Aeronautics and astronautics – Aircraft – heavier-than-air – Airplane sustained
Patent
1998-03-23
1999-11-30
Barefoot, Galen L.
Aeronautics and astronautics
Aircraft, heavier-than-air
Airplane sustained
244207, 244215, 244216, 244 45A, B64C 916
Patent
active
059927925
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an aircraft with jet flap propulsion and as presented in the preamble of claim 1, i.e. an aircraft with an ordinary main plane or a further development hereof as presented in the preamble of claim 2: An aircraft, which in addition to the main plane has a foreplane, a so-called canard plane.
Aircraft with jet flap propulsion have been known for many years, for example from U.S. Pat. No. 2,912,189 or U.S. Pat. No. 2,961,192. Also jet flap propulsion aircraft with a foreplane have been known for years, for example from U.S. Pat. No. 3,362,659. Even aircraft where both the foreplane and the main plane use jet flap propulsion are known, cf. for example U.S. Pat. No. 3,056,566.
In the past several aircraft have been made with special and extensive flap and slot arrangements to reduce stall speed and needed runway. These aircraft are called STOL (short take-off and landing) aircraft. The operating costs of such aircraft are in most cases approximately 30% higher than on conventional aircraft. This lies in added maintenance costs, higher fuel consumption per distance flown. The added wing area (lower wing loading) creates added drag and reduced cruising speed.
Most of all earlier aircraft designers using the blown flap theory have concentrated their efforts on increasing the lift coefficient of the wings to reduce landing speed or to obtain added control force. Blown flaps give extra thrust and this causes problems when the aircraft is being slowed down for landing. In most of the previous patents using blown flaps only a small part of the engine power is used to avoid the problem of extra thrust. If all engine power is used on blown flaps it is necessary to be able to deflect the jet sheet through more than 90 degrees to obtain drag on landing. To be able to deflect air by coanda effect, the outside pressure must balance the centrifugal force of the jet sheet. This is only possible if the radius of the control flap is relatively large compared with the slot height. Furthermore, the duct pressure must be relatively low.
SUMMARY OF THE INVENTION
With an aircraft designed as presented and characterized herein, it is achieved that the jet flap principle is used to reduce the wing area of the aircraft and hereby to reduce the overall drag of the aircraft; consequently, the fuel consumpsion is reduced.
The aircraft is using conventional landing speed, but the reduced wing area makes cruising more economical.
For cruise performance of aircraft the lift/drag*mach number must be a maximum. A great part of the drag is created by the wing. The wing drag can be reduced if the aspect ratio (wing span/chord) is increased and also with boundary layer control. The aspect ratio is gradually going up as improvements in materials are made. But there is a drawback. Wing tip drag (induced drag): ##EQU1## where K=Constant depending on taper ratio and aspect ratio C.sub.DO =airfoil profile drag ##EQU2## From this it is obvious that any improvements in stronger and lighter materials call for higher values of C.sub.L. Aircraft flying today use less than the optimum value of C.sub.L for cruising. Typical value of C.sub.L used for cruise on present day aircraft is 0.2 to 0.5. Optimum value would be approx. 0.8 to 1.4 typically, so there is a substantial difference. If optimum C.sub.L could be used, smaller wings could be used with lower all up drag. In the past blown flaps have been used to increase lift for landing and taking off. Efforts have been concentrated on obtaining maximum C.sub.L and less on power used. In this invention blown flap, boundary layer control and propulsion are all combined, resulting in lower drag and better cruise performance, but still making large speed range possible. A typical wing section is thickened to the rear and a relatively short chord control surface is employed with an included trailing edge angle, which is up to two or three times that of a typical wing profile. The control surface has a large leading edge radius. This way a fairly large duct c
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patent: 2479487 (1949-08-01), Goembel
patent: 2912189 (1959-11-01), Pouit
patent: 2920844 (1960-01-01), Marshall et al.
patent: 2961192 (1960-11-01), Davidson
patent: 2978207 (1961-04-01), Davidson
patent: 3056566 (1962-10-01), Davidson
patent: 3100094 (1963-08-01), Griswold, II
patent: 3127129 (1964-03-01), Petrie
patent: 3362659 (1968-01-01), Razak
patent: 3724784 (1973-04-01), Von Ohain et al.
patent: 3774864 (1973-11-01), Hurkamp
patent: 3887147 (1975-06-01), Grieb
patent: 4610410 (1986-09-01), Sibley
patent: 4615499 (1986-10-01), Knowler
Barefoot Galen L.
Verkfaedistofa Kristjans Armasonar
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