Gulfstream Aerospace issued a maintenance and operations letter on Monday to all Gulfstream operators stressing that the “freedom of flight control movement is the ultimate indicator the gust lock is fully released for all Gulfstream models.” The letter, MOL-14-0024, is a follow-on to another sent on June 13 in the wake of the May 31 GIV-SP accident near Boston, reminding “operators of the importance of adhering to Airplane Flight Manual (AFM) procedures to confirm flight control integrity and freedom of movement.”
The pilots of this accident airplane reported “control problems” after reaching rotation speed on takeoff, according to an NTSB preliminary report. (All seven aboard were killed in the runway excursion.) The NTSB preliminary report noted that the gust lock control lever was in the off position, but didn’t address whether the gust lock pin mechanically released before the crew began the takeoff roll.
According to the latest letter from Gulfstream, “While a throttle interlock is incorporated in the design of the gust lock system, if proper unlock procedures are not followed, movement of the throttle to a position capable of providing sufficient engine power for autothrottle engagement and takeoff power may be possible for GIV models. Throttle movement is not an absolute indicator of the gust lock status for any Gulfstream model.”
Gulfstream reiterated that crews should perform the following as set forth in the applicable AFM procedures: ensure the gust lock is off before starting engines (not applicable for G650); check flight controls for freedom and correct movement before taxi/takeoff; and confirm the elevators are free during the takeoff roll.