What happened
During a night flight in instrument meteorological conditions near Lewisville, Texas, a twin-engine aircraft entered an uncontrolled descent while maneuvering. The pilot contacted approach control to report that the aircraft's attitude indicator was malfunctioning and requested assistance in maintaining a straight flight path. Air traffic controllers provided instructions to maintain an altitude of 3,000 feet and directed the pilot through specific turns. Following these instructions, there were no additional communications from the cockpit.
The aircraft struck a wooded area in a near-vertical orientation, crossed a rural paved road, and ultimately collided with a house. Radar tracking indicated that the aircraft's magnetic heading had been erratic for the five minutes preceding the crash.
Findings
Investigation of the wreckage and flight instruments revealed significant discrepancies in the condition of the gyroscopic components. While the co-pilot's direction gyro and the turn and bank indicator showed evidence of rotation, the pilot's attitude indicator showed no signs of rotation at the time of impact. Instead, the interior of the attitude indicator housing exhibited blunt impressions from the gyro buckets.
Maintenance records indicated that the attitude indicator (part number 102-0041-04, serial number 92B0346) had been subject to recent service. Seven days before the accident, another company pilot had aborted a flight because this specific instrument had rotated. The component had been removed, cleaned, and adjusted, and was most recently reinstalled and ground-tested the night before the accident. Ultimately, the failure of the pilot's attitude indicator to rotate was the primary factor identified in the flight's erratic behavior.