CRUISE SPEED CONTROL FOR AIRCRAFT PERFORMANCE MANAGEMENT SYSTEM

A cruise speed control apparatus in an aircraft performance management system wherein target Mach command is supplied to the engine automatic throttle controls to establish an engine thrust to overcome and equate to the aircraft nominal drag characteristics at that commanded Mach speed and simultaneously the difference between the actual Mach number speed and the target Mach command speed is supplied to the automatic pilot pitch axis control to cause the aircraft to maintain the commanded Mach speed through change in pitch attitude and altitude. The integral of any altitude standoff is used to adjust required thrust to achieve the commanded Mach target and reduce the standoff to zero. If necessary, filtered altitude error may be used to provide dynamic damping of the throttle control loop and compensation for long term degradation in the aircraft's drag characteristic with time is provided by measuring the drag degradation ratio and adjusting the target Mach command in accordance therewith.