Incident Overview
Approximately 16 minutes after departure, the pilot informed Air Route Traffic Control Center (ARTCC) that the artificial horizon, directional gyro, and vacuum pump had failed. Shortly after this report, radio and radar contact with the aircraft was lost.
Investigation Findings
Examination of the vacuum pump after the incident did not reveal any evidence of failure or malfunction prior to impact.
Aircraft Equipment
The aircraft was equipped with a Piper Altimatic III autopilot. This autopilot incorporates a backup system known as the AutoFlite, which is entirely independent of the directional gyro, attitude gyro, and vacuum system. In the event of a failure of the primary gyroscopic instruments, the backup system can be activated by disengaging the roll and pitch functions of the autopilot and moving the AutoFlite toggle switch to the ON position. Once engaged, the all-electric AutoFlite assumes control of the aircraft's roll axis.
Additionally, the aircraft was reportedly fitted with an electric turn coordinator or a turn-and-slip indicator, which could provide backup attitude information.