Carver Editor-in-Chief, The Journal Of Air Traffic Control

Safety First This Summer Journal is full of great articles. If you have ever experienced lightning up close and personal, then this issue will be dear to your heart. “Balancing Safety and Efficiency of Airport Operations Under Lightning Threats” brings to the reader an understanding that weather threats are always difficult to deal with from a risk management perspective, especially threats which involve lightning.

Also regarding weather, we feature an article in this issue about volcanic ash by Dr. Michael Dunn that will keep you coming up for clean air. The Journal of Turbomachinery, produced by the American Society of Mechanical Engineering, has graciously allowed us a reprint of Dr. Dunn’s research; our Publications Committee pursued it due to its deep relevance to professionals in ATC. Similarly, on the topic of risk management and keeping ahead of threats, this issue also includes a paper written by the National Airspace System Security Operational Division. This paper gives insight to a division in air traffic that keeps their operational task

ahead of the security threat curve.

In “Moving NextGen Arrival Concepts from the Laboratory to the Operational NAS,” Harry Swenson and Steve Winter provide a perspective from NASA by applying a laboratory concept – NASA’s ATM Technology Demonstration-1 – to aviation and the National Airspace System.

On a final note, from this Editor’s Desk I would like to thank Ed Stevens for continuing to volunteer as the Publication Committee chair for ATCA. Ed retired from Raytheon last year and continues to have a love for aviation.

Although he can be seen most days on the golf course or following his daughter’s Olympic cycling efforts, Ed takes time out of his busy retirement schedule to keep the committee and myself moving in the right direction. Thank you, Ed, for all you do!

Steve Carver, Editor-in-Chief, The Journal of Air Traffic Control

Staff Marion Brophy, Director, Communications Ken Carlisle, Director, Meetings and Expositions Carrie Courter, Administrative Coordinator Jonathan Fath, World ATM Congress Communications Consultant Jessica McGarry, Communications Coordinator Christine Oster, Chief Financial Officer Paul Planzer, Manager, ATC Programs Claire Rusk, Vice President of Operations Rugger Smith, Director, International Accounts Sandra Strickland, Events and Exhibits Coordinator Tim Wagner, Membership Manager

The Journal of Air Traffic Control (ISSN 0021-8650) is published quarterly by the Air Traffic Control Association, Inc. Periodical postage paid at Alexandria, VA and additional entries.

EDITORIAL, SUBSCRIPTION & ADVERTISING OFFICES at ATCA Headquarters: 1101 King Street, Suite 300, Alexandria, Virginia 22314. Telephone: (703) 299-2430, Fax: (703) 299-2437, Email: info@atca.org, Website: www.atca.org.

POSTMASTER: Send address changes to The Journal of Air Traffic Control, 1101 King Street, Suite 300, Alexandria, Virginia 22314. © Air Traffic Control Association, Inc., 2013 Membership in the Air Traffic Control Association including subscriptions to the Journal and ATCA Bulletin: Professional, $130 a year; Professional Military Senior Enlisted (E6–E9) Officer, $130 a year; Professional Military Junior Enlisted (E1–E5), $26 a year; Retired fee $60 a year applies to those who are ATCA Members at the time of retirement; Corporate Member, $500–5,000 a year, depending on category. Journal subscription rates to non-members: U.S., its territories, and possessions—$78 a year; other countries, including Canada and Mexico—$88 a year (via air mail). Back issue single copy $10, other countries, including Canada and Mexico, $15 (via air mail).

Contributors express their personal points of view and opinions that are not necessarily those of their employers or the Air Traffic Control Association. Therefore The Journal of Air Traffic Control does not assume responsibility for statements made and opinions expressed. It does accept responsibility for giving contributors an opportunity to express such views and opinions. Articles may be edited as necessary without changing their meaning.

The Journal of Air Traffic Control

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Letter from the Editor

The Names & Faces of Air Traffic Gather at The Names & Faces of Air Traffic Gather at

The Names & Faces of Air Traffic

ATCA Members are part of the global air traffic dialogue. Your access to ATCA committees, publications, and meetings will increase your awareness of the current aviation landscape ATCA Members areATC part of the global airAirtraffic and current work towards improving safety, Trafficdialogue.

Control Association access toand ATCA committees, publications, and meetings will increase your awareness efficiency, capacity.

ATCA Members are part of the global air traffic dialogue.

#6%#

Your ofYour the access currenttoaviation landscape and current work improving ATC safety, efficiency, ATCA committees, publications, andtowards meetings will increase your awareness and capacity. of the current aviation landscape and current work towards improving ATC safety, efficiency,

What do you get an ATCA Member? andas capacity.

What you get as an ATCA Member What you get as an ATCA Member

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Daily Headline Administration, ICAO, CANSO, academic institutions, and many other global organizations. significant discounts to all ATCA events News, the ATCAMembers Bulletin, &get The significant Journal Reduced Rates. discounts to all ATCA events and conferences. and conferences. of Air Traffic Control.

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Spotlight On:

System Operations Security

The FAA Air Traffic Organization’s System Operations Security Office The organization responsible for protecting the U.S. air domain

Photographer: Kevin Kraft / Photos.com

By Carol Might and Charles Cornelius On the morning of September 11, 2001, when it became apparent the United States was being attacked by terrorists, the FAA established a conference call among air traffic control facilities, the Air Traffic Control System Command Center, and the Northeast Air Defense Sector. This call was quickly expanded in the immediate aftermath of the attacks to include other key national defense, homeland security, and law enforcement participants, including the Federal Bureau of Investigation. This call remains ongoing and was transformed into what is now called the Domestic Events Network (DEN), a crucial aviation security coordination platform in which more than 170 governmental nodes and, as needed, a number of key operators currently participate. The DEN is a core element of the System Operations Security directorate within the Air Traffic Organization (ATO) and, in many ways, symbolizes the careful balancing act performed by that office each day in collaboration with the FAA’s inter-agency partners, the

airlines, aviation operators, and other key National Airspace System (NAS) stakeholders.

Since September 2001, the nation has continued to grapple with the challenge of effectively guarding against additional 9/11-style attacks and other aviation-related terrorism threats while sustaining a vibrant NAS, which is critical to the U.S. economy. One of the FAA’s principal responses to the incident was the creation of System Operations Security in 2004, which is designed to address a number of the problems noted by the 9/11 Commission’s report, including the need to better communicate and operationalize intelligence on aviation threats. System Operations Security is also expected to balance the country’s security concerns regarding the safety and efficiency of the NAS, with the need to maintain air commerce by mitigating the impact of incidents.

This article takes a look behind the scenes of this unique office that has developed and evolved since

September 11, 2001. It looks into their air traffic management (ATM) security mission and its day-to-day operations as well as the people who work for the organization that keep ATM security operations flowing smoothly in the midst of the world’s busiest air traffic operations.

System Operations Security Office: a Deeper Look The leader of this intrepid organization is Frank Hatfield, known for his ability to get things done during the most chaotic of circumstances – a trait required for such a role. Hatfield has strong leadership skills and is driven to protect his country; he has high expectations of his people and they have high expectations of themselves. Reporting directly to Hatfield are managers of Strategic, Tactical, and Special Operations Security.

These gentlemen differ greatly from each other in temperament and personality. Together their diversity and depth of knowledge allow them to lead their teams to meet the ATM The Journal of Air Traffic Control

9

System Operations Security

Strategic Operations: Responsibilities & Accomplishments The Strategic Operations sector of System Operations Security is also responsible for the following: • Developing NAS ATM security programs • Processing and coordinating United States Department of Defense (DoD) requests to conduct GPS interference testing • Ensuring all appropriate coordination has been accomplished prior to the implementation of known ATM security measures or programs • Conducting interface with international air traffic system operations security counterparts for development of international ATM security procedures • Acting as the point of contact for planning, developing, and coordinating policy for Open Skies Treaty missions • Acting as the Office of Primary Responsibility (OPR) for the FAA Order JO 7610.4, Special Operations • Correlating all laser activity data • Overseeing all communication security (COMSEC) equipment for the ATO • Developing and overseeing the electronic programs and databases that are unique to System Operations Security and used in day-to-day operations to meet its mission A couple of Strategic Operations’ most recent accomplishments include the 2012 implementation of ICAO Document 9985, Air Traffic Management Security Manual, and the creation of the ATO Incident Response Management Center (AIRMAC). The AIRMAC is designed to be a conference room and operational incident management center – the central table and surrounding walls of the

security mission of the office.

System Operations Security’s ATM security mission is to protect the United States from threats and other major incidents involving the air domain while looking out for the economic considerations of the NAS. This commitment is fostered through interagency coordination at the strategic, operational, and tactical levels, with dynamic decision-making during real-time events. Responsibilities and organizations with which this office interacts are highlighted below, along with some of their day-to-day ATM security activities.

conference room can be converted instantly to establish a real-time incident management center staffed by multiple ATO elements and agencies supporting any specified emergency. The AIRMAC serves as ATO’s national level unified incident management facility for natural disasters and other crises affecting the NAS. The facility provides specialized systems and other infrastructure used to equip state-of-the-art Emergency Operations Centers, enhancing the ability of Service Units participating in ATO response efforts to carry out integrated, effective incident management. The AIRMAC also acts as a centralized link between ATO, incident management nodes operated by the rest of the FAA, and a broad range of external partners. Most recently, the AIRMAC was staffed by multiple agencies to support the response needed for the Hurricane Sandy incident response in late-October 2012.

Another accomplishment by this group was the creation of ICAO Document 9985, Air Traffic Management Security Manual. This work started four years ago and is in its final stages of translation into the official coordination languages used by ICAO. The Strategic Operations Group led the lengthy and complex coordination within the structure of ICAO to produce this new era ATM security concept.

Document 9985 outlines the role of ATM security in safeguarding the global aviation system. It also contributes to and leverages national security, aviation security, and law enforcement from the operational side in an effort to harmonize it on a global level. The document also explains risk management and crisis management as integral aspects of ATM security.

and policy development of homeland security/national defense needs within the NAS. It is the focal point for all ATM security-related requests, international harmonization of ATM security initiatives, and coordination of all ATM operation security procedures that impact the NAS. It is also responsible for the development and execution of ATO crisis response and emergency operations. In short, System Operations Security provides the foundational building blocks of the ATO.

Tactical Operations The Tactical Operations Security (TACOPS) group is responsible for Strategic Operations The Strategic Operations Security real-time management of the NAS Group of System Operations Security concerning ATM security incidents is responsible for planning, support, mainly through staffing of the head10

Summer 2013

quarters DEN, National Capital Region Coordination Center (NCRCC), North American Aerospace Defense Command (NORAD), and Continental NORAD Region (CONR). TACOPS is comprised of Air Traffic Security Coordinators (ATSCs) and System Operations Support Center specialists (SOSCs) who are the front line of the FAA operations-focused ATM security efforts. These specialists are the focal point for all active ATM security measures and adjustments made for operational considerations, as well as coordination of intelligence information and its concurrent impact on the NAS. By staffing numerous operational security positions, TACOPS maintains a close day-to-day relationship with homeland security and national

System Operations Security

Employees of FAA’s System Operations Security Directorate are pictured in the ATO Incident Response Management Center (AIRMAC), located in Washington Headquarters.

From left to right: John Lucia, Rob Sweet, Joe Heuser, Director Frank Hatfield, Paul Bartko, Gary Miller.

Photo courtesy of Brian Throop

Many people in the FAA are unaware this group [System Operations Security] exists. defense operational decision-makers and executes ATO’s security measures as appropriate. They implement national ATM security measures on a dynamic basis, and modify these actions in real-time as needed. As the focal point for regulating daily security measures, they analyze current measures and optimize timely coordination to ensure minimal impact to the NAS. They are the final approving authority regarding all real-time ATM security determinations regarding operations within the NAS. They also conduct thorough reviews and provide recommendations to improve ATO’s security operations.

Special Operations The Special Operations Group (SOG) is responsible for support of classified operations as well as defense and law enforcement liaison work.

The group works closely with various government agencies to plan and conduct classified and sensitive operations within the NAS. SOG is the focal point for coordination and planning of Temporary Flight Restrictions (TFRs) for sensitive locations, events, and activities that require ATM security measures such as the Republican National Committee Convention, Democratic National Committee Convention, the Presidential Inauguration, the Super

Bowl, and any Olympic Games conducted within the United States.

The SOG staffs and manages Air Traffic Control (ATC) senior representatives at a number of national defense locations including NORAD, CONR, Eastern Air Defense Sector (EADS), and Western Air Defense Sector (WADS). They plan and coordinate aviation security measures for national defense and homeland security missions. They develop and coordinate airspace protection plans for Presidential and other VIP movements. Furthermore, they identify and plan protective ATM security measures for National Special Security Events (NSSEs). The group’s specialists support and coordinate classified/sensitive operations within the NAS, while at the same time mitigating the impact of these operations on other system users.

Day-to-Day System Operations Security This unique group numbers less than 60 and operates entirely behind locked doors, embedded in locations with other agencies and departments across the United States. Many people in the FAA are unaware this group exists. 24 hours a day, every day, System Operations Security monitors real-time traffic for security anomalies utilizing customized tools and

technologies, including specialized computer software and radar displays designed for their unique mission.

Working in close partnership with the Air Traffic System Command Center in Herndon, Va., these Air Traffic Security Coordinators also monitor events on a global scale, always alert for possible security-related impacts to the NAS. All the while, the ATSCS are in constant communication with the Department of Defense and various other agencies with a role in national security and homeland defense.

Aside from constant real-time monitoring by the TACOPS group, the rest of System Operations Security usually starts before dawn each day. Before each morning’s briefing, most have been assessing the airspace situation from various sources. Once together, the pre-dawn hours are spent with a review of the previous evening’s activities in the NAS. Once reviewed, representatives from Tactical, Strategic, and Special Operations engage in information sharing. Determinations of immediate and near-term “watch” issues will be made and disseminated to the appropriate levels.

Coordination and outreach follow. The fine-tuned process between Strategic and Tactical is harmonized with Special Operations as everyThe Journal of Air Traffic Control

11

System Operations Security

System Operations Security’s ATM security mission is to protect the United States from threats and other major incidents involving the air domain while looking out for the economic considerations of the NAS. one works to accomplish classified and specialized operations that will hopefully go unnoticed in the NAS or on the ground. The day-to-day work of System Operations Security cuts across every function of the ATO. Their activities involve meetings and operations with United States Secret Service (USSS), the Military’s Joint Specialized Operations Command (JSOC), Customs and Border Patrol (CBP), and various state and local law enforcement agencies that many see only on television or in the movies.

The ultimate goal is making ATM security seamless and to maintain airspace efficiency.

However, not every scenario is by the book, and development of new procedures is often required. Flexibility and ingenuity are necessary skills, as well as a keen ability to think com-

12

Summer 2013

pletely outside of the box. Each individual brings a healthy background in air traffic control, flight service, automation, and technical operations, with specialized experience in international aviation, military aviation and joint operations, law enforcement, legal, and national security experience. This is a decisive group, not afraid to make a decision and stand by it.

Being part of the System Operations Security team is physically demanding work. The hours are irregular, with some positions spending a large amount of time on the road in disaster areas. Pre- and postemergency response activities are not for the faint of heart. The environment is challenging and requires physical and emotional stamina. For individuals not on travel, but acting as support staff or foundational players, the

work is tedious and requires incredible attention to detail and astute political savvy.

Most employees in this office have many years of experience within the FAA and other government agencies, and will maintain that System Operations Security is without a doubt their favorite career posting. System Operations Security’s mission is to protect the United States from threats and other major incidents involving the air domain, while balancing the demands of homeland security and national defense against operational integrity and economic considerations of the NAS. It is a mission that requires tremendous commitment, but in return provides a level of career and personal satisfaction that only comes from making a positive contribution to homeland security, each and every day.

Photographer: David Crockett / Phtos.com

From The Archives

The Role of the FAA Technical Center

By Dr. John J. Fearnsides, MITRE

Editor’s Note: This article was originally published in the January – March 1990 issue of The Journal of Air Traffic Control.

As ATCA gears up to go to Atlantic City for the annual Technical Symposium, we take a look back to the 1989 Journal archives when the role of the William J. Hughes Technical Center was first being established. Over the years, it has developed into one of the nation’s premier aviation research, development, test and evaluation facilities. It serves as the FAA national scientific test base for research and development, test and evaluation, and is the primary facility supporting NextGen.

This year at the ATCA Technical Symposium (May 21 – 23), Technical Center Director, Dennis Filler, will present alongside other FAA-focused panels. Attendees will spend the entire first day of the symposium at the venue, as we start up #TechCenterTuesday and FAA organizations will exhibit on-site. Attendees will return to the Resorts Hotel to continue programming and exhibits on Wednesday and Thursday. Learn more and register at www.atca.org/TechSymposium. See you in Atlantic City!

The Journal of Air Traffic Control

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From The Archives

The original article, as published in the January – March 1990 edition of The Journal of Air Traffic Control

It has been said that the first rule of business is to know what business you are in. This is true for public as well as private organizations. Our focus today is what the business of the FAA’s Technical Center is, should be, or could be. As many businesses have discovered, it is not always easy to articulate a basic organizational mission. The FAA is an example of an organization with traditionally well-defined operational, regulatory, and developmental missions. Indeed, the clarity and importance of these missions have enabled the FAA to perform brilliantly despite the constraints imposed by traditional federal budget, procurement, and personnel practices.

However, as has been discussed in previous issue forums, the FAA has, since deregulation, been charged with a new crucial mission; the management of the capacity of the nation’s airspace. Major strategic changes for an organization are traumatic enough. This change came upon the FAA right after a controller’s strike and the need to acquire and implement the NAS Plan. This has placed an enormous burden on FAA management and staff. There is so much to be done that the question of the role of the Technical Center should be “how can we best use this substantial human and technical capability

14

Summer 2013

to help us with all of this work?”

In the next few minutes, I will address three very difficult challenges for the FAA over the next 10 years, and try to show that the resources of the Technical Center are likely to be stretched to the limit during this period. Then I will try to address the question of expanding the research and development capability here. In the interest of time, I will not deal with all of the functions performed here at the Technical Center, such as the increasing efforts here to support aging aircraft issues.

The three major challenges I referred to are 1) the need for integrated operational test and evaluation of NAS Plan components prior to field development, 2) the emerging major question of how to perform software maintenance in the 90s, and 3) the need to add operational capability to all phases of the technical capability that will be provided by the NAS Plan.

First, let’s discuss integrated testing. The NAS Plan is coming, folks, and in the next few years, the products of J. Lynn Helms’ genius will look to the Technical Center like a very beautiful, high-tech, 800-pound gorilla. Imagine the work involved in integrating Mode S and its integral data-link with ARTS and the Host. How will the Central Weather Processer play with the Advanced Automation and Flight Service Automation Systems? While I haven’t seen the staffing plans for the care, feeding, test, and evaluation of that gorilla, it is hard to imagine that it will not strain both the human and building capacities here.

Indeed, the Technical Center will need substantial contract support to carry out even that mission.

The second issue is software maintenance. In 1989, the FAA had to maintain systems with 18 different languages and 11 different operating systems. In 1993, there will be 23 different languages and 25 different operating systems. In 1989, the FAA maintains systems with about 5 million source lines of code. That figure will double by 1993. Managing software configurations of this magnitude, while exercising quality control, will require a larger and increasingly expert software maintenance staff. Moreover, the systems will be more complex, and the need for software enhancements will be incessant and long-lasting. For example, the FAA will have to add new capabilities to the Host, to ARTS, to ISSS, and to the phases of the Advanced Automation System. I will expand on this topic later.

There should be a great demand for computer engineers and scientists, along with those with invaluable operational experience. These issues will have to be dealt with by the Air Traffic and Airways Facilities Organization and the role of the Technical Center in software maintenance will have to be evaluated. Further, I don’t expect this requirement to diminish ever again, so while this is presented here as a 10-year issue, it seems destined to sustain well past the turn of the century.

I have mentioned the need to add operational capability to the enormous NAS Plan technical capability. For example, how will the Mode S datalink actually be used?

From The Archives

The NAS Plan is coming, folks, and in the next few years, the products of J. Lynn Helms’ genius will look to the Technical Center like a very beautiful, high-tech, 800-pound gorilla.

Or, how can we incorporate improved metering functions into the Host? In short, how can we expedite the transfer of R&D products into field-deployment? The Technical Center is playing a major role in this area. And given the excellence of the staff and the facilities, that role is likely to continue. For example, the Technical Center is engaged in the experimental development of the following NAS Plan application projects; datalink applications, TCAS I, II, and III, and automatic dependent surveillance.

As with the challenges mentioned above, I anticipate the need for this function to continue into the indefinite future (certainly greater than 10 years).

Finally, I would like to address the issue of broadening the range of R&D activities at the Technical Center.

You have heard, or will hear today, that there should be more R&D at the Technical Center. I think that this recommendation is based on three premises: First in the eyes of some, the FAA has always struggled unsuccessfully to create a vital, sustaining research and advanced development program. Small wonder when you consider that the agency is trying to manage with less staff Facilities Equipment budgets that are orders of magnitude greater than pre-NAS Plan budgets. At the same time, the organization must deal with the new operational demands imposed by deregulation.

The second premise is that there is somehow the feeling that research and advanced development is better work than development test, operational test, or software maintenance. I believe this feeling has evolved from the failure of our engineering schools to value engineering practice and applications as highly as theoretical ideas.

This may be one of the reasons why we as a nation aren’t faring so well in international competition.

The third premise, I think, is that more research and advanced development work at the Technical Center will attract universities and high-tech entrepreneurs thereby improving the economic and cultural well-being of the area. I am not prepared to evaluate the correctness of that thesis. What I think I can say is that the government is no longer a strong competitor for the best and brightest

Glen A. Gilbert Memorial Award Winner J. Lynn Helms (referenced on page 14), and Former DOT Deputy Secretary Elaine Chao in 1989.

of the technical community. Given the aforementioned demands on the existing staff, it is hard to imagine who could be spared to do the R&D. It is the same microcosm as the generic problem the FAA has. If, in the light of the aforementioned staffing demands, the FAA decides to embark on a strategy of converting the Technical Center to an in-house research and advanced development facility, they will have to solve some fundamental recruiting problems. My most radical thesis in this regard is that to accomplish this, the FAA will have to convert the Technical Center to a private, not-for-profit corporation with the charter of a Federally Funded Research and Development Center.

FAA management clearly has some important challenges. First, it must take steps to recognize value and extol the importance of the work done at the Technical Center. Secondly, management must clarify its intentions as to the role of the Technical Center in supporting overall agency missions. Finally, there is an urgent need to give the Technical Center a long-range commitment to assure workplace stability and a continuing flow of projects to keep current and future capabilities vital.

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Balancing Safety and Efficiency of Airport Operations under Lightning Threats A look inside the ramp closure decision-making process

By Dr. Matthias Steiner and Dr. Wiebke Deierling, National Center for Atmospheric Research and Randall Bass, Federal Aviation Administration

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Summer 2013

Lightning

There can be considerable accuracy differences in determining the location, number and type (in-cloud or cloud-to-ground) of lightning detected, depending on which lightning information system is employed.

The present article discusses findings from such observations carried out during the summer of 2012 at a major United States airport to study lightning safety procedures and their implementation in situations of thunderstorm and lightning impacts. The novel aspect of this work is the documentation of actual ramp closures (information otherwise not available) and assessment of the uncertainties related to implementing the safety procedures.

Names or other information that might identify a particular person have been omitted from this article in accordance with Federal Policy for the Protection of Human Subjects (45 CFR Part 690).

Uncertainties Associated with Ramp Closures Figure 1 summarizes the wide range of uncertainties involved in the ramp closure decision-making process.

These uncertainties can be grouped into three main categories related to: • Lightning information utilized • Established safety procedures • Human factors Outdoor personnel safety is the responsibility of each airport and airline stakeholder. Currently, there is no centralized guidance for an airport in the United States, which yields situations where stakeholders utilize lightning information obtained from different sources (i.e., commercial vendors)[5]. In fact, many small and mid-size airports have no lightning warning procedures in place at all. There can be considerable accuracy differences in determining the

The Journal of Air Traffic Control

Photographer: Clint Spencer / Photos.com

Safety versus Efficiency Lightning poses a serious threat to the safety of people working or pursuing recreational activities outdoors. Every year, numerous people are injured or killed by lightning[1, 2], although it remains difficult to collect accurate data[3].

Personnel working outdoors in the airport area, such as people servicing aircraft (e.g., baggage handlers, airplane fuel suppliers, food suppliers) or airport grounds and infrastructure maintenance staff are exposed to lightning threats[4]. Therefore, when thunderstorms form or move near an airport, alerts are issued to suspend outdoor activities and bring people inside to safety. However, the resulting downtime periods affect airline and airport operational efficiency. The challenge is finding a good balance between personnel safety and operational efficiency.

In 2008, the Airport Cooperative Research Program (ACRP) released a report[5] that provides a general overview of the problem, safety procedures commonly used, and lightning detection sources available as a basis for making decisions to halt outdoor work. That report includes an analysis of the operational costs incurred by airport ramp/apron closures. These costs were estimated based on nominal ramp closure occurrence and duration using known safety rules applied to standard lightning data. This approach was taken because no records of actual ramp closures were available.

In order to optimize lightning safety procedures and assess true impacts of ramp closures on airport operations, the ACRP report[5] recommended detailed field observations at airports to document actual ramp closures and uncertainties associated with closure procedures.

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Lightning

location, number and type (in-cloud or cloud-to-ground) of lightning detected, depending on which lightning information system is employed. The uncertainties are a result of different lightning detection technologies, sensor network densities, and data processing associated with the various national and regional lightning measurement systems.

Since the lightning measurements and data processing algorithms continue to be improved, the detection accuracy of lightning events will change over time and may also vary geographically. Typically, the regional total (i.e., in-cloud and cloud-to-ground) lightning measurement systems provide lightning information with a higher detection efficiency and accuracy than the national networks currently available to airport and airline stakeholders.

Due to a lack of common guidance, airline and airport stakeholders have varied procedures in place to ensure safety of outdoor personnel. At those locations that do have lightning warning procedures in place, they frequently vary between airline and airport stakeholders due to a lack of common guidance. A commonality of all approaches is the closing of a ramp in response to a first lightning strike within a critical distance of the airport (i.e., a reactive approach) and then waiting for a period of time until it is deemed safe again to resume outdoor work. The primary source of uncertainty is related to the critical distance (from the terminal area where people work outdoors) and timing (i.e., waiting period after the last lightning strike) criteria. We found a wide range of values in use, yielding situations where multiple airlines may be utilizing different criteria at any given airport. Without a doubt, airlines aim toward minimizing the downtime caused by lightning-related ramp closures in order to maximize efficiency. It is also apparent that airlines display varied risk tolerances.

Finally, what clearly emerged from the summer 2012 field observations is that human factors aspects have to be considered. There are multiple factors related to a decisionmaker’s trust in the safety procedures and tools at their disposal, and how effectively the procedures are implemented (e.g., how efficiently closures are communicated to 18

Summer 2013

the outdoor workers and how fast a ramp can be cleared).

Furthermore, on several occasions, decision-makers were distracted by other operational demands (thus, yielding a delayed alert and ramp closure or none whatsoever) or their decisions were influenced by what other airlines were doing in a particular situation.

Example of Major Thunderstorm Impacts Safety and Inefficiency Aspects The observed lightning data can be translated into nominal ramp closures based on a stakeholder’s known safety procedures. For example, at the same airport, observed stakeholder 1 closes the ramp if lightning occurs within a critical distance of five miles, and they wait for 15 minutes after the last lightning strike within that distance before resuming outdoor work again. Stakeholder 2, on the other hand, employs a critical distance of three miles and waiting period of six minutes.

Comparing nominal ramp closures to the ramp closures observed and documented during our field observations revealed issues related to how effectively the safety procedures were implemented. Not following their own rules may be an indication of human factors and/or process issues.

Deviations from established procedures will invariably lead to safety and/or inefficiency concerns.

Figure 2 shows a time sequence of nominal and actual ramp closures for two observed airline stakeholders, plus additional impacting factors related to the weather and FAA traffic management initiatives. The nominal ramp closures based on the stakeholders’ operationally available lightning information and specific safety procedures are shown in green. The nominal ramp closures, if a regional and more complete total lightning dataset were utilized (currently not available to the airline operators), are shown in yellow. The observed actual ramp closures of stakeholders 1 and 2 are shown in purple and gray, respectively. The stakeholder 2 procedures yield shorter but more frequent ramp closures than the safety rules employed by stakeholder 1.

On this particular day, multiple storms impacted the

Lightning

airport during the afternoon and evening hours, yielding several ramp closures in a four to five-hour time window.

This day is of great interest, because it clearly showed the cumulative effects of multiple ramp closures. The FAA’s Air Traffic Control System Command Center (ATCSCC) put out an advisory that day for potential impacts of thunderstorms.

There was a short Air Route Traffic Control Center (ARTCC) internal ground stop, as well, just before a hailstorm impacted the airport. The hailstorm had a marked impact, because the aircraft had to be inspected afterward for possible damages.

Comparison of actual to nominal ramp closures revealed potential safety concerns. For example, it took stakeholder 1 several minutes to initiate closures and clear the ramp after the first lightning strike within the critical distance. The response time for stakeholder 2 was notably less, but they also utilize a stepwise reduction in operations approach and thus might have already been more alert. Comparison of the operationally available lightning information to the regional, more complete total lightning source showed that the stakeholders’ lightning information used for ramp closure decisions was missing an appreciable amount of (mostly in-cloud but also some cloud-to-ground) lightning, which constitutes a safety risk. This comparison also revealed that the ramp closure triggered shortly after 01:30 UTC was really a false alarm (due to lightning location error) of the lightning information used by the stakeholders.

This particular case is remarkable, because it reveals cumulative effects of lightning impacts and ramp closures.

Clearly, stakeholders were not strictly implementing their own safety procedures, and as multiple impacts occurred, a significant traffic backlog built up. For both stakeholders, we noticed there were occasions when the ramp should have remained closed but was reopened, or the ramp should have been closed but never was, while other times it stayed closed unnecessarily long (Figure 2). All these symptoms point toward significant human factors issues that play a role in the process of balancing personnel safety versus operational efficiency. Furthermore, this case elucidates that

Figure 2. Nominal and actual ramp closures for two airline stakeholders

the lack of common procedures among stakeholders causes confusion with ramp workers that can reduce safety and efficiency.

Impacts on Air Traffic Prolonged ramp closures invariably lead to airport operational inefficiencies. Studies such as the ones conducted

by Wang et al.[6] and Wang[7] shed light on various causes of flight delays incurred at the gate; however, weather impacts were not really addressed. Our analyses also go beyond what was discussed in the ACRP report[5] by looking at air traffic data in conjunction with actual ramp closures.

Figure 3 (next page) depicts air traffic delays incurred during the case discussed above (Figure 2). Shown are touchdown (in black) and taxi delays (blue) of incoming flights (left panel), as well as gate (red) and taxi delays (orange) of departing flights (right panel). The air traffic data was obtained from the Research and Innovative Technology Administration (RITA) Bureau of Transportation Statistics database. Ramp closures are expected to yield gate delays, as a gate-side parked aircraft cannot get serviced. This is clearly visible in the right panel of Figure 3, where the delays were dramatically increasing during and following ramp closures. There were also some taxi delays incurred by the departing flights, likely caused by the backlog of traffic that built up as aircraft queued up for takeoff.

Traffic delays, however, were also experienced by the incoming traffic. Some delays may have been incurred due to storms impacting the arrival fixes, which caused flights into airborne holding patterns, redirection to other arrival fixes, or possible diversions. The impacts of prolonged or multiple ramp closures may also be felt by the arriving traffic after they land while taxiing to a gate. The problem arises when aircraft already occupying gates cannot be readied for departure and are delayed. Eventually, no more gates become available for the incoming flights. Thus, the inbound taxiing aircraft have to wait in a designated area until their assigned gate becomes available. This is clearly seen in the left panel of Figure 3 (and was visibly observed The Journal of Air Traffic Control

Photographer: Stockbyte / Photos.com

Figure 1. Uncertainties associated with ramp closure decision-making process

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Lightning

Figure 3. Observed impacts of ramp closures on air traffic arrivals (left) and departures (right)

as well). Interestingly enough, there were no diversions of incoming flights that day, but there were seven cancellations for outgoing flights.

One of the key airport operational challenges is to keep the capacity of arriving and departing aircraft in balance to avoid gridlock. Reasons an airport gets out of balance may include emergencies (e.g., loss of a runway) or substantial unexpected weather impacts (e.g., convective storms).

Anticipated impacts are typically dealt with at a National Airspace System (NAS) level through traffic management initiatives, such as Ground Delay Program (GDP), Ground Stop (GS), or Airspace Flow Program (AFP) restrictions that aim to reduce the incoming traffic to an airport or region.

On average, the air traffic into an airport is balanced by the outgoing traffic. Under certain circumstances, such as convective storm impacts, the need may arise to land aircraft at the expense of departing flights to avoid airborne holding or diversions. However, such situations are not sustainable as a backlog of aircraft waiting for departure builds up. In high-impact situations, this typically results in a GS and subsequent GDP to facilitate recovery and get the airport back into balance.

The example discussed previously (Figures 2 and 3) illustrates how convective storms, and lightning in particular, induced ramp closures that can impact airport operations. Figure 4 shows the scheduled (left) and actual (right) arrivals and departures for the airport during that day’s thunderstorm impacts and associated ramp closures. The scheduled air traffic was supposed to ramp down after the last high demand period for the day around 1 UTC. Comparison of the scheduled and actual air traffic revealed that the incoming traffic (solid black lines in both panels) was not greatly affected, while departures (red dashed lines) were substantially delayed due to the multiple ramp closures, which brought the airport out of balance. An initial major departure delay was caused by the hailstorm impacting the airport at about 00 UTC (Figure 2), which was accompanied by longer lightning-induced ramp closures for airlines, and necessitated inspection of the aircraft for potential damages after the storm passed. Lightning-related ramp closures associated with this storm and subsequent storms pushed 20

Summer 2013

Figure 4. Impacts of ramp closures on airport balance

the departures to later times. The airport was able to recover later that evening, because there was not another peak demand period scheduled for that day.

Discussion The example presented above demonstrates that human factors play a major role in how well a stakeholder’s safety procedures are implemented. Our study found that the beginning of actual ramp closures frequently lagged the nominal time when a ramp closure should have started based on the lightning information and safety rules used by a particular stakeholder. Our field observations (including other cases not discussed here) suggest these delays can often be attributed to distractions of the person in charge of making ramp closure decisions. These distractions can originate from other operational demands (e.g., on phone or away from desk) that prevent them from paying attention to the lightning decision support tool.

We also found that trust (or lack thereof) in a decision support tool may result in actions that deviate from the safety protocol. One stakeholder switched decision support tools from one vendor to another, but for a while had access to both. In this case, the lightning information displayed on the two decision support tools was not identical, because it originated from two different lightning measurement systems.

Often the supervisor would compare the two systems and wonder which one to trust if they did not convey the same information. The person in charge would frequently go to the window to look outside (e.g., watch other airlines’ actions) or call someone else, which added to the delay incurred or no call being made to clear the ramp. Understandably, the operators are not meteorologists, and thus do not have a good sense of when the provided information may be flawed (e.g., false alarms). The fact that the data from two separate systems does not always agree further complicates the decisionmaking process.

Other reasons for a delayed ramp closure are related to the effectiveness of communicating decisions between the supervisor and the outdoor personnel, controllers responsible for aircraft movement on the ramp, gate agents, and pilots. The response time to a notification of clearing the

Lightning

One of the key airport operational challenges is to keep the capacity of arriving and departing aircraft in balance to avoid gridlock. Reasons an airport gets out of balance may include emergencies (e.g., loss of a runway) or substantial unexpected weather impacts (e.g., convective storms).

Suggested Improvements Safety Improvements Lightning is very challenging to predict[8, 9], and even its measurement can be difficult and complex[10]. A regional total Lightning Mapping Array (LMA)[11, 12] provides one of the most complete and reliable lightning information sources available today. However, use of LMA information as a basis for determining ramp closures would necessitate substantially longer ramp closures, which might not be in the interest of airline stakeholders because their operational efficiency would go down accordingly.

At those locations that have established procedures, airport and airline stakeholders close the ramp when a first lightning strike occurs within a critical distance. In addition, they wait a certain amount of time after the last lightning strike within that range until it is deemed safe to resume outdoor work again. Yet, the values for critical distance and waiting period vary significantly among stakeholders, which is a sign of different business models and risk tolerances. A set of recommended standardized procedures that can be implemented and tailored by each stakeholder for their operations - regardless of airport size – should be developed and promoted.

The point to focus on is what level of safety risk would be tolerable by a stakeholder, and then tune the critical distance and timing

criteria accordingly. These procedures have to include educating stakeholders about the uncertainties of using various sources of lightning information and the lightning predictability issues. According to lightning experts, a critical distance of eight to ten miles should be used to ensure safety of outdoor workers[13, 14, 15]. But unanswered questions remain with regard to the waiting period and what lightning information to use. Promising scenarios will likely combine information from various sources (lightning, radar, and other observations)[8, 16] to balance personnel safety with operational efficiency.

Implementation of Procedures Human factors showed up as a key aspect for ramp closure effectiveness. Clearly, stakeholders do not implement their own procedures effectively, as discussed above.

However, there are notable differences in this regard among the stakeholders, which may be a reflection of the corporate culture and other factors.

Use of audible and visual alerts is key to informing people about lightning-related safety risks in a timely fashion. Outdoor alerts are deemed essential as well as alerts inside an airline System Operations Control (SOC) center where the decision to close a ramp is made. We found that supervisors distracted by other operational demands may miss a first lightning strike within the critical distance and thus a ramp closure might only be initiated after some time has passed. Therefore, having both an audible and visual alert inside the SOC seems important. Moreover, we can foresee a system that automatically triggers a ramp closure a minute or less after the first lightning strike occurs within the critical distance. This would ensure outdoor personnel safety even if the supervisor were distracted by other operational demands. The slight delay time before a ramp closure is automatically initiated would likewise enable a human to assess the situation and overwrite the automation (i.e., not trigger a ramp closure) if necessary.

We also noticed the waiting period after lightning is not followed well. Some of today’s displays include a colorcoding of lightning strikes that changes with passing

The Journal of Air Traffic Control

Photographer: Stockbyte / Photos.com

ramp is also not negligible. It typically takes some time (often several minutes) until the ramp is cleared and people have moved inside to safety.

Lastly, the safety rules are not strictly enforced, as noted on several occasions. For example, it is not unusual to see actual gate arrival or departure times fall inside a ramp closure time window, which implies someone had to be outside (and in fact, our observers saw people) to either guide aircraft to the gate or push them back away from the gate.

We also noticed that multiple successive ramp closures can visibly increase the work stress and yield situations where “getting the job done” may trump safety protocol.

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Lightning

Photographer: Andreas Schulze / Photos.com

time, but it does not appear to be effective enough. A visible timer (or other visual alert) that automatically resets after each lightning strike within the critical range might help this issue. In fact, a manufacturer could build such a timer directly into the lightning detector display.

Ultimately, it also boils down to building trust in whatever approach or system is employed by a stakeholder.

This also requires appropriate training of both the staff that makes the decisions to close a ramp and the outdoor workers.

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of this material with Drs. David Johnson and James Pinto, as well.

We would like to express our gratitude to Drs. Paul Krehbiel and Bill Rison of the New Mexico Institute of Mining and Technology for granting us access to the regional LMA lightning data. We also thank Earth Networks, Vaisala, and WSI for the right to use their respective lightning data in our research.

This research is in response to requirements and funding by the Federal Aviation Administration (FAA). The views expressed are those of the authors and do not necessarily represent the official policy or position of the FAA.

Other Enhancements It would be beneficial to routinely document ramp closures by stakeholders and make that information accessible. This would help significantly in more broadly assessing potential References safety and inefficiency issues, and provide a basis for devel- [1.] López, R. E., R. L. Holle, and T. A. Heitkamp, 1995, Lightning casualties and property damage in Colorado from 1950 to 1991 based on oping enhanced procedures and decision support tools. storm data, Weather and Forecasting, 10(3), 114 – 126.

We envision that real-time performance feedback to [2.] Holle, R. L., R. E. López, and B. C. Navarro, 2005, Deaths, injuries, stakeholders would increase their awareness of how they are and damages from lightning in the United States in the 1890s in conducting business and what safety risks or inefficiencies comparison with the 1990s, Journal of Applied Meteorology, 44(10), 1563 – 1573. they might be incurring.

[3.]

López, R. E., R. L. Holle, T. A. Heitkamp, M. Boyson, M. Cherington, Sharing of lightning information across an airport would and K. Langford, 1993, The underreporting of lightning injuries and enhance the common situational awareness (which is done deaths in Colorado, Bulletin of the American Meteorological Society, at a few airports). This could be achieved if every stake74(11), 2171 – 2178. holder (i.e., airlines and airport authority, and possibly also [4.] Tan, H. H., and S. H. Goh, 2003, Lightning injury: Changi hospital experience, Hong Kong Journal of Emergency Medicine, 10(4), 223 the city seeking better lightning protection for outdoor ven– 232. ues) would provide support for a good system (e.g., regional [5.] Airport Cooperative Research Program (ACRP), 2008, Lightning LMA), where the amount of support could be scaled accordWarning Systems for Use by Airports, ACRP Report No. 8, ing to a stakeholder’s presence at that airport. Moreover, Transportation Research Board, National Academies, 81 pp. stakeholders could still apply their own safety procedures as [6.] Wang, J., J. F. Shortle, J. Wang, and L. Sherry, 2009, Analysis of gate-waiting delays at major us airports, 9th AIAA Aviation they deem necessary, given their corporate risk tolerance.

Technology, Integration, and Operations Conference (ATIO) and Finally, lightning-potential predictions could be introAIAA/AAAF Aircraft Noise and Emissions Reduction Symposium duced to the ramp closure decision-making process that (ANERS), Hilton Head, SC, 20 pp. incorporate all available information (lightning, radar, and [7.] Wang, J., 2011, Methodology for Analysis, Modeling and Simulation of Airport Gate-Waiting Delays, PhD Thesis, George Mason University, other relevant weather data) into a smart algorithm which Fairfax, VA, 193 pp. yields a highly reliable decision support tool[8]. The use of [8.]

Saxen, T. R., C. K. Mueller, T. T. Warner, M. Steiner, E. E. Ellison, E. W. such predictions could provide some lead-time rather than Hatfield, T. L. Betancourt, S. M. Dettling, and N. A. Oien, 2008, The reacting to a first lightning strike – as is currently done – operational mesogamma-scale analysis and forecast system of the that could be harmful to an unprotected outdoor worker. A U.S. Army Test and Evaluation Command. Part IV: The White Sands lightning prediction system could also provide some leadMissile Range auto-nowcast system, Journal of Applied Meteorology and Climatology, 47(4), 1123 – 1139. time for air traffic management personnel to take proactive [9.]

Dance, S., E. Ebert, and D. Scurrah, 2010, Thunderstorm strike probsteps for effectively managing inbound and outbound flight ability nowcasting, Journal of Atmospheric and Oceanic Technology, operations before the actual thunderstorm and lightning 27(1), 79 – 93. impacts occur.

[10.] Cummins, K. L., and M. J. Murphy, 2009, An overview of lightning Acknowledgements We greatly appreciated the opportunity to spend time in airline and airport facilities during the 2012 convective season to observe the operations under thunderstorm and lightning impacts.

The results reported here would not have been possible without the hard work of Kyoko Ikeda, Eric Nelson, and Ken Stone supporting our field observations and subsequent data analysis. We benefitted from stimulating discussions Summer 2013

location systems: History, techniques, and data uses, with an in-depth look at the U.S. NLDN, IEEE Transactions on Electromagnetic Compatibility, 51(3), 499 – 518.

[11.] Rison, W., R. J. Thomas, P. R. Krehbiel, T. Hamlin, and J. Harlin, 1999, A GPS-based three-dimensional lightning mapping system: Initial observations in central New Mexico, Geophysical Research Letters, 26(3), 3573 – 3576.

[12.] Thomas, R. J., P. R. Krehbiel, W. Rison, S. J. Hunyady, W. P. Winn, T. Hamlin, and J. Harlin, 2004, Accuracy of the lightning mapping array, Journal of Geophysical Research, 109, D14207, doi:10.1029/ 2004JD004549.

[13.] Holle, R. L., R. E. López, and C. Zimmermann, 1999, Updated rec-

Lightning ommendations for lightning safety–1998, Bulletin of the American Meteorological Society, 80(10), 2035 – 2041.

[14.] Holle, R. L., and N. W. S. Demetriades, 2010, GLD360 airport lightning warnings, 21st International Lightning Detection Conference and 3rd International Lightning Meteorology Conference, Orlando, FL, 5 pp.

[15.] Woodrum, C. C., and D. Franklin, 2012, Using a lightning safety toolkit for outdoor venues, 22nd International Lightning Detection Conference and 4th International Lightning Meteorology Conference, Broomfield, CO, 6 pp.

[16.] Murphy, M. J., and R. L. Holle, 2006, Warnings of cloud-to-ground lightning hazard based on combinations of lightning detection and radar information, 19th International Lightning Detection Conference and 1st International Lightning Meteorology Conference, Tucson, AZ, 6 pp.

About the Authors Dr. Matthias Steiner is Deputy Director for the Hydrometeorological Applications Program of the National Center for Atmospheric Research. His professional interests are in weather impacts on various sectors, with a particular focus on aviation. Email: msteiner@ucar.edu Dr. Wiebke Deierling is a Project Scientist at the National Center for Atmospheric Research. She is an expert in thunderstorm electrification and lightning observations. Email: deierlin@ucar.edu Mr. Randall Bass is the Project Manager for the Convective Weather Research Program at the Federal Aviation Administration. Email: randy.bass@faa.gov

With LightWave RadaR fRom C Speed, the piCtuRe iS BeComing CLeaReR. When the United Kingdom’s major aviation stakeholders, including major airport operators, orchestrated a test of wind turbine clutter mitigating radar in June 2012, they selected only one company – C Speed, an innovative designer and manufacturer of state-of-the-art, radar technology. This test, the mitigation of the Whitelee Windfarm in Scotland, was deemed successful as these major aviation stakeholders witnessed live demonstrations of very small radar cross-section aircraft being flown over the wind farm.

It was a major acknowledgement of C Speed’s LightWave Radar technology, an S-band solid-state primary surveillance radar system for wind turbine mitigation. C Speed has also installed its LightWave Radar for testing and certification at Glasgow Prestwick Airport and Manston Airport, which are located in the United Kingdom. These efforts integrated LightWave Radar technology into the airport’s ATM systems.

For more information, visit www.lightwaveradar.com.

316 Commerce Blvd. Liverpool, NY 13088 • (315) 453-1043 • cspeed.com

Figures 1-4 courtesy of Dr. Matthias Steiner

The Journal of Air Traffic Control

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FAA Employs New Model in Benefits Calculation Outlining the 2013 update to the NextGen Implementation Plan

By Joseph Post, Director of Systems Analysis and Modeling, Federal Aviation Administration If history is a guide, the graphic you see here will be remembered as one of the best-known features of the 2013 update to the NextGen Implementation Plan. Like similar graphics from the past three editions of the NextGen Implementation Plan, it provides, at a glance, the FAA’s best estimate of what the aviation community can expect from NextGen in reduced delays, fuel consumption, and carbon dioxide emissions, and the value of these reductions through the year 2020. The comparison is between implementing NextGen improvements according to current schedules, versus leaving the National Airspace System (NAS) as it is.

The simplicity of Figure 1 belies the complexity of the process by which it was generated. Estimates of NextGen benefits depend on the System Wide Analysis Capability (SWAC), a sophisticated model of the NAS. We in the FAA NextGen Systems Analysis and Modeling Office use SWAC to ask “What If” questions about NextGen deployments and other initiatives under varying NAS conditions. Top NextGen managers use estimates drawn from SWAC modeling in a number of ways: • To communicate with the public and our stakeholders, as in the Implementation Plan • As inputs in assessments of the business case and potential incentives for equipping private-sector aircraft to operate using NextGen systems • To inform trade studies For example, we used the simulation model to estimate operational benefits of Automatic Dependent Surveillance– Broadcast (ADS-B) surveillance in Gulf of Mexico high-altitude airspace to determine whether financial incentives would be necessary to persuade aircraft operators in this airspace to equip. ADS-B is a ground-based infrastructure that provides satellite-based surveillance. The technology can increase capacity in non-radar airspace, and help controllers to better sequence arrival traffic from greater distances, improving the predictability and efficiency of traffic flow.

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Summer 2013

NextGen Benefits

We found that operators with high-equipage levels experienced significant delay reduction in both fiscal years. Overall, there was a delay reduction at all equipage levels; delays were reduced by nearly half at 40 percent equipage.

Coverage The Houston Oceanic Control Area is responsible for high-altitude operations in the Gulf of Mexico, and radar coverage is available in only about half of this airspace. Airspace not covered by radar surveillance is subject to much wider separation standards. With recently deployed ADS-B ground stations, however, surveillance coverage is now available for virtually all of this airspace. Once these surveillance data are fully integrated with the en route automation platform and all aircraft are equipped, it will be possible to provide five nautical miles (nm) of longitudinal separation in this airspace.

We used SWAC to estimate the operational benefits of reduced in-trail separation over the Gulf to operators who equipped, to operators who did not equip, and to the rest of society. We compared the operational benefits for those who equipped with the cost of equipping in order to determine whether operators have enough incentive to invest in the absence of financial assistance, and if not, whether assistance is warranted. At the time of the 2010 simulation, 21 ADS-B ground stations had been deployed in and around the Gulf (in some cases on oil platforms), providing precise surveillance in an area that does not have complete radar coverage. Eight very high-frequency transceivers had also been deployed to provide voice communications. However, virtually no aircraft were equipped with the requisite DO-260Bcompliant ADS-B transponders because the technical standard had been approved only recently.

Using SWAC, we estimated the delay savings associated with ADS-B equipage and five nm of longitudinal separation in the Gulf. We modeled two scenarios – one with no ADS-B equipage and the other with some ADS-B equipage – for Fiscal Years (FY) 2014 and 2023. We represented each year with eight different days to capture seasonal traffic and weather variations. In the case of ADS-B Out surveillance in Gulf of Mexico high-altitude airspace, it would appear the potential operational benefits to equipped operators are large enough that incentives are not required.

Equipage Incentives In 2012, we applied SWAC to the Gulf of Mexico again in order to determine whether operational incentives are needed to encourage operators to equip with NextGen avionics.

We considered a scenario in which ADS-B Out-equipped aircraft over the Gulf received preferential altitudes, and thus used the SWAC model to estimate the effects of altitude segregation. We examined various levels of equipage.

In this simulation, traffic data ran for 12 days in FY 2014 and FY 2019. Flight Level (FL) 350 and above was reserved for ADS-B Out aircraft while non-equipped aircraft moved below FL 350. Equipped aircraft were left at filed altitudes, even if below FL 350, with 10 nm horizontal separation at and above FL 350 (we assumed for this analysis that Mexico requires 10 nm in-trail separation). We used standard oceanic separation below FL 350 for non-equipped operators (to simplify the modeling 15 minutes in-trail was used).

We found that operators with high-equipage levels experienced significant delay reduction in both fiscal years.

Overall, there was a delay reduction at all equipage levels; delays were reduced by nearly half at 40 percent equipage.

A fuel penalty of 200 kg to 300 kg per unequipped operation was also discovered.

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NextGen Benefits

Photographer: Jupiterimages / Photos.com

SWAC is a medium-fidelity model, detailed enough to represent all of the NextGen improvements beneficial to model and evaluate, but not so detailed that the implementation time and cost exceeds the ability to acquire the equipment and operate the system

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Evolving Technology SWAC is the second model we have used to analyze the NAS. The first was NASPAC – the NAS Performance Analysis Capability – that MITRE developed for the FAA in the late 1980s. NASPAC evolved gradually during the 1990s in a series of upgrades; however, we eventually needed a new model entirely. NASPAC was not robust enough to model the growing roster of NextGen improvements, and it was limited by its once modern, but eventually archaic, computer software. For example, NASPAC only modeled airspace in the continental U.S.; SWAC models domestic airspace plus oceanic airspace, a growing number of airports and arrival/departure fixes and restrictions. Increasingly, it became difficult and expensive to support NASPAC. We started developing SWAC in 2007 with CSSI, Inc. and Metron Aviation, which continue to support SWAC operations today. SWAC uses the Linux operating system, compared with the outdated Sun Microsystems Solaris system in NASPAC. SWAC’s programming language is Java (from the mid-1990s) in place of NASPAC’s FORTRAN (1950s) and Pascal (around 1970). And SWAC’s simulations language is C++/CSIM (early 1980s and 1986, respectively) instead of SimScript II.5 (a derivative with origins in 1962).

We changed the name formally from NASPAC to SWAC in 2011 because by then, SWAC’s elements had no real connection to their NASPAC forebears.

SWAC Moving Forward SWAC is a medium-fidelity model, detailed enough to represent all of the NextGen improvements beneficial to model and evaluate, but not so detailed that the implementation Summer 2013

time and cost exceeds the ability to acquire the equipment and operate the system. MITRE, The Boeing Company, and other organizations operate similar systems. By contrast, high-fidelity models like NASA’s ACES (Airspace Concept Evaluation System) can model and simulate operations involving greater complexity. ACES’ capability comes at a cost, however. It usually takes SWAC six to seven minutes to model a full day in the NAS, while ACES needs six to seven hours. SWAC operates on a standard desktop computer while ACES requires a network of computers.

In a single run, SWAC models a given day’s instrument flight rules operations in U.S. airspace and visual flight rules operations at selected airports. It tracks each flight’s trajectory at one-minute intervals using the Traffic Flow Management System flight plan. Until recently the model included limits on capacity at 110 airports representing 99.8 percent of all flight delays in the NAS. In May, we expanded the model to include more than 300 airports.

We model fuel burn, flight cancellations, the number of flights the system accommodates, and delays by phase of flight. As SWAC is a medium-fidelity model, we don’t consider the specific actions or performance of controllers. We use EUROCONTROL’s Base of Aircraft Data performance model to account for the capabilities of different aircraft.

We update SWAC continuously, and even as we do, we keep replacing pieces of it. You will be unaware of this as you read next year’s estimate of NextGen benefits, or even those from the following year. But you can count on a NAS model that reflects the most careful construction, cautious assumptions, and up-to-date software possible.

Images courtesy of the FAA

NASA’S ATD-1

NASA’s ATM Technology Demonstration-1 Moving NextGen Arrival Concepts from the laboratory to the operational NAS

By Harry Swenson, John E. Robinson III, Aerospace Engineers, NASA Ames Research Center and Steve Winter, Engineering Fellow, Raytheon Technical Services Company

tem, known as the Traffic Management Advisor (TMA), as well as the Standard Terminal Automation Replacement System (STARS) platform. The ATD-1 software-based technologies will be prototyped within TBFM and STARS systems, and the integration validated within high-fidelity human-in-the-loop simulations at NASA and FAA laboratories. This represents the completion of the concept exploration phase and the functional requirements definition phase for the ATD-1 technologies. It also provides the FAA with sufficient information to fully evaluate the impact of the ATD-1 technologies on its automation platforms to enable operational evaluation and accelerated transition of the technologies to the NAS. Although the concept and technologies are being developed for U.S. airspace, it is expected they would offer substantial benefits internationally.

Photographer: Anton Foltin / Photos.com

Introduction This paper describes NASA’s approach for transitioning NASA’s Air Traffic Management Technology Demonstration – 1 (ATD-1) NextGen arrival concepts and technologies from laboratory simulations to operational evaluations in the U.S. National Airspace System (NAS). The ATD-1 tools are an integrated and interoperable set of ground and airborne technologies that have demonstrated simultaneous increases in airport throughput and use of fuel-efficient descents from cruise to touchdown in high-fidelity simulations of congested traffic conditions. This article’s focus is on the overall approach and design trades used to facilitate the integration of the ATD-1 ground-based technologies into the NAS. This includes enhancing the FAA’s Time-Based Flow Management (TBFM) scheduling sys-

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NASA’S ATD-1

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Figure 1. ATD-1 technology components

Figure 2. ATD-1 Integrated Arrival Scheduling and Spacing Concept

NextGen and Terminal Arrival Operations The U.S. future Next Generation Air Transportation System (or NextGen) includes goals for expanding the capacity of high-demand airports, while increasing the fuel efficiency of arriving aircraft.1 Today, arrivals into high-density airports during high throughput time periods often experience significant inefficiencies resulting from use of static milesin-trail procedures, step-down descents, and significant vectoring close to the airport. These contribute to reduced airport capacity, increased controller workload, increased arrival delay, as well as increased fuel burn, emissions, and noise2. NASA has proposed to demonstrate capabilities to alleviate these inefficienceies while still maintaining high throughput by integrating a set of three ground and airborne research technologies into a project called Air Traffic Management Technology Demonstration – 1 (ATD1)3. ATD-1 has a primary goal to demonstrate these technologies in an operational evaluation in the NAS to validate the benefits demonstrated in high-fidelity simulations.

The challenges of sucessfully transitioning and evaluating automation technologies in the NAS are many.

In the early 1990s, the FAA worked with NASA and the MITRE Corporation’s Center for Advanced Aviation System Development to successfully evaluate prototype technologies that were “off-board” of the primary safety-critical air traffic automation plaforms. These technologies, called the Traffic Management Advisor (TMA)4 and the User Request Evaluation Tool (URET)5, then took nearly a decade to be implemented throughout the NAS, even though their benefits had been well-established in operational evaluations.

Much of this delay was associated with the full integration of these technologies into safety-critical FAA automation platfoms. More recently, both the FAA and Eurocontrol have conducted field evaluations of arrival metering using airborne technologies that included the Required Time of Arrival (RTA) capabilites of modern Flight Management Systems (FMS)6,7. The results have demonstrated that while there are potential benefits of the airborne techologies supporting fuel-efficient descent procedures, there is also a requirement for significant advances in ground-based air traffic automation platforms to make them operationally viable.

The ATD-1 project addresses the two-fold challenge of simultaneously 1) advancing new technologies for benefits validation through operational evaluations in the NAS, and 2) accelerating the transition to broad operational use.

This article highlights the key challenges of transitioning the ATD-1 concepts and technologies from laboratory prototypes to modified versions of the TBFM and STARS automation platforms, suitable for an initial operational field evaluation. This approach provides the highest potential that the FAA will be successful at introducing the ATD-1 concepts and technologies into full operation at the earliest opportunity.

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ATM Technology Demonstration-1 (ATD-1) The ATD-1 Concept3 leverages three NASA research efforts to create a single, integrated arrival solution, as shown in Figure 1: • TMA-TM: Traffic Management Advisor with Terminal Metering (TMA-TM) for precise time-based schedules to the runway and meter points within terminal airspace8 • CMS: Controller-Managed Spacing (CMS) decision support tools for TRACON controllers to manage aircraft delay better using speed control9 • FIM: Flight-deck Interval Management (FIM) aircraft avionics and flight crew procedures to conduct arrival-to-arrival airborne spacing operations10 Building on emerging Performance-Based Navigation (PBN) infrastructure, the ATD-1 technologies integrate into a single concept for arrival scheduling, sequencing, and spacing11. Figure 2 illustrates the flow of a number of arriving flights transitioning from cruise to landing following the ATD-1 operational concept and aided by its technologies shown in Figure 1.

• Starting at approximately 200 NM from the airport for jet transports, and somewhat closer for slower aircraft, the arrival sequence and time-based schedule are calculated for aircraft to a metering fix (“the TRACON Gate”) to provide an efficient arrival sequence for each runway.

This time-based schedule is based on calculated 4-D

NASA’S ATD-1

Figure 3. TMA-TM Timeline Display. Estimated Times of Arrival (ETA) are shown to the left of the timeline, Scheduled Times of Arrival (STA) are shown to the right of the timeline, with time increasing up the display.

Figure 4. Controller Display with integrated CMS decision support tools

trajectories that adhere to all required separation constraints at flow merge points throughout the terminal area (outlined in gray).

From about 100-160 NM from the meter fix, depending on aircraft type, the arrival sequence is frozen and displayed to En Route controllers providing a time to achieve the scheduled entry to the terminal airspace.

En Route controllers direct the arriving aircraft to meet the meter-fix scheduling and spacing goals, the same as today with the TBFM system.

FIM-equipped aircraft are issued voice clearances with scheduling information to engage their interval management automation, and begin maneuvering to achieve the required spacing behind a designated leading aircraft.

The aircraft are handed off to the TRACON prior to transitioning the metering fix.

Appropriately-equipped aircraft use their FMS to fly an Optimized Profile Descent (OPD) through the terminal area (FIM-equipped aircraft do this while trailing their leading aircraft).

Guided by the CMS decision support tools, TRACON Controllers issue speed-control corrections to adjust residual spacing errors (and other disturbances) at interim metering and merge fixes for non-FIM equipped aircraft.

The aircraft arrive at the runway threshold in an efficiently spaced sequence.

bility by including merge fixes inside TRACON airspace.

Its terminal delay model is enhanced to more-accurately represent PBN based trajectories, and enforcing separation constraints of flow merges within the terminal area. In addition, the TMA-TM scheduling system provides information to render, TBFM system, timeline displays on the terminal automation (i.e., STARS) for the terminal merge points for the TRACON controllers (Figure 3).

•

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• •

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TMA-TM TMA-TM is an advance prototype version of the FAA TBFM time-based scheduling tool, currently in use at the En Route ARTCC facilities throughout the NAS. TBFM assists air traffic controllers and traffic managers in matching arrival demand with airport arrival constraints, such as required separations and Airport Arrival Rate (AAR). It achieves this by providing recommended sequencing, scheduling, and spacing information for arriving aircraft to the TRACON Gate through the generation of scheduled times of arrival (STA) at the meter fix, merge fix, and runway.

TMA-TM extends the basic TBFM scheduling capa-

CMS The CMS tools enable sustained use of PBN procedures by terminal controllers and maximize throughput for capacity-constrained runways by giving them strategic and tactical visibility of the recommended sequencing and spacing from TMA-TM. The display of timelines (Figure 3) provides a strategic view that includes time-based information of the total arrival flow situation. Figure 4 shows the other CMS display features: Slot Marker Circles, displayed as map symbology, represent the current spatial position of the schedule on the aircraft’s planned 4-D trajectory, enabling controllers to instantaneously know how close an aircraft is to meeting scheduling objectives at terminal merge fixes and runway; and Speed Advisories, displayed in the data-block, which recommend the aircraft speed clearances that controllers should use to achieve the scheduling goals.

FIM FIM is an advanced avionics capability that enables an aircraft using Automatic Dependent Surveillance – Broadcast (ADS-B) data to fly efficient descents while achieving and maintaining a precise interval behind a lead aircraft, without controller intervention. FIM requires two components.

The on-board avionics component is represented by displays to enable the flight crew to enter sequencing and interval information received from air traffic controllers. The other requirement is ADS-B “In” information to achieve the required interval behind a designated lead aircraft. A complementary ground component provides an ARTCC and TRACON display capability presenting air traffic controllers continued on page 32 The Journal of Air Traffic Control

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Transforming the air traffic management (ATM) system is essential for improving safety, efficiency and the environment around the globe. Boeing is fully committed and uniquely qualified to help make ATM transformation a reality. It’s the right time and Boeing is the right partner.

NASA’S ATD-1

Figure 5. ASTOR Simulator Primary Flight Display with FIM information

with sequence and spacing interval information from TMATM, for transmission to the aircraft, as well as indications of the FIM capability and status of aircraft (e.g., that a FIMequipped aircraft is in-trail).

Figure 5 shows a simulated Primary Flight Display with the speed bug on the left speed tape indicating a 180-knot speed advisory to conform to the required spacing behind the lead aircraft at the final approach fix. This represents a potential end-state implementation of the FIM cockpit interface operating directly through the primary flight control displays. For the ATD-1 demonstration, the speed advisory information and FIM status are being prototyped as an auxiliary guidance display presented in the forward field of view with guidance information derived from algorithms within an electronic flight bag12.

ATD-1 Implementation Approach into Current FAA Automation Platforms The ATD-1 integration and development effort was started in 2011, bringing together technologies that had been the subjects of separate long-term research activities. Starting in January 2012, a number of human-in-the-loop (HITL) simulations have been conducted at NASA’s Ames and Langley Research Centers. These simulations have explored, at increasing levels of fidelity and maturity, the ATD-1 concepts using the laboratory prototypes including the NASAenhanced FAA TBFM system. The initial simulation results of these early fully integrated ATD-1 technologies confirmed similar levels of benefits from earlier studies with complete aircraft FIM equipage, although the ATD-1 studies concentrated on mixed equipage operations, thereby validating the higher precision of spacing control provided by the airborne FIM technologies with a mixed (10 percent FIM and 90 percent standard) equipage operation.

This initial study validated that the ATD-1 technologies were at a high level of maturity when compared with 32

Summer 2013

the NASA Technology Readiness Level (TRL)13 scale. The ATD-1 technologies are currently at a TRL-4-5 level, which is the level NASA typically concludes its aeronautics research unless compelling benefits or significant challenges warrant further study. Since the ATD-1 technologies represent a significant near-term step toward the NextGen goals, the decision was made to further develop the concept and technologies up the TRL scale. Beyond the significant investment in resources, this involves advancing the technologies by moving them off laboratory platforms to the actual operational systems. Thus, initiating testing and evaluations in an operational environment for benefits validation is the logical next step in the TRL. These steps are critical, as without them either the concepts will remain in the simulation phase, or there may be significant risk of premature commitment to full-scale development and deployment. The actual implementation in key FAA automation platforms has become a critical next step in the transition of the ATD-1 ground-based technologies from laboratory prototypes to operational systems to reduce the investment risk of fullscale development in the TBFM and STARS automation platforms.

NASA’s approach for TBFM is fairly straightforward. It heavily reuses the NASA TMA software developed for field evaluations in the late 1990s. Many of the original TMA designers and software developers are still involved with the current enhancements described in references 4, 8, and 12, and much of the original architecture and code is intact. In addition, NASA worked closely with the FAA and its prime TBFM development contractors in a joint development process during the early transition stages to NAS-wide deployment. Finally, NASA recently worked with the FAA to integrate and evaluate a research precision departure release capability within a version of the TBFM operational software14.

Thus, the challenge to “up-level” the FAA’s current TMA with NASA’s current TMA-TM features is considered relatively low-risk. Therefore, NASA acquired a current operational version of the FAA TBFM software, known as TBFM release 3.12, and began porting the TMA-TM features. Most of the software enhancements were constrained to three software modules of the TMA. The most significant changes were in the scheduling component, known as the “Dynamic Planner,” which included the addition of scheduling constraints associated with terminal merge fixes. Another change included enhancing the “Route Analysis” function to more precisely consider RNAV and PBN routing and procedures through the terminal airspace.

Finally, some changes were also made to the “Trajectory Synthesizer” component to support the 4-D calculation of the new trajectories defined by the Area Navigation (RNAV) and Performance Based Navigation (PBN) procedures. These changes comprised an addition of approximately 2,500 lines of code to the TBFM software. A final design consideration for the up-leveling software was to ensure that the baseline TMA functionality could be run without the enhancements.

This would enable both TMA-TM and the current operational TMA capability to be run within the same software, allowing quick reversions to the operational system.

NASA’S ATD-1

The ATD-1 integration and development effort was started in 2011, bringing together technologies that had been the subjects of separate long-term research activities. Starting in January 2012, a number of human-in-the-loop (HITL) simulations have been conducted at NASA’s Ames and Langley Research Centers.

along with the creation of a pre-production release of STARS suitable for use in an initial field evaluation. In parallel, a NASA Team is transitioning the TMA-TM capabilities for the NASA research platform to the FAA TBFM system, as discussed previously, including the eventual up-leveling of the TMA-TM to the TBFM automation software consistent with an operational evaluation in the 2015-16 timeframe.

To manage the technical and organizational complexity of conducting an operational evaluation in the NAS, a joint FAA and NASA ATD-1 Research and Transition Team (RTT) has recently been established. The RTT leverages the knowledge of the NASA technology development with the direct oversight and input of the FAA eventual end-user of the ATD-1 technologies. This will ensure the highest potential return on NASA’s investment.

ATD-1 Future Plans for the FAA Automation Platforms One of the first activities the RTT will oversee is the transition of the ATD-1 TMA-TM and STARS CMS prototype technologies to the FAA William J. Hughes Technical Center, in Atlantic City, for Operational Test and Evaluation. Once that is complete, the next stage expected in 2015 is to test the technologies at a major U.S. airport in a joint NASA-FAA field demonstration and evaluation. A series of operational evaluations will be performed, starting with a protracted period of shadowing operations and, as results permit, limited operational use. This approach is similar to the highly successful operational testing of the TMA conducted by the FAA and NASA in the late 1990s.15 Ultimately, following a successful field evaluation, the technologies will be transitioned to the corresponding FAA programs and scheduled for full development and release. An important goal for the NASA/Raytheon team is not to simply achieve a single transition of concept and technology to the FAA, but to create a repeatable transition process that will enable other NextGen innovations to be realized in less time than previous projects. To this end, NASA and Raytheon, supported by the FAA, are developing a comprehensive Transition Plan, with associated processes, for taking the ATD-1 capabilities from the lab to the FAA environments.

The Journal of Air Traffic Control

Photographer: Chris Downie / Photos.com

The approach for the STARS automation platform was entirely different since the Raytheon Company has been its sole developer for the FAA since the late 1990s to the present. Thus, NASA had no insight into the feasibility or design implications of integrating the CMS component of the ATD-1 technologies into the platform. Therefore, in 2012, Raytheon was contracted by the FAA and NASA to complete the following tasks: 1) assess the feasibility of augmenting the current TRACON automation system, STARS, with the CMS and FIM capabilities, 2) conduct a design trade study to evaluate potential designs and required system interfaces, and 3) develop a STARS software prototype to demonstrate, in a laboratory setting, the key CMS functions. The Raytheon team was provided with an opportunity to conduct a thorough evaluation of the CMS tools implemented in the Multi-Aircraft Control System (MACS3) simulation software, including observation and participation in NASA simulations. The Raytheon team then determined overall feasibility of porting the tools to the STARS platform.

The design and trade-study considered the following critical design constraints: 1) maintain the current FAA STARS architectural requirements, 2) produce and field a pre-production release within three years, and 3) maintain a minimal footprint within a FAA TRACON facility. The selected design included using STARS as the primary display with the partitioning of the CMS algorithms into trajectory-based computations that were allocated to TMA-TM and display presentation software within STARS. This required a significant addition to the existing TBFM-STARS interface including the development of a bi-directional data flow, but maintained the FAA architectural requirement of having trajectory-based computations within the TBFM automation. A final feasibility demonstration included the integration of the NASA enhanced version of the TBFM TMA 3.12 and a rapid prototyped CMS enhanced STARS running a simple SoCal TRACON adaptation driven by the embedded STARS ATCoachTM simulation environment at the Raytheon facilities.

The results of the study initiated a three-year contract to implement a full prototype of the ATD-1 tools within the STARS platform including the FIM related functionality,

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NASA’S ATD-1

Figure 6. Preliminary Schedule for ATD-1 Test and Evaluation

Activities addressed in the Transition Plan and planned for the next three years include the following: 1. Completion of prototype development for NASA laboratory simulations Now that the feasibility of creating the STARS CMS prototype software has been established, the prototype software must be completed. The prototype is designed to work in an integrated simulation environment.

2. Conduct of integrated human-inthe-loop (HITL) simulations Before the prototype software can be used as the basis for a pre-production release, it must itself be evaluated and validated in HITL simulations at NASA Ames Research Center.

3. “Up-leveling” of the prototype to create a pre-production release, suitable for test and evaluation at the FAA Tech Center Since the prototype software was developed for concept exploration for use in simulations using rapid prototyping techniques, the software will need to be “up-leveled” and matured to create a pre-production release using production software development techniques where all requirements are established, defined, and feasible. This software can then be tested by the FAA and certified as being suitable for evaluation at an FAA TRACON. There will be four main types of activities to make the software better suited for this purpose: functional changes, software development process enhancements, software documentation, and software testing activities. These processes will be based on the production STARS software development, together with best practices learned from other prototyping activities.

The goal is to ensure that the software meets all the non-functional requirements necessary for it to be suitable for testing and evaluation at the FAA Tech Center, and ready for evaluation at the Field Site.

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4. Operational test and evaluation of the preproduction release at the FAA Tech Center The pre-production release will be transferred to the William J. Hughes FAA Technical Center, where it will be subjected to systemic tests and evaluations to validate its suitability for further use for operational evaluations.

5. Release of the pre-production release to the designated FAA Field Site Provided that the operational test and evaluation at the FAA Technical Center is satisfactory, and subject to availability and other considerations such as impending upgrades and/or airspace enhancement and air traffic controller acceptance for the designated FAA field site, the pre-production software will be released to the Field Site for evaluation on the facilities STARS training platform. This is a critical step and the role of controller acceptance at this stage is paramount. The approach for achieving the acceptance is so important that the authors felt that it could not be adequately described within scope of this article, and should be treated as a subject in its own right.

6. Operational evaluation of the pre-production release at the FAA field site, including shadow operations and limited operational use It is planned that the system will undergo a number of operational evaluations at the field site. The evaluations will include offline testing in the STARS Training Laboratory, “shadow” operation in the STARS Training Laboratory, and, all being satisfactory, limited operation evaluation in live use during low-traffic periods, in conjunction with FIM-equipped test aircraft. This evaluation is expected to take place over several months.

NASA’S ATD-1 7. Decommissioning and removal of the preproduction release from the FAA field site It is important that once the field evaluation has been completed, the pre-production software should no longer be accessible for field use until FAA processes are completed for full-scale implementation. Therefore, an activity will be performed to ensure that this is the case by removing the software from the FAA field site.

A preliminary schedule for the activities is shown in Figure 6. The figure also shows the applicable NASA Technology Readiness Levels (TRLs) for the activities.

ATD-1 Future Challenges The future ATD-1 work faces a number of significant challenges. This section describes some of these and how the team intends to address them.

1. Proving ATD-1 operational concept and technology viability At the early TRL levels (below 5), ATD-1 has validated the concept including detailed simulations focusing on the critical elements of the operational concept.

These include complete definitions of computer human interfaces, concepts of use, and phraseology for controller and pilot interaction for both FIM and non-FIM equipped operations. ATD-1 has also established the general technological feasibility of integrated capabilities into the current FAA technology platforms. As ATD-1 technologies progress on the TRL scale, they will be evaluated in increasingly realistic environments to allow operational viability to be established and benefits to be verified. It is planned to include controllers from the designated FAA Field Site in the NASA simulations in order to give them the opportunity to provide facility-specific insights.

2. Ensuring that the “up-leveled” software has potential for field site evaluation There are several aspects of this potential that include operational functional suitability as well as utility that need to be addressed to transition to the higher TRL levels: • Functional suitability: i.e., is the ATD-1 functionality suitable for operational evaluation?

• Non-functional suitability: is the ATD-1 software of sufficient quality, does it have the necessary performance characteristics, and has it been adequately tested to permit it to be evaluated at the Field Site (including contingency and failure modes)?

• Usability: is the ATD-1 software and, in particular, the user interface usable by the operational controllers?

• Functional Compatibility: is the ATD-1 software functionally compatible with in-service releases of the FAA operational systems?

These issues will be addressed by a combination of incremental simulation, testing, and evaluation, together with close collaboration with the FAA.

3. Maintaining and modifying the “up-leveled” software It is inevitable that defects and potential improvements will be identified in the course of both the simulations and field evaluation. The Transition Plan will include detailed procedures and resources for managing and releasing changes to the pre-production software and adaptation in a controlled fashion that will permit new features and changes to be checked out as part of the ongoing evaluation.

4. Ensuring a smooth and safe transition at the Field Site to and from the ATD-1 software The modified software will be released to the Field Site in a similar way to production operational software releases. This will include adapting the processes used to transition between operational releases. These adapted processes are a key outcome of the RTT and will be thoroughly evaluated at the FAA Technical Center before performing them on the operational equipment at the site.

5. Coordinating evaluations across multiple systems and facilities The ATD-1 evaluations will involve changes to multiple systems, including STARS, TMA/TBFM and test aircraft avionics at both the TRACON and its ARTCC. Tight coordination of the introduction of technologies will be required ensuring that changes at these facilities avoid any interruption of operational services.

For Every NAS Challenge,

The Right Solution. n Acquisition Management n Information Technology & Security n Program Management n Systems Engineering n Unmanned Aircraft Systems

Proud Winner of ATCA’s 2012 Charles E. Varnell Memorial Award for Small Business

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NASA’S ATD-1

Building on emerging Performance-Based Navigation (PBN) infrastructure, the ATD-1 technologies integrate into a single concept for arrival scheduling, sequencing, and spacing.

Photographer: fotoVoyager / Photos.com

6. Avoiding resource conflicts between the ATD-1 activities and FAA program activities As the ATD-1 technologies are integrated into pre-production versions of the FAA platforms, the potential for conflict with FAA program activities, such as the Terminal Automation Modernization Replacement (TAMR) program, increases. To avoid this, Raytheon has set up a separate team for the STARS CMS development, based in Mount Laurel, N.J. In addition, NASA and Raytheon will include specific resource planning information in the Transition Plan that is under development. Furthermore, existing FAA processes and practices will be adapted to minimize the process impact of the ATD-1 evaluation.

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Summary and Lessons Learned NASA’s approach and challenges for the transition of groundbased and flight deck automation technologies into the NAS that enable a NextGen vision of an integrated set of ground and airborne-based arrival technologies is described. These include significant enhancements to the FAA’s TBFM and STARS automation platforms. The approach uses an innovative stepwise transition of research-proven laboratory technologies to operational evaluation in the NAS. The approach considers the unique and complex challenges for the introduction of substantial enhancements to current operational paradigms within the NAS and follows the NASA TRL scale to manage and judge progress. This will assist the complex interactions with NASA’s and FAA’s industry partners as well as NAS stakeholders to evaluate progress towards the goal of operational evaluations of the ATD-1 project. This is a success-driven approach that also enables the possibility of early adoption of some or all of the ATD-1 NextGen technologies within current FAA automation platforms.

A number of lessons learned and new approaches were defined to transition the ATD-1 technologies from laboratory concepts to pre-production prototypes with the potential for operational evaluation in the NAS. Key elements are summarized here, but could also be applied to other air-traffic management technologies attempting to implement the NextGen vision: • The value of an integrated Research and Development approach: By bringing the complementary technologies (TMA-TM, CMS, and FIM) that provide system benefits together, ATD-1 has been able to create a pathway to the systematic introduction of a

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•

•

•

•

•

•

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complex yet complete operational and technical solutions to achieve fuel efficient, high throughput arrival operations.

The importance of early user engagement: The early and continued involvement of controllers has not only built confidence in the ATD-1 concepts, but has refined the technologies and detailed operational requirements and provided quantitative benefits data and the capture of theorized system benefits.

The use of the NASA Technology Readiness Level (TRL) Model: The TRL model is an effective framework for the incremental evolution of the ATD-1 concepts from the research labs to the real world.

The benefits of human-in-the-loop (HITL) simulations: The use of HITL in increasingly high fidelity, representing simulations of actual terminal environments has enabled the early involvement of controllers and user evaluations. The controllers were able to offer real-world insights into the ATD-1 concepts and technologies.

Streamlining of the transition process for NextGen technologies: The creation of a standard transition approach, processes, and capabilities for NASA concepts and technologies should enable advanced capabilities to be delivered earlier, at lower cost, with less risk and improved outcomes for users.

Early involvement of FAA system developers and suppliers: The early involvement of engineers from FAA system developers has enabled up-front addressing of implementation issues, such as integration and interface development, allowed the engineers to offer insight into the research technologies to improve them, and ensured that operational system constraints (e.g., human-computer interface limitations) can be taken into account.

The importance of comprehensive transition planning: This is essential to ensure that all the processes, procedures, and resources required to safely evaluate the ATD-1 concepts and technologies are identified, and potential conflicts resolved early on.

The importance of open collaboration: The NASA team uses an open, collaborative approach, recognizing that for the ATD-1 concepts to be successful, all of the ATD-1 technologies must work effectively together.

NASA’S ATD-1 References [1.] Joint Planning and Development Office. (2010). Concept of Operations for the Next Generation Air Transportation System (Version 3.2 ed.).

Washington, DC. [2.] Federal Aviation Administration. (2010, May 3). Descent, Approach and Landing Benefits. Retrieved December 11, 2011, from http:// www.faa.gov/nextgen/benefits/descent/ [3.] Thomas Prevot, Brian T. Baxley, Todd J. Callantine, William C. Johnson Leighton K. Quon, John E. Robinson, Harry N. Swenson, “NASA’s ATM Technology Demonstration-1: Transitioning Fuel Efficient, High Throughput Arrival Operations from Simulation to Reality,” HCI-Aero 2012, Brussels Belgium, September 12-14, 2012.

[4.] Swenson, H. N., Hoang, T., Engelland, S., Vincent, D., Sanders, T., Sanford, B., and Heere, K., "Design and Operational Evaluation of the Traffic Management Advisor at the Fort Worth Air Route Traffic Control Center," 1st USA/Europe ATM R&D Seminar, Saclay, France, June 1997.

[5.] Daniel Brudnicki, “URET Conflict Probe – Performance Benefits Assessment.” 1st USA/Europe ATM R&D Seminar, Saclay, France, June 1997.

[6.] Mahesh Balakrishna, Thomas Becher, Paul MacWilliams, Joel Klooster, Patrick Smith, “Seattle Required Time-of-Arrival Flight Trials,” 2011 AIAA/IEEE 30th Digital Avionics Systems Conference, Seattle, WA, 16-20 October 2011 [7.] “CTA/ATC System Integration Studies 2, Version 1, 2010-02-12,” http://www.eurocontrol.int/tma2010/gallery/content/public/image/ Docs/CASSIS/CTA%20Issues%20Capture%20-%20v1.00.pdf [8.] Swenson, H. N., Thipphavong, J., Sadovsky, A., Chen, L., Sullivan, C., & Martin, L. (2011). Design and Evaluation of the Terminal Area Precision Scheduling and Spacing System,” Ninth USA/Europe Air Traffic Management Research and Development Seminar. Berlin, Germany, June 2011.

[9.] Callantine, T. J., & Palmer, E. A. (Sept. 21-23, 2009). Controller Advisory Tools for Efficient Arrivals in Dense Traffic Environments. 9th AIAA Aviation Technology, Integration, and Operations Conference (ATIO).

Hilton Head, South Carolina.

[10.] Murdoch, J. L., Barmore, B. E., Baxley, B. T., Abbott, T. S., Capron, W. R., “Evaluation of an Airborne Spacing Concept to Support Continuous Descent Arrival Operations,” 8th USA/Europe Air Traffic Management Research and Development Seminar (ATM2009), Napa, CA, June 29 – July 2, 2009.

[11.] Brian T. Baxley, Will C. Johnson, Harry N. Swenson, John E. Robinson, Tom Prevot, Todd J. Callantine, John Scardina, and Michael Greene, “Air Traffic Management Technology Demonstration-1 Concept of Operations (ATD-1 ConOps),” NASA TM-2012-217585, July 2012 [12.] Jaewoo Jung, Harry N. Swenson, Lynne Martin, Jane Thipphavong, Liang Chen, Jimmy Nguyen, “Design and Evaluation of PerformanceBased Navigation Arrival with Terminal Area Precision Scheduling and Spacing System.” Planned publication at the 10th USA/Europe ATM Research and Development Seminar (ATM2013), Chicago, IL, June 2013.

[13.] NASA - Technology Readiness Levels Demystified, NASA, 20 August 2010, http://www.nasa.gov/topics/aeronautics/features/trl_demystified.html [14.] Shawn A. Engelland, Alan Capps, “Trajectory-Based Takeoff Time Predictions Applied to Tactical Departure Scheduling: Concept Description, System Design, and Initial Observations,” AIAA Aviation Technology, Integration, and Operations Conference (ATIO), Virginia Beach, VA, 20-22 September 2011.

[15.] Hoang, T., Swenson, H.N.: The Challenges of Field Testing the Traffic Management Advisor in an Operational Air Traffic Control Facility” Proceedings of the AIAA Guidance, Navigation and Control Conference, New Orleans, LA, Aug 1997, AIAA-97-3734

Keynote Speaker Tom Ridge,

Former U.S. Secretary of Homeland Security

The Journal of Air Traffic Control

37

Volcanic Ash

Operation of Gas Turbine Engines in an

Environment Contaminated with Volcanic Ash

By Michael G. Dunn, Ohio State University

Reprinted with permission from the Journal of Turbomachinery, September 2012, Vol. 134

38

Summer 2013

Airborne volcanic ash poses a significant threat to the safe operation of gas turbine powered aircraft. Recent volcanic activity in Iceland and other parts of the world have resulted in interruption of air traffic and in the case of the April 2010 eruption of the Eyjafjallajรถkull volcano in Iceland, the interruption resulted in a significant loss of revenue. Over the past 30 years there have been several events involving commercial aircraft that have suffered significant damage to the propulsion system as a result of ingesting volcanic ash during a flight event, but a relevant engine focused database to provide guidance for dealing with the problem has not been generally available until recently. In Sept.

2010 after the Iceland volcano activity, a body of data that had not been in the public domain was released and those measurements that are described in some detail herein can be helpful to the airlines, the aircraft manufacturers, the engine manufacturers, those responsible for flight operations, and hopefully to the flight crews. The intent of this paper is to describe some of the more notable aircraft/ ash cloud events, the available data associated with those encounters and how those data can be used to effectively deal with this problem while maintaining safe flight operations. The paper specifically (a) illustrates the engine damage mechanisms, (b) estimates the potential operational life of a particular class of engines if the ash concentration is at a very low level, and (c) illustrates how this database is helpful in dealing with future interruptions of flight routes caused by volcanic eruptions. A section at the end of this paper provides the comments and concerns of the industry and government stakeholders regarding this general problem area. [DOI: 10.1115/1.4006236]

The Journal of Air Traffic Control

Photographer: Steve Burger / Photos.com

Volcanic Ash

39

cerns of the industry and government stakeholders regarding this general problem area.

[DOI: 10.1115/1.4006236]

Volcanic Ash

1

Introduction

Table 1 lists several of the more notable encounters of gas turbine powered aircraft with volcanic ash clouds.

The first of these events occurred in 1980 and involved a TransAmerica aircraft powered by Allison T-56 turboprop engines.

Upon takeoff from McCord Air Force base on May 25, 1980 the aircraft encountered an ash cloud from the eruption of Mt. St. Helens. The aircraft was in the ash cloud for approximately 3 to 4mins and lost two of its four engines, but it managed to turn from the cloud and land safely. This event switched the focus on an ongoing research program from the influence of overpressure waves on gas turbine engines [1–5] to dealing exclusively with the influence of foreign particle ingestion on the operation of gas turbine engines.

A second notable incident occurred on June 24, 1982 over Indonesia at an altitude of approximately 37,000-feet. British Airways flight BA009, a Boeing 747 aircraft powered by Rolls Royce RB 211-524 engines, intercepted an ash cloud from the recently erupting Mt. Galgunggung volcano. The flight crew was unaware of such an eruption and the aircraft, which was in the cloud for approximately seven mins, lost all four engines in rapid succession.

The aircraft was flown for approximately fifteen mins without power before recovering one engine at approximately 13,000 feet, the second at approximately 12,500 feet, and did not sink below 12,000 feet. Soon thereafter, the engine that came on initially had to be shut down due to repeated surging. Although this aircraft was able to land at Jakarta, it experienced severe windshield damage as a result of the dust particles and thus made vision during landing a bit difficult. A person who was aboard the aircraft wrote a book [6] 1 Corresponding author.

Contributed by the International Gas Turbine Institute of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received December 2, 2011; final manuscript received February 14, 2012; published online May 7, 2012. Editor: David Wisler.

Journal of Turbomachinery

describing the frightful event as seen by a passenger, which is a lot more pleasant to read than to experience.

The next incident occurred on July 13, 1982 and involved a Singapore Airlines flight of a Boeing 747 aircraft powered by Pratt/ Whitney JT9D engines that encountered ash from a later eruption of Mt. Galgunggung. It is not clear how long this aircraft was in the ash cloud, but the aircraft landed in Jakarta using two of the four engines.

In 1989 KLM flight 867, a Boeing 747 aircraft with General Electric CF6 engines encountered an ash cloud from Mt. Redoubt while on approach to Anchorage, Alaska and attempted to climb above the cloud. This aircraft initiated a high-power climb at 25,000 feet and within 58-seconds lost all four engines at an altitude of 28,000 feet. After approximately eight minutes without power, the crew managed to get all four engines re-lit at an altitude of about 13,600 feet and subsequently to land safely in Anchorage, but with substantial damage to the very new aircraft.

The next series of volcanic ash related events occurred in the Philippines during the 1991 eruption of Mt. Pinatubo. In this instance, there were approximately 15 separate encounters involving many different airlines and engines from all three of the major engine manufacturers.

Shortly after the 1991 series of events, the Boeing Company assembled a video [7], which remains to this day one of the most important sources of information for the aircraft flight crew. Permission was obtained to release limited features of the data set described in this paper for inclusion in the Boeing video and to publish some of the general features of the data set [8]. The full data set was released for public distribution in Sept. 2010 following the April of 2010 eruption of the Iceland volcano ‘Eyjafjallajo¨kull,’ which caused havoc with trans Atlantic flights.

Some geologists predict a high probability for volcanic activity to increase over the next 60 years. Reference [9] provides a world map of known volcanoes and includes known airline route trajectories relative to individual volcano locations. The airline industry

C 2012 by ASME Copyright V

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Summer 2013

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Volcanic Ash Table 1

Notable Volcanic Ash/Aircraft Encounters

Year

Aircraft

Engine

Volcano

1980

Trans-America Lockheed L-382 British Airways Boeing 747-200 Singapore Airlines Boeing 747-200 Qantas Boeing 747-200 KLM Boeing 747-400 15 Separate encounters in two-week period Airspace Closed

Allison T56

Mt. St. Helens

R-R RB-211

Mt. Galgunggung

P/W JT9-D

Mt. Galgunggung

R-R RB-211

Mt. Soputan

GE CF-6

Mt. Redoubt

RB-211, CF-6, JT9-D —

Mt. Pinatubo

1982 1982 1985 1989 1991 2010

and engine companies realize that even if an increase in volcanic activity does not occur this problem is not going to go away.

Therefore, they need to formulate a plan to deal with the potential consequences of operation in ash cloud environments and to learn how to deal effectively with the problem while maintaining safe operation.

The only warning signs that the flight crew has to an impending volcanic ash problem are: (a) the presence of fireflies on the windscreen, (b) observation of St. Elmo’s glow at the engine face if the dust concentration is in excess of 40 to 50 mg/M3 (more about this later), or (c) smokelike material coming into the environmental control system (ECS) with an ‘sulfur’ odor in the cabin or cockpit.

The fireflies on the windscreen will also be seen in the presence of ice crystals, but the St. Elmo’s glow at the engine face is associated with the presence of a dust cloud and represents a potentially seri-

Eyjafjallajo¨kull (ay-yah-fyah-lah-yer-kuhl)

ous impending problem. There are commercial aircraft for which the flight crew may not be able to visualize the engine face. In this case, the only advanced warnings are (a) and (c).

Although there are several potential damage mechanisms associated with operation of modern gas turbine powered aircraft within an ash-laden environment as illustrated by Fig. 1, the relative importance of the individual mechanisms depends very much upon the value of the turbine inlet temperature (TIT).

For engines with TIT in excess of 1283 K ( 2310 R), the initial damage mechanism is deposition of foreign material on the hot section components, most importantly on the high-pressure turbine inlet nozzles. All of the engines mentioned in Table 1 were operating at a sufficiently high value of TIT that significant deposition occurred on the high-pressure turbine nozzles. This deposition is very dependent upon the concentration of the foreign

Fig. 1 Potential damage mechanisms when traversing an ash cloud for an engine with turbine inlet temperature in excess of 2310 R

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41

Volcanic Ash particle environment, the properties of the glassy constituent within the particulates (discussed more later), and the surface temperature of the vane (the hotter the vane surface, the more favorable for deposition). It is possible to help alleviate this deposition in flight by proper operation of the engine as will be explained later in the paper, but one must be careful with the rate of throttle movement.

The second most important damage mechanism for a high TIT engine is erosion of the compressor and turbine airfoils, and unfortunately this erosion is irreversible. Again, this erosion is very dependent upon the concentration of the foreign material, but relatively independent of the cloud constituents and the compressor airfoil material (titanium or steel makes little difference [10]).

The third damage mechanism is deposition on the fuel nozzles, which involves carbonlike deposits on the fuel nozzles that are easily removed on the ground, but not in flight. As will be shown herein, when these deposits form it is very difficult to execute an in-flight engine restart. It is important to point out that the accumulation of these deposits is very dependent upon concentration of the dust cloud, since they are the result of a rich burn caused by the reduced airflow through the machine as material is deposited on the high-pressure turbine leading edge.

Other potential damage mechanisms are contamination of the oil system, the fuel supply, degradation of the engine controller (an example of this degradation will be shown later) and deposition of fine particulate material on anything exposed to air bleed from the compressor. As will be shown later in the paper, the engine does a wonderful job of pulverizing the ingested foreign particles and subsequently passing these fine particles through the environmental control system.

In the case of an engine with TIT less than 1283 K ( 2310 R), the number one problem becomes erosion of the compressor and turbine airfoils while deposition on the hot section components is much less of a problem. It will be shown later in this paper that for an engine operating at a TIT very near 1283 K, significant deposition did occur on the high-pressure turbine nozzles, but only after a relatively large amount of material was ingested. For the lower TIT operating case, one still can get deposition on the fuel nozzles and contamination of the oil and fuel supply.

There were three engines included in the matrix of engines to be discussed that fit into this low value of TIT class; the Pratt/ Whitney J57 turbojet, the Pratt/Whitney TF33 turbofan, and the Williams International F107 [10–13]. It will be shown that due to the absence of deposition of foreign material on the hot section components, this class of engine can ingest significantly more foreign material prior to experiencing an engine surge than an engine operating at higher values of TIT. In addition to measurements conducted using the three engines mentioned in the above paragraph, measurements were also conducted using the Pratt/Whitney F100 [14–16], the General Electric YF101 [17,18], and the Williams F112 [19,20] engines. In most cases, at least two engines and sometimes three engines were used during the matrix of conditions investigated.

A major focus of this paper is to present the results of the fullscale engine experiments outlined above. The database from which the material is extracted was obtained over the time period of 1976–1995, but the details of the experimental results were not publicly available until recently.

In addition to the full-scale engine measurements, combustoronly experiments were performed prior to the engine measurements in order to understand how the different components of the ingested material affect things. While only the highlights of these test results obtained using an Allison T56 combustor [21] and a Pratt/Whitney F100 combustor [22–24] are presented here, the details are provided in the publicly available references cited.

Reference [22] provides an extensive study using several different compositions of foreign material to determine the combustor exit temperature necessary to obtain deposition on the nozzle guide vane row. This study was also designed to measure the re-

42

Journal of Turbomachinery Summer 2013

spective capture ratio for each of the different materials investigated. As part of this work, an Allison T56 combustor and vane row were used along with Mt. St. Helens ash to demonstrate that the deposition pattern observed for the Trans America event described in Table 1 could be reproduced in the laboratory.

The measurement program described in Ref. [23] utilized a one-quarter sector of a F100-PW-100 annular combustor. The air entering the combustor was externally compressed and preheated to a pressure and temperature consistent with compressor discharge values in order to create the combustor exit temperature and the metal temperature required for deposition of foreign material. Effects that would be very difficult to study in a full engine, such as increasing or decreasing the vane metal temperature by varying the cooling air supply, could easily be studied in this combustor facility. The foreign material used for these measurements was representative of material found around the world. Deposition of foreign material was found to occur when the combustor exit temperature (CET) was in excess of 1450 K (2610 R) and when the metal surface temperature exceeded 1089 K (1960 R). The role played by the impurity calcium in the deposition process is described in Ref. [23] along with other related studies using coalderived liquid fuel.

1.1 Description of the Experiment. The J-57, TF33, F100, F107, and F112 engine measurement programs were all performed using the Industrial Acoustics Engine Cell located at Calspan Corporation and the YF101 measurement program was performed using an engine cell located at Edwards Air Force Base. The same dust ingestion system was used at both engine cells. The remainder of this section provides a description of how the full-scale engine measurements were performed and the measurements obtained.

1.2 Engine Cell. To subject the engines noted above to an environment containing foreign particulates, one needs: (a) a substantial thrust bed, (b) an enclosure to protect the surroundings in the event of a catastrophic engine rupture or fire, (c) a noise suppression structure to attenuate the engine noise, (d) a cell that provides sufficient flow of well-behaved air, (e) a fire suppression system, (f) a dust injection system, and (g) an appropriate fuel storage and delivery system. To meet these objectives, an aircooled large-engine noise suppression system was constructed and that portion of the cell in the vicinity of the engine was lined with triple woven steel wire (1.59-cm diameter) blast mats.

The particular engine cell used for this work could handle a weight flow rate of 227.3-kg/sec. The critical constraints that had to be met for proper operation of the engine within the test cell were cell depression, flow velocity into and over the engine, uniformity at the engine inlet, flow velocity in the exhaust stack, and flow temperature in the exhaust stack. Detailed measurements of all of these parameters were performed prior to initiating the measurement program. For more detail regarding the engine cell, the reader is referred to Ref. [25].

1.3 Dust Injection System. The dust injection system consisted of the following major components; a dust pipe, dispersion nozzles, pneumatic conveying lines, powder distributor, feeder, dust reservoir, air compressor, and process monitoring instrumentation. A 3.65-m (12-feet) long dust pipe provided a conduit to the engine face. A cluster of six evenly spaced nozzles was placed at the entrance of the dust pipe and provided a uniform and equilibrated dust cloud just upstream of the fan face. It is important that the velocity of the dust particles be in equilibrium with the local velocity of the air stream just ahead of the engine face in order to correctly simulate the encounter with a stabilized cloud.

The dust is delivered to each of the six nozzles as a highloading air-particle dispersoid that is transported by compressed air. Both the particulate material and the carrier airflow are carefully metered. The carrier airflow is constant at all feed rates and engine power settings. The lines are sized to limit the airflow to SEPTEMBER 2012, Vol. 134 / 051001-3

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Dow

Volcanic Ash 2% of the inlet air and to deliver the particles into the inlet air at a release velocity that is closely matched to the local air stream velocity. A gravimetric weigh-belt feeder with a variable speed belt that could provide 45-g/min to 10-kg/min was used to provide continuous and accurate feeding of the dry material. The spatial uniformity and particle characteristics in the airflow stream to the engine were determined by surveys using dust sampler probes in order to ensure uniform distribution. Additional detail regarding this entire system can be found in Ref. [26].

1.4 Measurements Obtained. For each data point over the entire matrix of conditions, the composition of the foreign particle mixture was measured in detail as will be explained in a following paragraph. Also measured for each data point was the weight of foreign material injected into the engine during the test period of that data point. In addition, all of the parameters available in the engine controller were continuously monitored (and made available to the operating crew) during the entire experiment.

The specific parameters measured were dependent upon the specific engine, but they were a consistent body of control parameters as reflected by the control system of the different manufacturers. In addition, cameras were used to continuously monitor the engine inlet, engine side, and engine exhaust. Photographs taken with the inlet and exhaust cameras showed critical features such as the St. Elmo glow at the engine face and fire at the engine exhaust as a result of surge.

Each of the technical reports describing a particular engine test series will provide significantly more detail on the specific measurements obtained as well as photographs of the engine components upon post-test disassembly of the engine.

1.5 Foreign Material Utilized in Experiments. The impact of many different foreign materials and relative amounts of each on engine performance were investigated during the course of the full-scale engine and combustor experiments making up this data set. Included in the matrix of materials considered were the following; Hollywood sand, Mt. St. Helen’s volcanic ash, Corona clay, Wyoming bentonite, Twin Mountain New Mexico volcanic ash, quartz, red art clay, and feldspar. The elemental spectrum and an associated scanning electron microscope photograph of each of the materials are provided within the specific reference reporting the individual experiment.

Throughout the experimental series, a great deal of detail was devoted to characterizing the foreign material to which the individual engine was subjected. The primary volcanic ash components of the foreign material are Mt. St. Helens ash and Twin

Fig. 2

Mountain black scoria ash. The results presented in this paper will concentrate on the engines subjected to environments made up of one of these two volcanic ash components.

When a volcanic activity occurs, it is very important to identify the elemental composition of the ash as soon as possible even though we know from previous experience with the eruption of Mt. Galunggung in 1982–1983 that the composition can change significantly on a daily basis [27].

It was shown in Ref. [23] that the element calcium plays a very large role in the deposition of foreign material on the turbine hot section components. For a combustor exit temperature in excess of 1450 K (2610 R) it was found that an increase in the magnitude of the calcium content resulted in an increase in deposition on the turbine hot section components. Therefore, it is very important that the airline community has information about the calcium content of the ash immediately upon the eruption of a volcano.

This is illustrated in Figs. 2, 3, and 4, which shows elemental spectrums of Mt. St. Helens ash, Twin Mountain New Mexico ash, and Eyjafjallajo¨kull volcano ash. Note the magnitude of the calcium peak relative to the silicone peak in each of these figures.

For the Iceland volcano, potassium shows up in the elemental analysis, but is absent in the other two ash sites. From a deposition viewpoint and for the same engine operating conditions, both of these ash clouds would be dangerous to fly through, but the Twin Mountain New Mexico ash and the Eyjafjallajo¨kull ash would present a significantly greater problem and risk due to the greater calcium content. Obtaining the SEM and elemental composition spectrum is a relatively quick process once the laboratory obtains the ash, e.g., the results presented in Fig. 4 were obtained in approximately twenty minutes after receipt of the ash material.

The major potential delay in knowing this information is obtaining a sample of the ash near the site.

On the other hand, the shape of the particle prior to striking the fan face is of little importance because the very early stages of the engine do a fantastic job of pulverizing the material into very tiny particles as will be shown. The scanning electron microscope photograph of the two ash materials suggests that the Mt. St. Helens ash is more spherical and the Twin Mountain New Mexico ash is more platelet in shape.

One of the principal issues that arose at the beginning of the dust ingestion work was deciding upon the average particle size of the foreign material to which the engine would be exposed. After many considerations that included settling time for lofted material, distance and time from the source of the foreign material, and approximate altitude of interest, it was decided that the average particle size of the mixture would be 37-l. Therefore, the engine measurement programs described herein were conducted with

SEM and elemental composition spectrum of Mt. St. Helens ash

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Volcanic Ash

Fig. 3

SEM and elemental composition spectrum of Twin Mountain New Mexico ash

Fig. 4

SEM and elemental composition spectrum of Eyjafjallajo¨kull ash

foreign material made up from the components described in the previous paragraph and having an average particle size of 37-l at engine inlet.

2

Experimental Results

The objectives of the research program were to; (a) recognize the engine degradation process, (b) determine the dust tolerance for each engine class, (c) recognize incipient engine failure, (d) determine operational procedure for a deteriorated engine, and (e) establish a technique for regaining control of the engine during a surge sequence.

It was noted in an earlier section that three of the engines used (the Pratt/Whitney J-57 and TF-33 and the Williams F-107) had combustor exit temperature or turbine inlet temperatures that were too low for deposition, and thus the primary damage mode for these engines was erosion.

The remaining three engine types investigated (the Pratt/Whitney F-100, General Electric YF-101, and Williams F-112) were all vintage 1980–1990 engines and all had relatively high turbine inlet temperatures. Thus deposition of foreign material on the high-pressure turbine inlet guide vanes became the primary cause of rapid engine degradation leading to surge for these engines.

44

Journal of Turbomachinery Summer 2013

Such would also be the case for modern engines, which would have higher TIT values than the engines just mentioned.

In the remainder of the paper selected examples from the engines investigated will be described in some detail and reference sites will be provided to which the interested reader can find additional relevant information.

2.1 Low TIT Large Full-Scale Engine Results. The Pratt/ Whitney J57 and the Pratt/Whitney TF33 engines were subjected to the volcanic ash environment as described in Ref. [10]. The TF33 is a derivative of the J57 with essentially the same high compressor except for material. The J57 had steel airfoils and the TF33 had titanium. Measurements were made to determine if the foreign material would deposit in the hot section even though the TIT was felt to be too low and if there would be any difference in compressor erosion due to the use of different materials.

Section 2 showed that deposition in the hot section did not occur in either of those engines and that the material used for the compressor blades made very little difference with respect to erosion.

However, the experiments showed that the foreign material caused problems with the bleed valve resulting in problems with the fan speed/core speed ratio for the TF33. Reference [11] describes the increased susceptibility of a deteriorated engine to SEPTEMBER 2012, Vol. 134 / 051001-5

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Volcanic Ash

Fig. 5 Photograph of ECS duct from P/W TF33 S/N 644908 engine after dust exposure

surge at low power settings and the respective roles that anti-ice and inter-compressor bleed play in surge avoidance. In addition, a predictive capability developed to describe deteriorated engine response that takes into account the effects of increased tip clearance, changes in blade profile, and changes in secondary flows shows good comparison with the measurements.

The damage to the ECS duct of the P/W TF33 caused by the ingestion of foreign particles is shown in Fig. 5. This damage significantly altered the air distribution within the system. It is critical to understand the effect that this damage has on the aircraft/ engine/passenger system. Reference [28] provides detailed information about collecting dust particle samples from the ECS bleed and the fan bypass. Reference [28] illustrates that the particulates subjected to the inlet divide in a ratio directly proportional to the bypass ratio.

The size of the foreign particles is also important. The particles collected just downstream of the fan stage had an average diameter on the order of 6-l and the particles collected from the ECS also had an average diameter on the order of 6-l, as shown in Fig. 6. As noted in Ref. [29], fine particles of sizes between 0.5-l and 10-l are most likely to be retained in the lungs. The nasal passages tend to trap particles larger than 10-l, while particles less than 0.5-l are mostly exhaled. In addition, any of the electronic components cooled by air taken from the ECS will also be sub-

Fig. 6 Average particle sizes in ECS for P/W TF33 engine

051001-6 / Vol. 134, SEPTEMBER 2012

Fig. 7

St. Elmo’s glow at face of P/W TF33 engine

jected to these relatively small particles, and it is not clear what the potential damage may be.

A difference in the amount of material ingested prior to engine failure was also observed. One of the TF33 engines ingested 566kg of foreign material over the course of 4.725-hours of operation prior to failure while another of the TF33 engines ingested 388.1kg of foreign material over the course of 1.25 hours prior to failure. This difference in the total amount of material ingested prior to failure is due to the age of the particular engines and the fact that the engine with the lower total mass ingestion was exposed to twice as much foreign material while operating at very high thrust setting (Military Rated Thrust).

If one were to ask the question, ‘What would an estimate be of the minimum operating time of the engine if subjected to 2-mg/M3 while operating at maximum power condition?’ a reasonable estimate would be on the order of 620-hours of operation. This is at least an order of magnitude larger than if deposition were to occur as will be shown later in the paper.

Figure 7 presents a wide-angle photograph of the engine face for a dust concentration of 480-mg/M3. This photograph shows the personnel screen, the dust tube, the dust injection nozzles, and the very important St. Elmo’s white glow at the fan face of TF33 engine S/N 645590. The glow shown in Fig. 7 is more yellow in color than would be seen by the naked eye (color would be more white in nature [7]) due to the photographic paper. It is this glow that the flight crew would see if the foreign particle concentration were substantially higher than the prescribed 2-mg/M3. As will be noted later, the St. Elmo’s glow can be seen for a dust concentration as low as 40-mg/M3, but would be very difficult for the flight crew to see for lower concentrations.

A close-up view of the photograph presented in Fig. 7 is given in Fig. 8 where one can clearly see the total pressure probe that is subject to clogging by the oncoming foreign particulates. When this clogging occurs, the flight crew will get a false airspeed indication and needs to be prepared to take the appropriate corrections. The second stage inlet guide vane appears as a shadow in the illumination field of the first and second rotors. The three silhouettes appearing in Fig. 8 are three of the dust injection nozzles, the location of which can be seen in Fig. 7. The first fan rotor tip/ shroud gap appears very bright because of the optical depth, and the second stage fan tip/shroud gap can be seen in the photograph.

During the 11.87-hours of dust exposure for this engine, the impacting dust removed all of the paint and some of the metal skin from the bullet nose.

For additional details relating to the J-57, TF33, and F107 measurements the reader is referred to the cited references.

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Fig. 8

Close-up view of St. Elmo’s glow at face of TF33 engine

2.2 High TIT Large Full-Scale Engine Results. The discussion will now move onto presentation of the results for the engines with sufficiently high turbine inlet temperatures that deposition of foreign material occurred on the hot-section components.

As previously noted, the engines investigated as part of this work were the Pratt/Whitney F100, the General Electric YF101, and the Williams F112. Figure 1 made it clear that for this class of engines the primary damage mode is deposition on the hot-section components, followed by erosion of compressor and turbine components, followed by deposition of carbonlike material on the fuel nozzles, engine controller degradation, and oil system contamination. Examples of each of these damages will be given in this portion of the paper beginning with a discussion of the P/W F100 engine.

2.3 P/W F100 Engine Subjected to Dust Environment.

Three different P/W F100 engines were subjected to different dust environments at different combinations of throttle settings. The objective of this effort was to determine which of the controller parameters provided early warning of an incipient problem, how the different dust mixtures influenced the damage modes, and how one might prevent an incipient problem from becoming an active problem. Only the highlights of those experiments and sample results from all three engines will be shown. The reader is referred to Refs. [14–16] for more in-depth discussion of the particular conditions to which each of three engines was subjected and for an in-depth discussion of the results.

The range of dust particle concentrations over which the F100 engine was subjected varied from 50-mg/M3 to 500-mg/M3.

Although it was still possible to see St. Elmo’s glow at the engine face for the 50-mg/M3 case, the glow was very dim. It was noted earlier that in addition to the photographic coverage of the inlet, the tailpipe, and the side of the engine, all of the measurements available to the engine control system were monitored during the entire dust ingestion. The controller parameters that most effectively showed an incipient engine problem were the burner pressure (PB) and the compressor discharge pressure (PS3), which mirror each other. Unfortunately, neither the burner pressure nor the compressor discharge pressure is available to the flight crew.

The fan turbine inlet temperature (FTIT) does show an increase during continuing damage to the engine, but the change is sufficiently small that unless the flight crew were looking specifically for this change, it would not be obvious.

The time histories of the fan total pressure ratio, the fuel flow, the high-compressor speed, and the burner pressure are shown in Fig. 9 for a dust concentration of 250-mg/M3 and an exposure time of six minutes with the engine operating at a TIT of 1586 K (2855 K). This particle concentration is two orders of magnitude greater than being considered for flight operation. Note that

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Journal of Turbomachinery Summer 2013

Fig. 9 Time history of engine parameters during dust exposure

the burner pressure has increased by approximately 2.2-atmospheres while the other parameters have increased relatively little.

The corresponding time history of the fan turbine inlet temperature measured at the first stage of the low turbine and the engine pressure ratio (EPR) are shown in Fig. 10. The fan turbine inlet temperature has increased only from approximately 2070- R (1610- F) to approximately 2100- R (1640- F) and the engine pressure ratio has increased very little. Even if the flight crew

Fig. 10 Time history of FTIT and EPR during dust exposure

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Fig. 12 time

Fig. 11 Burner concentration

pressure

history

for

increased

dust

knew what to be looking for, it would be difficult to rely on the increase in FTIT. If the engine throttle setting remains fixed, the dust concentration is doubled and the exposure time cut to one-half, what would happen to the burner pressure history? Figure 11 shows that the resulting increase in burner pressure at the end of the three minute exposure time has increased by approximately 2.3-atmospheres, which is reasonably close to the increase shown in Fig. 9 for onehalf the dust concentration but twice the exposure time.

Next the dust concentration was returned to 250-mg/M3 and the exposure time was increased from the six minutes shown in (Fig. 9) to twelve minutes shown in Fig. 12 in order to investigate the magnitude of the dust concentration versus exposure time. The burner pressure at the end of the twelve minutes of exposure has increased by 3.3-atmospheres, whereas the burner pressure for the six minute exposure and the three minute exposure at twice the concentration increased by 2.3-atmospheres. Also note that the magnitude of the burner pressure increase at the six minute location of Fig. 12 is very close to the 2.3-atmospheres seen on Fig. 9 after six minutes of exposure.

Experience obtained during the measurement program suggested that when the increase in burner pressure exceeded 2.5atmospheres, the engine was in serious danger of surging. The exact value at which the engine surged depended upon several things, i.e., the current deteriorated stage of the engine, the throttle setting, and the history of previous dust exposure events to mention a few.

These results suggest that the deposition process is not linear.

However, to a first order approximation in the absence of additional data, it can be considered to be linear for estimating the vulnerability of the propulsion system in the event that the dust concentration is different from what one might estimate it to be.

In doing so, it is important to be on the conservative side of the estimate of operational life.

051001-8 / Vol. 134, SEPTEMBER 2012

Time history of engine parameters for longer exposure

The fan total pressure ratio and the fuel flow are also shown on Fig. 12. The changes in these parameters are consistent with the changes in burner pressure for the different cases.

The FTIT and the engine pressure ratio for this longer exposure time are given in Fig. 13. The FTIT value at the six minute point of exposure in Fig. 13 is seen to be very similar to the FTIT value at the six minute point of exposure in Fig. 10. For this longer exposure experiment, the increase in FTIT is on the order of 70 R, but again this change probably wouldn’t be observed by the flight crew. The change in EPR is also sufficiently small that the flight crew would be unlikely to notice the increase.

An obvious question of interest is ‘what can one do to prevent deposition on the high-pressure turbine vanes and thus avoid the increase in burner pressure shown in the previous figures?’ Based on the combustor measurements described in an earlier section of the paper, the most effective way to do so is to reduce the TIT to the point where the calcium impurity in the dust material does not melt. The obvious way to do this is to retard the throttle to idle and therefore significantly reduce the TIT. Figure 14 illustrates what happens if the dust concentration remains at 250-mg/M3 but the TIT is reduced to 2305 R. Both the compressor discharge pressure and the burner pressure remain constant during the dust exposure time as does the fuel flow and

Fig. 13 Time history of FTIT and EPR for longer dust exposure time

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Fig. 15 Time history of engine during throttle cycling to remove deposits

Fig. 14 Time history of engine parameters with throttle at idle position

the fan total pressure ratio. This result is the origin of the request that when the flight crew recognizes the presence of an unacceptable dust cloud in the form of St. Elmo’s glow at the engine face, they reduced the throttle to the idle position and take the action recommended in Ref. [7]. This recommendation involves the flight crew making a left-hand descending turn and returning to where they came from. The reader is referred to the Boeing video for a more detailed discussion, which is consistent with the standard ICAO guidance.

Another question of interest relates to how one might be able to clear the deposits from the high-pressure turbine vanes while operating in flight at a penetration throttle setting. While conducting the measurements described above, we observed that it was possible to clear much of the deposited material by cycling the throttle.

On the basis of the results presented in Fig. 9 to Fig. 12, it was concluded that once the increase in compressor discharge or burner pressure exceeded 2.5 atmospheres, the engine was in serious danger of surging. A convenient parameter to use for indicating incipient surge was found to be the ratio of burner pressure to compressor discharge pressure. When the value of this parameter exceeded approximately 1.05, it was important to attempt to clear the engine of deposits.

To address this surge concern, we used another F100 engine [15] that had accumulated 295-hours of flight time prior to these measurements. The concentration of the New Mexico black scoria was the volcanic ash was set at 500-mg/M3, which was the same as used for S/N P680071. The engine was allowed to operate until it was close to surge, that is, until the ratio of PB/PS3 reached approximately 1.05 as described above. Then the throttle was slowly retarded, dwelt for a short time, and slowly advanced to military rated power (MRT). Repeating this process two times cleared the engine of a substantial amount of the deposited material. The reason this occurred was determined during the combustor experiments. The deposited material has a different coefficient of expansion than the metal on to which it is deposited and by changing the temperature of the metal, one could break the bond.

Photographs taken at the tailpipe of this engine will be shown later illustrating the deposited material exiting the engine while this purge event is taking place.

The time history of the total life of this particular engine is shown in Fig. 15. The operating time for the engine to get to the

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initial purge sequence was approximately five minutes and the time to the second purge sequence was approximately six minutes.

The same throttle sequence was performed for the second sequence, but due to the relatively slow response of the data acquisition system in use at the time of these measurements, the entire sequence wasn’t recorded.

After the second purge sequence, it was decided to let the engine continue to run to see how high the ratio of PB/PS3 could become without encountering a surge event. After about eight minutes of exposure time, the ratio began to look very different than normal and a decision was made to initiate the purge sequence. Unfortunately, when the purge sequence was initiated, the engine went into a violent series of surges and it was not possible to re-start the engine after this event.

The total life of this engine when subjected to the dust environment was on the order of twenty minutes. The engine was subsequently taken apart and photographs of the internal components will be shown in later figures. Similar photographs will be shown for the General Electric engine and for the Williams International engine because the damage suffered by the compression system has some significant differences for the individual engines as will be shown by the photographs of each. The high-pressure compressor of the P/W F100 engine is a 16-stage system, for the GE F101 it is a nine-stage system, and for the WI engine it is a mixed axial/ centrifugal system so one should anticipate significant differences in the damage mechanisms. The deposition of foreign material in the high-pressure turbine section of the respective engines is also different as should be anticipated because of the different design configurations. Thus, the foreign particle deposition in each of the three engines will also be shown later in the paper.

The burner pressure and FTIT history just prior to and during a typical surge event series are shown in Fig. 16. As illustrated by the time history of the measured parameters there is very little warning of an impending surge event from either the pressure or the FTIT measurement. This engine continued to surge and the TIT continued to increase until the throttle was retarded at 2 seconds after the initial surge.

An expanded time history of the compressor discharge pressure for this engine is shown in Fig. 17 for a case for which the engine was allowed to surge for 1.9-seconds prior to retarding the throttle. On this figure it is relatively easy to see that there is a small variation in the compressor discharge pressure leading up to surge, but the value of the variation is on the order of a few kPa out of over 2000-kPa. A fast Fourier transform (FFT) of the pressure signal indicates that this engine surges at a frequency of approximately 10-Hz. It was mentioned earlier that cameras were used to film the engine inlet and the engine exhaust throughout the experimental SEPTEMBER 2012, Vol. 134 / 051001-9

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Fig. 16 Burner pressure and FTIT just prior to and during surge events

Fig. 17 Compressor discharge pressure and FTIT prior to and during multiple surge events

series. Figures 18 and 19 show photographs of the tailpipe of a F100 engine during the surge events. It is not possible to see material exiting the tailpipe in Fig. 18 because the fire masks the particulates leaving the engine. However, in Fig. 19 is taken later in a

different surge sequence the material is clearly seen leaving the engine. Surge helps to remove deposited material from the engine, but it is neither as effective nor as desirable as cycling the throttle as described during the discussion of Fig. 15. Unfortunately, these

Fig. 18 Photograph of tailpipe during early part of surge event

Fig. 19 event

051001-10 / Vol. 134, SEPTEMBER 2012

Photograph of tailpipe taken during late part of a surge

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Volcanic Ash Table 2

Post-test oil sample taken from engine S/N P680071

Sample

R time R dust (min) (Kgm)

#1 #2 Field (Max) Kelly (Max)

84.92 84.92 84.92 84.92

Fe

Ag

Al

Cr Cu Mg Ni Si

59.46 48 9 8 2 59.46 45 8 9 2 59.46 0-10 0-2 0-10 0-4 59.46 0-5 0-2 0-2 0-2

0 0 3 3

4 4 8 8

3 2 0-4 0-2

54 54 15 15

Ti 10 10 0-20 0-10

relatively long series of surge events cause significant damage to the compressor as will be shown in subsequent discussion.

Each of the P/W F100 engines subjected to the dust environment were disassembled after the engine could no longer be operated to view in detail the form of the damage to the machine. In addition, samples of the oil and fuel were analyzed to determine if either of those systems had been compromised by the dust ingestion.

Table 2 shows the results of two oil samples taken from S/N P680071, which ingested 59.46-kg of material over a total exposure time of approximately 85 minutes. The bottom two rows of the table give the maximum allowable parts per million of the specific element for the field and for Kelly AFB, respectively. The numbers given in red are elements for which the amount measured were out of the allowable range. The two major contaminants are iron, which was approximately five times greater than allowed in the field and silicon, which was over three times the amount allowed in the field.

The elemental analysis for the dust material to which this engine was subjected was shown previously in Fig. 3, where the iron and silicon peaks are prominent. The results presented in Table 2 suggest that a portion of the ingested material does find its way into the oil system, since it is difficult to imagine where else the silicon would have come from. Similar analysis for the fuel system suggested that the fuel was clean of any dust material contamination.

As noted in Table 2, engine S/N P680071 was subjected to 59.46-kg of foreign material over the course of 84.92 minutes, and it is of interest to look at the engine damage incurred as a result. Figure 20 shows a photograph of the worn 4th stage compressor blade tip compared to the tip profile of a new blade. The tip of the blade exposed to the dust environment is severely eroded and is very sharp.

The 9th stage blade for the same engine is shown in Fig. 21 and illustrates a similar severe erosion of the blade tip. Note also for this stage that the very thin trailing edge of the airfoil is folded away from the pressure surface.

For the engine described in Figs. 15 and 16 that underwent some rather severe sustained surging, the damage to the compressor was not only blade tip erosion but also the more severe damage shown in Figs. 22 and 23. The total life of the engine in the dust environment was on the order of twenty minutes. Part of the reason for this short life was due to the severe compressor damage that occurred as shown in the figures. Very similar damage also occurred for the 8th stage compressor airfoils. This kind of damage to the compression system along with erosion of the blade tips,

Fig. 20 Post-test photograph of 4th stage compressor blade tip P/W F100, S/N P680071: middle blade is new blade & Outer blades are worn

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Journal of Turbomachinery Summer 2013

Fig. 21 Post-test photograph of 9th stage compressor blade tip folding of thinned trailing edges for P/W F100 S/N P680071

Fig. 22 Post-exposure photograph for P/W F100 S/N P680043 7th stage compressor airfoils

Fig. 23 Post-exposure photograph for P/W F100 S/N P580043 9th stage compressor airfoils

and deposition on the high-pressure nozzle guide vane and fuel nozzles made it very difficult to operate this engine.

As a result of the erosion damage to the compressor shown in Figs. 20 and 21 and the deposition on the high-pressure turbine nozzle guide vanes, the engine controller was feeding increased amounts of fuel as shown by Figs. 9, 11, and 12. Thus, the combustor was running rich and carbon was being deposited on the fuel nozzles as shown in Fig. 24. A chemical analysis performed for the deposited material confirmed that the deposit was carbon.

The center hole of the fuel nozzles was clear and the nozzles were flowed to confirm that the proper amount of fuel was flowing.

Unfortunately, the swirl vanes were plugged and the fuel could not be atomized. For this particular engine, twenty-one unsuccessful attempts were made to restart the engine.

Typical deposits on the high-pressure turbine nozzle guide vane are shown in Fig. 25. It is important to note that EACH of the vane leading edges had deposits similar to the one shown as ‘Leading-edge deposits,’ but they were removed to better show the accumulation of deposit on the pressure surface. It is interesting to note that many of the cooling holes were still open in that the holes coming out of the deposit were open all the way back to the vane surface. The shape and texture of the vane deposit on the SEPTEMBER 2012, Vol. 134 / 051001-11

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Fig. 24 Photograph of carbon deposits on fuel nozzles for P/W F100 S/N P680043 for which 21 attempts to re-start engine were unsuccessful

Fig. 25 Deposits on high-pressure turbine vane leading edge for P/W F100 S/N P680054

HPT were very similar to the deposits removed from the P/W JT9D engine noted in Table 1 that encountered the Mt. Galunggung volcano as shown in Fig. 26. On the left side of the picture are deposits taken from the P/W F100 S/N P680054 engine operated in the laboratory and on the right are deposits taken from the JT9D engine that flew through the aftermath of the Mt. Galunggung eruption over Indonesia on July 13, 1982. The deposits are very nearly identical.

2.4 GE YF101 Engine Subjected to Dust Environment. Two GE YF-101-GE-100 engines were subjected to four different foreign particle environments, and the details of each are described in Refs. [17] and [18]. Both engines suffered severe damage as a result of the ingested material. In the remainder of this section,

Fig. 26

Fig. 27 Particle size distribution at the 5th stage ECS duct for YF101 engine

some of the important results from those measurement programs will be described. All of the parameters available in the controller were monitored on a continuous basis and the inlet to and exit from the engine were continuously filmed.

Consistent with the results for the P/W F100, the time history of the compressor discharge pressure was the major indicator of an incipient surge. For a discussion of incipient surge, the reader is referred to Ref. [30], which provides significantly more detail related to the F100, YF101, and F112 engines.

Prior to exposing the engine to any dust environment, a green line record of core speed versus fan speed was measured over the entire throttle range.

The damage mechanisms for the GE YF-101-GE-100 engine were very similar to those for the P/W F100 in that the number one damage mode was deposition on the high-pressure turbine nozzle guide vane and the number two mode was erosion of the compressor. The fuel nozzles for the YF101 did not become damaged nor did the oil become contaminated.

Once again, the average particle size of the foreign particles entering the engine was 37-l. Samples from both the 5th and 9th stage ECS ducts were taken during the course of the measurements, and the results of are shown in Figs. 27 and 28. The average particle size at the 5th stage bleed was 8.5-l and at the 9th stage bleed it was 3.5-l, both of which were under the 10-l limit for breathing.

As was the case for the P/W F00 engine, the principal indicator of incipient surge for the YF101 was the change in compressor discharge pressure. It was generally observed that when the compressor discharge pressure increased by an amount equal to two to three atmospheres, surge was likely. However, unlike the surge of the P/W F100 engine, the GE YF101 engine surged in pairs of fireballs at a frequency of 16 to 20-Hz as shown by the pyrometer time history and compressor discharge pressure shown in Fig. 29.

The presurge time history of both parameters does not suggest any

Comparison of laboratory deposits with flight deposits

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Fig. 31 Photograph of YF101 S/N GEE470058 9th stage airfoils after dust exposure and multiple surge events Fig. 28 Particle size distribution at the 9th stage ECS duct for YF101 engine

Fig. 29 Time history of compressor discharge pressure and pyrometer temperature during surge event for GE YF101 engine

warning of the event that is about to occur. An expanded view of the discharge pressure does not show the small pressure variation that was seen in Fig. 17 for the P/W F100 engine.

During the course of the surge events with the throttle remaining in a fixed position, the engine attempts to recover. After approximately four seconds of surging, the throttle was returned to the idle position and the engine recovered. Engine recovery is possible by retarding the throttle so if the engine does not shut itself down, then one might want to consider not turning it off unless absolutely necessary because if deposition has occurred on the fuel nozzles, like that shown in Fig. 24, it may not be possible to restart the engine.

The YF101 engines also sustained significant erosion of the compressor airfoils as shown in Fig. 30 for engine S/N GEE470049,

Fig. 30 Photograph of YF101 S/N GEE470049 stage 5 through stage 9 compressor airfoils after dust exposure

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which was exposed to 224.4-kg of foreign material over a period of 4.36 hours. During this exposure time, many different surge events occurred. It was mentioned earlier that the pattern of damage to the airfoils was engine dependent. As illustrated by Fig. 30, the leading edges of all of the airfoils from about 60% span on to the tip region are severely eroded. In addition, the tip region is thinned and eroded.

As a result of the multiple surge events experienced by the engine, some of the 9th stage airfoils were severed at the root as shown in Fig. 31. With the airfoils in the condition shown in these figures it was still possible to generate takeoff thrust, but one had to be a bit careful with the rate at which the throttle was advanced.

Significant deposition did occur on the high-pressure turbine components for both YF101 engines. Engine S/N GEE470058 ingested 176.3-kg of foreign material over a period of 2.96-hours and during the process sustained significant damage to the compressor and turbine. Figure 32 illustrates the very thick deposition on the leading edges and pressure surfaces of the HPT vane row.

This deposition, which creates a significant flow blockage to the turbine, is primarily on the leading edges and on the pressure surfaces, with relatively little deposited on the suction surface as shown by a rear view photograph of this vane given in Fig. 33. As illustrated, the deposits on the suction surface are mainly near the outer hub wall and are relatively minor as compared to the deposits on the pressure surface. In addition, some distress in the vane can be seen at approximately 25% span on two of the airfoils near the center of Fig. 33.

The blade of the YF101 turbine was also damaged by exposure to the ash environment as shown in Fig. 34. For this particular engine, there was an air filter located between the cooling air supply and the entrance to the blade cooling intake. This filter became partially plugged with foreign material and thus the weight flow of cooling air to the blade row was significantly reduced. As shown by Fig. 28 the average particle size at the 9th stage bleed was on the order of 3.5-l so these small particles passed through the filter. With the airflow reduced, these small particles plugged

Fig. 32 Front view of deposition on high-pressure turbine vane of YF101 S/N GEE470058

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Fig. 33 Rear view of deposition on high-pressure turbine vane of YF101 S/N GEE470058

Fig. 34 Photograph of YF101 S/N GEE470058 HP turbine blades after dust exposure

many of the holes in the showerhead as can be seen in Fig. 34.

The combination of reduced cooling airflow and blocking of some of the cooling holes resulted in significant damage to the airfoils.

The leading edge of several of the airfoils was burned away as was the tip region.

However, it is important to note that with some care by the operator in advancing the throttle, it was still possible to generate takeoff rated thrust even with the damage to the high-pressure compressor shown in Fig. 30, the deposition on the high-pressure turbine vane shown in Fig. 32, and the damaged to the highpressure turbine blades shown in Fig. 34. The reason the test matrix with this engine was terminated was because of high vibration indications in the region of the compressor exit/turbine region.

In addition to the high vibration level in the rear portion of the engine, it was obvious as one worked through the matrix of dust exposure points that the control system was not operating as it had prior to exposure to the dust environment as shown in Fig. 35. This is not surprising since the input parameters to the controller are not aware of what is causing the increases in compressor discharge pressure and changes in other parameters, and thus hasn’t been taught how to respond to prevent a subsequent problem. The dashed line in Fig. 35 represents the predust exposure green line operation of core speed versus fan speed. The colored line portions show the operating condition during subsequent dust exposure runs. Clearly, soon after initiation of the dust exposure, the fan speed relative to the core speed was not operating on the predust green line. The initial surge is shown by Matrix point #7 and one can see the very rapid fall in fan speed at the time of surge initiation.

2.5 Williams YF112 Subjected to Dust Environment. With a total mass flow of this engine is on the order of 8-kg/sec, the 051001-14 / Vol. 134, SEPTEMBER 2012

Fig. 35 Time history of YF101 engine controller during dust exposure

Williams YF112 is obviously a much different engine than either the Pratt/Whitney F100 or the General Electric YF101 engines that have mass flows of 105-kg/sec and 164-kg/sec, respectively.

The YF112 has a mixed axial/centrifugal compression system and a turbine inlet temperature of 1244 K (2240 R) that is near the lower limit for deposition to occur in the hot section based on earlier investigations. However, it is sufficiently high that deposition does occur but at a much slower rate than for the two larger engines. It is appropriate to address the damage mechanisms for this engine since this class of engine may also be exposed to the environment that is the subject of this paper.

Only the Williams YF112 S/N E001 engine, which was exposed to 8.7-kg of foreign material over a period of three hours and 51 minutes while operating at full power before the engine could no longer be operated, will be described here. Two of these engines were used in the investigation, but only a brief summary of the measurement program can be given. More complete details for both engines are given in Refs. [19] and [20].

The initial surge events occurred after 8-kg of exposure for a period of three hours and 27 minutes. The damage mechanism responsible for engine surge was material deposition within the high-pressure turbine. Degradation of this engine was best described by a reduction of fan speed and core speed with continuing exposure to the foreign material. The engine control system was responsive to the changing engine damage and resisted changes in compressor discharge pressure and thrust.

The initial series of surge events for this engine is shown in Fig. 36. As illustrated, this engine surges at a frequency of approximately 27.5-Hz. At the conclusion of approximately 0.75 seconds of surging, sufficient deposited material was blown out of the engine so recovery began. With continued exposure to dust, the surging event started all over again.

Fig. 36

Williams YF112 initial series of surges

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Fig. 37

Surge precursor for Williams YF112 engine

Unlike the previous engines discussed, this engine displayed a presurge window of sufficient duration that it may have been possible to invoke an electronic control system modification to delay the onset of surge. Figure 37 shows that one has approximately 0.150-sec of warning prior to surge and that the magnitude of that warning amounts to a pressure signal of approximately 2.4% of the compressor discharge pressure at a frequency of 27.5-Hz. The time and magnitude of this warning is significantly more than that seen for either the P/W F100 or the GE YF101 engines investigated using the standard engine measurements available from the controller. The precursors of engine surge for all three of these engines is described in more detail in Ref. [30].

The YF112 compression system sustained erosion damage during dust exposure and during the subsequent surge events. However, the nature of the damage was different than previously shown for the P/W F100 and the GE YF101 engines, perhaps because of the mixed compression system. The compressor blades were damaged, but the tips and the leading edge were not worn thin or eroded away as previously shown for the other engines.

Rather, the trailing edge of the centrifugal compressor diffuser was eroded as shown in Fig. 38. The repeated surging caused many of the fan blades to be bent, but they were not fractured and remained in one piece.

Another significant difference between the respective damage mechanisms was the significant amounts of fine material that passed through the various seals and ended up being deposited throughout the internal components of the machine. An example of such a collection of ‘talcum-powder like’ material is shown in the photograph of Fig. 39. In addition to these kinds of internal deposits, the engine oil filter also became plugged with foreign material.

It was noted earlier that the principal damage mechanism for both of the YF112 engines was deposition on the high-pressure turbine nozzle. Figure 40 is a photograph looking from the rear of the vane row showing substantial deposits on the leading edge that extended around onto the suction surface. The deposit also

Fig. 38 Photograph of erosion damage to YF112 S/N E002 diffuser after dust exposure

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Journal of Turbomachinery Summer 2013

Fig. 39 Substantial fine deposits found within internal cavities of YF112 S/N E002

Fig. 40 Photograph of YF112 S/N E001 vane row after dust exposure

extended over a good portion of the vane pressure surface. The insert on Fig. 40 is a typical piece of the leading-edge deposit that was removed from one of the vanes. It clearly shows the significant magnitude of the deposit and the form of the vane leading edge.

2.6 General Comments Regarding Use of These Data and Lessons Learned. One can use the results presented here for the three different engines to estimate what the operational time might have been prior to initial surge if the concentration of foreign material would have been 2-mg/M3 instead of the values used for the experiments. Keep in mind that for these engines the primary damage mode was deposition of foreign material on the surface of the high-pressure turbine inlet guide vanes.

The data in Figs. 9, 10 and 11 suggest that assuming a linear relationship between ingested material and operation time prior to first surge may not be strictly correct, but for the purposes of an estimate of the approximate operational time it is a reasonable first approximation. To obtain the operation time given in Table 3 the total mass ingested by the representative engine to first surge was multiplied by the density of air at the altitude of ingestion (sea level in this case), multiplied by one over the air mass flow of the core, multiplied by one over the allowed concentration of ash in the environment. Using this linear approach, Table 3 suggests that the two relatively high turbine inlet temperature machines, the GE SEPTEMBER 2012, Vol. 134 / 051001-15

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Volcanic Ash Table 3

Sea level estimate of operational time prior to initial surge If 2 mg/M3, avg.

Core Flow Dust to Turbine Inlet Kg/sec 1st surge Kg Temp. K ( F) time of operation Hrs

Total m Kg/sec

bpr

GEE YF101

163.6

1.9

56.2

23.0

P/W F100

104.6

0.63

64.1

7.25

8

1.0

4

8.0

Engine

YF112-WR-100

YF101 and the P/W F100 would operate at sea level conditions for 22.4 hours and 12.8 hours, respectively. In making these estimates, the amount of dust ingested to first surge for the individual engine within a group that had the shortest operational life was used. Correction for high altitude air mass flow and turbine inlet conditions could be made to these estimates if desired. It should be kept in mind that these estimates are for vintage 1980 – 1990 engines and that for modern engines the time to first surge could be shorter as a result of the higher turbine inlet temperatures associated with these newer engines. It would be possible to impact the operational time given in the table by various reductions due to the higher operational temperatures just noted, but in the absence of a data base to use for this purpose this approach was not implemented.

An engine of the type represented by the Williams YF112 engine that operates at significantly lower turbine inlet temperature would have an operational life of approximately 104 hours prior to initial surge. Note that because the YF112 is an expendable engine it is designed to have an operational life on the order of 25 hours.

Continuing with the linear assumption, if the actual dust cloud density is greater than predicted by a factor of 10, then the operational life of the YF101 and the F100 become 2.2 hours and 1.3 hours, respectively. If flight is going to be permitted into a volcanic contaminated airspace, several things become important; (a) the predictions of contamination density and spatial location and movement need to be accurate, (b) development of in-flight detection systems should be pursued, (c) application of the numbers presented here for vintage 1980s and 1990s engines to modern engines, and (c) flight crew training to rapidly detect the presence of a cloud density that is higher than anticipated to mention a few.

Reference [31] describes the application of a Defense Nuclear Agency software system known as Prototype – Environment and Aircraft Responses ModeL (P-EARL) to a volcanic dust event to demonstrate the characteristics of such predictions on commercial aircraft performance. Reference [31] describes the application of the dust dispersion and aircraft and engine performance models to the 1992 eruption of Mt. Spurr for a Boeing 747-200B flying at 30,000 ft. over several different routes.

Engine response models for use in P-EARL were developed using the data described in this paper and are reported in detail in Refs. [32,33]. The computer code P-EARL, which is described in detail in Ref. [34], was designed to help route planners evaluate the responses of aircraft systems, components, and crew to nuclear burst induced changes in the atmosphere. The version of P-EARL used for [31] utilized the code TORAS [35] for predicting the dust environment as a function of space and time. This computational approach and the associated engine models could be a useful tool to both military and civil route planners to assess potential routes and associated engine/aircraft damage as interruptions to air travel because of volcanic ash clouds arise in the future.

It was noted early in this paper that if St. Elmo’s glow can be seen at the engine inlet, then the ash concentration is significantly greater than 2-mg/M3 and evasive action should seriously be considered. Another observation that suggests a dust environment has been entered is the presence in the cabin of smokelike material with a sulfurlike odor coming through the ECS. 051001-16 / Vol. 134, SEPTEMBER 2012

1644 (2500) 1617 (2450) 1256 (1800)

22.4 12.8 104

Among the lessons learned while operating the engines in the presence of the volcanic ash environment were that the engine operator may have very little knowledge of an impending problem until the failure sequence begins. The engine control system attempts to compensate for the engine degradation but usually worsens the problem. If the presence of the dust environment can be recognized, then modifying the operational procedure can extend the time of engine operation. Modification of operational procedure means that if the dust presence manifests itself in a St. Elmo’s Glow and/or sulfur odor in the cabin, then the power setting should be reduced to idle, the flight crew should exit the cloud and land at the nearest airport. The reader is referred to the Boeing video [7] for the detailed procedure to be followed. In the event that deposition has occurred on the high-pressure turbine inlet vanes, slowly decelerating and accelerating the engine throttle makes it possible to remove a significant portion of the deposited material, and thus delay surge for a limited period of time.

Obviously, this is best done one engine at a time for multiple engine aircraft.

3

Conclusions

Modern gas turbine engines operating in the presence of volcanic ash clouds will be damaged to some degree, and pulverized ash will enter the environmental control system. The primary question of concern is the rapidity with which the engine damage occurs and the degree of damage, both of which depend upon the dust concentration, time of exposure, dust cloud composition, and engine power setting. It should be noted that for the operation that did take place in the Spring of 2010 that may have encountered some very light ash levels, no damage has been found to date in the engines.

There are at least eight potential damage mechanisms to which the engine is subjected in the dust environment: (1) deposition of foreign material on the hot section components, (2) erosion of the compressor airfoils, (3) cooling hole blockage of the highpressure turbine, (4) unwanted changes to the control system, (5) compressor airfoil damage as a result of repeated engine surging, (6) oil system contamination, (7) ingestion by humans of very small particles passing through the ECS, and (8) potential damage to electronic parts cooled by the ECS air. If the dust cloud concentration is sufficiently high, these small particles will appear as smoke in the cabin and tend to have a ‘sulfurlike’ odor.

For engines with TIT in excess of 1283 K ( 2310 R), the initial damage mechanism is deposition of foreign material on the hot section components, most importantly on the high-pressure turbine inlet nozzles. This deposition is very dependent upon the concentration of the foreign particle environment, the properties of the glassy constituent within the particulates, and the surface temperature of the. Therefore, it is very important that the airline community has information about the calcium content of the ash immediately upon the eruption of a volcano.

The second most important damage mechanism for a high TIT engine is erosion of the compressor and turbine airfoils. This erosion is very dependent upon the concentration of the foreign material, but relatively independent of the cloud constituents and the Transactions of the ASME The Journal of Air Traffic Control

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55

Volcanic Ash compressor airfoil material, titanium or steel makes little difference.

Rapid increases in the compressor discharge pressure and the burner pressure are the primary indicators of impending difficulty.

Unfortunately, neither of these parameters is available to the flight crew. A relatively small increase above normal operating condition will be seen in the turbine exit temperature and some form of this parameter is often available to the flight crew; however, it could easily be overlooked if one weren’t specifically looking for the increase.

If the dust density is at least 50-mg/M3 the flight crew should be able to see the St. Elmo’s glow if ambient light conditions are not bright and if they have a view of the engine inlet. If the flight crew can clearly see the St. Elmo’s glow at the fan face, then the dust concentration is far greater than 2-mg/M3 and the evasive action recommended in Ref. [7] should be taken immediately. If the flight crew cannot see the fan face, then they have only the fireflies on the windscreen and the ‘sulfurlike’ odor in the cockpit as warning. It is important that the predictions of contamination density are accurate and that the flight crew be trained to rapidly detect the presence of a cloud density that is higher than anticipated in the event of a poor prediction of dust concentration.

Table 3 of the paper presented estimates indicating that two relatively high turbine inlet temperature machines would operate for 22.4 hours and 12.8 hours, respectively without surging if the dust concentration were 2-mg/M3. If the actual dust cloud density were greater than predicted by a factor of ten, then the operational life prior to initial surge become 2.2 hours and 1.3 hours, respectively.

It should be kept in mind that these estimates are for vintage 1980 – 1990 engines and that for modern engines the time to first surge could be shorter as a result of the higher turbine inlet temperatures associated with these newer engines.

3.1 Concerns and Actions of the Stakeholders. The various stakeholders involved with the commercial air traffic community have been offered an opportunity to comment on the problem in general and on this paper. Several of those offered the opportunity to comment have done so and their comments are provided in quotes below.

(1) The letter reproduced in the next paragraph was provided

by Captain Eric Moody who was the pilot of BA009 (with 247 passengers and a crew of 16 on board), which encountered volcanic ash over Indonesia at 37,000 ft [6,7] as described in Sec. 1 of the paper. Captain Moody and his flight crew avoided a catastrophic event by their expert handling of the ‘all-four engine out’ situation in getting the engines re-started at 12,500-feet after descending from 37,000 ft. over a time on the order of fifteen minutes. Fifteen minutes in an aircraft without power is obviously a very scary event, and survival requires a very capable pilot and flight crew.

“This excellent paper makes me realize how lucky we were in the 1982 incident as the slow degradation of the engines’ performance and the relatively limited parameters available to us on the flight deck did not make the flight crew’s job in recognizing and handling the situation easy ... and we had no idea what was happening to us at the time!! Throughout the passing 29 years, I have maintained a great interest in aircraft operation around volcanic ash and through that have developed a great friendship with Prof. Mike Dunn, which leads me to comment thus: Volcanic eruptions are and will continue to be a potential threat to aviation that must be carefully managed. For example, there are 92 volcanoes on the island of Java that the experts consider to be ‘active.’ Of these, four or five are continually erupting to provide residual ash; yet we continue to fly through their airspace every day and night. Interruption in air traffic as we experienced in Europe and parts of the Atlantic in 2010 can be obviated only if a scientific and reasoned solution to the problem is developed. Funding is required to accomplish this.

56

Journal of Turbomachinery Summer 2013

For a reasoned approach, it is also vitally important to have the technology and means to determine the concentration and composition of the ash in the airspace affected by the active volcano. During the 2010 incident, the only aeroplane that could have coarsely measured ash concentration and composition was grounded being painted. This paper illustrates my assertions that one cannot make sensible decisions as to operations in the vicinity of volcanic ash unless one knows accurately the concentration of the ash in the air, its composition and its particle size. From this paper we learn that it is also vitally important to determine the amount of calcium in the ash. While finding this subject and paper fascinating, I am just frustrated that more hasn’t been done about finding a solution to the problem throughout the world. I feel that certain responsible agencies too often either overreact to the situation or act like ostriches.

The research has been done by Mike Dunn over many years. Please let’s use it. I will not be happy until we get the message through that volcanic ash is and can be dangerous and we have procedures in place to manage operations around it sensibly and safely. As I have stated above, we have operated and are still operating all over the world every day in ‘residual ash,’ and although that may cause some damage it is my opinion that in the long term it is not dangerous if the knowledge and solutions described above are in place.”

Captain Eric Moody.

(2) “Pratt & Whitney acknowledges the work presented in the subject paper and would anticipate that this body of work along with future studies will continue to provide insight into the characteristics, mechanisms, and operational impacts associated with volcanic ash ingestion. Future related systems and procedures will benefit as knowledge is gained. In the interim, given the range of variables, and boundary conditions, Pratt & Whitney continues to emphasize that operators follow appropriate operating procedures and available guidance material as currently exists and as updated going into the future.” Eric (Rick) Krueger Pratt/ Whitney.

(3) “In parallel with a range of other relevant activities (e.g., related to detecting, forecasting and confirming ash cloud position, extent and composition), there is a continuing desire among European aviation regulators, and among those supporting airspace infrastructure across Europe and the North Atlantic, to advance our understanding of the effects of volcanic ash clouds on current and future aircraft and their occupants. Progress across this complete suite of activities is crucial to improvements in safety assurance and airspace availability when ash contamination represents a hazard to flight operations.” Padhraic Kelleher, UKCAA. (4) “The U.S. Government funded research conducted by the Calspan Corporation into volcanic ash ingestion of turbofan engines is one of the most important sources of data available on the topic. This paper is a good summary of this research. The engine and component testing duplicated the deterioration modes and operability impacts of volcanic ash ingestion observed in fleet operations. The research demonstrated three key items: (1) volcanic ash ingestion is a real airworthiness concern if steps are not taken to avoid operation in volcanic ash, (2) The engine deterioration observed is cumulative and irreversible, and (3) the rate of deterioration of the engines is a function of material being ingested (chemical composition, concentration, particle size, etc.), engine architecture/design, engine operating conditions, and time of exposure where engines with higher operating temperatures deteriorated at an accelerated rate. Additional research is appropriate into the ingestion effects when exposed to lower concentrations of volcanic ash in modern turbofan engines. The OEM recommendations remain consistent to avoid intentional encounters with volcanic ash and to take action to exit contaminated airspace if volcanic ash is inadvertently encountered.” Roger Dinius, General Electric Aviation.

SEPTEMBER 2012, Vol. 134 / 051001-17

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Down

Volcanic Ash

Acknowledgment The work described in this paper was funded by the former Defense Nuclear Agency (now DTRA) under many different contract numbers over many years. The author would like to express his appreciation to his co-authors who worked tirelessly to complete the research program described herein without blowing up an engine or hurting anyone, especially Mr. Jeff Barton who was at the throttle of the engines being subjected to the adverse environments. He would also like to thank the many Defense Nuclear Agency contract monitors who contributed significantly to this measurement program during its entire duration. The author would like to thank Captain Eric Moody (Captain of BA007) for the many discussions that we have had since the 1982 event over Indonesia, and for his comments in the ‘Concerns and Actions of the Stakeholders’ portion of the paper. Thanks also to the industry and government people who have contributed to the ‘Concerns and Actions of the Stakeholders’ portion of this paper. The author would also like to express his appreciation to David Wisler for significantly improving the resolution and the quality of the photographs presented in this paper. Thanks also to Lee Langston of the University of Connecticut for providing a sample of the Eyjafjallajokull volcano ash and thanks to Cameron Begg of The Ohio State University for performing the SEM and elemental analysis given in Fig. 4. Finally, he would like to express his appreciation to those within DTRA and the U.S. Air Force who worked to make it possible to discuss this previous work in an open literature presentation. All of the previously unavailable reports describing this research can now be found at the website address given below. http://www.dtra.mil/Info/FOIA/FrequentlyRequestedRecords.aspx

Nomenclature CDP ¼ CET ¼ ECS ¼ EPR ¼ FFT ¼ FTIT ¼ MRT ¼ P-EARL ¼

compressor discharge pressure combustor exit temperature environmental control system engine pressure ratio fast Fourier transform fan turbine inlet temperature military rated power Prototype – Environment and Aircraft Response ModeL PB ¼ burner pressure PS3 ¼ compressor discharge pressure TIT ¼ turbine inlet temperature

References [1] Dunn, M. G., 1980, “Nuclear Blast Response of Airbreathing Propulsion Systems: Laboratory Measurements with an Operational J-85-5 Turbojet Engine,” Calspan Advanced Technology Center, Report No. DNA 5268F, Calspan 6484A-1.

[2] Dunn, M. G., Davis, A. O., and Rafferty, J. M., 1979, “Nuclear Blast Vulnerability of Airbreathing Propulsion Systems: Laboratory Measurements and Predictive Modeling,” 6th International Symposium on Military Applications of Blast Simulation, Cahors, France.

[3] Davis, A. O., and Dunn, M. G., 1978, “Blast Induced Distortion Experiments on an Engine Inlet,” Calspan Advanced Technology Center, Report No. DNA 4513F. [4] Dunn, M. G., and Rafferty, J. M., 1982, “Nuclear Blast Response of Airbreathing Propulsion Systems: Laboratory Measurements with an Operational J-85-5 Turbojet Engine,” ASME J. Eng. Power 104, pp. 624–632.

[5] Dunn, M. G., Padova, C., and Adams, R. M., 1987, “Response of an Operational Turbofan Engine to a Simulated Nuclear Blast,” ASME J. Fluids Eng. 109, pp. 121–129.

[6] Tootell, B., 1985, All Four Engines Have Failed, Pan Books, London, p. 208.

[7] “Volcanic Ash Avoidance,” Flight Crew Briefing, 1992, Boeing Co. Customer Training and Flight Operations, Boeing Commercial Airplane Group, Seattle.

[8] Dunn, M. G., Baran, A. J., and Miatech, J., 1996, “Operation of Gas Turbine Engines in Volcanic Ash Clouds,” ASME J. Eng. Gas Turbines Power 118, pp.

724–731.

051001-18 / Vol. 134, SEPTEMBER 2012

[9] Casadevall, T. J. and Thompson, T. B., 1995, “World Map of Volcanoes and Principal Aeronautical Features,” U.S. Department of the Interior, U.S. Geological Survey. Geophysical Investigations Series Map GP-1011 [10] Dunn, M. G., Padova, C., Moller, J. E., and Adams, R. M., 1987, “Performance Deterioration of a Turbofan and a Turbojet Engine Upon Exposure to a Dust Environment,” ASME J. Eng. Power 109, pp. 336–343.

[11] Batcho, P. F., Moller, J. C., Padova, C., and Dunn, M. G., 1987, “Interpretation of Gas Turbine Response Due to Dust Ingestion,” ASME J. Eng. Power 109, pp. 344–352.

[12] Padova, C. and Dunn, M. G., 1991, “Response of an Operational Turbofan Engine to a Simulated Nuclear Dust Environment,” Calspan Advanced Technology Center, Report No. DNA-TR-91-26, Calspan 7170-A-1.

[13] Baran, A. J., and Dunn, M. G., 1993, “The Response of an F-107-WR-102 Engine to a “Most Probable” Nuclear Dust Environment,” Calspan Advanced Technology Center, Report No. DNA-TR-92-111, Calspan 7749-4.

[14] Dunn, M. G., 1991, “Exposure of Airbreathing Engines to Nuclear Dust Environment Volume I - Performance Deterioration of an Operational F100 Turbofan Engine Upon Exposure to a Simulated Nuclear Dust Environment,” Calspan Advanced Technology Center, Report No. DNA-TR-90-72-V1.

[15] Dunn, M. G., 1991, “Exposure of Airbreathing Engines to Nuclear Dust Environment Volume III — Performance Deterioration of Second F100 Turbofan Engine Upon Exposure to a Simulated Nuclear Dust Environment,” Calspan Advanced Technology, Report No. DNA-TR-90-72-V3.

[16] Baran, A. J., and Dunn, M. G., 1996, “The Response of a Third F100-PW-100 Engine to a “Most Probable” Nuclear Dust Environment,” Calspan Advanced Technology Center, Report No. DNA-TR-94-110.

[17] Baran, A. J., and Dunn, M. G., 1993, “The Response of a YF101-GE-100 Engine to a “Most Probable” Nuclear Dust Environment,” Calspan Advanced Technology Center, Report No. DNA-TR-92-121.

[18] Baran, A. J., and Dunn, M. G., 1995, “The Response of a Second YF101-GE100 Engine to a Dust-Laden Environment,” Calspan Advanced Technology Center, Report No. DNA-TR-94-24.

[19] Baran, A. J., and Dunn, M. G., 1995, “The Response of a F112-WR-100 Advanced Cruise Missile Engine to a Dust-Laden Environment,” Calspan Advanced Technology Center, Report No. DNA-TR-94-45.

[20] Baran, A. J., and Dunn, M. G., 1995, “The Response of a Second F112-WR100 Advanced Cruise Missile Engine to a Dust-Laden Environment,” Calspan Advanced Technology Center, Report No. DNA-TR-94-46.

[21] Moller, J. C., and Dunn, M. G., 1989, “Dust and Smoke Phenomenology Testing in a Gas Turbine Hot Section Simulator,” Calspan Advanced Technology Center, Report No. DNA-TR-90-72-V2, Calspan 7170-A-10.

[22] Kim, J., Dunn, M. G., Baran, A. J., Wade, D. P., and Tremba, E. L., 1993, “Deposition of Volcanic Materials in the Hot Sections of Two Gas Turbine Engines. ASME J. Eng. Gas Turbines Power 115, pp. 641–651.

[23] Weaver, M. M., Dunn, M. G., and Heffernan, T., 1996, “Experimental Determination of the Influence of Foreign Particle Ingestion on the Behavior of Hot-Section Components Including Lamilloy,” 41st International Gas Turbine Conference1996, Birmingham, UK. [24] Kim, J. Baran, A. J., and Dunn, M. G., 1991, “Design and Construction of a F100 Engine Hot-Section Test System (HSTS) for Dust Phenomenology Testing,” Calspan Advanced Technology Center, Report No. DNA-TR-159.

[25] Oran, F. M., and Schiff, M. I., 1979, “Design of Air-Cooled Jet Engine Testing Facilities,” ASME International Gas Turbine Conference, San Diego, California.

[26] Dunn, M. G., Seymour, P. J., Woodward, S. H., George, W. K., and Chupp, R. E., 1989, “Phase resolved Heat-flux Measurements on a Blade of a Full-Scale Rotating Turbine,” ASME J. Turbomach. 111, p. 8-19.

[27] Katili, J. A. and Sudradjat, A, 1984, Galunggung, The 1982-1983 Eruption, Volcanological Survey of Indonesia, Director General of Geology and Mineral Resources, Department of Mines and Energy, Republic of Indonesia.

[28] Dunn, M., Padova, C., and Adams, R., “Operation of Gas Turbine Engines in Dust-Laden Environments, in AGARD,” Advanced Technology of Aero Engine Components, Paris, France.

[29] Steere, N. V., 1985, CRC Handbook of Laboratory Safety, 2nd ed., CitionRC, CRC Press, crcpress.com.

[30] Baran, A. J., and Dunn, M. G., 1996, “Indicators of Incipient Surge for Three Turbofan Engines Using Standard Equipment and Instrumentation,” 41st International Gas Turbine Conference, Birmingham, UK. [31] Versteegen, P. L., Dunn, M. G, Drake, J., and Vopatek, A., 1993, “Utility and Uncertainty of P-EARL in Prediction Volcanic Ash Impacts on Commercial Aircraft,” Proceedings of the Cloud Impacts on DOD Operations and Systems Conference (CIDOS).

[32] Baran, A. J., and Dunn, M. G., 1995, “Response Models for the F112, F100, and F101 Turbofan Engines Operating in Dust-Laden Environments,” Calspan Advanced Technology Center, Report No. DNA-TR-95-84, Calspan 8289-1.

[33] Baran, A. J. and Dunn, M. G., 1992, “Response Models for the F101, TF33, and F107 Turbofan Engines to Dust Environments,” Calspan Advanced Technology Center, Report No. DNA-TR-93-124, Calspan 8075.

[34] Versteegen, P. L., Monteith, M. M., Embt, D. J., Singer, H. A., D’Autrechy, D. D., Grote, R. S., and Bruno, J. E., 1993, “P-EARL: An Aircraft Response Model,” DNA-TR-92-183.

[35] Versteegen, P. L., Bruno, J. E., Edwards, R. C., 1992, A’Autrechey, D. D., Frey, D. S., Monteith, M. M. and Singer, H. A., “Multiple Nuclear Cloud Prediction Methods,” DNA-TR-92-51.

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Saab Sensis Corporation East Syracuse, NY SAIC Washington, DC Searidge Technologies Inc. Hull, QC, Canada

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TASC Inc. Chantilly, VA Technical And Project Engineering –LLC (TAPE) Kingstowne, VA TELEGENIX, Inc. Cherry Hill, NJ Telephonics Corporation Farmingdale, NY Tetra Tech AMT Washington, DC Thales ATM, Inc. Shawnee, KS TKO’s-Technical Knockouts East Syracuse, NY UFA, Inc. Woburn, MA

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Advertiser Index

60

Annual Conference and Exposition..................................................................23

C Speed, LLC..........................................................................................................23

ATCA Technical Symposium................................................................................2

NATCA.......................................................................................................................4

Aviation Cyber Security Day..............................................................................37

Raytheon Company...................................................................................Cover 4

B3 Solutions, LLC..................................................................................................35

Telegenix, Inc...............................................................................................Cover 2

Centuria Corporation.............................................................................................6

The Boeing Company.................................................................................... 30-31

Summer 2013

Save The Date!

Mark your calendars for these upcoming ATCA events: ATCA Technical Symposium May 21-23, 2013 Atlantic City, NJ Find more information on this annual event at http://www.atca.org/TechSymposium ATCA’s Aviation Cyber Security Day June 20, 2013 Arlington, VA Register and learn more at http://www.atca.org/cyber 58th Annual ATCA Conference and Exhibition October 20-23, 2013 National Harbor, MD For more information on the conference, visit http://www.atca.org/58Annual

AIR TRAFFIC MANAGEMENT

SAFER SKIES

FROM TAKEOFF

TO TOUCHDOWN. For more than 60 years, Raytheon has delivered the most innovative Air Traffic Management (ATM) solutions. We invented or perfected many of the technologies that form the backbone of today’s global ATM infrastructure, and continue to pioneer training and innovation that provide safe transportation for more passengers than any company in the world. Raytheon solutions will make it possible for initiatives like NextGen to modernize the airspace and enhance customer safety.

See how Raytheon is modernizing air traffic management and enhancing customer safety.

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