Gulfstream IV-SP Crash Investigators Eye Control Wheel Gust Lock
The NTSB’s investigation into the Gulfstream IV-SP that crashed while taking off from Runway 11 at Bedford Hanscom Field near Boston on May 31 appears to be focusing on the twinjet’s control wheel mechanical gust-lock system, according to a preliminary accident report released by the agency today. “After the rotate callout, the cockpit voice recorder captured comments concerning aircraft control,” the report notes. All seven aboard—three crewmembers and four passengers—died in the accident.
“Review of [flight data recorder] data parameters associated with the flight control surface positions did not reveal any movement consistent with a flight control check before the commencement of the takeoff roll,” the NTSB report continues. “The FDR data revealed the elevator control surface position during the taxi and takeoff was consistent with its position if the gust lock was engaged. The gust lock handle, located on the right side of the control pedestal, was found in the forward (OFF) position, and the elevator gust lock latch was found not engaged.”
The Gulfstream IV-SP’s mechanical gust-lock system locks the ailerons and rudder in the neutral position and the elevator in the down position to protect the control surfaces from wind gusts while parked. “A mechanical interlock was incorporated in the gust-lock handle mechanism to restrict the movement of the throttle levers to a minimal amount (6 percent) when the gust lock handle was engaged,” the NTSB said.
According to the report, “A witness observed the airplane on the takeoff roll at a ‘high speed’ with ‘little to no altitude gained.’ The airplane subsequently rolled off the end of the runway, on to a runway safety area, and then on to grass. The airplane continued on the grass, where it struck approach lighting and a localizer antenna assembly, before coming to rest in a gully, on about runway heading, about 1,850 feet from the end of the runway.”
Flight data recorder (FDR) information indicated the airplane reached a maximum speed of 165 knots during the takeoff roll and did not lift off the runway. FDR data “further indicated thrust reversers were deployed and wheel brake pressures increased as the airplane decelerated.” The FDR data ended about seven seconds after thrust reverser deployment, with the airplane at about 100 knots, the NTSB said. Tire marks “consistent with braking” began about 1,300 feet from the end of Runway 11 and continued for about another 1,000 feet through the paved runway safety area, the Safety Board report adds.
A post-crash fire consumed a majority of the airplane aft of the cockpit, but all major portions of the airplane were accounted for at the accident site. The nose gear and left main landing gear separated during the accident sequence and were located on the grass area between the safety area and the gully, according to the NTSB.
The FDR data “did not reveal evidence of any catastrophic engine failures and revealed thrust lever angles consistent with observed engine performance,” the Safety Board said. “The flap handle in the cockpit was observed in the 10-degree detent. FDR data indicated a flap setting of 20 degrees during the takeoff attempt.” The wreckage was retained for “further examination,” and an installed quick-access-recorder “was retained for download” by investigators.
Night visual meteorological conditions prevailed and an IFR flight plan was filed for the Part 91 flight to Atlantic City (N.J.) International Airport. Both pilots completed a Gulfstream IV recurrent PIC course and proficiency check in September last year. At that time, the pilot and copilot reported 2,800 and 1,400 hours, respectively, of total flight time in Gulfstream IVs.