875,799. Grounded aircraft trainers. GENERAL PRECISION Inc. Sept. 3, 1957 [Sept. 21, 1956], No. 27777/57. Class 4. Grounded aircraft training apparatus comprises a cockpit mounted for pitching movements about a transverse axis disposed to the rear of the cockpit, and rolling movements about a fore-and-aft axis, means for effecting movement of the cockpit in response to signals representing simulated flight variables received from a computer, one or more cockpit instruments indicating the variables, and means for generating erratic signals representing simulated rough air effects and super-imposing the erratic signals on the input signals to the cockpit moving means and those to the cockpit instruments. In Fig. 1, a rough air motor 193 energized through an instructor's on/off switch S 156 and a " weight on wheels " relay contact S 157 drives the sliders of three potentiometers R 158 , R 159 , R 160 through irregularly shaped cams 161, 162, 163. The potentiometers are energized through instructor's on/off switches S 154 and S 155 from constant voltages modified by an instructor's intensity control through potentiometers R 152 and R 153 and a computer Mach number servo through potentiometers R 150 and R 151 , so that the sliders derive signals simulating random rough air effects.. One signal is fed to the flight computer side slip angle summing ampliffer U 12 , one to the rate of roll (Ï) summing amplifier U 182 , and one over terminal 105 to the servomotor moving the cockpit in pitch and to a summing amplifier U 174 computing the simulated vertical acceleration, indicated in the cockpit as instantaneous " g " through an accelerometer servo U 188 . The signal across potentiometers R 158 to R 160 is also fed through switches S 167 and S 168 intermittently closed by the rough air motor, to the indicated air speed indicator servo U 172 , to simulate the effects of rough air on air speed. In Fig. 2, the Ï signal (including the rough air simulating signal described above is applied at terminal 101 to the computer roll angle servo U 115 , and to an integrator I 101 coupled to a limiter comprising a double diode V 102 biased by positive and negative voltage sources applied through potentiometers R 147 to R 150 . The values of feed-back resistors R 118 and R 119 determine the time constant of the integrator which is such that after five to ten seconds, the integrand falls to zero. The output signal is fed to summing amplifier U 102 . The voltage representing sideslip # (including the rough air simulating signal described above) is applied at terminal 102 and fed through the upper contact of switch S 101 to amplifier U 103 . The feed back path of amplifier U 103 is resistor R 125 and potentiometer R 124 the slider of which is driven by the computer lift coefficient (CL) servo U 13 and the upper contact of switch S 103 , so that the output of amplifier U 103 is then #/CL. When the "weight on wheels " actuator 11 indicates that the aircraft is on the ground and sideslip is zero, the lower contacts of switches S 101 and S 103 are made, feeding to amplifier U 103 a signal MR where M is the Mach number and R the rate of turn, the feedback path of amplifier U 103 then being resistors R 123 , R 126 . The amplifier output at all times represents #, the simulated ball angle, and is fed to amplifier U 102 , the output of which is passed through a limiter 106 to actuate the valve 111 of the servo positioning the cockpit in roll and also operating a potentiometer R 130 producing a feed back signal to amplifier U 102 . The cockpit is thus positioned in roll according to the simulated ball angle, and also in accordance with the output of integrator I 101 which is such that the cockpit rolls when the value of Ï is altered, and is returned gradually to its previous attitude over a period of time depending on the time constant of integrator I 101 . The flight computer pitch angle (#) servo U 14 positions the slider of potentiometer R 108 to derive a # signal fed to a limiter V 101 and thence to amplifier U 106 . A voltage representing aircraft velocity energizes potentiometers R 101 and R 102 the sliders of which are controlled by the left and right brake pedals. The derived signals are summed in amplifier U 104 and fed, during "weight on wheels " through a switch transient filter to amplifier U 1 06 . The signal representing the effects of rough air on angle of pitch, as described above, are applied at terminal 105 and fed to summing amplifier U 106 . A further signal representing the forward acceleration Ax is applied through terminal 112 to summing amplifier U 105 , the feed back resistor R 142 of which seals the output to Ax/g. Alternatively Ax may be divided by Az, the vertical acceleration apart from gravity. This output is also fed to amplifier U 106 . To simulate buffeting, the erratic output of a multivibrator V 103 is fed to amplifier U 106 when either of switches S 104 or S 105 is closed, the former when a critical value of CL is reached indicating impending stall, and the latter when a critical value of dynamic pressure or Mach number is reached. The output of amplifier U 106 is fed through a limiter and buffer amplifier to the valve 110 of the servo operating the cockpit in pitch, and also operating a potentiometer R 131 providing a feed back signal to amplifier U 106 . The quantity Ax/y or Ax/A2 may be fed to an integrator I 102 for computer purposes. Fig. 4 shows the cockpit which is mounted on three universal joints, one 317 on a fixed pillar 316 to the rear of the cockpit, a second 321 on the hydraulic actuator 302 controlling the cockpit in roll, and a third 320 on the hydraulic actuator 301 controlling the cockpit in pitch. In addition, a roller is mounted on a fore-and-aft axis forward of the cockpit, and engages the sides of a vertical groove in a fixed pillar 322. The roller guides the cockpit vertically during changes in pitch, and acts as a pivot during changes in roll.