Patent GB-918311-A (GB)
Title: Aircraft stabilising system
Inventor: DAVIDSON IVOR MACAULAY
IPC: B64C9/38
Filed: 1960-08-16
Abstract: 918,311. Aircraft. POWER JETS (RESEARCH & DEVELOPMENT) Ltd. Aug. 4, 1961 [Aug. 16, 1960], No. 28353/60. Class 4. An aircraft comprises a wing having a rounded trailing edge, its upper and lower surfaces each having a spanwise extending aperture arranged to discharge a fluid stream as a layer rearwardly over the wing surface, means for varying the relative discharge areas of the apertures, and means responsive to up- and downgusts and operable to effect a relative increase in the area of the upper aperture in response to an upgust, and a relative decrease in response to a downgust. Fig. 1 shows a plan view of an all-wing aircraft, the wing 1 having end plates 2, and supporting engines in rods 3, or in wing leading edge nacelles, or buried in the wing. The wing is of substantially elliptical cross-section, the trailing part being shown in Fig. 2. The apertures 11 and 12 are supplied from manifolds 13 and 14 connected to a compressed air source through pipes 15, 16, and valves 17, 18. The trailing surface 19 is of porous sintered material or has small holes or slots, so that boundary layer suction can be effected by connecting a chamber 20 with a suction source through pipes 21. The compressed air may be supplied from the by-pass streams of gas turbine engines, which also provide suction. The relative areas of the apertures 11, 12, are varied by flaps 22, 23, connected to a single rod 24 movable by actuator 25. With equal discharge areas, the downstream stagnation point is at X, and with flaps 22, 23 moved to the broken line positions the stagnation point moves to X 1 , with consequent generation of lift. In normal cruise, the centre of gravity is at the wing centre of area C, Fig. 1, and the aircraft flies at zero incidence. Lift is generated by moving flaps 22 and 23 to position the stagnation point below point X. Alternatively, the wing may be cambered, having its maximum camber at about the mid chord point, the stagnation point being at X. In either case, the effective centre of lift is at point C. The apertures are divided into inboard and outboard parts, the parts being controlled by individual actuators, as shown for parts 11a, 11b, 11c, 11d, in Fig. 1. Gusts are detected by vertical accelerometers 31, 32, 33, producing electrical output signals A 1 , A 2 , A 3  respectively. In the case of an upgust, the lift due to the effective incidence is applied at the mean quarter chord point P, Fig. 1, causing a nose up pitching moment. Operation of the two outboard actuators only in accordance with the value of A 1 -¢(A2, + A 3 ), applies increased lift on the outboard parts of the wings, which on account of the sweepback, is effectively applied at point Q, to produce a compensating nose-down moment. This, however, produces an increase in the total lift, and to avoid bodily vertical acceleration, all four actuators are operated in accordance with the value of A 1  + A 2  + A 3  to keep the total lift constant. The opposite effects occur in the case of downgusts. Stability in roll is obtained by operating one outboard actuator in accordance with A 2 -A 3  and the other in accordance with A 3 -A 2 . Manual demand signals obtained from potentiometers responsive to fore-and-aft and lateral movements of a pilot's control column are superimposed on the total lift and roll stability signals, in place of conventional elevator and aileron control. The actuators 25 may be electric or hydraulic. The accelerometers may be replaced by angular accelerometers or gyroscopes detecting pitching and rolling moments and a linear accelerometer measuring bodily vertical acceleration, or gusts may be detected by pivoted vanes or static pressure probes mounted ahead of the aircraft in known manner. A number of detecting devices may operate in parallel to allow for failures. The flaps 22, 23 may be replaced by flexible diaphragms caused to bulge to a greater or lesser extent by varying the fluid pressure on one side of the diaphragms. The aperture discharge velocity is very high, possibly supersonic, so that movement of the stagnation point in response to discharge area variation is rapid. Fig. 4 shows a modification providing high lift for take-off and landing. Further slots 51, 52 on the under surface can discharge towards one another. When these are operative, slot 12 is closed. The streams from slots 11 and 51 reinforce each other, and the stagnation point lies between slots 51 and 52, as at X 2 . The discharge areas of slots 51 and 52 may be varied for control and stability purposes, if variation of the area of slot 11 above is not sufficient. The end plates 2 are of elliptical horizontal section, each having a vertically extending variable area discharge slot on each side of its trailing edge, the slots areas being varied to obtain yaw control, and stability in response to signals from accelerometers or gyroscopes. Specifications 883,865 and 913,754 are referred to.