Accident Description
The aircraft overran the departure end of the runway during an aborted takeoff, resulting in substantial damage. The crew initiated a rejected takeoff when the pilot flying could not rotate the airplane normally.
Aircraft Systems
The aircraft is equipped with a two-position horizontal stabilizer system that reduces elevator control forces. For takeoff or landing, the stabilizer moves two degrees down; the normal cruise position is one degree up, with no intermediate positions. The stabilizer is commanded to the takeoff position when the cockpit flap handle is moved out of the 0-degree detent.
Investigation Findings
Post-accident inspection revealed the horizontal stabilizer was in the cruise position. Examination of the aft fairing feedthru connector uncovered an unseated (pushed-back) pin, which supplied electrical power to the hydraulic arming valve for stabilizer repositioning. Black marks near the pin tip suggested electrical arcing. After installing a new pin, the stabilizer successfully moved to the takeoff/landing position.
Warning Systems
Two independent warning systems alert the crew if the stabilizer is improperly positioned. A stabilizer miscompare (STAB MIS COMP) annunciator illuminates when the flap handle and stabilizer positions do not correspond. A no-takeoff (NO TAKEOFF) annunciator flashes with a master caution and a warning horn when the aircraft is on the ground and stabilizer is not in takeoff position and throttles are advanced above climb thrust.
Cockpit Warnings and Crew Actions
During post-accident electrical power application without changing cockpit settings, both STAB MIS COMP and NO TAKEOFF lights were illuminated. Initial attempts to reposition the stabilizer were unsuccessful. The flight manual before-takeoff checklist requires all annunciator lights except the ground idle light to be extinguished before takeoff. Abnormal procedures state that a STAB MISCOMP indication must be corrected prior to flight, and a no-takeoff indication requires aborting the takeoff.
Cockpit Voice Recorder Evidence
The cockpit voice recorder transcript showed the crew was aware that the horizontal stabilizer was not in the takeoff position before starting the takeoff roll. A sound similar to the no-takeoff warning horn was recorded over the cockpit area microphone during the takeoff roll, sounding for approximately twelve seconds before the rejected takeoff was initiated.
Subsequent Testing
After replacing the pin, the stabilizer repositioned normally, and both warning systems functioned as per the flight manual. The no-takeoff warning horn was heard over the cockpit speaker when thrust levers were advanced above climb thrust.