CarterCopter
Encyclopedia
The CarterCopter is an experimental compound autogyro
developed by Carter Aviation Technologies
to demonstrate slowed rotor technology. On 17 June 2005, the CarterCopter became the first rotorcraft to achieve mu-1 (μ=1), an equal ratio of airspeed to rotor tip speed, but crashed on the next flight and has been inoperable since.
autogyro with wings and a twin boom tail, intended as a prototype and a technology demonstrator. The rotor is a two-bladed design weighted with 55 pounds (24.9 kg) depleted uranium
at each tip, and it is mounted on a tilting mast, allowing the wing to stay at optimum wing efficiency at all speeds.
It is an all-composite design.
The tricycle undercarriage is retractable, and has a large travel to allow for landing at up to 20 ft/sec without bounce. The aircraft had been modified and rebuilt after an accident (a gear-up landing) in 2003.
NASA
had funded $1 million of the development using three research grants, and the aircraft managed to accomplish at least one of NASA's five goals.
) and the center of lift aft of the blade center line.
At high speed (above about 100 mph) the aircraft flies mostly using the fixed wings, with the rotor simply windmilling. The rotor spins with a tip speed below airspeed, which means that the retreating blade flies completely stalled. On a helicopter this would cause massive lift asymmetry
and insoluble control issues but the fixed wings keep the aircraft in the air and stable.
The low rotation speed and flat feathering of the rotor means that it causes little drag, and the company claims that the aircraft would be potentially able to leverage the advantages of fixed wings as well as gyrocopters, giving almost all the capabilities of helicopters (except hovering) but with a relatively simple mechanical system. Carter Aviation also claims the system is safer than a typical fixed-wing aircraft, and others have remarked that the design is much safer, much less complex and less expensive than a helicopter, a tilt-rotor or the Boeing X-50 Dragonfly Canard Rotor/Wing
. The CarterCopter should be capable of higher airspeeds now only be achieved by fixed-wing aircraft, but also able to land like an autogyro in any small area in an emergency.
due to heavy counterweights in the tips that it can hover
for a short time safely. The pilot then applies full power to the rear pusher propeller and the vehicle starts to move forwards. As it does so, air is forced through the main rotor, spinning it faster and generating more lift. The vehicle climbs into the air, flying as an autogyro.
Normally a helicopter or gyrocopter cannot fly forward at the same speed as or faster than its rotor tip speed. This is because the low airspeed of the retreating rotor blade would cause retreating blade stall
, whilst the advancing rotor blade would be traveling at twice the speed of the aircraft, producing uncontrollable flight due to dissymmetry of lift
.
However, with the CarterCopter, the fixed wings provide the lift required to remain aloft. Since the rotor is unloaded, the aerodynamic forces on the rotor are very minor. This means that a CarterCopter can theoretically fly much faster than the tip speed of the rotor. The rotors would still experience flapping as they rotate due to dissymmetry of lift between the two sides of the vehicle, but Carter Aviation claims this is manageable.
The claimed theoretical maximum speed of a CarterCopter is around 500 mph (800 km/h), which would be about twice as fast as the helicopter flight airspeed record.
A helicopter to go the same speed would need almost twice this power. Thus the CarterCopter seems to be about twice as efficient.
At 4,000 lbs weight, the CCTD can climb 750 fpm.
From 1999 to 2001 there were 4 recorded instances of non-fatal crashes, while Carter claims 10 accidents over 7 years, all non-fatal.
The maximum mu that has been achieved (mu is the ratio of airspeed to rotor tip speed) is 1.0 for a brief moment on June 17, 2005, the first time any rotary aircraft has reached this level. CarterCopter's pilot claimed that there was no great drama, and mu 1 was reached accidentally due to normal variations in rotor RPM and vehicle airspeed; the pilot described it as 'smooth' with no significant vibration. The tests were performed under a US Army contract.
However, on the next test flight the same day, the CarterCopter made a hard landing (crashed), causing significant damage, but the pilots were unhurt. The crash was caused by failing propeller bolts which damaged wires controlling the rotor. It was initially believed that the CarterCopter was unrepairable; later inspection showed that it could be repaired, but the company chose to work on a small open wingless autogyro demonstrator instead. Also later in 2005 and using lessons learned from the CarterCopter, design began on the subsequent compound aircraft, the Carter Personal Air Vehicle (PAV), which flew in 2011.
The company claims that the testing indicated
that the vehicle architecture could potentially outperform helicopters on every dimension except sustained hover, and should be much cheaper to buy and maintain. The company also claims that it also very nearly matches the L/D
of fixed wing General Aviation
aeroplanes at cruise speed - but with near-vertical takeoff and landing.
controllable pitch propeller
weighs 15 lbs and has a thrust of 1850 lbf.
Autogyro
An autogyro , also known as gyroplane, gyrocopter, or rotaplane, is a type of rotorcraft which uses an unpowered rotor in autorotation to develop lift, and an engine-powered propeller, similar to that of a fixed-wing aircraft, to provide thrust...
developed by Carter Aviation Technologies
Carter Aviation Technologies
Carter Aviation Technologies is a privately held aviation research and development company based in Wichita Falls, Texas, United States....
to demonstrate slowed rotor technology. On 17 June 2005, the CarterCopter became the first rotorcraft to achieve mu-1 (μ=1), an equal ratio of airspeed to rotor tip speed, but crashed on the next flight and has been inoperable since.
Design and development
The CarterCopter is a pusher configurationPusher configuration
In a craft with a pusher configuration the propeller are mounted behind their respective engine. According to Bill Gunston, a "pusher propeller" is one mounted behind engine so that drive shaft is in compression...
autogyro with wings and a twin boom tail, intended as a prototype and a technology demonstrator. The rotor is a two-bladed design weighted with 55 pounds (24.9 kg) depleted uranium
Depleted uranium
Depleted uranium is uranium with a lower content of the fissile isotope U-235 than natural uranium . Uses of DU take advantage of its very high density of 19.1 g/cm3...
at each tip, and it is mounted on a tilting mast, allowing the wing to stay at optimum wing efficiency at all speeds.
It is an all-composite design.
The tricycle undercarriage is retractable, and has a large travel to allow for landing at up to 20 ft/sec without bounce. The aircraft had been modified and rebuilt after an accident (a gear-up landing) in 2003.
NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
had funded $1 million of the development using three research grants, and the aircraft managed to accomplish at least one of NASA's five goals.
Concept
The CarterCopter concept is a gyrocopter with an unusually stiff, relatively heavy rotor, supplemented with conventional wings. At low speed, the vehicle flies as a gyrocopter, and can pre-spin the rotor for a vertical takeoff and very brief hover, and can land more or less vertically. Several technical challenges make flying a slow rotor difficult, but rotor stability is achieved through the combination of the rotor tip weights' location ahead of the blade center line (forward center of gravityCenter of gravity
In physics, a center of gravity of a material body is a point that may be used for a summary description of gravitational interactions. In a uniform gravitational field, the center of mass serves as the center of gravity...
) and the center of lift aft of the blade center line.
At high speed (above about 100 mph) the aircraft flies mostly using the fixed wings, with the rotor simply windmilling. The rotor spins with a tip speed below airspeed, which means that the retreating blade flies completely stalled. On a helicopter this would cause massive lift asymmetry
Dissymmetry of lift
Dissymmetry of lift in rotorcraft aerodynamics refers to an uneven amount of lift on opposite sides of the rotor disc. It is a phenomenon that affects single-rotor helicopters in lateral flight, whether the direction of flight be forwards, sideways or in reverse.The dissymmetry is caused by...
and insoluble control issues but the fixed wings keep the aircraft in the air and stable.
The low rotation speed and flat feathering of the rotor means that it causes little drag, and the company claims that the aircraft would be potentially able to leverage the advantages of fixed wings as well as gyrocopters, giving almost all the capabilities of helicopters (except hovering) but with a relatively simple mechanical system. Carter Aviation also claims the system is safer than a typical fixed-wing aircraft, and others have remarked that the design is much safer, much less complex and less expensive than a helicopter, a tilt-rotor or the Boeing X-50 Dragonfly Canard Rotor/Wing
Canard Rotor/Wing
The Canard Rotor/Wing is a class of VTOL aircraft capable of both fixed-wing and rotary-wing flight. For vertical take-off, hovering, low-speed flight, and vertical landing, the main airfoil is spun like a helicopter's rotor by directing the exhaust from a jet engine through thrust nozzles in the...
. The CarterCopter should be capable of higher airspeeds now only be achieved by fixed-wing aircraft, but also able to land like an autogyro in any small area in an emergency.
Takeoff
At takeoff the pilot angles the top rotor flat (zero angle of attack) and spins it to very high speed (between 365 and 425 rpm). The rotor is then disconnected from the engine and the angle of attack of the main rotor blades is increased suddenly so that the vehicle leaps into the air. The aircraft's main rotor has enough momentumMomentum
In classical mechanics, linear momentum or translational momentum is the product of the mass and velocity of an object...
due to heavy counterweights in the tips that it can hover
Hover
Hover may refer to:*Hovering , the process by which an object is suspended by a physical force against gravity, in a stable position without solid physical contactIn transport* Hover , nearly stationary flight in a helicopter...
for a short time safely. The pilot then applies full power to the rear pusher propeller and the vehicle starts to move forwards. As it does so, air is forced through the main rotor, spinning it faster and generating more lift. The vehicle climbs into the air, flying as an autogyro.
Cruising
Once the CarterCopter gets up to a forward speed of about 90 miles per hour (40.2 m/s), its stubby, lightweight wings provide most of the lift. The pilot can then flatten the angle of attack of the main rotor so it produces very little lift, dramatically reducing the amount of induced drag created by the rotor. Although the rotor is unused at high speed, the rotor is kept spinning as the rotation keeps the rotor rigid, preventing excessive flapping.Normally a helicopter or gyrocopter cannot fly forward at the same speed as or faster than its rotor tip speed. This is because the low airspeed of the retreating rotor blade would cause retreating blade stall
Retreating blade stall
Retreating blade stall is a hazardous flight condition in helicopters and other rotary wing aircraft, where the rotor blade rotating away from the direction of flight stalls. The stall is due to low relative airspeed and/or excessive angle of attack...
, whilst the advancing rotor blade would be traveling at twice the speed of the aircraft, producing uncontrollable flight due to dissymmetry of lift
Dissymmetry of lift
Dissymmetry of lift in rotorcraft aerodynamics refers to an uneven amount of lift on opposite sides of the rotor disc. It is a phenomenon that affects single-rotor helicopters in lateral flight, whether the direction of flight be forwards, sideways or in reverse.The dissymmetry is caused by...
.
However, with the CarterCopter, the fixed wings provide the lift required to remain aloft. Since the rotor is unloaded, the aerodynamic forces on the rotor are very minor. This means that a CarterCopter can theoretically fly much faster than the tip speed of the rotor. The rotors would still experience flapping as they rotate due to dissymmetry of lift between the two sides of the vehicle, but Carter Aviation claims this is manageable.
The claimed theoretical maximum speed of a CarterCopter is around 500 mph (800 km/h), which would be about twice as fast as the helicopter flight airspeed record.
Achievements
The prototype's engine was normally aspirated, and hence limited to just 320 hp (240 kW) and the fastest Carter Aviation Technologies prototype has achieved is about 173 mph (270 km/h); which is still ~40% faster than a conventional autogyro but slower than gyrodynes of the 1950s. A custom gyroplane can go 168.29 km/h (104.6 mph).A helicopter to go the same speed would need almost twice this power. Thus the CarterCopter seems to be about twice as efficient.
At 4,000 lbs weight, the CCTD can climb 750 fpm.
From 1999 to 2001 there were 4 recorded instances of non-fatal crashes, while Carter claims 10 accidents over 7 years, all non-fatal.
The maximum mu that has been achieved (mu is the ratio of airspeed to rotor tip speed) is 1.0 for a brief moment on June 17, 2005, the first time any rotary aircraft has reached this level. CarterCopter's pilot claimed that there was no great drama, and mu 1 was reached accidentally due to normal variations in rotor RPM and vehicle airspeed; the pilot described it as 'smooth' with no significant vibration. The tests were performed under a US Army contract.
However, on the next test flight the same day, the CarterCopter made a hard landing (crashed), causing significant damage, but the pilots were unhurt. The crash was caused by failing propeller bolts which damaged wires controlling the rotor. It was initially believed that the CarterCopter was unrepairable; later inspection showed that it could be repaired, but the company chose to work on a small open wingless autogyro demonstrator instead. Also later in 2005 and using lessons learned from the CarterCopter, design began on the subsequent compound aircraft, the Carter Personal Air Vehicle (PAV), which flew in 2011.
The company claims that the testing indicated
that the vehicle architecture could potentially outperform helicopters on every dimension except sustained hover, and should be much cheaper to buy and maintain. The company also claims that it also very nearly matches the L/D
Lift-to-drag ratio
In aerodynamics, the lift-to-drag ratio, or L/D ratio, is the amount of lift generated by a wing or vehicle, divided by the drag it creates by moving through the air...
of fixed wing General Aviation
General aviation
General aviation is one of the two categories of civil aviation. It refers to all flights other than military and scheduled airline and regular cargo flights, both private and commercial. General aviation flights range from gliders and powered parachutes to large, non-scheduled cargo jet flights...
aeroplanes at cruise speed - but with near-vertical takeoff and landing.
Specifications
The 8 ft scimitarScimitar
A scimitar is a backsword or sabre with a curved blade, originating in Southwest Asia .The Arabic term saif translates to "sword" in general, but is normally taken to refer to the scimitar type of curved backsword in particular.The curved sword or "scimitar" was widespread throughout the Muslim...
controllable pitch propeller
Controllable pitch propeller
A controllable pitch propeller or variable pitch propeller is a type of propeller with blades that can be rotated around their long axis to change their pitch...
weighs 15 lbs and has a thrust of 1850 lbf.
See also
- Sikorsky S-72Sikorsky S-72|-See also:-External links:* * *...
- compound helicopter with rigid stoppable rotor - Fairey RotodyneFairey RotodyneThe Fairey Rotodyne was a 1950s British compound gyroplane designed and built by Fairey Aviation and intended for commercial and military applications...
- McDonnell XV-1McDonnell XV-1|-See also:-Bibliography:* Connor, R. and R. E. Lee. . 24 September 2001. Smithsonian National Air and Space Museum, Washington, DC. Accessed 4 December 2007....
- McCulloch J-2McCulloch J-2-Related content:Related development:Comparable aircraft:Designation sequence:-References:*...
- an autogyro with clutched rotor