Abstract: An aircraft autoland flare control system which augments the autopilot's aircraft flare control commands in the event the aircraft exceeds defined flare envelopes, monitors aircraft longitudinal position, altitude, altitude rate, lateral position and lateral position rate during flare, and outputs commands to correct aircraft position thus minimizing touchdown dispersion in both the longitudinal and lateral axes. When the aircraft deviates from the flare envelopes, such as may be due to extreme atmospheric conditions such as wind gusts, a signal commanding pitch or roll correction is output to the pitch or roll control loop which subsequently acts to adjust aircraft position such that the aircraft's flarepath is returned to within the flare envelopes.

Abstract: A signal selection and fault detection system that provides triple functional redundancy using the outputs (Y.sub.A, Y.sub.B) of two unmonitored primary channels and the output of one or the other of two complementary filters (22, 34) that each receive and process a signal (Y dot IRU) that is derived from a third, independent primary signal source (18) and that is representative of the rate or first derivative of the primary signals (Y.sub.A, Y.sub.B). During non-failure conditions, the system output (Y.sub.CF1) is generated by a normal mode complementary filter 22 from the synthesized rate signal (Y dot IRU) and the selected (10) midvalue one of this output signal (Y.sub.CF1) and the primary signals (Y.sub.A, Y.sub.B). In the event of a suspected failure in one of the primary signals, the output (Y.sub.IRU) of a failure mode complementary filter is substituted (16) for the system output signal (Y.sub.CF1) as the third input (C) to the midvalue selector (10).