Recovered recorders from Bedford, MA, Gulfstream incident May 31
investigators say the pilots of a Gulfstream IV that was destroyed after a rejected takeoff and runway excursion at Hanscom Field on May 31 did not perform a pre-takeoff control surface movement check.
According to a preliminary report released today, the flight data recorder (FDR) parameters associated with flight control surface positions "did not reveal any movement consistent with a flight control check prior to the commencement of the takeoff roll." Control surface movement checks are typically standard checklist items before departure.
At the "rotate" speed where the pilots pull back on the elevator control to lift off, the crew discussed "comments concerning aircraft control," according to the cockpit voice recorder. Though traveling as fast as 165 kt. during the attempted departure, the aircraft did not lift off, and pilots shortly thereafter began applying brakes and reverse thrust in an attempt to stop. The FDR showed the flaps to be set at the typical value of 20 deg., although the lever in the cockpit was set to 10 deg.
Skid marks were found on the final 2,300 ft. of runway and overrun area, with the aircraft traveling another 1,850 ft. through grass, hitting approach lighting and localizer equipment before coming to rest in a gully and burning. All seven on board were killed.
The missing check could be significant, as a primary factor or a distraction, as investigators also found that the elevator surface position during the taxi and takeoff "was consistent with its position if the gust lock was engaged." The aircraft has a mechanical gust lock system, which locks the ailerons and rudders in the neutral position and the elevator in the down position as a method of protecting the surfaces from wind gusts while the aircraft is parked. The system is also supposed to prevent the throttles from being pushed to takeoff power with the lock engaged. Post-crash, investigators found that the gust lock handle, located on the right side of the control pedestal, was in the forward, or "OFF" position, and the elevator gust lock latch not engaged however.
The NTSB says the FDR data also showed that the twoturbofan engines performed as expected, with no evidence of a catastrophic failure.