Error Correction in Orbital Flight

Abstract

As part of an investigation of possible future forms of air traffic control, an analysis is made of orbital motion around an Omni-Range DME station. It is assumed that each aircraft would be assigned an azimuth-vs-time schedule, and that maintenance of the schedule would be by path variation: reduction of radius when behind schedule and increase of radius when ahead of schedule. In order to estimate the precision of the proposed type of orbital guidance an autopilot control system is formulated. Aircraft motion is assumed to be governed by the equations of a "coordinated turn". Feedback of azimuth and heading and their first derivatives are shown to be needed for stabilization. Linear approximation procedures are shown to be fairly satisfactory for estimating the control system behavior. For appraisal of azimuth deviation characteristics, computations are made using reasonable assumptions for various parameters. Results are: (1) Assuming no wind and constant aircraft speed, an initial error in azimuth of up to 20° could be reduced about 30% in 1 minute and 80% in 2 minutes. (2) Assuming 1 mile per minute per minute deceleration, an aircraft on schedule at the beginning of deceleration would be 10° behind schedule after 2 minutes. (3) Maximum azimuth errors caused by wind are of the order of 0.1 [w over V] where w = wind speed and V = aircraft speed. Deviations due to wind might be reduced by means of heading compensation.