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NTSB: Series of errors by flight crew caused fatal Gulfstream G-IV crash
9 September 2015
The G-IV came to rest in a gully (NTSB)

The G-IV came to rest in a gully (NTSB)

The probable cause of the crash of a Gulfstream G-IV jet at Bedford-Hanscom Field, last May was a series of errors by an experienced flight crew, the National Transportation Safety Board concluded. Specifically, the pilots failed to perform a flight control check before takeoff then attempted to take off while critical flight controls were locked because a gust lock was engaged. Finally, they delayed rejecting the take-off after they became aware the flight controls were locked.

On May 31, 2014, the Gulfstream G-IV business jet bound for Atlantic City crashed after it overran the end of runway 11 during a rejected takeoff at Laurence G. Hanscom Field in Bedford, Massachusetts. The airplane rolled through the paved overrun area; continued across a grassy area, striking approach lights and an antenna; and traveled through the airport fence before coming to rest in a ravine. A postcrash fire engulfed the airplane almost immediately. Everyone aboard – two pilots, a flight attendant and four passengers – were killed.

During the engine start process, the flight crew failed to disengage the airplane’s gust lock system, which locks the primary flight control surfaces while the plane is parked to protect them against wind gusts. The flight data recorder and cockpit voice recorder indicated that neither of the two flight crewmembers, who had flown together for about 12 years, had performed a basic flight control check that would have alerted them to the locked flight controls. A review of the flight crew’s previous 175 flights revealed that the pilots had performed complete preflight control checks on only two of them. The flight crew’s habitual noncompliance with checklists was a contributing factor to the accident.

About 26 seconds into the takeoff roll, when the airplane had reached a speed of 129 kts, the pilot in command indicated that the flight controls were locked, but the crew did not begin to apply the brakes for another 10 seconds and did not reduce engine power until four more seconds had passed. The NTSB determined that if the crew had rejected the takeoff within 11 seconds of the pilot’s comment, the airplane would have stopped on the paved surface and the accident would have been avoided.

The G-IV gust lock system design was intended to limit the operation of the throttles when the system was engaged so that the flight crew would have an unmistakable warning that the gust lock was on should the crew attempt to take off. However, the investigation revealed that Gulfstream did not ensure that the gust lock system would sufficiently limit the throttle movement on the G-IV airplane, which allowed the pilots of the accident flight to accelerate the airplane to takeoff speed before they discovered that the flight controls were locked.

The NTSB said that the Federal Aviation Administration’s certification of the gust lock system was inadequate because it did not require Gulfstream to perform any engineering certification tests or analysis of the G-IV gust lock system to verify that the system had met its regulatory requirements.

Also contributing to the accident were Gulfstream’s failure to ensure that the gust lock system would prevent an attempted takeoff with the gust lock engaged and the FAA’s failure to detect this inadequacy during the G-IV’s certification.
As a result of the investigation, the NTSB issued a total of five safety recommendations to the FAA, the International Business Aviation Council and the National Business Aviation Association.

In addition, the NTSB developed a Safety Alert for all pilots on the importance of following standard operating procedures and using checklists to guard against procedural errors.

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