Accident Overview
During an approach in mountainous terrain, an instrument-rated private pilot requested assistance due to a malfunctioning directional gyro. The controller initiated vectors for a no-gyro approach, which included a climb. Shortly thereafter, the pilot reported that the attitude indicator had failed. The controller continued providing guidance until radar contact was lost less than two minutes later. The airplane subsequently impacted a mountain approximately 2,300 feet below the last assigned altitude.
Sequence of Events
The pilot initially reported a directional gyro malfunction. The controller began providing vectors for a no-gyro approach, which involved a climb. Shortly afterward, the pilot advised the controller that the attitude indicator had failed. Despite continued guidance from the controller, radar contact was lost within two minutes. The airplane struck a mountain at an elevation about 2,300 feet lower than the altitude last assigned by the controller.
Investigation Findings
Examination of the wreckage revealed evidence that the airplane entered an uncontrolled descent before impact. Analysis of the vacuum system showed that the "B-Nut" fitting on the vacuum inlet line to the attitude indicator was loose. Contamination had entered the instrument, indicating a vacuum system leak and insufficient vacuum pressure for the associated instruments.