AUTOMATIC PILOT MARK VIII: INTRODUCTION AND THEORY [Main Title]

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  • Title: AUTOMATIC PILOT MARK VIII: INTRODUCTION AND THEORY [Main Title]
  • Film Number: AMY 231
  • Other titles:
  • Summary: A very detailed technical film explaining the fundamental principals incorporated into the design of the Autopilot Mark VIII. This is followed by a complete description of the assembly for an Autopilot Mark VIII, using a series of film clips, extensive animated diagrams and a clear commentary. The Autopilot Mark VIII is a mechanical and electrical device, and as such is a marvel of workmanship and construction of its time.
  • Description: When the horizon is visible to the pilot he can maintain the aircraft on course and attitude, but without this datum instruments are necessary to maintain course and attitude. Three axis of reference independent of the motion of the aircraft are required to replace the datum given by the horizon. The directional gyroscope indicates motion about the axis of yaw, the artificial horizon indicates motion about the axis of roll and the artificial horizon also indicates motion about the axis of pitch. The Autopilot must not only detect but also correct any change in course of attitude by operating the appropriate flying control systems. Film cuts to large circular metal box, the cover is removed to reveal a mass of interconnected sub components which form the Autopilot. A gyroscope forms the basis of most Autopilots. The heavy spinning rotor, driven by compressed air, is mounted within two gimbals mutually at right angles which move if the aircraft deviates from the axis of the rotor. Any deviation in flight is detected by pneumatic detectors attached to the gimbals and are connected by a thin flexible pipe to servo motors to actuate the appropriate aircraft control thus restoring the original flight path. In addition to the direction of the spinning rotor remaining fixed there is another fundamental property of the gyroscope, precession, the tendency of the gyroscope to turn when under the influence of a torque that tries to change the direction of its axis of spin. To counteract this effect a relay valve is operated by a mechanical link fixed to outer of the two gimbals that applies a corrective force to the axis of spin. Precession can upset the functioning of the gyroscope but the precession can be minimised by the use of precision bearings during construction. It is necessary to provide a Pitch datum for the gyroscope to prevent toppling which can lead to errors in both the angles of yaw and pitch. Use is made of the earth’s gravitational field by deploying a vertical axis pendulum also coupled to the outer of the two gimbals to provide the datum. When axis of the rotor spin is fore and aft of the aircraft, the gyroscope will not detect the axis of Roll, likewise a rotor mounted vertically will not detect the axis of Yaw. By tilting the axis of the rotor spin to 45o in the fore and aft plane, all three axis are detected by the gyroscope. Having explained the fundamental principals of the gyroscope, the heart of the Autopilot Mark VIII, a description of the components that comprise a complete installation is given with the aid of a large schematic diagram. A compressor driven by one of the engines supplies air at 60 psi, is cooled by re-circulated oil, and piped to the gyroscope in an air tight casing via a control cock that provides the facility to use an alternative air supply on the ground for testing purposes. This cock is also used to run the rotor up to speed before engaging the Autopilot. In an emergency the elevator, aileron and pitch servo-motors may be disconnected by the pilot, to regain direct control with the Bowden cable system, the standard for all aircraft. A relay box operated by the aircraft’s distant reading (DR) compass repeater monitors the azimuth of the gyroscope unit, and energises either the port or starboard relays to maintain a pre-set course.
  • Alternative Title:
  • Colour: B&W
  • Digitised:
  • Object_Number: AMY 231
  • Sound: Sound
  • Access Conditions:
  • Featured Period: 1939-1945
  • Production Date: 1946
  • Production Country: GB
  • Production Details: Air Ministry (Production sponsor) Science Films ()
  • Personalities, Units and Organisations:
  • Keywords:
  • Physical Characteristics: Colour format: B&W Sound format: Sound
  • Technical Details: Format: 35mm Number of items/reels/tapes: 4 Footage: 3725ft; Running time: 41 mins
  • HD Media:
  • Link to IWM Collections page:

    AMY 231

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