What happened
During the initial phase of the takeoff roll, the aircraft's horizontal stabilator abruptly shifted from a near-neutral position to a full or near-full nose-up deflection. This sudden change caused the aircraft to pitch up sharply and yaw to the left as it became airborne. The pilot appeared to attempt corrections through right aileron input and power reduction, but the aircraft entered a left-turning flight path.
Photographic evidence from the flight indicates that the stabilator remained in this nose-up position throughout the entire event. As the aircraft descended later in the sequence, it stalled with an increasing angle of bank and rapid descent rate before colliding with terrain. The maintenance logbook revealed that required instrument and radio inspections under Civil Aviation Order 100.5 were overdue, though these did not affect the stabilator system.
The investigation
Investigators examined the flight control and trim systems but found no pre-accident defects. The selected stabilator trim was correct, neither control seat had slid rearward, and the anti-servo tab appeared to be operating correctly. There was no evidence of an autopilot servo malfunction, external influences such as animal strikes, or intentional actions by the pilot or passengers.
The investigation also reviewed maintenance records, noting that while IFR annual inspections were required before the flight, the overdue status of certain VFR-related instrument checks did not contribute to the stabilator malfunction. The lack of these specific inspections reduced assurance in system accuracy but was unrelated to the control surface failure.
Findings
The primary contributing factor was the uncommanded movement of the horizontal stabilator to a nose-up position during the takeoff roll, which likely persisted for the duration of the flight. This deflection initiated an abrupt pitch-up and left yaw, exacerbated by the aircraft's natural left-turning tendencies at high power and low speed.
While the exact cause of the stabilator deflection could not be determined, no mechanical failure, pilot error, or external interference was identified. The overdue instrument inspections increased risk but were not causal to the accident sequence.