Patent GB-855516-A (GB)
Title: Improvements in and relating to ground aviation trainers
IPC: G09B9/20
Filed: 1956-12-07
Abstract: 855,516. Grounded aircraft trainers. LINK AVIATION Inc. Dec. 7, 1956 [Dec. 8, 1955], No. 37549/56. Class 4. A ground aviation trainer comprises an analogue device computing the velocity and direction of movement of a simulated aircraft both on the[ ground and in the air, and computing the angle of side-slip as an intermediate output, wherein means are provided for a " wind " input and the effect on side-slip of take-off and landing is simulated by modifying the side-slip output. In Figs. 1 and 2, a potential Mz derived in a conventional manner from part of the computer not shown, and representing the total yawing moment, is applied via terminal 101 to an integrator U-1, the output of which represents r, the rate of yaw. The integrator may be electronic or a velocity feed back servo system. The r signal excites a resolver R-104 directly and through a phase or polarity reversal amplifier U-2. The cosine wiper of the resolver, which is controlled by the computer bank angle (°) servo S-1 derives a signal r cos ° fed to amplifier U4- through resistor R-108. A potential derived.elsewhere in the computer representing the rate of roll q is applied through terminal 102, and buffer amplifier U-5, to a resolver R-107 also controlled by the bank angle servo. The sine wiper derives a signal q sin ° fed to amplifier U-4 through resistor R-109. A further signal -# cos # where # is the heading angle and # the angle of pitch, derived as described later, is also applied to amplifier U-4 through resistor R-110. The output of amplifier U-4 is fed through terminal 207 (see Fig. 2) to the computer heading servo S-2 which drives a tachometer generator TG-200 providing outputs Œ # at terminals 205,206 (see Fig. 1). These excite a resolver R-130 controlled by the computer pitch angle servo S-3, so that the cosine wiper derives a signal - # cos # fed to amplifier U-4. The servo S-2 thus solves the equation # = (c cos ° + q sin °) /cos # and its shaft position represents #. A further signal g cos y sin Ï/V P  where g is the acceleration due to gravity, y is the flight path elevation and V P  is the airspeed is derived elsewhere in the computer and applied through terminal 103 and resistor R-114 to integrator U-6. A signal Ay representing the total lateral force on the simulated aircraft is applied through terminal 104, resistor R-125, and summing amplifier U-8, to a potentiometer R-128, the slider of which is driven by the computer Vp servo S-4 and grounded through resistor R-129. The signal on the wiper is thus -Ay/VP, which is fed to integrator U-6 through resistor R-115. A signal r is also added through resistor R-113. The inputs to integrator U-6 are thus [(g cos y sin Ï-A y /V P  + r] = #, where # is the angle of side-slip, and the output # excites a resolver R-118 driven by the computer y servo S-5 to derive a signal # cos y to energize a potentiometer R-119 the slider of which is controlled by the Vp servo S-4 to derive a signal VP # cos γ fed to terminal 204. A constantly energized potentiometer R-131 is driven by the Vp servo S-4, and energizes a resolver R-134 driven by the y servo S-5, to derive signals VP cos y fed to terminal 203 and VP sin y. In Fig. 2, the VP cos y signal is taken as the horizontal component of airspeed along the X- axis of the aircraft, though the more rigorous value VP cos γ cos # could be used if desired. This signal is applied to a resolver R-202 controlled by the # servo S-2 to derive voltages VP cos y cos # and VP cos y sin # representing North-South and East-West components, and fed to amplifiers U-17 and U-18 through resistors R-217 and R-218 respectively. Similarly, the horizontal component of lateral velocity is taken as VP # cos y, though a signal VP sin # cos y could be used, and is applied to a resolver R-203 deriving N-S and E-W components VP # cis y sin #, and VP # cos γ cos # fed to amplifiers U-17 and U-18 through resistors R-223 and R-224 respectively. Wind velocity components are derived from a potentiometer R-206, the wiper being adjusted by an instructor to derive a wind speed (Vw) signal which excites a resolver R-201 controlled by the instructors wind direction #w knob 202, so that the cosine and sine wipers derive signals - Vw cos # w and - Vw sin #w fed to amplifiers U-17 and U-18 through resistors R-211 and R-212 respectively. The outputs of amplifiers U-17 and U-18 thus represent the N-S and E-W components of ground speed, and energize integrators I-200 and I-201 to derive simulated aircraft position co-ordinates, used for actuating a ground track recorder and simulated radio aids and visual display apparatus (not shown). The North-South ground velocity VNS is fed to a resolver R-204 controlled by the #servo S-2 to derive one component of fore-and-aft ground velocity fed to amplifier U-23 through resistor R-236. The East-West ground velocity V EW  is fed to a resolver R-205 also controlled by the # servo S-2 to derive the second fore- and-aft component of ground velocity fed to amplifier U-23 through resistor R-235. The output of this amplifier thus represents fore-andaft ground velocity VEX. Similarly the resolvers R-204 and R-205 derive components of the lateral ground velocity which are summed in amplifier U-21 to provide a lateral ground velocity signal VEY on terminal 208. This is fed, Fig. 1, to one arm a of a switch S-101 having other arms b, c, each being closed when the computer altitude integrator servo S-6, energized by a rate of climb VP sin y signal from resolver R-134, registers zero altitude. The VEY signal is then fed to the lateral forces summing amplifier U-8 through resistor R-126, modifying the input to the # integrator U-6 through resistors R-128 and R-115. As a result, when the simulated aircraft is on the ground, the side-slip angle is modified until VEY = O, i.e. until there is no lateral velocity. The rate of yaw signal is also modified by closure of contact c of switch S-101, adding a feed back signal to integrator U-1. When the pitch servo S-3 indicates that the nose wheel is on the ground, switch S-102 is also closed. The signal derived by the trainee's steering control 108 on potentiometer R-120 is then multiplied by airspeed VP by potentiometer R-121 (the more correct factor VEX may be used by energizing potentiometer R-120 from terminals 212, 213 of Fig. 2 and omitting potentiometer R-121) and fed to integrator U-1 over contact b of switch S-101 and resistor R-122, so that the rate of yaw is determined principally by the steering control. As so far described, when the aircraft is stationary, negative potentials corresponding to the wind components would be fed to integrators I-200 and I-201, Fig. 2, whereby the simulated aircraft would appear to be blown backwards. To avoid this, a small negative bias on resistor R-245 is added to the VEX signal through resistor R-246 in a summing amplifier U-24 and the output applied through rectifier X-201 to a relay K-201. While VEX is negative, the relay contacts disable integrators I-200 and I-201, but as soon as a small positive ground speed is attained, the negative bias on resistor R-245 is overcome, and the relay operates to render integrators I-200 and I-201 operative.