Patent GB-801842-A (GB)
Title: Improvements in and relating to flight performance computers
IPC: B64D45/00
Filed: 1955-01-05
Abstract: 801,842. Electric flight performance computers. LINK AVIATION, Inc. Jan. 5, 1955 [Jan. 7, 1954], No. 355/55. Class 37. [Also in Groups XXVI and XXXVIII] Apparatus for computing the available range of an aircraft depending on the weight of fuel available (Wf), the instantaneous weight of the aircraft including the fuel, cargo, &c. (W1), the final weight of the aircraft (W2), and the speed (V), comprises a circuit arrangement for computing this value based on (a) a constant speed flight, or (b) a constant altitude flight, a mathematical analysis showing that this range is given by Computing circuit (Fig. 1).-A signal repre- /dWf senting V/- is obtained at terminal 51 from / dt a voltage representing the ground velocity V fed in at 50 and amplified by U4, whose output is modified at a potentiometer R52 set in accordance with the rate of fuel flow dWf/dt, the amplified signal at 51 energizing a servomotor M1 to drive an indicator IC and a potentiometer R55, an anti-hunting signal being supplied by a tacho-generator G1. The sliders of three A.C.-fed potentiometers R10, R11, R12 are set according to the final weight of the aircraft W2, the weight of the cargo, and the weight of fuel in the tanks Wf respectively, the first two being set manually, and the latter automatically. The three representative voltages are amplified at U1 to give an output signal at 11 representative of the total instantaneous weight W1, which energizes a servomotor M4. When the main selector switch S1 is in the position shown a voltage is fed to amplifier U6 (a) from terminal 1 of switch S1 obtained from a log-wound potentiometer R18 fed with the total instantaneous weight W from terminal 11, and with its slider manually positioned in accordance with the final weight W2, so that this voltage is W1 loge W2, and (b) from terminal 4 of S1 obtained from a log-wound potentiometer R19 fed with the W voltage from terminal 11, after amplification at U2, and with its slider automatically positioned by servomotor M4 in accordance with the instantaneous weight W1, so that this voltage is - W1 loge W1. Hence the output voltage of amplifier U6 is proportional to the algebraic sum of these voltages, W2 W1 loge - and is fed to a potentiometer R30 W1 whose slider is positioned by servomotor M1, whereby the output is and represents the range for a constant-speed flight, and is shown on a meter IR. When the main selector switch S1 is in the next position a voltage is fed to amplifier U6 (a) from terminal 8 obtained from the output of amplifier U2 and therefore representing 2W1, and (b) from terminal 11 obtained as follows. The voltage 2W1 is fed to a square-law wound potentiometer R17 whose slider is manually adjusted together with that of potentiometer R10 to the final weight W2, so that the voltage output of an amplifier U3 represents - 2W1#W2 and is fed across a further square-law wound potentiometer R21 whose slide is positioned by servomotor M4 in accordance with W1, so that the voltage at terminal 11 of switch S is With switch S1 in this position the output of amplifier U6 is therefore proportional to the algebraic sum of the input voltages, representing the range for a constant altitude flight. In both positions of switch S1 a further indicator IE shows the range of the aircraft in hours based on a constant speed flight. When the fuel supply is low the switch S1 is manually or automatically switched to its third position, and meter IR indicates the range based on constant weight and constant fuel usage. Measuring rate of fuel flow (Fig. 2).-A propeller 61 in the flow line is rotated by the fuel and drives a cylindrical magnet 66 which drags a hollow aluminium cylinder 67 by eddy currents against a spring 70 so that the angular rotation of the cylinder 67 is proportional to the rate of flow, and is transmitted via shaft 68 to potentiometers R52, R35. Measuring aircraft ground speed (Fig. 3).- The slider of a potentiometer R70 fed with A.C. is positioned manually in accordance with the wind speed, and the signal voltage is split into its N-S, E-W components by a resolver T2 positioned manually in accordance with the wind direction, the components being applied to a further resolver T3 set either manually or automatically in accordance with the aircraft heading, the wind components in the direction of the heading and perpendicular thereto being fed to a third resolver T4, the former component being augmented by a true air speed signal from computer COMP. 1. The sine winding 72 of the rotor of T4 is connected to a servomotor M4 which rotates the rotor to eliminate the signal, thereby indicating the angle between the flight path and the heading. The output from the cosine winding 73 of the rotor is then representative of the ground speed along the flight path.