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: Methods and apparatus are provided for a fail-operational global time reference for a synchronous redundant data bus including multiple pluralities of timing servers cross-coupled between a plurality of buses in said redundant synchronous data bus system, the apparatus comprising each said timing server of the multiple pluralities of timing servers configured to transmit, receive, and monitor synchronization signals, to store a unique constant, and to independently and automatically select as timing master one or more timing servers from among the multiple pluralities of timing servers based on said synchronization signals received from one or more of said timing servers of said multiple pluralities of timing servers and further based upon a relationship among said unique constants stored in each timing server. Methods comprising selection protocols are also provided.