Groen Hawk 6 / Revcon 6G / Cessna Skymaster
Groen Brothers Aviation, Inc. (GBA) has developed a plan that can rapidly bring the gyrodyne into the modern age. Implementing this plan would enable the design, development, production and delivery of safe, fast, vertical takeoff and landing, long range high payload rotorcraft. These aircraft will have the ability to hover and will be economical, reliable and easy to maintain. This can be accomplished using a tiny fraction of the cost and time that would normally be necessary.
Gyrodyne components and flight control systems can be incorporated into certain existing production high wing airplanes with only small modification to the airframe. The time and cost savings benefits of using an existing production airplane are possible because neither the airframe nor most of its systems will need to be designed, engineered, developed, structural loads measured, analyzed, tested, redesigned and engineered, tested again and then prepared for production. And, since the technology is simple, engineering risks are low.
Groen Brothers Aviation has also developed proprietary mission adaptive rotor blade technology. This technology allows GBA's rotor systems to be optimized for hover flight and then during transition from hover to forward flight it can change to be optimized for high speed. Load sharing between the rotor and the aircraft's fixed wing adds to the high speed capability of GBA's gyrodyne aircraft designs.
Using an airplane that is already in production also means that the production plan, materials management system and massive supplier chain, quality assurance system, tooling, and production line are already in place and do not need to be designed, developed and paid for again, nor will there be a production learning curve to overcome. The only components that will need this development are the tip-jets (which have no moving parts), rotorblades, rotor head, mast and flight control system. Since the airframe is suspended from the rotor exactly from where it is suspended from its wing, in-flight loads to the airframe should be virtually unchanged.
This concept was successfully tested by Groen Brothers Aviation through modifying a Cessna Skymaster airplane. It's two piston engines were removed. The forward engine was replaced with a Rolls-Royce model 250 gas turbine engine, and the aft engine was replaced with a large clam-shell cargo door. The wings were clipped and the existing twin boom tail was inverted to give rotor clearance. The rotor system from one of GBA's Hawk 4 Gyroplanes was directly connected to the high wing attach points that were already carrying the Skymaster's fuselage. This conversion, using minimal assets, took less than one year from first conception to first flight. This aircraft demonstrated its exceptional stability and ease of flight, characteristic of a well designed gyroplane.
A technology demonstrator development of the Hawk 4 was announced in late 2000 as Hawk 6G with an expected first flight (prototype N9112A) in January 2001. The first flight was eventually made on 22 September 2001. Based around Cessna 337 fuselage with a single 335kW Rolls-Royce 250-B17F2 turboprop in the nose for propulsion, driving a FC9684C-6RX three-blade propeller, and a Rolls-Royce 250-C18 above the fuselage for rotation. The craft was fitted with an inverted Cessna 337 tailplanes and shortened wing with spoilers and two-blade rotor system from the Hawk 4. External fuel tanks are mounted at wingtips, and are modified Piper PA-24 Comanche wingtip units. Fuel capacity 416 litres. Estimated cruising speed was 209 to 241km/h, and a useful load of 907kg.
Price was US$950.000 in 2003.