What happened
Following a gate delay caused by late-arriving passengers, the flight received clearance for departure on runway 28L. Approximately four seconds after the pilot announced rotation speed, the stickshaker activated, prompting an immediate abort of the takeoff. Cockpit voice recorder data indicated that the thrust reversers were deployed eleven seconds later. The aircraft was brought to a halt in the dirt overrun, coming to rest approximately fifty feet past the end of the runway.
The investigation
The aircraft had been dispatched from Seattle, WA, with an inoperative anti-skid system, properly placarded for this condition. A subsequent examination revealed that the right flap position transmitter had malfunctioned due to corrosion. This component failure is critical because a malfunction of either flap position transmitter can send an erroneous flap setting signal to the stall warning computer.
Findings
The erroneous signal from the faulty transmitter caused the stall warning computer to activate the stickshaker and stall warning system at incorrect airspeeds during the takeoff roll. Despite the alarming warning, only minor damage was sustained by the aircraft, and there were no injuries among those on board.
Safety message
This incident highlights how a single component failure in the flap position sensing system can trigger false stall warnings, potentially leading to unnecessary aborts or confusion during critical phases of flight.