GB1133081A - An aircraft computing and director system for take-off and overshoot - Google Patents

Abstract

1,133,081. Aircraft take-off and overshoot computer. MINISTER OF TECHNOLOGY. 17 Nov., 1965 [17 Aug., 1964], No. 33561/64. Heading G4G. In apparatus for producing a display to the pilot of an aircraft during take off or overshoot, a pitch rate director signal is given by Q - QD (1) where Q is pitch rate Q D is a required pitch rate to develop the required climb path, given by Q D = K2 TV + K2V - K2 V D (2) or allowing for any loss of engine thrust where V is airspeed V is longitudinal acceleration V D is required steady climbout speed T is constant determining the ratio V/#V K 2 is an aircraft characteristic and loading constant 1 is an exponential term wherein 1 + #D # is a time constant D is a differential operator. A pressure transducer operated by a static pitot tube produces an airspeed signal connected to operational amplifier 2 with smoothing feedback path, whose output - V is connected to adder amplifier 3a direct through resistor R 2 and through a differentiating network comprising resistor R 1 and capacitor T developing longitudinal acceleration signal. Potential divider 5 is also connected over series resistors R 4 , R 5 to adder 3a to introduce a preset demanded steady climbout speed V D , and a variable capacitor T 4 is switchable at S 1 between earth and the junction of R 4 , R 5 , while a potential divider VR 5 is switohable at S 2 to the junction of S 1 and T 4 . The output of the adder is connected over potential divider 6 to operational amplifier 7 with limiter feedback, which energizes adder amplifier 9a with smoothing feedback; a smoothing network comprising resistors R 7 , R 8 and variable capacitor T 5 being connected between the input of 9a and the output of pitch rate gyro 12. Shunt resistor R 9 is switchable by S 5 while the input of 9a is also connected over series resistors R 11 , R 12 to a potential divider VR 9 ; the junction of R 11 , R 12 being earthed either direct over switch S6 or capacitatively through switch S7. Output of amplifier 7 is earthable over normally open S4, and the output of the potential divider 13 in the output adder amplifier 9a is applied to a pilot's head-up display 15 and over a modulator 14 to an automatic pilot or head-down control display 16. The output of amplifier 2 also energizes threshold circuit 17 controlling switches S2 to S 7 , which may be transistorized, and the amplifier 18 energizing potential divider VR5. In directing take-off during acceleration to rotation speed V R , the smoothed airspeed signal (-V) at the output of 2 energizes the threshold circuit to operate first at e.g. a speed (V R - 15) slightly in defect of the rotation speed and subsequently at the rotation speed, so that initially, switches S 1 to S 7 are closed and the output of amplifier 7 is earthed. The pilot's display then indicates at the bottom of its screen a smoothed and attenuated pitch rate signal Q. At speed (Vr - 15) switch S6 is opened and a positive voltage is applied from VR 9 to adder 9a, through warning circuit 11, and exponentially deflects the Q signal from the bottom to the centre of the pilot's display screen in the time for the aircraft to accelerate from (V R - 15) to (V R ). At speed V R switches S 2 , S 4 , S 5 , S 6 , S 7 are open and S 1 is closed by threshold circuit 17. A (- v) signal from amplifier 2 and a V D signal from potential divider 5 produce a signal (-TV-V) at the input of adder 3a. Network 4 operates on V D to add a signal VD/1 - # D, so that the total signal at the potential divider 6 represents equation (3), but the signal V D is delayed to rise exponentially with time through the rotation manoeuvre to allow and compensate for any engine failure during take-off, by applying an instantaneously lower required climbout speed which progressively approaches the full value thereof. Limiter amplifier 7 reverses the sense of Q D and limits it so that rotation is directed at a constant rate, and a minimum value to limit any nose-down tendency. An achieved pitch rate signal Q from gyro 12 is combined with Q D in adder 9a, and the difference (Q-Q D ) operates the pilot's display and auto pilot 16; amplifier 18 being disabled by S 2 from the instant the aircraft speed reaches VR. In directing overshoot, the apparatus operates during landing approach with switch S 1 open and switch S 2 closed. Amplifier 18 applies a (-V) signal to capacitor T4, which follows and stores the airspeed signal throughout the approach. On decision to abort landing, S 1 is closed. If airspeed exceeds V R , threshold circuit 17 opens S 2 to disconnect amplifier 18 and the instantaneous airspeed signal Vi stored on T4 is transferred exponentially to adder 3a so that the speed demand signal rises exponentially from Vi to VD. The required pitch rate signal representing demanded rate of rotation from potential divider 6 and given by equation (3), and the difference signal from (Q-QD) from potential divider 13 appears on the pilot's display and/or at the automatic pilot to direct the pull-out. If airspeed is in defect of V R , the system operates similarly to its function for normal take-off. Azimuth and bank deflections may be superimposed on the pitch director signal in the pilot's display, the longitudinal acceleration signal may be obtained from an accelerometer, and the pitch rate signal by differentiation of the output from an attitude gyro.