THE DTSB
The DTSB determines the Probable Cause of this accident to be a mechanical in flight seizing of the elevator control system from the autopilot servo which became bound. This following a prolonged high speed descent. The aircraft descended and successfully leveled off at around 1400 MSL following the descent and began slowing, but then encountered a single defining mechanical event causing the yoke to no longer be effective for pitch control. This event is likely when the pilot attempted to disengage the autopilot but found that the yoke could not be moved fore or aft. The pilot then attempted to utilize full nose up elevator trim and advanced power on both engines in order to try to arrest the locked in descent caused when elevator control became frozen in place. It is likely that the autopilot was engaged and functioning perfectly prior to the accident pilot intentional disengagement of the autopilot system. The defining event occurred 20 seconds prior to impact. The accident aircraft impacted wings level with gear and flaps retracted, and both engines making full power. The crash path was long and straight, indicating full control of the other two axis. The accident aircraft was found to have impacted with both elevator trim tabs deflected to the full nose up position, eliminating a nose down runaway elevator trim condition as a cause. The elevator trim tabs are controlled via a jack screw and would remain in existing position after the crash.