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Aviation History
2001
2001 - 1147.PDF
ADVANCED technology also lies at the heart of another gyroplane venture, the CarterCopter (CC). Founded in 1994 by Jay Carter and Paul Redding, the Texas- based company has completed the last of a three-phase NASA small business initia tive-sponsored research contract and is pursuing technology for a final design that will cruise as high as 50,000ft (15,000m) and at speeds up to 435kt (500mph). Despite several flight test setbacks, including three crashes, CC is setting its sights on breaking the "Mu-1 barrier" - the theoretical limit on the top speed of any rotorcraft. Flight above Mu-1 would involve generating forward speed greater than the tip-speed of the rotor, which Carter believes is possible by slowing the rotor and yet still maintaining rotor stabil ity. The company has proved the concept's viability on a 1/6 scale model, but needs to repeat the feat using the full-scale gyro plane. Carter says: "We want to break world records, and demonstrate the capa bility of this aircraft which we believe could be as good as a second-generation [V-22] Osprey without having to tilt the rotors." Unlike earlier machines, with the notable exception of the Fairey Rotordyne - developed intheUKinthelate 1950s- allgyroplaneshave been underpowered, the company says. Virtually all used a 134kW (180hp) piston engine and had weight-to-power ratios of more than 6kg/lkW. GBAs design, using a 3 UDkW turbine engine, changes that. Further develop ments will all have higher powered engines, adds Groen. Additionally, all earlier designs had two seats and small useful loads of around 230kg (5001b). The Hawk 4T, on the other hand, is designed with a gross weight of around 1,500kg, a useful load of around 545kg, a range of approximately 925km (500nm), a take-off roll of between 0 and 45m (150ft) and a landing roll between 0 and 15m. Maximum level flight speed is 135kt, and rate of climb is l,000ft/miri(5m/s). Besides having a large market in its own right, •tGroen views the Hawk 4T as a bridge to larger gyroplanes. GBA is also close to taking the first steps towards this second goal with the maiden flight of a Hawk 6 - a converted i Cessna C337 Skymaster - due to take place, as Flight International closed for press. Intended as a proof-of-concept test vehicle for carrying either larger cargo or eight to 10 passengers, the Cessna gyro plane has been greatly modified. INVERTED TWIN BOOMS The rear pusher engine has been removed to provide access to what, on a production version, would be clamshell cargo doors. The forward 'tractor' engine is replaced by a Rolls-Royce 250-B17F2 turboprop, while the t^ki booms have been inverted so the tails point down, which keeps them out of the way of the two-bladed rotor taken straight from the 4T GBA expects the wing stubs - required as structural supports for the booms - to pro vide lift which it will cancel with new spoil ers. Ultimately, it plans to add wing I Even James Bond has taken to the skies in a gyroplane - in the 1967film "You Only Live Twice" extensions to help offload the rotor, though GBA adds that this will be done cautiously to avoid upsetting the weight and airspeed balance of die autorotative rotor system. "We needed to learn about tractor gyro planes, though since we started it we have had interest from government agencies about using it as an uncertificated aircraft for things like bor der patrols," says Groen. The FAA turned down GBAs request for supplemental type certifica tion for the conversion. The main aim, there fore, remains the development of a larger version for companies such as Fedex, interested in an aircraft that could carry at least It of pay- load. GBAs original designs for such a vehicle "looked very much like a Cessna Skymaster, so that's where we got the idea to use one as a tech nical demonstrator". Ultimately, Groen foresees a large family of gyroplanes, the largest of which could be a range of regional transports carrying 18,35 and 50 passengers. Inspired by the Fairey Rotordyne, which was technically a compound aircraft, GBA is "working with a major aerospace firm" on this. Like the Rotordyne, which was scrapped in 1962, the proposed transport versions will have tipjet-powered rotors to allow vertical take-offs and landings. Groen sees this as the key to the family's promised flexibility, freeing it from the need for runways and slot congestion at airports. "The Fairey Rotordyne was killed by politics and not technology, so with what we have available today in terms of modern plastics and compos ites even if we did no better than the Rotordyne we'd be doing well," he adds. Thanks to GBA and CC, the gyroplane may beset for a renaissance in the 21 st century. • FLIGHT INTERNATIONAL 3 - 9 April 2001 35
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