Understanding BizAv Avionics: Surveillance

FIGURE 1: Situational awareness for each aircraft relies on the monitoring of the following conditions

The progress of flight crew and ATC integration has advanced to datalink and direct avionics flight information, and to ATC automated systems. From the aircraft perspective, the evolution of aircraft systems (avionics) has been the primary game-changer, and – from a surveillance perspective – has expanded to horizons never imagined in the mid-20th century.

However, keep in mind that pilots are still responsible to see and make final trajectory decisions, based on human surveillance, but now have many system tools at their disposal. These range from sensors, databases, RADAR, pulse transceivers, and collision avoidance (see Figure 2). Having all of these tools visualize their findings on large flat panel displays is also very convenient, making flight decisions easier.

Situational Awareness Conditions

The system tools used by aircraft crews and ATC, monitor different situations of the airspace environment. The situations are diverse involving:

• Weather • Terrain • Airport & terminal environment • Other aircraft • Air Traffic Control monitoring • Own aircraft status, and more…

To be responsible for this much information, pilots are highly trained where safety is the highest goal of vigilance.

Tools for Situational Awareness

The system tools used to monitor and inform airspace situations form several independent evolved technologies. When reviewing an aircraft equipment list as part of a trade, you may not see many of them.

Here are the common avionics considered as fundamental for an aircraft transaction:

• Traffic Alert & Collision Avoidance System (TCAS) • Mode S (Transponders w/ADS-B Out) • Weather Radar • Terrain Avoidance & Warning System (TAWS) • Controller Pilot Data Link Communications – Future Air

Navigation (CPDLC-FANS) • Enhanced Flight Vision System or just Head Up Display (EFVS/HUD)

Reviewing Figure 2, it is apparent there are several other less familiar required and optional system tools for awareness, surveillance and flight performance monitoring. It should be useful to at least discuss these equipage options during an aircraft evaluation or pre-purchase.

System Tools Outlined

Automated vs Manual: There is a delicate balance between automated authority and pilot override. Aircraft manufacturers are keenly aware of human factors inside and the dynamic environment outside of the fuselage.

System tools – mostly avionics – must not compete for attention. Prioritization of information, alerts and responses is integrated into the design of a modern business aircraft.

Colors indicate the level of alert on cockpit displays and primary information is displayed directly in front of, and especially at eye-level, for each crew member to see. Audio alerts occur in both headsets and speakers, overriding other audio in progress.

Standard Fit

Transponder: For years, transponders have been standard fit in all corporate aircraft. Originating from military ‘friend or foe’ identification, the device has slowly expanded its

FIGURE 2: Modern avionics used as system tools to monitor the situations shown in Figure 1

capability to broadcast data sets.

Through several iterations, the Transponder Mode S is providing significant aircraft performance and identification information to other aircraft systems such as ADS-B and TCAS, as well as to ATC.

Radar Altimeter: Sitting in the background of most aircraft is the Radar Altimeter. This is the only system that can provide an accurate height above the ground. Naturally, this is crucial in the airport environment, or close to mountainous terrain (and usually anything below 2,500ft above ground level).

Like the transponder, the Radar Altimeter provides information to other systems – in this case the TAWS, TCAS and directly to the crew.

Weather Radar: Developed during the Second World War, this trusted pilot tool holds pride of place between the pilots. Today, with its multiple colors, ground mapping, precipitation detection, vertical view, and turbulence prediction, it is a very useful awareness and avoidance tool.

Modern radars integrate their display information with other system data on the MFD. Here lightning detection and other related weather can be combined with the radar depiction, all as a background to the route being flown.

Pilots can select navigation waypoints, moving them around inclement weather or turbulence to define a modified flight plan. The position of the newly placed waypoint will be inserted into the active plan during flight.

Stall Warning & Angle of Attack (AOA): While not strictly an avionics function, stall warning and angle of attack are used heavily by the modern aircraft autonomous systems. Apart from pilot presentation, the possibility of an oncoming stall is relayed to various sensors and systems to calculate a stall prediction.

Warnings and alerts are immediately provided to the crew and the flight control (and augmentation) systems to take corrective action.

Emergency Locator Transmitter (ELT): Originating from beacons in boats, emergency locator transmitters have saved many lives, providing a continuous locatable transmission from a crashed or disabled aircraft. The ELT is automatically triggered by a G switch, and is independent of any aircraft system – it has its own battery.

Today’s ELTs, having an additional 406 MHz signal, provide greater user information and last known GPS position to the search and rescue organizations. Regular checks of the battery and functionality are required. This also helps prevent unwanted emergency transmissions.

Evolution from Optional- to Standard-fit: Different manufacturers of both avionics and aircraft arrange their systems in individual ways. The primary avionics manufacturers are Honeywell, Collins Avionics, Thales, and Garmin. Universal Avionics also features across many airframe.

These manufacturers’ avionics form suites by aircraft type, with variations and different options for each model. Surveillance systems are no exception. Be aware that many of the system tools shown in Figure 2 will be optional. Matching up system tools to all the possible internal and external conditions can be a stretch if an aircraft is not fully equipped.

While options are not considered minimum required equipment, they can be very useful when the need arises. For years EFVS was considered a luxury in a busines jet, with many owners settling for the lower-cost EVS as a situational awareness tool.

Within the past few years, aircraft developers have 

THE MODERN INSTRUMENT PANEL, LOADED WITH SITUATIONAL AWARENESS INFORMATION FOR THE CREW. PHOTO COURTESY OF GARMIN AVIONICS.

provided EFVS as standard equipment across many of their models. (Note that the HUD is an integral part of EFVS, and it is rare that a legacy HUD-only aircraft can be upgraded to EFVS, while retaining or upgrading the existing HUD.)

Other systems that are evolving from optional to standard-fit include SVS, lightning detection, electronic fight bags, or integrated flight information and aircraft health monitoring.

Electronic Flight Bag (EFB): Electronic Flight Bags can be considered portable or installed, with the degree of installation a reflection of aircraft integration and level of software. EFBs are strictly for information and not for primary navigation. The aircraft position may be displayed on the EFB during taxi and in flight, if also displayed on a primary aircraft display. There are different operating rules for Part 91, 91K, 125 and 135 operators, so be careful to fully understand how you are permitted to operate your iPad, EFB or integrated display in your own aircraft.

Synthetic Vision System (SVS): Because Synthetic Vision relies on a current database and is not ‘live’, it has been difficult to garner credit for operations using SVS alone. This is slowly changing, thanks to the strenuous efforts of RTCA SC213, FAA, and the avionics and aircraft manufacturers.

The biggest concern has been the depiction of obstacles, and the potential for a database error. When certified as a guidance tool, the synthetic vision is termed ‘Synthetic Vision Guidance System’ (SVGS).

Aircraft Health Monitoring: This relatively new technology comes in all shapes and sizes. For most new business aircraft, it is built into the avionics as a self-check mechanism, alerting the crew with amber and red warnings as failures emerge, and storing a history on memory chips.

However, the growth and future direction involves the communication of health data in real time, and the ability to monitor non-avionics aircraft systems, with RFID devices or other means.

Recording: Some health monitoring systems are complex, and will store significant amounts of data. The Quick Access Recorder (QAR) is one storage method, and is currently a popular upgrade for aircraft. Aircraft engine manufacturers find the QAR very useful.

The aircraft Digital Flight Data Recorder (DFDR) and Cockpit Voice Recorder (CVR) have a shared surveillance purpose to maintain a semi-permanent record of aircraft performance for post flight/incident analysis.

Meanwhile, the parameters of the DFDR have dramatically increased and the CVR can now record data, as well as voice. For those adding FANS to their aircraft, as an upgrade make sure the CVR is modified or capable of recording both voice and data.

Note that some recording systems are combined as CVDFR, where voice, data and aircraft performance are all monitored in the same unit. Also, because DFDR’s need to be integrated into many complex aircraft systems that differ from aircraft to aircraft, most include a Flight Data Acquisition Unit (FDAU). This is a separate device from the recorder itself.

Newer Surveillance as an Operational Requirement

Systems such as ADS-B Out and CPDLC-FANS are operational dependent. ADS-B Out is pretty much required everywhere, while FANS is currently tailored for Oceanic/Remote operations.

Flight tracking can be achieved with the emerging SpaceBased ADS-B Out, but already there are several novel and low-cost non-ADS-B aircraft tracking systems on the market. These will track, then relay an aircraft’s global position 

continuously. Disappearing aircraft should be much less of an occurrence in the future.

Aircraft Collision Avoidance System (ACAS-X)

In Europe, ACAS-X is the future of TCAS II. This ‘other aircraft’ collision alert and avoidance tool comes in different flavors, with light aircraft systems termed TCAS I or, in a different form, TAS.

The lower cost TCAS I and TAS systems display other traffic and provide useful intended flight path information. However, TCAS II predicts future path and directs the pilot as to the action to be taken, helping avoid aircraft impact.

The latest version of TCAS II is 7.1 and is required for aircraft operations in Europe and for some operators in Mexico after December 2021. The progression of TCAS II to ACAS-X is a sensible step, however, and involves minimal changes to the aircraft’s equipment and antennas.

ACAS-X uses probabilistic modelling, enabled by advancements in electronics and software since the days of TCAS II development. As with TAS and TCAS, there will be variants, reflecting the emergence of new airspace users, including:

• ACAS-Xa: For general purpose users. • ACAS-Xo: A later version, planned for specific users on closely-spaced parallel runways and other restricted spacing maneuvers. • ACAS-Xu: For unmanned, remotely piloted aircraft. • ACAS-Xp: A future passive system relying solely on ADS-

B data while not interrogating other aircraft. This is targeted for General Aviation on the continued assumption they will not require a TCAS-II or ACAS-Xa later.

In Summary

As with Communication and Navigation, Surveillance is a vast topic reaching into communication with FANS and Navigation via GPS, as well as tapping many other aircraft primary systems.

With the impending arrival of additional unmanned, remote pilot, and eVTOL platforms, there will be many additional airspace users. Surveillance will be subject to greater vigilance, where margins for error will tighten. Other airspace users, such as growing air carriers, and eventually supersonic aircraft, will present new challenges.

The one outcome of more people flying will be reduced airspace spacing. Parallel runway and in-trail spacing will rely on new features of ADS-B and the soon to arrive ACAS-Xa, along with version -Xo, to sense potential conflict.

This article has not touched on cybersecurity, which can be considered surveillance of a different kind. While advancements of technology are further developed to accommodate less available airspace and more user groups, they need to laser focus on protections from electronic and human interference, where vulnerabilities will exist in both hardware and software. ❙

KEN ELLIOTT

has 52 years of aviation experience focused on avionics in General and Business Aviation. Having a broad understanding after working in several countries on many aircraft types and avionics systems, he has contributed to several work groups and committees, including for NextGen, Airport Lighting, Human Factors, Unmanned Aircraft and Low Vision Technology. In retirement, he is striving to give back the knowledge gained with an eye on aviation’s future direction.

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