Patent GB-947155-A (GB)
Title: Improvements in or relating to aircraft simulators
Inventor: SCHWARM EDWARD G
IPC: G09B9/20
Filed: 1959-12-18
Abstract: 947,155. Grounded aircraft trainers. GENERAL PRECISION Inc. Dec. 18, 1959, No. 43196/59. Heading B7W. A grounded aircraft trainer comprises means for deriving components of the velocity of a simulated wind along the projection into the horizontal of an axis fixed in the aircraft, means for deriving the velocity component of simulated airspeed along the same projection, and means for summing the components to derive ground speed along the projection. In Fig. 1, constant positive and negative voltages at terminals 4 and 2 are fed through reversing switch means 6, 8 for purposes described later, to energize a resolver R-10 adjusted by the instructor's wind azimuth (#w) knob 16. The signals on wipers 12 and 14 energize potentiometers R-22 and R-24, the wipers of which are driven by the instructor's wind speed (Vw) knob 26, to derive signals representing the northerly and easterly wind speed components VWN and VWE. Each of these signals is fed through buffer and polarity reversal amplifiers to excite a resolver R-40, R-42 driven by an aircraft heading (#) servo, to derive signals -VWN cos #, -VWE sin #, -VWN sin #, and +VWE cos #, at terminals 50, 52, 54, 56, respectively. These signals, together with other inputs assumed to be available from the computer are used in Fig. 2. A shaft S, in all figures shown, operates a number of two-way switches, so that the upper switch contacts are made during simulated flight, and the lower switch contacts during simulated ground operations. During flight, the ground speed component Vxe along the horizontal projection of the X body axis is computed as -VWN cos #, - VWE sin # + Vp cos γ, where Vp is the airspeed, and γ the flight path elevation angle. Signals representing the first two terms are available at terminals 50, 52, Fig. 2, and fed over the upper contacts S-102, S-104, to summing amplifier A-146 having a feedback resistor R-164. A cos γ signal at terminal 58 energizes potentiometer R-72 driven by a Vp servo, to derive the third term fed over upper contact S-106 to amplifier A-146, the output -Vxe of which is available at terminal 166, and with reversed polarity at terminal 174. A limiting network prevents the output of amplifier A-146 from going positive. During simulated ground operation, the only input to amplifier A-146 is an X-axis acceleration signal Awx the derivation of which is not described, fed over the lower contact S-106. Switch S-134 open circuits resistor R-164, and amplifier A-146 becomes an integrator with feedback capacitor 162, its output being again Vxe. During flight, the ground speed along the horizontal projection of the Y body axis is computed as VYe = -Vp # cos γ +V WN  sin #-V WE  cos #, where # is the angle of side slip. A signal representing the first term is obtained by energizing a potentiometer R-90 from the Vp cos γ signal of potentiometer R-72, and driving the potentiometer R-90 by a # servo, the signal being fed over the upper contact of switch S-108 to amplifier A-184 having a feedback resistor R-188. Signals representing the other two terms are available at terminals 54 and 56 and fed over switches S-110 and S-112 to amplifier A-184 which thus has an output VYe available at terminal 192, and with reversed polarity, at terminal 200. During simulated ground operation, the inputs to amplifier A-146 are an aerodynamic lateral acceleration signal AYS, at terminal 64, and signals representing the lateral forces on the main wheels and nose wheel at terminals 66 and 68, the derivation if these signals not being described. The signals are fed over switch contacts S-116 and S-118 to amplifier A-146, and switch contacts S-137 and S-136 replace resistor R-188 by capacitor 190, so that amplifier A-184 integrates to provide a VYe output. The signals ŒV Xe  and ŒV Ye  are resolved in conventional manner by resolvers driven by a # servo, into VN and Ve, the northerly and easterly ground speed components used for operating speed or position indicators or recorders, or visual display apparatus. Vp is derived as shown in Fig. 4. During flight, an X-axis acceleration signal A Xw  on terminal 402 is fed over switch S-404 to amplifier A-410 with a feedback capacitor 412. The amplifier thus integrates and has an output -Vp, energizing a servo 416. While on the ground, the inputs to amplifier A-410 are Vxe from terminal 420 and switch S-414, and Vwe sin # and V WN cos # from terminals 422 and 424. Amplifier A-410 becomes a summing amplifier by operation of shaft S. This shaft also reverses the polarity of the potentials energizing resolver R10, Fig. 1, during ground operations, thus reversing the polarity of the signals at terminals 50, 52, 54 and 56. The signals on terminals 50 and 52 are then those required at terminals 422 and 420. Those on terminals 54 and 56 are those required at terminals 506, 508, Fig. 5, where # is computed. During flight, # is computed from d#/dt = rw - rs, where rw and rs are the rates of yaw measured in the wind and stability axis systems respectively, and are assumed to be available at terminals 502, 504. These signals are fed over switch contacts S-510 and S-512 to amplifier A-522 having a feedback capacitor C-524. The amplifier thus integrates to provide an output # to energize servo 554. While on the ground, # is computed from #Vp + -VWN sin # + Vwe cos # The two terms on the right are taken from terminals 506 and 508, and added by amplifier A-506. The output of this is fed over switch S-514 to amplifier A-522. Switch S-515 now provides a feedback circuit comprising resistor R-546 and potentiometer R-544 driven by the Vp servo, so that the amplifier effects division by Vp and has an output #.