Abstract: In an autothrottle system having the capability to reduce engine throttle setting from a first position to an idle position, an improvement including calculating a rate of throttle reduction as a function of the combination of a nominal retard rate value (10) and a retard rate adjustment value (12). In one embodiment, the nominal retard rate value (10) is equal to the angular difference between a current engine throttle control lever position (TRA) and an idle engine throttle control lever position (TRAIDLE), the difference being divided by an amount in the range of about 3 seconds to about 10 seconds. The retard rate adjustment value (12) is calculated as a function of the difference between current airspeed (VC) and a commanded airspeed (VCMD). During an underspeed condition, the retard rate adjustment signal decreases the rate of throttle reduction from the nominal retard rate value (10).

Abstract: Disclosed is a method of and apparatus for processing flight control signals in an automatic landing system so that automatic landings can be executed within the bounds of current certification requirements (Category III weather minimums) and in a manner that in effect emulates standard manual landing procedures. Included is provision for introducing engine-out sideslip that insures that the automatic landing approach and touchdown is made with the aircraft wings level or with the upwind wing low. Also provided is the generation of rudder and wheel (aileron) compensation for lateral ground effects that occur during a landing with sideslip when the aircraft altitude is approximately one wingspan or less. Provision also is made for rudder control to offset yawing moment that occurs when the thrust of the operative engines is retarded prior to touchdown.