GB1222524A - Improved device for increasing the safety of aircraft during automatic landings by improved overall longitudinal control - Google Patents

Abstract

1,222,524. Automatic control of aircraft. SUD-AVIATION SOC. NATIONALE DE CONSTRUCTIONS AERONAUTIQUES. Feb.23, 1968 [April 3, 1967], No.8924/68. Heading G3R. In an electric automatic landing system for an aircraft: - (a) a warning device is operated by excessive deviation from the long term average of pitch attitude. As described, signals from a pitch attitude gyro are applied through a high-pass filter and an amplifier to relay-operate the warning device if nose-down deviation occurs in excess of a predetermined value. This value is automatically adjusted by a radio altimeter to be different above and below the altitude at which flare-out commences, and may vary progressively during flare-out. Lack of agreement between the gyro signals and signals from a similar gyro associated with the autopilot also operates the warning device. (b) the autopilot elevator servomotor is rendered ineffective by an excessive combination of signals from a rate of pitch detector and a rate of change of altitude detector. As described, signals from a pitch attitude gyro, differentiated by a high-pass filter, and signals from a vertical accelerometer, integrated by a low-pass filter, are applied through an amplifier to relays which render the elevator servomotor of the autopilot ineffective if the signals are excessive. The relay responsive to nose-up movements is made less sensitive than that responsive to nose-down movements. The signals from the accelerometer may be eliminated during flare-out by a relay controlled by a radio altimeter. The amplifier output is also compared with a similar output derived by integrating and differentiating signals from the vertical accelerometer and pitch attitude gyro associated with the autopilot so that any lack of agreement operates a warning device. (c) a warning device is operated by excessive rate of change of altitude during flare-out. As described, signals from a radio altimeter, both directly and after differentiation by a high-pass filter, are combined with signals from a vertical accelerometer, integrated by a low-pass filter and applied through an amplifier to a relay which renders the elevator servomotor of the autopilot ineffective and operates a warning device if the signals are excessive in a nose-down sense during flare-out. The signals from the radio altimeter are prevented from increasing at higher altitudes. Lack of agreement between the radio altimeter signals and signals from the radio altimeter associated with the autopilot also operates a warning device. and (d) a warning device is operated by an excessive time interval before touchdown. As described, a time delay relay, actuated at the commencement of flare-out, operates the warning device unless a switch is operated by the undercarriage on touchdown within the allowable period.