Abstract: Methods and apparatus are provided for more reliably transferring operational control for various aircraft flight control surfaces from a first sub-system to a second sub-system. The present invention provides an Actuator Control Electronics (ACE) wrap-back module that monitors the output of the normal mode control module and switches control to the direct control module based upon the detection of an error condition. The switching function is controlled by a monitoring system that monitors the output from an integrated heartbeat module that emits a pre-programmed signal. The pre-programmed signal is encoded and sent over a communication bus where it is then decoded and validated by comparing the decoded signal to the expected results. Any irregularity in the heartbeat signal automatically triggers a change of control from the first flight control sub-system to the second flight control sub-system.

Abstract: The dynamic stiffness of a flight control actuator is assessed by providing an actuator control system that includes an actuator and a portion of the actuator is coupled to an aircraft control surface. A command signal is applied to the actuator control system, which causes the production of a pressure differential across the actuator in response to the command signal that is based on the ability of the actuator to react to an inertial load generated by an acceleration of the aircraft control surface. A pressure signal representative of the pressure differential across the actuator is processed and the pressure signal is compared to known pressure differential values produced under similar conditions for specific actuator and specific control surface combinations.

Abstract: A method for assessing the dynamic stiffness of a flight control actuator comprising the steps of (1) providing a control surface actuator system including an actuator having a portion thereof coupled to an aircraft control surface; (2) applying a command signal to the actuator control system, causing the production of a pressure differential across the actuator in response to the command signal based on the ability of the actuator to react to an inertial load generated by the attempted acceleration of the control surface; and (3) processing a pressure signal representative of the pressure differential produced across the actuator.

Abstract: A monitoring system for detecting failures, or impending failures, in subsystems of a fly-by-wire primary flight control system of an aircraft. The system monitor a critical variable of at least two controllers acting in concert, in real time. Differences between the critical variables are calculated and, after filtering to remove insignificant variations, structural fatigue damage is estimated based on significant detected variations. Depending upon the relative severity of the estimated fatigue damage, the aircraft's primary flight control computer is programmed to shut down the malfunctioning subsystem, display a message indicating need for repair, or take other appropriate action.