The CarterCopter is a
pusher configuration 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
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. with a hull
pressurized up to 0.69
bar. 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.
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 (about 5 seconds), 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 gravity) and the center of lift aft of the blade center line. The CarterCopter should be capable of higher airspeeds now only achievable 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
momentum 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.
Cruising Once the CarterCopter gets up to a forward speed of about , 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 at about 80 RPM as the rotation keeps the rotor stretched, 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, 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 type aircraft 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 aircraft went 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), and Carter says the
Carter Personal Air Vehicle goes . At 4,000 lbs weight, the CCTD can climb 750 fpm. while Carter claims 10 accidents over 7 years, all non-fatal.
Test pilot Larry Neal claimed that the CarterCopter is a challenge to fly because it is a combination of helicopter, autogyro and
fixed-wing aircraft. The CarterCopter achieved its maximum mu (mu is the ratio of airspeed to rotor tip speed) of 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 (at 107 rpm) The tests were performed under a US Army contract. causing significant damage, but the pilots were unhurt. The crash was caused by failing propeller bolts which damaged wires controlling the rotor. The propeller was designed by Carter, and was an 8 ft
scimitar controllable-pitch propeller weighing 15 lbs 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 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 ==Specifications==