Accident Overview
A pilot departed on a 329-nautical-mile cross-country flight over mountainous terrain without filing a flight plan. Approximately 88 miles from the departure point, the aircraft crashed. It remained missing for about eight months before being discovered at approximately the 12,200-foot level of a mountain, about two miles west of the direct course line from the departure point to the destination.
Wreckage Examination
Examination of the wreckage indicated an in-flight breakup. Debris was scattered over a 1,500-foot area. The empennage had separated from the fuselage but was not found; however, the rudder and elevator counterweights were located in debris north of the fuselage.
Equipment and Systems
The aircraft was equipped with an area navigation system, LORAN-C, and a portable GPS. The autopilot was found engaged during the examination.
Component Failure
Investigation of the wreckage revealed that a pitch trim spring in the autopilot pitch servo had failed due to fatigue.
Additional Findings
Further examination revealed that the avionics in the accident aircraft belonged to another airplane that had been reported stolen. No records of any inspections or maintenance being performed on the accident aircraft were found.
Probable Cause
The official investigation report did not state a probable cause.