Accident Details
The aircraft crashed after it overran the end of runway 11 during a rejected takeoff at Laurence G. Hanscom Field (BED) in Bedford, Massachusetts. The airplane rolled through the paved overrun area and across a grassy area, collided with approach lights and a localizer antenna, passed through the airport’s perimeter fence, and came to a stop in a ravine. The two pilots, a flight attendant, and four passengers died. The airplane was destroyed by impact forces and a postcrash fire. The corporate flight, destined for Atlantic City International Airport in New Jersey, was conducted under 14 Code of Federal Regulations (CFR) Part 91. An instrument flight rules flight plan was filed. Night visual meteorological conditions prevailed at the time of the accident.
Sequence of Events
During the engine start process, the flight crew neglected to disengage the airplane’s gust lock system, which locks the elevator, ailerons, and rudder while the airplane is parked. Before initiating takeoff, the pilots also neglected to perform a flight control check that would have alerted them of the locked flight controls. A review of data from the airplane’s quick access recorder revealed that the pilots had neglected to perform complete flight control checks before 98% of their previous 175 takeoffs in the airplane, indicating that this oversight was habitual.
A mechanical interlock between the gust lock handle and the throttle levers restricts the movement of the throttle levers when the gust lock handle is in the ON position. According to Gulfstream, the interlock mechanism was intended to limit throttle lever movement to a throttle lever angle (TLA) of no greater than 6° during operation with the gust lock on. However, postaccident testing on nine in-service G-IV airplanes found that, with the gust lock handle in the ON position, the forward throttle lever movement that could be achieved was 3 to 4 times greater than the intended TLA of 6°.
During takeoff, the pilot-in-command (PIC) manually advanced the throttle levers, but the engine pressure ratio (EPR) did not reach the expected level due to the throttles contacting the gust lock/throttle lever interlock. The PIC did not immediately reject the takeoff; instead, he engaged the autothrottle, and the throttle levers moved slightly forward, allowing the engines to attain an EPR value that approached but never reached the target setting. As the takeoff roll continued, the second-in-command made standard takeoff speed callouts as the airplane reached 80 knots, takeoff safety speed, and rotation speed. When the PIC attempted to rotate, he discovered he could not move the control yoke and began calling out “(steer) lock is on.” At that point, the PIC understood the controls were locked but still did not immediately initiate a rejected takeoff. If the flight crew had initiated a rejected takeoff at the time of the PIC’s first comment or within about 11 seconds after, the airplane could have been stopped on the paved surface. However, they delayed applying brakes for about 10 seconds and further delayed reducing power by 4 seconds, making the rejection too late. Among the victims was Lewis Katz, co-owner of the Philadelphia Inquirer.
Probable Cause
The National Transportation Safety Board determined that the probable cause of this accident was the flight crewmembers’ failure to perform the flight control check before takeoff, their attempt to take off with the gust lock system engaged, and their delayed execution of a rejected takeoff after they became aware that the controls were locked. Contributing to the accident were the flight crew’s habitual noncompliance with checklists, Gulfstream Aerospace Corporation’s failure to ensure that the G-IV gust lock/throttle lever interlock system would prevent an attempted takeoff with the gust lock engaged, and the Federal Aviation Administration’s failure to detect this inadequacy during the G-IV’s certification.