Final Report: Autothrottle blamed for runway overrun

 - September 14, 2006, 6:14 AM

Gulfstream IV, Teterboro, N.J., Dec. 1, 2004– The NTSB blamed the GIV accident on the flight crew’s inadvertent engagement of the autothrottle and their failure to realize they had done so. Factors were the lack of switch guards, lack of an audible warning tone and gusty winds.

After disengaging the autothrottle and autopilot following their clearance for the ILS Runway 19 approach at Teterboro (TEB), the ATP-rated flight crew was not aware that the autothrottle re-engaged at 35 feet agl, just before touchdown. The autothrottle was commanded by one of the engage/disengage paddle switches on each power lever, which were not equipped with switch guards. The target speed was set at 138 knots, and as the GIV slowed below 138 after touchdown, the autothrottle gradually increased power. Since the power levers were not in idle, the spoilers and thrust reversers would not work, and the crew evidently did not use enough force to override the autothrottle system.

The system disengaged, according to the flight data recorder, 16 seconds after the weight-on-wheels switches were activated, three seconds after the spoilers deployed. The pilot used the emergency brake but the jet ran off the right side of the runway when the tires burst. There were no injuries. Wind was 25 knots, gusting to 32.