The FAA published an Airworthiness Directive December 12 on the Gulfstream G350/450 after what is described as routine maintenance testing by the manufacturer uncovered a fault in one of the aircraft test systems—the flap/stabilizer electronic control unit—used during normal checks by pilots before the first flight of the day. The test that failed normally confirms the operational readiness of the hydraulic brake used to stop the pitch trim motor in the event of a runaway of that system.
A Gulfstream spokesman told AIN that neither the pitch-trim motor nor the brake is in question, only the software that is used to test the system each morning. While a software fix is being developed, Gulfstream has issued an Alert Customer Bulletin, as well as a Maintenance Operations Letter that outlines a manual procedure for crews to guarantee the pitch-trim brake is actually functioning correctly. Gulfstream says the manual procedure adds only a few more steps to each morning’s cockpit checks.
The Gulfstream spokesman told AIN that the company notified the operators of 97 percent of the 260 aircraft in the field about the problem and the fix before AD 2012-NM-219-AD was issued. No G350s or G450s have experienced any pitch-trim problems stemming from this issue, Gulfstream said.