GB965276A - Indicator device for vertical-landing aircraft - Google Patents

Abstract

965,276. Electric analogue calculating. SOC. NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. June 7,1961 [June 9, 1960; Feb. 7, 1961], No. 20532/61. Heading G4G. [Also in Division B7] In a vertical landing aircraft, the measured values of altitude h rate of climb v, and vertical acceleration γ t , and the assumed values of the maximum lift engine thrust P and total mass m are used to compute the values of the following variables by electric anologue means:- (a) the maximum vertical acceleration obtainable, given by γ m = P/m-g, where g is the acceleration due to gravity; (b) the vertical acceleration γ, required to achieve touch down at zero rate of descent, given by γ1 = v<SP>2</SP>/2h; (c) the altitude h (γt) at which # would become zero if the instantaneous acceleration γt were maintained, given by h (γt) = - #<SP>2</SP>/2γt + h (d) the altitude h (γ m ) at which v would become zero if the maximum acceleration γ m were attained and maintained, given by h (γ m ) = v<SP>2</SP>/2γ m + h and (e) the time interval t after which h (γ m ) will no longer be positive if the instantaneous acceleration γt is maintained. A square generator supplies a signal representing v<SP>2</SP> from an input representing v,when required, and where division is necessary, it is performed as in Fig. 6. In this Figure the maximum available lift engine thrust P is computed in a device 17,from inputs representing the nominal maximum thrust, ambient temperature and pressure, and v. The output representing P is fed as one input to a high gain amplifier 19. The total mass m is computed from the take-off mass,fuel consumed, and mass of articles dropped in an amplifier 20a, the output of which forms one input of a multiplier 18. The other multiplier input is the output of amplifier 19. The high gain of the amplifier requires that the total input be very small, and thus the output is P/m = γ m + g. A signal representing -g is added in amplifier 20, to derive γ m . Other additions, multiplications, and divisions are affected similarly, except that the term v<SP>2</SP>/2γ m required for h (γ m ) is derived by controlling a potentiometer, energized by a signal representing #<SP>2</SP>,by a device computing ¢ γ m . An explicit formula for t is given, but it is computed as shown in Fig. 7, where an electronic switch feeds a sampled value of γ t to two integrators in series, which have simultaneously sampled values of v and h as initial values for the integrations, to produce outputs v (#) and h (#) where # is "accelerated" time. v<SP>2</SP>(#) is generated from #(#), and divided by 2γ m , and the result subtracted from h (#), to give h (γ m ) (#), the predicted value of h (γ m ), and the value of # is registered when h (γ m ) goes negative. This computation is repeated, say, 50 times per second,fresh samples of γ t , v, and b, being taken for each computation.