What happened
Approximately 16 minutes after departure, the pilot communicated with Air Route Traffic Control Center (ARTCC) to report a critical system failure. The pilot stated that he had lost the artificial horizon, directional gyro, and the vacuum pump. Shortly following this transmission, radio and radar contact with the aircraft was lost.
The investigation
Investigators examined the vacuum pump associated with the aircraft's flight instruments. This examination failed to reveal any pre-impact failure or malfunction of the component. The aircraft was equipped with a Piper Altimatic III autopilot system, which provides a backup mechanism entirely independent of both the directional gyro and attitude gyro, as well as the vacuum system.
If the primary gyroscopic systems fail, the pilot can disengage the roll and pitch of the autopilot and place the toggle switch of the "Autoflite" (backup system) to the on position. This action allows the all-electric Autoflite to take over and control the roll axis of the aircraft. The aircraft was also reportedly equipped with an electric turn coordinator or turn and slip indicator.
Findings
The loss of attitude reference and vacuum power occurred in flight. While the vacuum pump showed no signs of mechanical failure prior to impact, the pilot's report indicates a total loss of gyroscopic instruments. The presence of independent backup systems suggests that manual control via electric instruments was theoretically available, though the outcome of the event remains unknown due to the loss of contact.