Patent GB-812748-A (GB)
Title: Improvements in computers for determining the optimum cruising altitude of an aircraft
IPC: G05D1/00
Filed: 1957-01-16
Abstract: 812,748. Controlling aircraft ; aircraft indicators. BENDIX AVIATION CORPORATION. Jan. 16, 1957 [Jan. 23, 1956], No. 1675/57. Class 4. [Also in Groups XXXVI and XXXVIII] The optimum cruising altitude of an aircraft is calculated by obtaining signals representative of the instantaneous altitude, ambient temperature and gross weight, and detecting deviations of the combination of these signals from the value which corresponds with optimum conditions. In Fig. 1 the units 10, 11 and 13 produce signals corresponding to altitude, temperature and weight respectively. The aneroid barometer 20 displaces the rotor 22 relative to the stator 2 4 and develops in the latter a signal indicative of the magnitude and direction of displacement. This signal is applied via potentiometer 25 (see below) and amplifier 26 to a motor 27 which drives the stator 24 to a new null position and at the same time displaces the rotor 30 relative to the stator 32. The temperature-sensitive element 41 is mounted outside the aircraft in a position such that air is driven by a vane to create a vortex around, the element; the cooling effect of the vortex then compensates for the dynamic heating and the reading is correct for ambient temperature. When the latter changes, the bridge 40 is unbalanced and the voltage so generated energises the motor 45 to drive the slider 47 until the bridge output is zero: At the same time the rotor of the differential transformer 49 is displaced relative to the stator. The instantaneous weight is calculated from a setting of the initial gross weight and measurement of the rate of consumption of fuel. The latter flows past two pivoted vanes 54 and displaces them against the action of springs. The rotors 60, 64 are thus turned relative to their stators and the voltages so produced are summed, amplified and passed to the motor 72. This turns the rate generator 73 to supply negative feedback to the source, and also displaces the rotor 80. The initial gross weight of the aircraft is set up by the knob 83 as the angular position of the stator 82. A voltage is supplied to rotor 30 and passed on through windings 32, 49, 82 and 80, and if values of temperature and weight are correct for the particular altitude no voltage is developed at the rotor 80. If one of the three parameters changes, a signal is obtained at 80 indicating by phase sense and amplitude the direction and amount of the change. This signal is applied via the transformer 89 to a motor 105 in conjunction with the signal from a vertical gyro 100, and the difference between the two displaces the elevator surface 107 until the followup device 111 brings the difference to zero. The aircraft then climbs or descends until the changing signal from the altitude sensor 10 restores the output 80 to zero, when the motor 105 brings the elevator back to the level position. By a similar circuit the transformer 89 also controls the throttle via the motor 122, and a third winding operates the indicator 130 to show when the aircraft deviates from the correct altitude. The adjustment of elevator and throttle may be carried out manually instead of automatically. For correct compensation it is necessary that the signals from the circuits 10 and 11 be non-linear functions of the altitude and temeperature respectively. This is achieved by causing the motor 27 to operate a potentiometer 25 which injects a further signal into the circuit, of amplitude depending on the output signal. A further potentiometer 152 driven by the same motor varies the input to the temperature bridge in accordance with variations in the altitude signal.