A Theoretical Analysis of the Stability of annAeroplane on Northerly Headings when Controlled by an Aileron-Steering Autopilot Monitored from a Gyro-Magnetic Compass

摘要

Long-period lateral oscillations of an aeroplane under automatic control on Northerly headings are shown to be due to high speed in a region of large magnetic-dip angle accompanied by strong monitoring of the gyro-magnetic compass and autopilot. Aerodynamic characteristics are not important, and speed is the predominant aircraft parameter. An approximate analysis assuming that the motion consists of co-ordinated turns is found reliable for many purposes.nThe requirement of weak monitoring for ensuring stability conflicts with the need for strong monitoring to restrict datum errors caused by random precession torques on the azimuth gyro and by drifts in the autopilot. Modifications to the compass precession signal may stabilize the motion, but usually at the expense of a deterioration in datum errors, or with insufficient reduction in oscillation amplitude on account of thresholds of rate gyros.