What happened
While completing a cross-country flight in instrument meteorological conditions, the pilot attempted an instrument landing system (ILS) approach. During the initial approach, the tower controller revoked landing clearance because the aircraft appeared to be off the localizer. When queried by approach control regarding potential navigation indicator issues, the pilot confirmed a problem. Despite being offered an alternative ASR approach, the pilot opted to retry the ILS approach.
After receiving a new clearance and confirming localizer indications, the aircraft joined the localizer and began its descent. Shortly after being instructed to contact the tower, the aircraft drifted left of the centerline approximately 3 nautical miles from the outer marker. The pilot notified the tower of a problem, but failed to respond to instructions to climb to 3,000 feet and turn to a heading of 180 degrees. Data shows the aircraft's descent rate accelerated sharply from 1,500 to approximately 5,450 feet per minute in the final seconds. The aircraft struck the ground 1 nautical mile left of the localizer in a left-wing-down and nose-down attitude at 90 knots, resulting in a postimpact fire.
Findings
Investigation of the wreckage showed no mechanical anomalies, though the cockpit and instrument panel were largely destroyed by fire. Acoustic data from nearby security footage indicated a sudden drop in propeller speed from 2,500 to 1,200 rpm just before the collision. While the aircraft's avionics were receiving valid localizer signals, the pilot had previously reported that the horizontal situation indicator (HSI) was displaying incorrect heading information. It remains unconfirmed if the pilot had installed a replacement HSI prior to the flight. Erroneous heading information from the HSI may have increased pilot workload and led to a failure to recognize the deviation from the course and the descent below the glideslope.