Incident Overview
A single-engine airplane impacted a lake following an uncontrolled descent after the pilot lost spatial orientation during night flying conditions. The event occurred while the pilot was conducting an instrument approach to runway 18R.
Sequence of Events
During the approach, the pilot reported to air traffic control (ATC) that he had a 'full failure.' Approximately one minute later, he reported a 'static failure,' and shortly thereafter stated that the 'DG' (directional gyro) was out of order. Following these transmissions, ATC lost both radio and radar contact with the aircraft.
Controller Observations
The controller tracking the airplane noted that it appeared to be 'going around in circles' just before it disappeared from the radar scope.
Survivor Account
A survivor, who was rescued from the lake the following morning, reported that during the flight the pilot had tapped on an instrument described as 'the instrument with the blue horizon' and stated that 'this instrument is not working.'
Post-Accident Examination
A post-accident examination of the vacuum pump, conducted by the NTSB Materials Laboratory, revealed that the vacuum pump had failed in-flight. Examination of the electrically driven turn coordinator did not produce sufficient evidence to determine whether it was functioning at the time of impact.