Overview
A private pilot was conducting an IFR flight plan to his home base under night and instrument meteorological conditions. During the flight, he experienced a failure of his instrument gyro.
Flight Sequence
Several minutes before the accident, the pilot informed ATC that his instrument gyro had failed. He later reported that his instruments were working but noted a 'light on'. He subsequently reported being 'in trouble'. ATC observed the aircraft in a rapid descent before losing radar contact. The aircraft impacted wooded terrain in a steep, nose-low attitude.
Investigation Findings
Examination of the vacuum system revealed that the engine-driven vacuum pump had failed due to oil ingestion. Further investigation determined that an engine oil leak had been repaired in June 1993, originating from the engine accessory drive seal where the vacuum pump attaches. The failed pump had been installed as new approximately one week prior to that oil leak repair. Interestingly, the pump that was removed in June 1993 had also failed due to oil ingestion.