FAA published an airworthiness directive requiring a modified system power-on self-test (SPOST) of the flap/stabilizer electronic control unit (FSECU) on Gulfstream G350 and G450 aircraft.
(Gulfstream G450--photo courtesy of Gulfstream Aerospace)
The agency said a software glitch in the procedure for power-on testing could possibly lead to the uncontrolled movement of movable panels located at the rear of the wings. This is the result of the FSECU executing the SPOST before power becomes available, which means the testing of the software that recognizes a runaway stab and stops it from happening wasn't taking place.
A spokeswoman for Gulfstream said the company discovered the problem internally, and has come up with a new manual power-on testing procedure that avoids the software glitch.
“There’s a self-test that occurs to make sure the software works. That test was occurring earlier than it should have, before power was available,” said Heidi Fedak, spokeswoman for Gulfstream Aerospace.
Fedak said Gulfstream will eventually release a software update to address the problem, but for now G350 and G450 pilots will perform the power-on testing manually. FAA’s directive indicates flight manual revisions were distributed earlier this month.