Requires Update Of Engine Control Software

The FAA has posted an AD in the Federal Register requiring an update of engine control software on some of Boeing's new 747-8 and 747-8F airplanes.

The AD requires removing certain defective software and installing new, improved software. The FAA says the AD was prompted by a determination that the existing electronic engine control (EEC) software logic can prevent stowage of the thrust reversers (TRs) during certain circumstances, which could cause the TRs to move back to the deployed position.

The FAA is issuing the AD "to prevent in-flight deployment of one or more TRs due to loss of the TR auto restow function, which could result in inadequate climb performance at an altitude insufficient for recovery, and consequent uncontrolled flight into terrain."

The agency has determined that the existing EEC software logic can prevent stowage of the TRs if the airplane changes back into air mode during a rejected or bounced landing for certain The Boeing Company Model 747-8 and 747-8F series airplanes powered by certain GE engines. If this occurs and the hydraulic isolation valve closes before the TRs are fully stowed, there is no hydraulic pressure for the auto-restow function and aerodynamic loads could cause the TRs to move back to the deployed position.

It is estimated that the cost of acquiring and updating the software, including labor, will be $3,570 per airplane.

The AD is effective on April 9. Interested parties may offer comments until May 9.

FMI: AD