CONTACT! ISSUE 83 PAGE 1
By Patrick Panzera
PO BOX 1382 Hanford CA 93232-1382 United States of America 559-584-3306 Editor@CONTACTMagazine.com
Volume 14 Number 6 Mar-Apr 2006
Issue #83 MISSION CONTACT! Magazine is published bi-monthly by Aeronautics Education Enterprises (AEE), an Arizona nonprofit corporation, established in 1990 to promote aeronautical education. CONTACT! promotes the experimental development, expansion and exchange of aeronautical concepts, information, and experience. In this corporate age of task specialization many individuals have chosen to seek fresh, unencumbered avenues in the pursuit of improvements in aircraft and powerplants. In so doing, they have revitalized the progress of aeronautical design, particularly in the general aviation area. Flight efficiency improvements, in terms of operating costs as well as airframe drag, have come from these efforts. We fully expect that such individual efforts will continue and that they will provide additional incentives for the advancement of aeronautics. EDITORIAL POLICY CONTACT! pages are open to the publication of these individual efforts. Views expressed are exclusively those of the individual authors. Experimenters are encouraged to submit articles and photos of their work. Materials exclusive to CONTACT! are welcome but are returnable only if accompanied by return postage. Every effort will be made to balance articles reporting on commercial developments. Commercial advertising is not accepted. All rights with respect to reproduction, are reserved. Nothing whole or in part may be reproduced without the permission of the publisher. SUBSCRIPTIONS Six issue subscription in U.S. funds is $24.00 for USA, $28.00 for Canada and Mexico, $40.00 for overseas air orders. CONTACT! is mailed to U.S. addresses at nonprofit organization rates mid January, March, May, July, September and November. Please allow time for processing and delivery of first issue from time of order. ADDRESS CHANGES / RENEWALS The last line of your label contains the number of your last issue. Please check label for correctness. This magazine does not forward. Please notify us of your date of address change consistent with our bimonthly mailing dates to avoid missing any issues. COPYRIGHT 2006 BY AEE, Inc.
It started out as a simple e-mail, introducing myself and asking for an article on their prop. The people at Carter Aviation Technologies were very responsive and helpful. I wasn’t looking for a article for this issue, but I had not completed the cover story when they offered me a story on their CarterGyro Demonstrator/Trainer. I couldn’t pass up the offer. As I began to work with Carter, the more I learned, the
more I wanted to know, and one thing leading to another, I scrapped the entire layout I was working on and began putting together this; the all Carter issue. One of the articles has been written in the futuretense, as we wanted the article in Continued on page 21
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Update: The CarterCopter and Its Legacy Rod Anderson of Carter Aviation Technologies brings us up-to-date on the current state of the record-breaking, ill-fated CarterCopter demonstrator aircraft.
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PIREP: Flying the CarterGyro Demonstrator/Trainer AKA CGD/T Carter Aviation Technologies’ test pilot, George D. Mitchell gives us the rundown on preflight and the operation of their new demonstrator.
10 Is the AeroTwin Engine in the CarterGyro’s Future? A brief look at the new AeroTwin engine and how it may end up powering the CarterGyro. By Greg Lynch 11 Carter’s High Performance, Hollow-blade Propellers An in-depth look at the unique propellers being developed by Carter, include ing construction techniques, ground test and flight tests, as well as data spreadsheets. By Jeff Lewis and Claudius Klimt 18 Carter FutureFlight-I, April 2-5, 2006 To showcase the everyday utility of their newest VTOL technologies, Carter is planning a demon stration flight from Atlanta, GA to Sun 'n Fun, using the CarterGyro to visit the same places along the way that we would visit using an auto mobile on the same trip. By Anita C. Infante 22 NASA Personal Air Vehicle (PAV) Challenge -- Postponed or Canceled? Rod Anderson looks at the NASA general aviation con test announced last summer and how it led to the creation of Carter’s newest aircraft design. 25 New 2+2 “CarterCopter” Announced It hasn’t stopped with the CarterCopter. Carter Aviation Technologies has been working behind the scenes and is ready to unveil their new focus; a CONTACT! Magazine exclusive. By Jeff Lewis On the cover: George Mitchell practicing 20-ft takeoffs and "stop & drop" landings in the CarterGyro Demonstrator/Trainer (CGDT) at Wichita Valley Airport, Wichita Falls, Texas, on 9 March 2006. This photo, along with several others throughout this issue are courtesy of Mark Robinson, Carter's mechanical technician
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By Rod Anderson CarterOne@cableone.net Rod Anderson is the fifth person to fly in the CarterCopter, and flew right seat for several weeks in May 2001 as flight test engineer. He was first to propose the CarterCopter flight simulator -- which he prototyped in cooperation with X-Plane software creator, Austin Meyer. Rod serves as Carter’s VP of Marketing and resides in Prescott, Arizona. The remains of the CarterCopter Technology Demonstrator (CarterCopter or CCTD) are stored in an airport hangar in Texas. I have not seen them. I have only seen photos of the June, 2005, crash, but to my knowledge, the photos have never been released. No one was hurt, and most of the aircraft remains intact. If the aircraft had not landed in a large patch of mesquite trees, it could probably have been repaired. After long deliberation, it was decided that the money needed to rebuild the CarterCopter would be better spent on prototyping and flighttesting a new aircraft, which would incorporate everything learned from the 7-years of flying the CarterCopter.
mph with an impressive L/D ratio of 7:1. To put this accomplishment into perspective, it took 44 years from the first manned flight to break the sound barrier, 66 years to put a man on the moon and 102 years to break the mu-1 ratio. The rotorcraft curator at the Smithsonian NASM has expressed an interest in the CarterCopter on several occasions. The CarterCopter proved that the a notional study conducted by Georgia Tech, a national Rotorcraft Center of Excellence, was correct. The study proposed that SR/C aircraft had the potential for high-speed performance, with an operational envelope exceeding that of fixedwing aircraft and helicopters. The report cautioned that slowed-rotor dynamic considerations could be the limiting factor. On its last flight before the accident, the CarterCopter clearly demonstrated that its slowed-rotor dynamics are not a limiting factor by breaking a rotorcraft record established 49 years ago by a US Army experimental SR/C aircraft called the McDonnell XV-1 Convertiplane, shown below.
The beginning, middle and end to the saga of the CarterCopter, as a flying test-bed, has been written. The eventual ramifications of the technology it helped pioneer will determine its place in the history books. Once slowedrotor/compound (SR/C) aircraft are a common sight, then hopefully a museum, large corporation, or wealthy individual will fund the cost of rebuilding the CarterCopter so it can be put on permanent display in a major museum. It was the first to achieve the mu-1 ratio, which it did at 170
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The record was for an engineering term called mu-ratio, which has direct bearing on the total drag produced by a rotorcraft's rotor. The mu-ratio of any rotorcraft in flight is determined by simply dividing the rotorcraft's forward airspeed by its rotor-tip speed relative to the aircraft; generally, the lower the mu-ratio, the higher the rotor RPM and drag. We all know that if we lower the total drag on a car, it can go faster and farther on less gas. The same is true for rotorcraft. Helicopters normally fly at low mu-ratios of 0.3 and suffer very high rotor drag -which results in low airspeeds and ranges. The CarterCopter flew with a stable rotor at an amazing mu-1.0, breaking the XV-1's previous record of mu-0.95. Of special importance is that the flight test data indicates the technology used to break the record should routinely permit SR/C aircraft to fly at mu-2 ratios or higher. Low rotor RPM and drag will permit speeds of 400 mph or better in addition to unrefueled ranges of 2500 miles
For additional information on the accomplishments of the CarterCopter and the accident that followed, look for the hyperlinks under the photo of the CarterCopter on the front page of the Carter web site, http://www.cartercopters.com/. The website provides a tail camera video, strip chart data, a review of the events, and additional flight-test findings.
A LITTLE MORE ON MU Mu is the English spelling of the Greek letter μ. It can be pronounced "mew" or "moo," with "mew" being the most prevalent. It is commonly used to represent a ratio in rotorcraft engineering, sometimes called the rotor tip advance ratio. To put it about as simply as it can be put into words, the μ ratio is the ratio of the forward speed of the aircraft to the rotor tip speed relative to the aircraft. To put it into a picture, which is worth a thousand words:
All Carter SR/C aircraft can take off and land vertically. Travelers will need much less time to travel point-to-point than they need today when flying in fixed-wing aircraft. In the near future, the small wings and the slowly turning rotor of a Carter SR/C aircraft will be the recognized hallmark of efficient, high mu-ratio flight. Vertical takeoffs and landings combined with safe, fast, and affordable air travel will become an everyday part of aviation and the true legacy of the CarterCopter. Someday, before the CarterCopter is rebuilt for museum display, I'd like to take the cabin "egg", the landing gear and the remains of the high-inertia rotor on tour to show people some of the Carter technology that insures survivability of an aircraft's occupants when something goes terribly wrong. If nothing else good comes from the accident, it proved Jay Carter’s point that aircraft can be designed to be safe -regardless.
IMPORTANT FINDINGS FROM THE CARTERCOPTER’S MU-1 FLIGHT:
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The CarterCopter demonstrated stable mu-1 flight, something no rotorcraft had done before. The pilots reported that the aircraft flew so smoothly that no vibration or sound indicated they were in a rotary wing aircraft -much less one flying at 170 mph at a mu of 1. • The CarterCopter achieved a lift to drag ratio (L/D) of 7:1 at 170 mph; comparable to GA fixed-wing airplanes and much better than conventional rotorcraft. • L/D increased as airspeed increased -- from 100 mph up to the maximum speed of 170 mph achieved during this flight. The trend indicates that it would have continued to increase at least a little, at higher airspeeds. • The increase in L/D with airspeed was due to the wing coming out of a deep stall, which also caused flow separation on the lower aft section of the fuselage. Both of these high-drag conditions can be corrected in future SR/C aircraft. • The L/D achieved at 170 mph exceeded that of Carter's initial performance estimates calculated years previously -- showing that the initial estimates were conservative.
Where Vtip is the tip speed of the rotor, VA is the speed of the aircraft, and μ is the mu ratio. In hover, μ is equal to zero. As the rotorcraft flies faster, μ increases. The airspeed of the advancing blade increases and the airspeed of the retreating blade decreases. When μ reaches a value of 1.0, the retreating blade of the rotor has reversed airflow over its entire length. It has long been believed that above a certain tipspeed ratio, somewhere below 1, a rotor will become unstable. The highest tip-speed ratio ever achieved by a helicopter was 0.8 on the Lockheed Cheyenne compound attack helicopter prototype. The McDonnell XV-1 SR/C autogyro was μ champion and achieved a μ of 0.95 during flight tests, until 49 years later by the CarterCopter, another SR/C autogiro, which achieved a μ of 1.0 during routine flight tests on June 17th, 2005. Rod Anderson
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By George D. Mitchell Test pilot for Carter Aviation Technologies George has over 3000 hours of rotorcraft time, most of which was acquired as a USAF helicopter instructor and later as a civilian instructor. He owns a KB-2 autogyro, similar in size to the CarterGyro. He also owns what is probably the world’s only slowed-rotor/compound (SR/C) ultralight aircraft, a Quicksilver MXL Sport ultralight combined with the rotor from his KB-2. He calls it the “Kittyhawk”. George admits there is no practical use for the aircraft except having fun. He resides in Cloudcroft, NM. When Carter Aviation Technologies (Carter) asked if I’d like to fly their new 1place autogyro, I wondered how much I should offer to pay them. Somehow it didn’t seem right to get paid for having so much fun. This PIREP should help answer some of the questions pilots have after seeing the aircraft and watching it perform.
Video clips of George Mitchell piloting the CarterGyro can be seen on the Carter web site at www.cartercopters.com
The CarterGyro is a new flying experience. From the moment you first glimpse the machine, you suspect something great is about to happen in the gyro world. As you approach, you begin noticing features totally unlike anything found on typical 1-2 place gyros. The most obvious new feature at this point in its development is the Carter scimitar propeller located between the engine and the tail assembly. It's a beautifully crafted, hollow-blade composite prop with an exceptionally wide chord, giving it lines like a shark's fin. The Carter high-inertia rotor that will soon be added is even more futuristic looking than the prop. When it is installed by the later part of May 2006, it will provide 4-times the lift of the metal rotor blades now used. The following preflight inspection is offered for readers who hope someday to fly a CarterGyro. Others may find it equally interesting if they were ever curious about rotorcraft. Although the numerous procedures listed seem complex at first, they can be easily learned and will become fewer and more user-friendly as the technology is refined. The CarterGyro was created to demonstrate that VTOL gyro flight can be safe, practical and community friendly for the average pilot.
PREFLIGHT INSPECTION Begin and end on the left side of the seat by going clockwise around the aircraft. First and foremost, all switches
should be in the off position. Start by ensuring the 4 toggle switches located on the top of the throttle lever (explained in detail later) are positioned towards the front of the gyro. Locate the power master-switch below the pilot's seat on the left side and make sure it is in the “off” rear position. Later in the inspection you can rotate the prop knowing it is safe to do so. ♦Check the seat fuel tank to ensure you have an appropriate fuel level, a tight filler cap, and no obvious leaks around the tank or the fuel line connection under the seat. ♦Move the pilot's control stick to check for secure and free control linkage connections and for the correct corresponding movement of the rotor head. ♦Check the control cable connections to the rudder and the front wheel. ♦While moving the pedals full left and right, check for appropriate movement, binding, and excessive play in the rudder and nose wheel.
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The engine is a 2cylinder, 2-stroke, 65 HP Rotax 582 made in Austria. As with any engine used for flying, it demands a careful inspection for loose bolts or wiring. ♦While still on the right side of the gyro, make sure the radiator is full by checking the liquid level in the small transparent tube along the top Although many features of the of the engine. CGDT are unique, the engine is Opening the cap is an off-the-shelf, liquid-cooled, 2stroke, 65 HP Rotax a “no-no”. ♦The rudder cables must be positioned on the guide pulleys and not frayed and the rudder must move freely side-to-side without binding or excessive play. ♦Check for cracks at the junction of the rudder and horizontal stabilizer. Check the tail wheel for proper rotation. The nose gear is straight out of the bicycle industry, with the tire and wheel from a BMX and the fork from a mountain bike. ♦The CarterGyro nose wheel is many times larger than what is found on most gyros -- to provide excellent handling on soft surfaces and high grass. It must be properly inflated, rotate freely and the wheel strut extended to the correct position. ♦Lift the nose wheel off the ground until the gyro is resting on its tail wheel and check where it bolts to the frame while moving the nose wheel side-to-side. Also, check for play at the other attachment points for the steering system along the full length of the gyro. ♦The battery must be secure in its nose mount and the wiring harness from the battery to the instrument pod must be tight. ♦You are now on the right side of the gyro. Take a good look at the Carter landing gear assembly, which has humongous energy absorbing capability with 14 inches of free travel at the wheel. It will prevent a pilot from bending an axle in a hard landing. See photo to the right. ♦Check the right wheel and hydraulic brake for good rubber and no leaks. ♦At the top of the mast behind the pilot seat, check the rotor head and rotor hub bolts for security. Rotate the rotor at least one full turn and walk out each rotor blade while checking for damage. ♦While rotating the blades, check the pre-rotator drive belt for sound condition and tightness. ♦Next wipe down the rotor blades with a wet rag to remove all dust and bugs that might have collected since the last flight. It’s worth the extra effort for optimum gyro flight performance.
Although it may appear like a typical aluminum tube, the strut mounted between the wheel axle and the engine mount is a state-of-the-art shock absorber good for handling loads that would destroy a “normal” gyro. This photo also gives a good view of the propeller that’s featured in another article later in this issue.
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You’re now on the left side at the Carter prop. The prop hub is an important part of the aircraft’s jump-takeoff capability. It is an automatic, 2-position prop controller for near zero pitch during prerotation, then full pitch for takeoff and cruise. ♦Make sure the prop is secure to the hub and the blade-pitch-control flyweights are in the correct position with all linkages secure. ♦The left main wheel strut assembly must look as good as the right gear did. ♦Check the left side of the engine, including the new pre-rotator system. The CarterGyro has a belt and idler clutch drive from the engine accessory drive to a 90° gearbox. A tubular, telescoping drive shaft goes from the gearbox up to the rotor-head belt drive gear reducer. Added together, these components give the gyro a 10:1 reduction from engine RPM to rotor prerotate RPM. The 65 HP engine can deliver 35 HP to the rotor prior to take-off, only because the prop is in near zero-pitch during this time. Otherwise, this much HP would be impossible. If the belt and clutch system looks OK, stand back and give the gyro one final “look-see”.
PRE-START PROCEDURES The CarterGyro is a flying broomstick. Step #1 is to remove anything you find in your open pockets, or count on it to dribble out during your flight and chip that magnificent prop. ♦Put on your helmet, which helps muffle engine noises, and unbuckle the seat belt. ♦Carefully stow the seat belt along the airframe toward the nose wheel. The belt is long enough to get into the prop if it gets loose. ♦Stand on the right side of the pilot’s seat. ♦Ensure that the four switches located on the end of the throttle control are in the forward “flight” position. ♦Now move the first switch marked "C" for clutch, to the aft position. This is a master control switch for the other switches on the throttle control. ♦Do the same for the second switch marked "B" for brakes. This routes all hydraulic pressure to the main wheel brakes and, at the same time, activates an inline, one-way check valve in the main brake line. The “brake handle” at the top of the pilot's control stick controls a hydraulic fluid reservoir. Use the handle to pump up the brakes until the system “locks” under pressure from just one hand.
ENGINE START Place the throttle control in the full aft position, then hand-prime the fuel system with the in-line fuel handpump until fuel stops flowing in the clear fuel line. On the first start of the day, the engine will also require at least two pumps on the engine primer. ♦Check that your instruments on the instrument pod are reading accurately for a power-off condition. ♦Reach over the seat and move the power master switch to the forward “on” position. ♦Check your instruments again to ensure they have become active and read correctly. ♦Move the throttle control forward until it is one-quarter inch off the stop.
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♦Call "prop clear" and check the area. ♦Grasp the engine start lanyard located at the top of the mast and pull briskly downward. If the engine is adequately primed and is tuned properly, it will start but run roughly. ♦Immediately adjust the throttle to obtain 1800 RPM and the engine should smooth out.
ROTOR PRE-ROTATION Move the “B” brake switch on the throttle control to the aft position and pump up the brakes again. ♦When finished, turn slightly and look up at the rotor head. Adjust the pilot’s control stick, if needed, until the pre-rotator’s telescoping drive shaft is aligned with the belt drive reducer input pulley. If this shaft is not in alignment during pre-rotation, torque loads will feed back through the control stick linkage and vibrate the controls excessively. Look closely and you can see that George has the ♦Once you start pre-rotation, the front tire off the ground. control stick cannot be moved fore and aft to reposition the drive shaft TAXIING because the torque tubes lock up Get seated, buckle your seat belt under load. and adjust your goggles or glasses ♦Now advance the throttle to 2200 while you let the engine warm up. I RPM. can attest that getting a bug in ♦Move the third switch marked "P" your eye at 70 mph is quite painfor pre-rotate on the throttle control ful. to the aft position. ♦When the engine is ready to go, ♦Carefully and slowly begin pumpgrip and compress the brake haning the brake handle with full dle with your right hand and restrokes while watching one rotor lease the hydraulic brakes with blade tip. The pumping will cause your left thumb by pushing the “B” the pre-rotator system to begin brake switch forward on the throtengaging. tle control. Braking can now be ♦When you see the rotor blade tip controlled manually with the brake begin to move, start watching the handle. engine RPM indicator while slowly ♦Advance the throttle as necesadding more pressure to the brake sary to taxi to your takeoff position handle. Your objective is to slowly facing into the wind. In the near accelerate the rotor RPM while future, your driveway will be all keeping the engine RPM above you need in most cases. 1800. ♦When you reach a point where Rudder pedal movement will not the rotor RPM will not increase cause the nose wheel to turn until without bogging the engine RPM the pedals are pressed nearly to below 1800, add a little more throttheir limit. This allows for full rudtle each time you increase brake der deflection before any nose wheel movement occurs. This de- The brake hand grip serves a dual func- handle pressure. sign, combined with the in-line tion. In addition to actuating the brake ♦With the pre-rotator drive in corcastering nose wheel, works great system, it is used to engage the pre- rect alignment, there will be no buzz or heavy vibration in the confor cross wind landings. rotor clutch.
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trol stick. When the rotor and engine join together above 1800 engine RPM, the brake/ clutch pump can be pumped up to 200 psi on the instrument pod gage. At this pressure, the pre-rotator clutch will not slip, and engine RPM can be slowly increased to 3500 and full throttle. With the current rotor blades, the gyro will now begin to lift up in a nose low attitude, extending the landing gear struts and trying to skew to the right. That's all the pre-rotation you can do. It's time for lift off.
TAKEOFF With your left thumb, toggle the “P” pre-rotate switch on the throttle handle to the forward position. Listen for the engine to increase in RPM; this is your signal that the clutch disengaged. ♦Immediately toggle the “B” brake switch forward to release the brake, and move the cyclic control stick to the full aft position. You are in for a thrilling ride. ♦As soon as the engine RPM increases above 3500, the 2-position prop automatically changes over to cruise pitch and full engine power kicks you in the pants. Depending on the headwind, lift-off will occur in 10 to 20 feet of roll. Lift-off usually happens as quickly as you can manage to pull the control stick into the full aft position. Once the new Watching the videos on the Carter website is pretty amazing. Carter rotor is installed, zero-roll takeoffs with This photo was shot maybe 1 second after the brakes were rejumps 50-ft or higher will be possible. On lift-off, leased and the craft rolled only a few feet forward. you must push the cyclic control forward as necUse your rudder pedals to keep the essary to maintain proper climb out aircraft pointed into the wind. If there attitude. You’re now riding an “upis zero forward airspeed due to a noelevator”. Best climb is around 40 wind condition, most gyros will demph. From this point, the CarterGyro scend with the nose down about begins flying about like any other nine degrees. In such situations, you small 1-2 place gyro, with good cruise must raise the nose of the gyro a at 60 mph. little just before touchdown. This attitude adjustment will place the LANDING gyro’s center-of-gravity over the It's when you enter your final apmain wheels and prevent the aircraft proach to an upwind landing site that from pitching fore or aft and hitting the CarterGyro shows you the future hard on the nose or tail wheel. The of vertical flight. A steep or shallow landing gear, with the shocks fully angle approach with flare before landextended, will absorb all the "g" ing is not necessary. You simply fly loads of landing with about the same over to the spot where you want to impact on the pilot as dropping into a land, such as your driveway or the recliner at home. The much higher parking lot at a truck stop, and slow to lift of the new Carter rotor will make zero ground speed -- then cut the most such gyro landings even more power. Your resulting landing apuser friendly, regardless of wind conproach will be vertical like a glass ditions. Like trying to eat just one elevator with a view in all directions. potato chip -- you will find that doing This “stop and drop” landing is a rush! just one “stop and drop” landing is First time is a real gut wrencher beimpossible. You can’t even wipe the cause you just know you are going to crash. Keep the faith and steer the The “stop and drop” landing tech- smile off your face. It’s just too much vertical descent directly to your land- nique can only be described as is a fun. George D. Mitchell rush! ing spot using the cyclic control stick.
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Height: 83.75 inches (1/4" shy of 7 ft) from the bottom of the keel to the top of the rotor head. Length: 11 ft 10 inches. Width: 7 ft 10 inches – outside of wheels. Landing gear: provides a 14-inch vertical stroke and was tested to 3600 lbs and 6 G of impact without failure. It is able to absorb 1000 fpm vertical impacts -- decelerating the aircraft at a constant G with no energy remaining at the bottom for a rebound. Engine: Rotax 582 - 64 HP @ 6500 RPM, at MSL. Propeller: 60-inches, produces 325 pounds of static thrust at 5882 engine RPM (59.6 HP). During subsequent static ground tests, using a Corvette engine, the prop was run in cruise pitch briefly to 3890 RPM (tip speed Mach .915). It required 273 HP to spin the prop at 3800 RPM. The maximum RPM the prop should ever see in normal operation is 2650, which would occur at full throttle in a 100 mph dive. Rotor: current 23-ft diameter will be switched for 26-ft version to compensate for the increased weight of the larger fuel tank added for the SnF trip. Both rotors are Dragon Wings manufactured by Rotor Flight Dynamics www.rotorflightdynamicsinc.com Fuel tank (pilot’s seat):
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125 lbs - 20 gals of gas. 670 lbs - total MGW.
Normal instrumentation: Hydraulic pressure gauge. Airspeed and altitude indicator. Digital tach (engine) and hour-meter. Rotor tach will be installed along with new Carter rotor in May 2006. Engine exhaust and water coolant temperature
Instrumentation added for the Atlanta-SnF trip:
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175 lbs - test pilot with flight suit and helmet.
Range: 150-200 miles (see comments below).
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370 lbs - CarterGyro with 26 ft rotor.
Cruise speed: 60 mph.
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GPS. 2-way communication with chase crew
Original gyro kit:
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By Greg Lynch
Carter tank: 21 lbs - holds 23 gals (125 lbs with 20 gal).
Max gross weight (MGW):
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Original: 8 lbs - held 7 gals (43.75 lbs).
Monarch Butterfly. Cost $16,000 in 2004.
Manufacturer: The Butterfly, LLC www.thebutterflyllc.com/.
On 10 March 2006, the CarterGyro was flown from Wichita Valley Airport (8 miles NW of Wichita Falls) to Olney, Texas and back to Wichita Falls, landing outside the Carter office. During the 90 miles roundtrip, the aircraft burned about 5.5 gals going (flying into a headwind) and 3.5 gals returning -- for an estimated 10 mpg fuel burn.
Greg recently retired from the USAF, after logging more than 2,500+ hours in helicopters. He purchased and is building the Butterfly kit (previously mentioned) for use as his personal gyro. Greg is VP of Grinchworks LLC and a long time Carter shareholder. He resides in Woodbridge, Virginia.
Carter has proven its prop, rotor, and landing gear technology during 8-years of flight testing. With the right engine, the CarterGyro is positioned to lead a revolution in the use of small, efficient autogyros for safe and practical VTOL transportation. One outside development Carter is closely watching is the joint project between The Butterfly LLC and Grinchworks LLC to integrate and flight-test a beta production copy of the new aerobatic AeroTwin engine on a Butterfly kit gyro. The engine, manufactured by AeroTwin Motors of Henderson, Nevada, was designed in New Zealand and is US produced with final fabrication taking place in Ft. Worth, TX. www.aerotwinmotors.com The engine is an amazingly simple and reliable in design. The dry-sump air-cooled 2-cylinder, 4-cycle engine dynos at 69 HP @ 93 ft-lbs of torque. Max torque is produced at a little over 4,000 RPM. For cooling at high power settings and low forward speeds, a conformal carbon fiber plenum with a belt driven axial blower sucks cooling air past the cylinders. This makes it ideal for use in a pusher configuration. The AeroTwin also promises sea-level power output equivalent to the out of production Rotax 618, but because it’s turbocharged, 4-cycle and digitally controlled, it should maintain rated power at altitude and be twice as fuel efficient. We hope to prove this in instrumented flight tests this summer. One final note; the AeroTwin engine can be configured to rotate in either direction and can be mounted either horizontally or vertically. Look for a detailed article on this engine in a future issue of CONTACT! Magazine Greg Lynch
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By Jeff Lewis and Claudius Klimt Jeff is a design engineer working for Carter. He was the lead in developing the complex spreadsheet programs that permit the design of new propellers in a reasonable time. He is also lead programmer for the Carter X-Plane based flight simulator, configuring it to research high-µ flight in preparation for prototyping and flight-testing new Carter SR/C aircraft. Jeff resides in Wichita Falls, Texas.
and soft in the flatwise direction, allowing the blades to bend or “cone” when they develop thrust or to “flap” as needed to reduce gyroscopic loads when the aircraft’s direction changes.
Claudius is an ER doctor at the Greater Baltimore Medical Center. He has been an active shareholder in Carter since 1999 and has taken the lead in finding a company to manufacture Carter propellers. Last year he completed a 6-year project to build an AirCam from a kit, and has since flown the AirCam more than 200 hours. Claudius dreams of someday equipping it with two Carter propellers. Carter Aviation Technologies (Carter) is a small research and development company known for pioneering and flight-testing a number of advanced concepts. Among these is a revolutionary propeller design that is stronger, delivers significantly improved performance and yet weighs much less than other propellers designed for use on the same aircraft. To date, Carter has designed, fabricated, tested and flown three different size propellers; a 28-inch diameter propeller for a 30 HP engine, a 60-inch propeller for a 65 HP engine, and a 100-inch propeller for a 400 HP engine. All three propellers were built using the same procedures -- demonstrating that the technology is fully scalable. The result is a family of propellers unsurpassed for beauty, light weight, quietness, strength and high performance. As an R&D company, and not a manufacturer, Carter hopes to find partners with expertise in precision composite manufacturing to help make this technology available to the aviation community.
PITCH CHANGE PROCESS The blade shells are torsionally very stiff, permitting them to be rotated (without deforming) about the spar centerline in order to adjust pitch. When this happens, the torsionally soft spar inside the blade shells is twisted between the spar hub and the point where it attaches to the blade at the 3/4 radius. The x-shaped piece seen in the photo is used only to support the spinner. The rectangular bar seen behind the x piece is used to rotate the blades by way of links and ball joints at the bar and the blade pitch horn attachment. The bar is mounted on a 1.375” dia. tube that extends through the propeller drive shaft and slides in and out on Teflon bearings. This tube is attached to a hydraulic cylinder on the end of the propeller shaft that is pressurized by engine oil pressure and controlled by a spool valve operated by a computerized controller or by manual override.
PROPELLER DESCRIPTION The amazingly low weight of the propellers comes from the fact that the two carbon composite blades are hollow shells at the root section. A carbon composite spar with an "I" beam shaped cross section extends from blade tip to blade tip inside the two shells. This continuous "I" beam spar is connected at its center to the propeller drive shaft, then extends outward to approximately the 3/4 radius in both directions (through the blade shells) before it attaches to the blades. The further from the center the "I" beam spar extends, the narrower it becomes until the top and bottom caps of the "I" beam finally come together at the attachment point for each blade. The spar then continues from the attachment points to the blade tips. The "I" beam spar is stiff in the edgewise direction
PROPELLER PITCH MECHANISM A weight-arm extends from the round root cuff of each blade to the otherwise empty space inside the spinner (see illustration, next page), and is located 90° to the blade's dynamic center-of-mass. This weight-arm balances the pitch moment caused by the centrifugal force trying to force the blade's dynamic center of mass to the propeller plane of rotation. The addition of this arm greatly reduces the moment required to control the propeller pitch and makes the moment nearly constant throughout the entire pitch travel. The spar can be twisted ± 25° (50° total) as installed in the propeller. It was proof tested at ± 40° at 3 times its max centrifugal force in a special pull fixture.
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Propeller pitch mechanism, viewed from the side: Flat pitch, mid pitch, full pitch. Illustration by Mat Recardo.
ELECTRONIC CONTROL SYSTEM The electronic control system measures RPM and torque (horsepower), air temperature, thrust, and airspeed (Note: Carter has developed a special true airspeed indicator, which can measure speeds as high as 500 mph, but is still sensitive enough to differentiate the airflow at 4 and 5 mph on the ground). Based on this information, the controller then calculates the RPM needed for optimum efficiency and changes the propeller pitch to obtain this RPM. Propeller efficiency is calculated and displayed in the cockpit to allow optimization of the RPM and pitch setting. This computerized controller does more for propeller efficiency than solid state ignition and fuel injection did for internal combustion engine efficiency. In the event that one of the controller input sensors should fail, the controller will signal an alarm, go to the backup sensor and continue to function. In the unlikely event both sensors should fail, then the controller will hold an RPM based on certain assumptions. The pilot can at any time go to manual control and use the propeller efficiency display to fine tune the RPM for maximum efficiency.
MAXIMUM EFFICIENCY AT CRUISE SPEED AND ALTITUDE The blades use a 25% thick airfoil at the root which allows the root to operate at very high angles-of-attack at low forward speeds without stalling. At the tip the thickness drops to 10%. The root fits very close to the spinner to reduce root losses due to the air spilling over the edge. The blade chord increases from the tip to the root
to accelerate the air nearly uniformly over the full diameter, (uniform acceleration is the most efficient way to generate thrust). The blade twist distribution is a compromise between low speeds and the predetermined max cruise speed where the aircraft will spend most of its time. By sacrificing just a small amount of efficiency at cruise speed, Carter is able to greatly improve thrust at low speeds and statically, which is what’s needed for quick acceleration. For max efficiency, it is important to match the propeller design to the engine and predetermined cruise speed and altitude. For example, if the aircraft was designed to cruise at 300 mph at 30,000 feet then the propeller's blade twist needs to be less severe than one designed for 400 mph. This less severe twist would slightly improve propeller efficiency for all speeds lower than the 300 mph cruise speed (when compared to the 400 mph propeller design). This improved efficiency would manifest itself by slightly improved static thrust for the same HP. Propeller efficiency will suffer if the aircraft is flown faster than the cruise speed for which the propeller was designed.
4-BLADE PROPELLER Two of the 2-blade propellers can be combined to make a 4-blade propeller. The system was purposely designed to provide this flexibility. To make a 4-blade propeller, a second set of blades is installed behind the first set. The control bar is then changed to a cross configuration so there are 4 points at which to connect the control rods that go to the blades.
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95%- 40.2” from edge of cuff 95%
85%- 35.4” from edge of cuff “Fanned out” spar bonding area
85%
75%- 30.6” from edge of cuff 75%
65%- 25.8” from edge of cuff 65%
55%- 21” from edge of cuff 55%
45%- 16.2” from edge of cuff 45%
35%- 11.4” from edge of cuff 35%
ABRASION AND NOISE In order to handle rain impact, a nickel or stainless steel abrasion strip is bonded to the leading edge of the blades in a molded-in groove. The choice depends on the calculated top forward speed of the propeller in flight. To achieve a low-noise profile, the tip of the blades is shaped like a shark's fin to increase the critical Mach number. The fact that the propeller controller limits blade tip speeds to Mach 0.85 at full horsepower regardless of forward speed also helps produce a very quiet-running propeller.
PROPELLER DESIGN Carter propellers are designed and analyzed using a combination of Carter proprietary programs and traditional hand analysis. The performance of the propellers is analyzed using blade element theory, where the propeller is broken into several elements, the performance calculated for each element, and then summed together to get the performance of the propeller as a whole. Calculations are based off of standard aerodynamic theory,
using lift and drag coefficients for the airfoils used. The program accounts for induced velocity, propeller sweep, and drag rise due to compressibility. However, the propellers are designed such that compressibility effects are small. The design of these propellers is a complex process that includes many important considerations and compromises. It is often said that a propeller is a rotating wing. While this is true in principle, when actually analyzed, it quickly becomes apparent that the process for analyzing a propeller is much more involved than doing the same for a wing. For example: the thrust the propeller produces is dependent on the airflow into the propeller, but the airflow into the propeller is affected by the thrust. As the Wright brothers once wrote on this subject, “With the machine moving forward, the air flying backward, the propellers turning sidewise, and nothing standing still, it seemed impossible to find a starting-point from which to trace the various simultaneous reactions.” (Century Magazine, September 1908) Continued on page 16
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Prop Performance Analysis User Specified CL. See below L/D See below Dia. in. 99
Prop coeff. lift Assumed Lift to Drag Prop Diameter (in.)
Calculated VI VB=VA+VI RTP
91.83 91.83 964.23
Increase in average velocity through prop (ft/s) Total average velocity through prop (ft/s) Resultant tip speed (ft/s)
SP. IN.
Spinner Diamter (in.)
AREA
48.65
Actual swept area of prop (ft )
29.7
3
2
ρ M VA RPM HP # Blades
0.0023769 1116 0 2222 391 2
Air Density (slug/ft ) Airspeed of Mach 1 (ft/s) Airspeed of Aircraft (ft/s) Prop RPM Engine HP Number of Blades
L
Mtip θ φ A B
34.65 0.8640061 See below See below See below See below
Blade length (in.) Mach numer at tip Angle of drag to lift component based on given L/D (deg) Blade angle of attack based on given CL (deg) Calculated constant (see notes) Angle of the resultant airflow relative to the plane of the prop rotation
μ γ
3.737E-07 8.0294726
Viscosity (slug/ft-s) Prop Twist
C chord span
See below See below See below
Calculated constant (velocity , see notes) chord at blade section (in.) span of blade section (in)
S Thrust
See below See below See below
reference area of blade section (in ) Thrust of each blade section (lbs) Calculated efficiency
η
%R 1 0.95 0.85 0.75 0.65 0.55 0.45 0.35 0.25 0.15 0.05
VA Ttotal HP η AC Span AC chord IHP Fig of Merit k (static only)
R 49.50 47.03 42.08 37.13 32.18 27.23 22.28 17.33 12.38 7.43 2.48
0.00 1,950.03 391.00 0 31.24684 1.6615461 325.58132 0.8326888 8.9321226
chord actual 6.800 10.179 14.562 15.746 16.881 18.062 19.521 22.800 0.000 0.000 0.000
span 4.95 4.95 4.95 4.95 4.95 4.95 4.95 4.95 4.95 4.95 49.50
S 50.39 72.08 77.94 83.56 89.41 96.63 112.86 0.00 0.00 0.00 582.87
CL 0.55 0.42 0.50 0.69 0.82 0.87 0.93 1.05 1.14 1.13 0.63
VI assuVI calc VI Error 0 0 39.43 39.429 82.37 82.366 99.1 99.105 110.3 110.29 111.7 111.65 111.8 111.81 98.12 98.121 0 0 0 0 0 0
L/D Compressi Corrected L/D CD subsonic bility CF 0.01 61.04 1.00 61.04234 0.01 46.94 1.00 46.94451 0.01 53.06 1.00 53.05702 0.01 68.25 1.00 68.24687 0.01 75.37 1.00 75.37303 0.01 75.59 1.00 75.58992 0.01 75.59 1.00 75.59292 0.01 70.64 1.00 70.63812 0.02 70.94 1.00 70.93885 0.02 70.59 1.00 70.59365 1.66 0.38 1.00 0.381585
θ 0.94 1.22 1.08 0.84 0.76 0.76 0.76 0.81 0.81 0.81 69.11
2
2
φ 1.48 0.38 -0.57 0.18 0.73 1.43 2.50 5.87 9.03 9.03 74.03
φ+B 1.48 2.86 5.20 8.03 10.76 13.38 17.03 22.17 9.03 9.03 74.03
Θ norm actual -6.55 -5.17 -2.83 0.00 2.73 5.35 9.00 14.14 1.00 1.00 66.00
Mapp Mdd 0.70 0.36 0.70 0.42 0.67 0.63 0.63 0.58 0.60 0.54 0.58 0.47 0.55 0.40 0.52 0.27 0.52 0.22 0.49 0.13 0.56 0.04
Mcr
Mdd
φ> 20º M 0.86 0.82 0.73 0.65 0.57 0.48 0.40 0.31 0.22 0.13 0.04
Sweep Sweep req act 41.58 65.53 34.06 59.50 28.40 30.90 22.44 26.15 0.00 17.84 0.00 11.73 0.00 -0.84 0.00 -30.26 0.00 0.00 0.00 0.00 0.00 0.00
0 0 0 0 0 0 0 0 0 0 0
Even the CarterGyro has done time in the “pit”.
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A 7.89E 6.02E 7.16E 9.88E 1.16E 1.24E 1.33E 1.50E 1.63E 1.61E 9.07E
E-05 E-05 E-05 E-05 E-04 E-04 E-04 E-04 E-04 E-04 E-05
The 100" Carter prop mounted to the LS6 powered portable test rig.
The 100" Carter prop being test on the CarterCopter.
B 0.00 2.48 5.77 7.85 10.03 11.95 14.53 16.29 0.00 0.00 0.00
ωR 959.84 911.84 815.86 719.88 623.89 527.91 431.93 335.94 239.96 143.98 47.99
2
C (vel ) 921,283.41 833,012.95 672,411.35 528,043.64 401,406.58 291,153.97 199,062.02 122,485.00 57,580.21 20,728.88 2,303.21
FR per C with sweep blade 158,069.66 214,580.13 37.6102 495,079.92 147.591 425,478.31 189.363 363,731.99 204.547 279,120.32 178.605 199,019.23 148.208 91,381.14 89.5948 57,580.21 0 20,728.88 0 2,303.21 0
Thrust Thrust per whole VI Blade prop Area (ft2) assumed 0.00 10.6912 0 37.5319 75.06 10.1567 39.4293 146.537 293.07 9.08755 82.3655 187.192 374.38 8.01842 99.1046 200.928 401.86 6.9493 110.292 174.229 348.46 5.88018 111.65 142.967 285.93 4.81105 111.813 85.6314 171.26 3.74193 98.1213 0 0.00 2.67281 0.00 0 0.00 1.60368 0.00 0 0.00 0.53 0.00 1,950.03 53.46
VB
Determinan 0 0 39.42929 6218.676 82.36553 27136.33 99.10462 39286.9 110.292 48657.34 111.6501 49862.94 111.8129 50008.51 98.12126 38511.13 0 0 0 0 0.00 0.00
VI calc 0 39.42929 82.36553 99.10462 110.292 111.6501 111.8129 98.12126 0 0 0.00 652.78
Thrust cal Thrust cal frm VI ass frm VI cal Airfoil 65-410 400.4703 75.06374 75.06374 65-411 748.5007 293.0749 293.0749 65-613 794.6629 374.3844 374.3844 65-715 766.4526 401.8559 401.8559 65-817 656.5222 348.4571 348.4571 65-819 537.938 285.9335 285.9335 65-821 367.163 171.2628 171.2628 65-823 0 0 0 65-823 0 0 0 65-825 0.00 0.00 0.00 0 4,271.71 VI*A
HP per Blade
HP whole prop
4.022082 26.109801 37.424031 43.451954 37.716006 30.679392 16.096734 0 0 0
8.0441639 52.219603 74.848062 86.903908 75.432012 61.358785 32.193467 0 0 0 391.00
Θ 1.479 2.859 5.199 8.029 10.759 13.379 17.029 22.169 9.029 9.029 74.029
Although full power is never applied, even the little 28” prop feels the wrath of the 400 hp LS6 engine.
RPM-controlled pitch change mechanism for the 60" prop.
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By Anita C. Infante OSACpresident@bwsys.net Anita is Carter's most experienced PR person, focusing on Carter's general aviation marketing and licensing requirements. She also works for large national companies at EAA fly-ins, the Reno Air Races, and other major aviation events. Anita devotes much of her time to the Organization for Sport Aviation Competition (OSAC), which is a public charity whose primary purpose is to support and provide educational programs to the general public. Following the CarterCopter's accident in April 2003, OSAC teamed with Carter to create the Mu-1 Member's Club, www.cartercopters.com/members_club.html which aided in the aircraft's restoration and led to its µ-1 record. Anita resides in Kewanee, Illinois. For decades man has been involved in a quest to create a true Personal Air Vehicle (PAV) – a way to stick wings on an automobile and make it fly. When the first viable only one prototype, so its systems were constantly being rotorcraft was introduced in 1923 a whole new generatested, re-tested, improved, and then tested again. In the tion of PAV-wannabes began to slide off the drawing seven years that the original protoboards. Since that time millions of dollars have been spent trying to de- The Small Business Technology type was flown its only public flight velop an aircraft that combines the Transfer (STTR) Program awards was in 2002. In order to broaden visivertical take-off and landing capabili- contracts to small business con- bility for our technology, Carter made ties of a helicopter with the high- cerns for cooperative research and the decision to downscale our next speed efficiency of a fixed-wing air- development with a non-profit re- demonstrator and build more protocraft. The ultimate goal is to gain per- search institution (RI), such as a types. In 2004 Carter released a desonal control and escape the bounda- university. The goal of the Con- sign for a two-place, PAV under a ries of traditional airports. With the gress in establishing the STTR pro- NASA STTR award in cooperation introduction of the newest prototype gram is to facilitate the transfer of with Georgia Tech (see the artistic and PAV design from Carter Aviation technology developed by an RI rendering by Mat Recardo on page Technologies (Carter) man’s vision of through the entrepreneurship of a 27). They are now ready to prototype personal flight is at hand. small business. The small business a revised PAV design. As a first step, and its partnering institution are the CGDT has undergone flightAfter making aviation history by required to sign an agreement on testing and is set to preview Carter’s breaking through the µ-1 barrier in how intellectual property will be plan for improved personal flight. June of 2005, Carter Aviation Tech- shared between them. The newest Carter demonstrator is a nologies is about to prove the validity somewhat standard tube-frame autoof our unique aviation technology in gyro, (pictured above and on the cover) but with the the ‘real world’ with the introduction of the first Carteradded Carter Landing Gear and Carter Propeller, it has Gyro Demonstrator/Trainer (CGDT). much improved safety and performance features, including the ability to do very short take-offs and drop-in landCarter’s original prototype (the CarterCopter) was the ings. These technological improvements allow the CGDT proving platform for all of our research and development to act more like an automobile than an aircraft. In looks, in slowed rotor/compound (SR/C) aircraft technology for the CGDT resembles what one might think of as an aemore than a decade. It was an impressive, five-place rial motorcycle. aircraft. However, as a very small company, Carter had
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FUTUREFLIGHT-I Carter believes that aircraft based on its patented SR/C Aircraft Technology will eventually replace the family car for trips over 200 miles. To prove our point, we are planning “Carter FutureFlight-I.” The flight plan is from Atlanta, GA to Tampa, FL with the final destination the Sun ‘n Fun Fly-in at Lakeland, FL. The flight is scheduled to leave Atlanta on April 3, 2006. When fully developed, Carter’s PAV technology will allow a small, fourplace aircraft to be parked in your garage and you will be able to takeoff on a vacation trip from your own driveway or yard. You will be able to stop for fuel at an automotive gas station, visit a restaurant for lunch and spend the night at a hotel by landing on their air vehicle ramps next to their auto parking lots. Carter FutureFlight-I is going to showcase this capability. The CGDT will leave from a hotel in Atlanta and then “drop-in” at gas stations, restaurants, attractions and other hotels along the flight path. We want to demonstrate a typical family vacation trip. To our knowledge, this will be the only aircraft flight of this kind ever made and should bring our technology to the forefront in the public eye and in our own industry. Our technology has been proven with more than seven years of very stringent flight-testing, but with only one public flight during that time people think that our technology is still a fantasy. We need to prove that it is real.” Carter FutureFlight-I is planned as an educational tour as well as a means to publicly demonstrate our technology. A preview of Carter’s technology and the CGDT will take place at a demonstration to be held at the Georgia Institute of Technology on Sunday afternoon, April 2nd at 2:00 PM on campus at the Rose Bowl Field. The demonstration is sponsored by the School of Aerospace Engineering with coordination through Dr. Daniel Schrage, Director of the Center of Excellence in Rotorcraft Technology at the institute. Georgia Tech is one of only three universities in the country to be designated a Rotorcraft Center of Excellence.
Map by Mat Recardo
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Continued from page 16 Carter used the knowledge accumulated from its successes and failures to develop a very powerful spreadsheet for the aerodynamic analysis of propellers. On the previous two pages are one part of that spreadsheet, showing some of the factors that are analyzed. This is an iterative program which uses a finite element approach. As mentioned on page 13, the propeller is divided into multiple sections for analysis, and the thrust and drag are calculated at each section. The thrust at each section determines the induced velocity, or “propeller-wash,” which in turn affects the performance. Small changes are made to the initial conditions until a solution is found. From the drag calculation, the propeller’s power can be determined. This analysis uses the standard lift and drag curves as a starting point for the performance at a section. The effects of wing sweep are also taken into account. Compressibility effects are also determined where the velocity over the sections gets higher and exceeds first the critical Mach number and then the drag divergence Mach number. Flat plate theory is used to predict the section performance for conditions where the sections are operating at extremely high or low angles of attack, well beyond the stall angle, where very little measured performance data exists. When designing a propeller from scratch, the first step is to make an initial selection of the airfoil (or airfoils) that will be used, and then using those airfoils, determine the theoretically best planform and twist for the propeller. (See the illustration on page 13) The theoretical “best propeller” will be different for different flight conditions, and even with the use of composites would be impossible to build. So the next step is to come up with a compromise planform and twist that can actually be constructed. A series of iterations then follows; slightly changing the planform, the twist, and the airfoil for each selection until the best compromise is found for the range of conditions in which the propeller will be operated. As the aerodynamic design iterations are nearing completion, the structural design can begin. Carter developed a separate finite-element-based spreadsheet for the structural analysis, which incorporates the aerodynamic loads calculated in the performance spreadsheet found on the previous page.
The propeller construction tools shown in the photos below are for the 60-inch propeller now flying on the CarterGyro. A large market should exist for this propeller since it will work on a majority of autogyros and ultra-lights flying with 65 HP engines. The main requirement is that the engine turns the propeller counter-clockwise when the viewer is standing at the front of the aircraft and looking towards the tail. The 60-inch propeller can probably be extended to 65-inches without much effort -- for use on aircraft able to take the larger diameter (the larger the diameter, the better the efficiency). The next Carter propeller will be 76 inches and designed for 200 HP at 2500 RPM. It will be used on Carter’s new 2+2 Personal Air Vehicle (PAV). The same technology will someday be used to design and build propellers as large as 24-ft in diameter for heavy lift transports and “propeller-rotors” for use on high altitude airships (HAA) -- such as the Dynalifter by Ohio Airships. www.ohio-airships.com
www.aerialaspectphoto.com The Dynalifter is a heavier-than-air, twin engine, prop-driven, tri-foil aircraft. Half the gross weight of the aircraft is carried by helium, the other half is by way of traditional aircraft aerodynamics.
PROPELLER CONSTRUCTION The “hand-built” experimental method of construction used by Carter is optimized to permit the incorporation of design changes, if design weaknesses are discovered during the R&D process. However, the method is labor intensive, requiring 60+ man-hours per propeller. Carter believes the process can be simplified and the build-time greatly reduced by using modern composite materials and manufacturing processes. Construction methods optimized for mass production should be able to decrease the labor to 15 to 20 hours per propeller. A production propeller could be made using prepreg instead of the current wet lay-up, which would make the propeller even lighter and stronger than the current Carter version.
Spar molds halves and a completed spar.
CARBON SPAR The spar for the propeller is built in an aluminum mold that comes apart in pieces to release the spar. The tip is splayed over a foam core. The unidirectional carbon fibers are pulled through a resin bath and into the mold.
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Tip of spar mold halves and tip of a spar. One half of the fibers are laid over one side of the foam tip plug and the other half are laid over the other side of the foam tip core. A top piece of aluminum mold is used to compress the fibers and eliminate the excess resin. Special attention is focused on assuring that all fibers remain parallel and straight in the lay up and curing process. The spar then gets several circumferential windings of carbon in specific places to hold the fibers in place. One propeller blade skin mold with the blue tape for the nickel abrasion strip.
PROPELLER SKINS
PROPELLER BOLT ATTACHMENT BLOCKS Next blocks are built up of fiberglass layers to a fixed thickness and machined to exact dimensions. Holes are drilled and threads are cut. Steel inserts are glued into the threaded holes. These three blocks are then glued to the center section of the spar. The propeller bolts go into the steel inserts.
The propeller skins are a wet lay up of carbon cloth. The mold has a tape placed where the leading edge nickel wear strip will be glued in later. Then there are 6 pieces of 3/16� honeycomb that are placed in specific areas on the inside of the carbon outer shell. The location of the pieces of honeycomb is very specific. It involves measuring from specific points on the rim of the mold. The wetted carbon is squeegeed prior to application over the open honeycomb so that the honeycomb does not fill with resin. The skins with the honeycomb are vacuum bagged and cured in the integral oven. The position of the honeycomb needs to be exact so that the spar and the ribs can fit between the honeycomb onto the skin at their exact places. There are a total of 7 ribs or shear webs and one spar that must be glued into place after the skin with its honeycomb is complete.
RIBS AND SHEAR WEBS The ribs, shear webs and the spar are bonded to one skin in exact locations between the places where the honeycomb is placed. The exact locations are defined by measurements from hard points on the mold. The second skin is prepared like the first and then the two halves are mated. The initial glue-up is performed with a plastic barrier to clearly define an exact glue line. The two halves are separated and any extra glue that has run onto the spar or ribs is removed. One propeller skin then has the attachment for the pitch link glued in place. The plastic barrier is then removed and the two halves are bonded with a very thin layer of glue. The same procedure is done with the other blade. Continued on page 23
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PAV 2+2 ANNOUNCED Carter plans to release the design of our new PAV to the public during the Georgia Tech demonstration. (CONTACT! Magazine readers are the first to read about the PAV in detail, as an exclusive. ~Pat) Jay Carter, Jr., Carter’s President and Chief Engineer, comments, “Releasing our new PAV design at Georgia Tech seemed like a natural progression. The engineering team there was instrumental in documenting the increased performance of our technology and the original PAV design. They were able to document cases where our technology will show improvement over conventional aircraft designs.” Dr. Schrage has supported Carter’s efforts for some time as an emerging technology. His expertise in rotorcraft has been helpful to Carter in our development process. Dr. Schrage expressed his thoughts, “To be viable, a PAV is going to have to be quiet, flexible, economical, easy to use and above all safe. Carter’s technology is the only currently available technology that can meet all of these criterion.” After the Georgia Tech demonstration, Carter will then regroup at the Hampton Inn-Atlanta Southlake in Morrow, GA for a more public demonstration later on Sunday afternoon. The flight plan for the public demonstration will be between the Hampton Inn Hotel and the Sunoco Gas Station in Stockbridge, GA. The CGDT will have a pre-flight check and then take-off from the hotel parking lot and fly to the Sunoco station as if to be fueled. The aircraft will then take-off from the gas station and return to the hotel to land for the night. A brief flight demonstration will take place at each business location so the public will actually be able to view the flight in person.
FUTUREFLIGHT-I, DAY ONE The actual x-country flight will begin early on Monday morning, April 3rd. The first leg of the flight will recreate the take-off from the Hampton Inn and fly to the Sunoco Gas Station to fuel for the flight. The flight will then continue south on I-75 and down to Americus, GA, where a technology demonstration will be given at South Georgia Technical College (SGTC). The technology demonstration at SGTC is being sponsored by the Aerospace Engineering College. The college is the first technical college in the country to incorporate NASA’s Aerospace Academy into their curriculum. Sparky Reeves, SGTC’s President, commented on Carter’s visit, “SGTC has a rich history of aviation dating back to Charles A. Lindbergh. That proud past, combined with the opportunity for SGTC to be able to touch the newest aviation innovation, goes hand-in-hand with our mission to motivate students to pursue careers in science, technology, engineering and mathematics, through the implementation of SGTC’s new NASA Aerospace Education Lab in the Griffin B. Bell Aerospace building.” The NASA Academy allows grade school and high school students the opportunity to gain hands-on experience in a wide variety of aviation related fields. The college also offers courses in Aviation Maintenance, Avionics Maintenance and Structural Aircraft Technology. The CGDT demonstration is planned for the college students and local school students.
What family vacation would be complete without a restaurant stop? The final Georgia stop for the Carter crew after a long day will be at the Longhorn Steakhouse in Tifton, GA where the CGDT will drop–in for dinner. Flight demonstrations are planned from the restaurant parking lot. Tifton community plans for the demonstration include working with the local schools to get technology information to students. Longhorn Managing Partner, Todd Cook, explains their reason for supporting Carter FutureFlight-I, “Longhorn Tifton is always looking for ways to support our community. I feel like the flight of the CGDT will bring interest into the community of Tifton. As one of the top three technological cities in Georgia, this will be a wonderful event for our town.” After the demonstrations the CGDT will be tucked back into its trailer to make the evening drive to the Florida destination.
FUTUREFLIGHT-I, DAY TWO April 4th, will start in Gainesville, FL where the flight will begin at the Best Western Gateway Grand. The hotel is just off of I-75 outside of Gainesville in a location very suitable for future PAV stops. Next to the hotel is Gainesville Harley-Davidson and Buell. The CGDT has been referred to as an aerial motorcycle so a “By Land and By Air” demonstration is planned with a few local Harley owners. The CGDT will then travel to an attraction stop at the Florida Museum of Natural History on the University of Florida Campus. The museum has an extensive exhibit area and a newly opened Butterfly Rainforest exhibit. A brief tour of the museum is planned before leaving Gainesville and heading south to Tampa. Day two will end along the waterfront at the Sailport Resort where the flight plan will bring the CGDT in along Olde Tampa Bay – something even the family automobile can’t do. The hotel’s support for Carter’s effort is expressed by George Hoch, Sailport’s General Manager, “Sailport Resort at Rocky Point in Tampa is proud to be part of this grand step into the future of travel. We are delighted to be a showcase ‘landing site’”.
FUTUREFLIGHT-I, DAY THREE The final day of the trip, Wednesday, April 5th will, again, begin with a brief public flight demonstration at the resort and then the flight plan will take the CGDT around Tampa and east along I-4 to Lakeland, FL where Carter will showcase our technology at the Sun ‘n Fun Fly-in. Carter has an exhibit area in Choppertown and will be making two daily flight demonstrations along the main air show runway. Carter also has a Sun ‘n Fun Forum planned to discuss our newest developments and upcoming plans for the new PAV. The Forum is at 10:00 AM on Sunday, April 9th in Forum Tent 10.
SOUNDS SIMPLE ENOUGH... Carter FutureFlight-I sounds simple when explained in a few short paragraphs on paper. The logistics were to find demonstration areas about 100 miles apart with businesses that had ground area to accommodate landing operations (50 feet x 50 feet) and enough clear area around the ground devoid of fences, trees and power lines to gain altitude on takeContinued on page 22
CONTACT! ISSUE 83 PAGE 20
Switch On! continued from page 3 this issue, but the events written about haven’t happened yet. The release of the magazine should coincide with the events outlined, making the story extremely relevant at the time of publication, but a bit awkward to read down the road. We certainly wish Carter well with this endeavor and pray for the safety of all who are involved. We were a bit leery about yet another issue completely devoted to a single topic, but there were so many branches to this story that we just couldn’t help it. In a discussion with Associate Editor, John Moyle, he told me, "I'd like to believe that our audience is broad and inquisitive enough to enjoy our technical content regardless of the topic. An occasional venture into ‘all one aircraft, it's power, and it's systems’ is appropriate when the target has so much to offer in new and interesting material; in fact, to do less would be a violation of our mission.” ...and I agree with John. I would certainly like to thank all who were involved with getting me the material to print in our magazine, with a special thanks to Rod Anderson who was highly instrumental in the process, and who probably spent as many sleepless nights as I have in the past few days.
FUTURE AEROTWIN ARTICLE On page 10 you’ll find a little blurb on a fascinating little engine. The people at Carter brought this engine to our attention, and we plan to do a complete article on it, to be published in a future Iissue. In this same fashion, we would encourage you to bring engines or other items of interest to our attention. We are always on the look-out for interesting topics to feature.
ALTERNATIVE ENGINE ROUND-UP We mentioned in the last issue that we will be hosting a “grass roots” type of fly in, at the airport in Jean, NV, the last weekend in April. April 28-30, 2006 to be exact. We hope to see you there. Details can be found on our website, www.ContactMagazine.com or in the event that you don’t have issue #82 or the internet, just give me a call. (559) 584-3306
ROBERT J. COLLIER TROPHY We’d like to congratulate Eclipse Aviation for winning this year’s coveted trophy, but while meaning no disrespect toward Eclipse, we have to question the motives of the Trophy Selection Committee’s decision to award the trophy to them. This stems from the fact that the Criteria for awarding the trophy clearly states that it will be presented “...for the greatest achievement in aeronautics - with respect to improving the performance, efficiency, and safety..." and "...which has been thoroughly demonstrated by actual use in the previous year” These are very specific requirements, yet in the declaration of the winner, these terms are not used. Instead we have "... the selection committee’s criteria included recognition of the rich heritage of the Collier Trophy", and
“...the spirit of entrepreneurship, technical innovation, and the impact on American aviation,” exemplified by the Eclipse 500. Was the selection committee not given the stated criteria, or did it choose to ignore them and instead substitute criteria of their own? Take the requirement, "...for the greatest achievement in aeronautics...". In what way does the Eclipse 500 stand head and shoulders above the rest of the Very Light Jet (VLJ) field, the Adam A700, ATG Javelin, or Cessna Mustang, all flying or in certification testing? The selection committee went on to say, "Perhaps the company’s [Eclipse] greatest contribution is making jet technology available to a larger segment of the population." Eclipse Aviation is not alone in this; as shown before, there are other companies that have entered the VLJ category, and have airplanes flying. The committee continues: "With an acquisition cost onethird of today’s small jets and the lowest operating cost per mile of any jet, the Eclipse 500 provides the lowest jet costs ever achieved." But that has yet to be proven in actual commercial operation! The Eclipse 500 is still an experimental aircraft, in the certification testing phase. In my opinion, these claims will only be borne out once the aircraft is given FAA certification and has entered into service. Until then, these are only claims, and subject to the typical company press-release embellishment. We’re certainly not saying that anyone is being less than truthful, but just how many of us have ever actually experienced the claims of an aviation engine or airplane, especially one that’s experimental? Considering all this, the winner declaration also does not substantiate the requirement "... thoroughly demonstrated by actual use in the previous year." It seems to me that with the awarding of one of this nations most prestigious aviation trophies to a company which has not yet proven the commercial viability of its aircraft, even with the large number of pre-certification orders, the NAA has put its reputation and integrity in concert with this airplane's acceptance. If this company and its aircraft fail to live up to its promises, as did the Beechcraft Starship, or the Vjet and Safire VLJs, or even go into financial failure (which we certainly don’t wish on any company), as have so many in the past, that would definitely not bode well for the credibility of NAA and its administration of the Collier. I would not be at all surprised if others, too, express this same concern to the committee, (and to the world at large) their opinions on the award being presented to Eclipse Aviation. I think it is very controversial at the least. Maybe in the future, the Criteria could be changed to simply "...awarded annually for the greatest achievement in aeronautics or astronautics in America, in the opinion of the Collier Selection Committee.” In this way, there are no specifics that could be points of discussion by critics. ~ Patrick Panzera
CONTACT! ISSUE 83 PAGE 21
Continued from page 20
By Rod Anderson off (50 feet x 100 feet). The natural place to look was along the I-75 corridor where large truck stops abound, hotels are out in the open and restaurants are situated at every exit, but it became a tedious task to explain the concept over and over as local managers who were excited about the opportunity were turned down because corporate management was afraid there might be some liability. I suppose revolution and change always meet with resistance. We have certainly seen that as Carter makes attempts to release its technology into the aviation industry. But, change always comes and it is the visionaries who usher in progress. I think of our supporters as visionaries. These are the people who will begin to think about planning for a transportation revolution as their businesses expand or to change their curriculum before it becomes outdated. Without the support of these few educational facilities and businesses this flight would not be possible. Carter indeed owes them credit and a tremendous amount of gratitude for their support. The depth of understanding of Carter’s supporters is evidenced by comments from two of the hotel managers. “Our hotel staff is excited to support the FutureFlight-I effort. We understand how important it is to be innovative and to stay ahead of the crowd.” Rachel Ewert, Director of Sales, Hampton Inn-Atlanta Southlake. “We at the Best Western Gateway Grand are excited to be a part of the family vacation of the future and anxiously await what this new mode of travel will mean for the tourism industry.” Rebecca Neville, Director of Sales. Carter was also supported by Gulf-Coast Avionics in Lakeland, FL who provided equipment for the flight. Carter’s main purpose for the development of the CGDT is to provide a demonstration platform and training vehicle for future Carter designs. According to Jay Carter, Jr., “This newest prototype will demonstrate our very basic technology. Then each additional prototype will showcase improved developments. The most impressive will be our 2 – 4 place Personal Air Vehicle. Ultimately, the landing gear strut, propeller and eventually the rotor on the CGDT will be fitted to the PAV. Plus, the CGDT will be a good flight-training platform for our future aircraft since its flight characteristics will be similar.” Since some elements of the PAV will have been flight-proven on the CGDT Carter expects to have the PAV prototype ready for flight-testing in early 2007. Carter believes its PAV will revolutionize transportation not just the aviation industry. When it does family vacations will never be the same. For More Information on Carter visit: www.CarterAviationTechnologies.com
Rod is an active Carter shareholder who would like to see Carter develop a low cost, tandem VTOL SR/C gyro, produced throughout the world for personal aerial transportation, much like motorcycles are used for ground travel. Rod resides in Prescott, AZ. General aviation (GA) enthusiasts were excited last summer when NASA and the Comparative Aircraft Flight Efficiency (CAFE) Foundation, www.cafefoundation.org, announced their intention to pursue the first aeronautical competition in the Centennial Challenges program. The Personal Air Vehicle (PAV) Challenge would award annual prizes totaling $250,000 to the teams that could best design, develop, and demonstrate technology improvements in various GA aircraft capabilities. Two $25,000 awards would be for technology developments that minimized aircraft noise, inside and outside the aircraft. $50,000 would be awarded for the best handling qualities and overall ease-of-use. The remaining $150,000 was for the team whose aircraft demonstrated the best overall flight performance measured in a calculated score that included door-to-door trip velocity, energy consumption, and passenger carrying capability. Congress voted to make the prize money available each year for 5 consecutive years, beginning in 2006. The announcement came shortly after the CarterCopter’s accident in 2005. Carter decided to prove its technology and gain worldwide publicity by entering a new slowed-rotor/compound (SR/C) gyro designed specifically for the contest. Thus was born the tandem “Carter Model-A”, (pictured on page 27) with the race version named the “Carter Challenger-1 (CC-1) racer”. It was designed to “quietly” carry 400-lbs of useful load 300 miles at 130+ mph, while achieving 27.5+ mpg. An improved version, the CC-2, would compete in the 2007 race, cruising at 200+ mph by flying at higher µ-ratios and higher altitudes with lower drag. Carter’s challenge was to scale down and simplify the CarterCopter’s technology in the short time remaining until the first race in mid-summer 2006. Following the initial media flurry, little more was said by either NASA or CAFÉ. Inquiries to CAFÉ revealed that funding had not been provided to conduct the contest and they were having difficulty raising the funds. NASA, to my knowledge, has not announced whether the contest has been delayed or canceled. The good news is that the R&D effort spent on the CC-1 provided new design ideas that were used for the very similar looking 2+2 PAV announced in this issue of CONTACT!
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Continued from page 17
The molds for the ribs and shear webs. The nickel abrasion strips are then glued onto the leading edges of both blades in the recess created by the tape in the mold. The final step is to paint and balance the propeller. The Carter composite technicians can usually build the two propeller blades so expertly that balancing the blades requires only an extra coat of paint on one half of one blade.
The test rig is powered by a Chevrolet LS6, good for 400 HP, and is operated in a “pit” for safety reasons. Shown above is the 100” Carter prop powered through a 2.5:1 ratio redrive.
PROPELLER TESTING Proof testing a new Carter propeller design is always dramatic. The 60-inch propeller, which was designed for 65 HP, was powered with 273 HP on the test stand, causing the airflow over parts of the skin to approach the speed of sound. The propeller produced 16% more static thrust on 92% of the HP when compared to a traditional fixed-pitch climb propeller. The complete 60-inch propeller in the ground adjustable version weighs 10.5 lbs with the 2-position prop-pitch controller attached. The following discusses the testing of the 100-inch Carter propeller designed to absorb 400 to 600 HP as a two bladed design and 800 to 1,200 HP as a four bladed design. The same procedures were used to test the smaller 60-inch propeller and 28-inch propeller. The propeller shown being tested below weighs 34 lbs by itself and 40 lbs with the pitch-change mechanism. Its diameter at rest measures 99.5-inches, but this diameter changes slightly as the propeller pitch changes.
GENERAL METHODOLOGY
Although the 60” prop was designed for 65 HP, Carter ran the prop direct-drive on the 400 HP LS6 test stand. Most other tests were with the redrive.
The propeller was tested on a specially designed test stand. Torque was measured by mounting the engine on a support bracket, free to pivot at one end, and mounted on a load cell at the other end. Knowing the moment-arm from the pivot to the load cell, the torque was easily calculated from the load. Engine RPM was measured using the Carter computer. Propeller RPM was calculated from
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engine RPM, factoring the reduction drive. Engine horsepower was calculated from the torque and engine RPM. Propeller thrust was measured using a bracket that carried the entire thrust load from the propeller. The bracket used a hydraulic mount, such that the pressure was measured to determine thrust.
accelerating the air (not the same as how much power you are producing). A F.O.M. of 1 is the maximum possible. η is efficiency, defined as the ratio of horsepower being produced to the horsepower being put into the propeller (η = T*V / Pavail ). η is also limited to 1. Note that as airspeed goes to zero, η also goes to zero, by the definition of power (thrust * velocity).
TECHNICAL RESULTS The propeller produced 1,900 lbs of static thrust at 2,222 RPM and 391 HP (note: engine RPM was 5,555 in order to make the HP). The pitch was 9.7º. This compared quite closely to the values calculated by Carter’s analytical program, which at the same horsepower and RPM, predicted that the propeller would produce 1,881 lbs of thrust and be at 9.9º of pitch. This is only a 1% difference in thrust values. The actual figure of merit for the propeller (defined as induced horsepower over shaft horsepower) was 0.826. At a lower RPM and power setting, the propeller produced 1,203 lbs of static thrust at 1,778 RPM and 180 HP. The pitch was 10.2º. For the same horsepower and RPM, Carter’s analytical program predicted 1,113 lbs of thrust at 8.85º of pitch. The difference in thrust values is 8%. The actual figure of merit was 0.904
IMPORTANT FINDINGS AND CONCLUSIONS The static performance matched very closely to that predicted by Carter’s analytical program, so cruise performance and performance on a 600 HP engine can be expected to match Carter’s predictions, as well. The analytical program predicted that at 25,000’ MSL, operating at 400 HP, the propeller would be 91% efficient at 250 mph and 92% efficient at 300 mph. With the already demonstrated high static thrust values, the propeller should have very good performance throughout the flight regime. The performance is expected to be even better with the propeller installed on the aircraft, when the spinner is in place and the airflow into the propeller is not as turbulent due to the test stand’s 6,000 lb concrete blocks and steel structure.
Measured Static Performance HP
Thrust (lbs)
Thrust/ HP
193
1,275
6.606218 9.35
0.88
320
1,710
5.34375
8.95
0.83
380
1,855
4.881579 8.66
0.79
k
F.O.M.
Projected Cruise Performance @ 300 HP Airspeed (mph)
RPM
Thrust (lbs)
Pitch
F.O.M.
η
100
1,926
1092.78
16.09
0.917
0.767
125
1,909
943.12
18.34
0.923
0.827
150
1,887
819.95
20.91
0.926
0.863
175
1,862
719.3
23.68
0.926
0.883
200
1,833
637.01
26.56
0.923
0.894
Projected Cruise Performance @ 380 HP Airspeed (mph)
RPM
Thrust (lbs)
Pitch
F.O.M.
η
100
1,726
892.85
17.57
0.924
0.794
125
1,707
763.09
20.17
0.929
0.848
150
1,683
658.51
23.11
0.93
0.878
175
1,655
574.69
26.24
0.929
0.894
200
1,622
507.01
29.47
0.925
0.901
Just as important as the excellent performance of the propeller is its extremely light weight. The total weight for the propeller, able to efficiently absorb 600 HP, is just 40 lbs, including the pitch change mechanism. This is onethird (or less) than the weight of other propellers designed for the same application. Because of the highly swept tip, the propeller is unusually quiet for the tip speed at which it was tested and was later flown.
FLIGHT-TEST PERFORMANCE OF THE SCIMITAR PROPELLER Carter has statically tested the scimitar propeller on both the test stand and in the aircraft. The data provided below was collected with the propeller and spinner installed on the aircraft. The company did not have enough steady state flight time to measure propeller performance in flight. Note that F.O.M. is Figure of Merit, defined as the ratio of the induced horsepower over the horsepower put into the propeller. It is a measure of how well you are
With the CarterCopter airframe secured in the “pit”, the scimitar propeller and its components have been tested on the ground, prior to any flight testing.
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A CONTACT! Magazine exclusive
By Jeff Lewis Jeff is a design engineer who works for Carter. He performed the aerodynamic analyses of the PAV airframe to minimize drag, using CFDesign computational fluid dynamics software. He also developed the PAV model for use in Carter's XPlane based flight simulator, and configuring it to research high-µ flight in preparation for PAV prototyping and flight-testing. Jeff resides in Wichita Falls, Texas. Carter Aviation Technologies (Carter) will reveal the existence of its new slowed-rotor/compound (SR/C) aircraft project at a press conference scheduled for Sunday, 2 April, at the Georgia Institute of Technology (Ga Tech) in Atlanta, Georgia. Carter has changed its focus from the aircraft designated as the Next Generation CarterCopter (NxCC) with 2+4 seating, to a different aircraft designated the Personal Air Vehicle (PAV) with 2+2 seating. Although the fuselage of the PAV is slightly smaller than that of the NxCC, the PAV is a very capable aircraft, and is being designed to be very versatile.
Show n here is the 34’ span version of the 2+2 PAV, powered with a 200 HP Delta Hawk turbo-normalized diesel engine.
PAV DESIGN The baseline aircraft will have a 34’ diameter rotor and wingspan, and will utilize a 100 HP Rotax 914 engine. It will have an expected empty weight of around 800 lbs, and a max gross weight of 1600 lbs. A 200 HP diesel version will have an estimated empty weight of 1,000 lbs, and a max gross weight of 2,400 lbs. A military version will use the same fuselage shape and most of the same parts, but will use a 45-ft rotor and wingspan. With a 1200 HP gas turbine engine, the aircraft will have an expected empty weight of 1,500 lbs, and will operate at a maximum of 4,500 lbs. For all versions, the aircraft will perform either a vertical take-off or short rolling takeoff, depending on the density altitude, gross weight, and available horsepower.
Carter PAV 2+2 modeled in X-Plane, an inexpensive, commercially available, home computer program.
PAV X-PLANE FLIGHT MODEL To aid in the investigation of the flight characteristics and dynamic flight responses, Carter developed a model of the aircraft for use in its X-Plane based flight simulator. Carter had previously used X-Plane to model the CCTD and found the simulator to match very closely with performance and handling characteristics as determined in actual flight testing.
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21’-0”
Currently, the X-Plane flight simulator is being used to test control philosophies for the tilting mast. It is invaluable to see how the aircraft responds dynamically in realtime. A plug-in has also been written for use with the XPlane aircraft model to simulate automatic controls. www.x-plane.com
9’-10”
Early in the design phase of the PAV, Carter used the XPlane model to experiment with controlling the aircraft with rotor and rudder only -- not having ailerons or elevators. The concept was that for a low-tech version of the PAV designed specifically for moderate flight speeds and with the rotor providing 50% of the lift during cruise, there would be sufficient pitch and roll control authority from the rotor to make the other controls unnecessary, thus saving weight and complexity. However, flight testing in the simulator revealed that it was too easy to accidentally enter into a flight condition where the wings provided all of the lift and the rotor became completely unloaded, making the aircraft uncontrollable. In actual flight testing, this condition would likely have led to mast bumping, a condition where the mechanics of the rotor hub can “bump” the shaft. The term “bump” may be misleading, being a fairly innocuous term, when in fact, it’s a very serious condition and a highly destructive phenomenon that no rotorcraft pilot would want to endure.
PAV CONSTRUCTION To avoid the problems associated with having only a single prototype that Carter experienced while testing the CCTD, the company will initially construct three prototypes of this aircraft. It is expected that two of these aircraft will be used in flight testing while the third will be used in wind tunnel testing (explained later). After the wind tunnel testing is completed, the third aircraft will also be available for flight testing. Although detailed engineering design remains to be done on many of the internal systems for the PAV, many of the external features have been defined with a high degree of confidence that the shape will not change. To save time in construction of the aircraft, work has already begun on the tooling for some of these external components. The molds for the horizontal stabilizer have been completed. The top half of the plug for the 45-ft span wing has been completed, but no work has been done on the mold. The shape of the fuselage is frozen. Carter investigated various options for making the fuselage plug, including machining the entire plug on a CNC mill; cutting templates at various stations and rough-shaping by hand; or cutting the foam itself to the proper shape at various stations with a CNC hot wire cutter and then stacking those sections. All methods would have required significant work by hand to attain a suitable surface finish. In the end, the template method was decided upon since it could be completed in the least amount of time. The templates for the fuselage, including the tail boom and rudder, have already been cut, and the foam has been placed between the templates and roughly cut to shape.
45’-0”
PAV 2+2 3-view and isometric view, shown with the 45’ rotor and wingspan. With either the 34’ or the 45’ version of the PVA 2+2, the rotor and wing will be of equal span.
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will be tested by itself first, The 34-ft diameter rotor and then the fuselage and blade skin molds and spar rotor will be tested together. mold have been completed. By comparing the data from The rotor blade was dethe two tests, it will be possigned with a long segment sible to determine the overof constant cross section, all contribution of the rotor. and the molds were conThe fuselage itself or the structed with several removlanding gear attach points able sections for that segwill act as the test stand. ment. By varying which secWith this approach, there tions are used in that segwill be no need for a sepament, the mold can be used rate test stand for testing to make rotor blades varying the rotor. in diameter from 20-ft to 34ft (note: these molds have Initially, the rotor will be already been used to build a continuously engaged to 26-ft rotor blade for use on the engine so that the RPM the CarterGyro Demonstraof the rotor can be contor/Trainer). It is expected These are the actual blades that will be fitted to the trolled with the engine. By that the first PAV prototypes new single-place Carter autogyro (CGD/T) featured measuring the torque from will use a 34-ft rotor, but throughout this issue. The plan is to have them fitted the engine to the rotor, it depending on the size of the some time in May of 2006 and have it fully tested bewill be possible to deterwind tunnel used, a 20-ft fore flying it to AirVenture 2006 (Oshkosh). mine how accurately the rotor may be constructed for rotor RPM controller is able wind tunnel testing. Other to hold a given rotor RPM. The goal will be to develop variants of the aircraft will use a 45-ft rotor, which would the control system such that aerodynamic forces can be constructed using slightly modified versions of the hold the rotor at a desired stable RPM. Once this has molds that were used to build the 45-ft rotor flight-tested been demonstrated satisfactorily, the next step will be to on the CCTD. disengage the rotor from the engine to fully test Carter’s control system in autorotation and verify that the system truly can control rotor RPM at a high µ or low RPM Although the 40’ x 80’ wind tunnel at the Ames Research Center is still the preferred tunnel to use for testing the aircraft, Carter has begun looking into other options in case that wind tunnel is not available. If only a smaller wind tunnel is available, the rotor diameter or wingspan will be varied to fit the tunnel’s size. Illustration Courtesy of Mat Recardo
CFD analysis of the fuselage section at centerline .
PAV FLUID DYNAMICS MODELLING Ongoing with the design iterations of the PAV, Carter has performed aerodynamic analyses of the aircraft using CFDesign computational fluid dynamics software, making any necessary adjustments to ensure good airflow over the aircraft. An example of the results from the latest iteration are shown above.
WIND TUNNEL TESTING Plans are underway to test the fuselage, rotor and control systems of the PAV in a wind tunnel. The fuselage
An artistic rendering of what the future might bring if the same mass production that put Ford on the map were applied to SR/C aircraft. Shown in the rendering is the “Carter Model A”, a predecessor to the 2+2
CONTACT! ISSUE 83 PAGE 27
WEIGHT ESTIMATE
Original Carter CCTD which slowed the rotor to 106 rpm at 170 mph, achieving an advance ratio (µ) of 1, and an L/D of 7.
PREDICTED PAV PERFORMANCE The following figures show the predicted performance for the PAV in two different variants – a diesel powered version with a 34-ft diameter rotor and wingspan , and a military gas turbine powered version for high performance with a 45-ft diameter rotor and wingspan. AWD= AWL= AHS= AVS= FW= MW= BW= LGW= SPW= CDR= CDA= CDW= WDM= CD= FDM= TDM= VISC= MU= SPN= RD= AB= RPMR= P.E.= HP SL= BSFC= WTG= WTE=
86 100 10.5 16 190 5 40 20 4 0.012 0.008 0.004 0.6 0.3 0.6 0.2 3.74E-07 0.92 34 34 34 135 0.85 200 0.43 2,400 2,000
AREA WING DRAG -SQ FT; AREA WING LIFT - SQ FT AREA HORIZONTAL STAB - SQ FT AREA VERTICAL STAB - SQ FT FUSELAGE WETTED AREA - SQ FT MAST WETTED AREA - SQ FT TAIL BOOM WETTED AREA LG NACELLE WETTED AREA SPINNER WETTED AREA - SQ FT COEFFICIENT OF DRAG (ROTOR) COEFF DRAG AIRFOIL COEFF DRAG WETTED WING + LG DRAG MISC - FLATE PLATE SQ FT COOLING DRAG - FLATE PLATE SQ FT FUSELAGE, PYLON, HUB DRAG MISC- FLATE PLATE SQ FT TAIL DRAG MISC - FLATE PLATE SQ FT ABSOLUTE VISC COEFF- slug/(ft)(s) WING EFF SPAN - FT. ROTOR DIA. - FT. AREA OF BLADES - SQ FT RPM - ROTOR PROP EFF. HORSEPOWER AVAILABLE @ SEA LEVEL BRAKE SPECFIC FUEL CONSUMPTION WEIGHT GROSS - LBS WEIGHT LANDING - LBS
To the right are the initial weight estimates for the major components of the PAV. They were determined by several methods, including the scaling of parts used on the CCTD, actual measurements of known components (engine, battery, fuel, etc), calculations from parts for this aircraft that are already designed to a high level of detail (landing gear), and estimates derived from a comparison to state-ofthe-art aircraft of comparable size. As the design progresses, these initial estimates will be replaced with calculations based on actual computer aided designs, and later by weighing completed parts. Jeff Lewis AWD= AWL= AHS= AVS= FW= MW= BW= LGW= SPW= CDR= CDA= CDW= WDM= CD= FDM= TDM= VISC= MU= SPN= RD= AB= RPMR= P.E.= HP SL= BSFC= WTG= WTE=
100 114 10.5 16 190 5 40 20 4 0.012 0.008 0.004 0.6 0.3 0.6 0.2 3.74E-07 0.92 45 45 50 100 0.85 1,200 0.45 4,500 3,000
2+2 2+2 PAV, PAV, 1600# 1600# gross gross wt, wt, Rotax Rotax 914 914 Engine Engine 800# 800# useful useful includes includes 200# 200# fuel, fuel, 10# 10# luggage luggage Item Item
Weight Weight
Fuel Fuel (32.25 (32.25 gallons) gallons) Nose Nose LG LG Main Main LG LG Fuselage Fuselage Tail Tail Boom Boom Vertical Vertical Stab Stab Horizontal Horizontal Stab Stab Wing Wing Windshield Windshield Engine Engine & & Drive Drive Pre-Rotator Pre-Rotator + + Gearbox Gearbox Rotor Rotor Head Head + + Pylon Pylon + + Mast Mast Rotor Rotor + + Hub Hub Prop Prop governor governor Battery Battery Radiator Radiator Controls Controls Instruments Instruments + + Data Data Collection Collection Seats Seats Water Water Pilot Pilot Co Co Pilot Pilot Rear Rear Passengers Passengers Luggage Luggage Prop Prop Spinner Spinner Propeller Propeller
200 200 25 25 70 70 80 80 20 20 15 15 14 14 50 50 30 30 170 170 20 20 20 20 130 130 5 5 25 25 10 10 12 12 25 25 20 20 10 10 200 200 200 200 200 200 10 10 4 4 20 20
Misc Misc -- wire, wire, solenoids, solenoids, servo servo
25 25
Gross Gross Wt Wt Empty Empty Wt Wt CG CG @ @ Gross Gross Wt Wt CG CG @ @ Empty Empty Wt Wt
1600 1600 800 800 77.2 77.2 92.2 92.2
AREA WING DRAG -SQ FT; R=3.5', T=.75' AREA WING LIFT - SQ FT AREA HORIZONTAL STAB - SQ FT AREA VERTICAL STAB - SQ FT FUSELAGE WETTED AREA - SQ FT MAST WETTED AREA - SQ FT TAIL BOOM WETTED AREA LG NACELLE WETTED AREA SPINNER WETTED AREA - SQ FT COEFFICIENT OF DRAG (ROTOR) COEFF DRAG AIRFOIL COEFF DRAG WETTED WING + LG DRAG MISC - FLATE PLATE SQ FT COOLING DRAG - FLATE PLATE SQ FT FUSELAGE, PYLON, HUB DRAG MISC- FLATE PLATE SQ FT TAIL DRAG MISC - FLATE PLATE SQ FT ABSOLUTE VISC COEFF- slug/(ft)(s) WING EFF SPAN - FT. ROTOR DIA. - FT. AREA OF BLADES - SQ FT RPM - ROTOR PROP EFF. HORSEPOWER AVAILABLE @ SEA LEVEL BRAKE SPECFIC FUEL CONSUMPTION WEIGHT GROSS - LBS WEIGHT LANDING - LBS
Parameters for performance calculation: 200 HP turbo Delta Hawk engine, 34' rotor & wingspan, 2,400 lb gross wt, 1,000 lb empty wt, 1,000 lb payload, 400 lb Max Fuel
Parameters for performance calculation: 1200 HP gas turbine engine, 45' rotor & wingspan, 4,500 lb gross wt, 1,500 lb empty Wt, 1,500 lb payload, 1500 lb Max Fuel
Altitude Air Density Vel (ft/s) Vel (mph) CL Profile HP Induced HP Rotor HP Engine HP Req'd Engine HP Avail Total Drag MPG L/D Range Rotor Flate Plate Total Flat Plate
Altitude Air Density Vel (ft/s) Vel (mph) CL Profile HP Induced HP Rotor HP Engine HP Req'd Engine HP Avail Total Drag MPG L/D Range Rotor Flate Plate Total Flat Plate
0 7.5K 10K 12.5K 15K 17.5 20K 25K 0.00238 0.001898 0.001756 0.001622 0.001496 0.001378 0.001267 0.001065 260 280 287 294 302 310 308 303 177 191 195 200 206 211 210 206 0.25 0.27 0.28 0.29 0.30 0.31 0.35 0.44 163.39 162.14 161.61 161.03 160.38 159.67 144.25 115.41 11.90 13.88 14.63 15.44 16.32 17.26 18.89 22.84 24.70 23.99 23.76 23.53 23.30 23.07 20.86 16.75 200.00 200.00 200.00 200.00 200.00 200.00 184.00 155.00 200.00 200.00 200.00 200.00 200.00 200.00 184.00 155.00 359.08 333.85 325.66 317.54 309.51 301.59 279.10 239.01 12.77 13.74 14.08 14.44 14.82 15.20 16.43 19.19 6.68 7.19 7.37 7.56 7.75 7.96 8.60 10.04 903 972 996 1022 1048 1076 1162 1357 0.65 0.63 0.63 0.62 0.62 0.62 0.62 0.62 4.28 4.27 4.26 4.26 4.26 4.25 4.25 4.26
0 7.5K 10K 12.5K 15K 17.5 20K 25K 0.00238 0.001898 0.001756 0.001622 0.001496 0.001378 0.001267 0.001065 470 469 469 468 468 467 466 463 320 319 319 319 318 318 317 315 0.08 0.12 0.14 0.16 0.18 0.20 0.22 0.28 992.39 786.32 725.30 667.54 613.01 561.70 513.17 423.86 13.22 16.62 17.98 19.49 21.16 23.01 25.08 30.02 194.39 154.04 142.10 130.79 120.11 110.07 100.57 83.10 1200.00 956.97 885.38 817.82 754.29 694.79 638.82 536.97 1200.00 956.97 885.38 817.82 754.29 694.79 638.82 536.97 1192.86 953.33 882.89 816.50 754.17 695.90 641.21 542.14 3.84 4.81 5.19 5.62 6.08 6.59 7.15 8.46 3.77 4.72 5.10 5.51 5.97 6.47 7.02 8.30 1134 1419 1532 1657 1793 1944 2109 2495 0.86 0.86 0.86 0.86 0.86 0.86 0.86 0.86 4.61 4.61 4.61 4.61 4.61 4.61 4.61 4.61
CONTACT! ISSUE 83 PAGE 28
Classified ads– minimum $15 donation from subscribers. All ads must include a price. No commercial ads allowed. Ads will run for 3 consecutive issues or until sold. Must be renewed after the 3rd printing. CONTACT! Magazine reserves the right to refuse any ad. FOR SALE: Miscellaneous parts. One of our supporters donated the contents of his garage. Listed below is a smattering of what we have available, and the value we declared for his donation. No reasonable offer will be refused. Please contact Pat Panzera with your questions or offer. CONTACT! Magazine, 559-584-3306 panzera@sti.net Subaru 2.0 engine, extra head REDUCED MORE New Mazda A10 engine Brock master brake cylinders Vari-Eze Vari-Eze spinner SOLD! Dragonfly project, no engine Dragonfly project, no engine Dragonfly project, ready to taxi
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For Sale: B0208/MFI-9 (Messerschmitt built) A unique recreation of the mini-coin Biafra Baby #BB905. Historically accurate and documented. New zero-time TMX IO-240. A highly maneuverable small ship for a small pilot. Registered Experimental/Exhibition warbird. New prop, paint, interior, instruments, wheels and brakes. NOT LSA qualified. Contact italmotion1@comcasr.net for brochure or go to www.italmotion.com for images under “current project.” Priced at $38k FL59 Ft. Myers FL. Partial or full trades for aircraft or vintage racecar considered. Don Black 107 For Sale: Instruments- Falcon GH-002 3 1/8" Vacuum Attitude Gyro ACS 10-22955 $250 * Airborne 1J7-1/D9-18-1 Filter ACS $25 * 4" Venturi ACS 15050 $35 (has fiberglass streamlined housing) These units have about 300 hours total.* CONTACT! Magazine (559) 584-3306 Sales@ContactMagazine.com 103 For Sale: Subaru EJ-22 Firewall Forward. 300 hours TT w/o any problems. Ross redrive, all electronics, engine mount and some spare Subaru parts included. See CONTACT! issues #6 and #8 for a full description of this engine as installed on a Dragonfly. $5,000 Ruidoso NM. Randy (575) 937-3586 lsbp1919@yahoo.com 102 For Sale: Two RV6 Motor mounts for 4.3L Chevrolet V-6. One tail dragger, one with nose wheel. $1,000 each. Ruidoso NM. Randy (575) 937-3586 lsbp1919@yahoo.com 102
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ALTERNATIVE ENGINES VOLUME 3 The third in the series from Mick Myal is available only through CONTACT! Magazine. See the back inside cover wrap of this issue for ordering info or visit www.ContactMagazine.com For Sale: 3.8L Ford V6 with Blanton redrive, as pulled from an RV-6 shown on Youtube.com by searching for “V-6 airplane engine” (yellow plane). Includes three-blade Warp Drive prop, all manuals and engine instruments. $2,000.00 Buyer pays shipping from Benbrook TX. (817)692-6742 Richard luggman@sbcglobal.net 102
ALTERNATIVE ENGINES VOLUME 2 Once again available! See the back inside cover wrap of this issue for ordering info or visit www.ContactMagazine.com For Sale: Glasair 1 TD kit. Fairly complete, unstarted kit with extras. $4500.00 Located in Hanford California. Please contact Pat Panzera with your questions or offer. CONTACT! Magazine, 559-584-3306 Sales@ContactMagazine.com 106 For Sale: Ross Redrive with aluminum flywheel. $1800.00 For Sale: Warp Drive Propeller threeblade, 66” diameter, left-hand rotation with nickel leading edges. Comes with spinner. $500.00 Or buy both for $2000 total. These components were bolted to a Subaru EA-81 and tested for a maximum of 30 minutes only. Buyer pays shipping from Las Vegas NV 89104. Don Thompson (702) 236-1691 106
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