A PROMISING NEW VERTICAL TAKE-OFF AND LANDING (VTOL) AIRCRAFT CONCEPT
by John Lawrence
Abstract - This paper introduces a design for a very simple dual-rotor VTOL aircraft. It is a “tail-sitter” which takes off with its fuselage oriented vertically but cruises with its fuselage oriented horizontally. It is fully supported by only its rotor blades in all its flight modes: hover, transition and cruise. The transition between hover and cruise is discussed at length; transition can be accomplished in level flight with an amount of power similar to what is needed for the hover and cruise modes. This novel design offers higher cruising speeds for a given power and weight than most fixed-wing aircraft, very low noise generated when cruising, power loadings and rotor disc loadings typical of most helicopters, and an excellent lateral maneuvering capability when hovering. It promises dramatic improvements in performance for manned and unmanned aircraft. Many diverse applications are possible ranging from small songbird-size unmanned aircraft to large manned aircraft carrying a dozen people at over 400 MPH.
For a long time there has been a great deal of interest in finding an aircraft configuration which can take off and land vertically and also offer efficient high-speed cruise performance – and a surprising number of different VTOL concepts do exist.
This paper describes a simple and promising VTOL concept which heretofore has been mentioned only once, and very briefly, in published literature. (Ref. 1) It offers both vertical takeoff and a very high speed flight capability which can meet a number of existing needs. A small prototype model three feet long has been designed for flight testing and studies have been made to evaluate the basic aircraft’s capabilities and anticipate possible applications.
This paper reviews past work and suggests some applications for this new “tiltplane” that seem appropriate. More detailed studies need to be done to confirm previous assessments and to evaluate this flight concept in depth for specific applications. If the results of these studies are promising, then the next step would be to build and test an unmanned prototype.
POSSIBLE APPLICATIONS FOR TILTPLANES
1) Unmanned and armed escorts for V-22s. These could have a top speed of 340 Knots and fly ahead of V-22s, allowing V-22s to be used more widely than they are at the present time. One challenge would be to provide on-board fuel capacity sufficient for a 6 to 7 hour mission using gas turbine power.
2) Unmanned and lightly armed scouts for Coast Guard vessels. Helicopters cannot land on the smaller Coast Guard vessels, but small tiltplanes with rotors 8 feet in diameter can. With a search speed of 300 Knots these small craft could dramatically speed up search and rescue efforts. When people at sea are located it could drop a collapsed life raft and emergency supplies. The tiltplane pilot would fly the craft from the hosting Coast Guard vessel.
3) Manned and lightly armed rescue craft for the Coast Guard. Two pilots would fly this larger craft from a cockpit forward of the first rotor giving them excellent visibility. A sphere in the center of the craft would carry perhaps six passengers. The pilot's seats and the sphere in the craft's center would remain upright when the orientation of the tiltplane's fuselage changes. To pick up people on the water surface the craft would hover and open its landing gear. Then a cable-supported basket about three feet in diameter would be used to move people between the water surface and the center sphere. With a cruising speed of 300 or 400 Knots this craft would be able to rescue people and return them to safety very quickly. These proposed rescue craft would operate from the larger Coast Guard vessels and from ports.
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