Zenair CH601 — Maricopa, AZ

What happened

The pilot departed from his home airport for a night flight to an airport he had flown to in the past. The flight was in trail with another airplane as they approached the airport from the north. Flight track data indicated that the accident airplane overflew the airport midfield about 300 ft below the traffic pattern altitude. The flight progressed well beyond the airport environment and descended to about 600 ft below the traffic pattern altitude. As the airplane began what appeared to be an extended base turn to the southeast, about 2 miles from the runway threshold, it struck an isolated and unlit hill just below its summit.

Examination of the wreckage did not reveal any mechanical anomalies with the airplane or engine, and damage signatures to the propeller indicated that the engine was producing power at impact.

Based on autopsy findings, the pilot had mild-to-moderate atherosclerosis in his coronary arteries. While the atherosclerosis placed the pilot at some increased risk for an acute cardiac event, there was no evidence to suggest such an event occurred and, given the pilot was communicating with air traffic control and the other airplane right up until the accident, the pilot’s cardiovascular disease was not a factor. Given the operational issued of the accident, the ethanol concentrations identified in liver tissue were from sources other than ingestion.

At the time of the accident, the sun had set, but there was still light on the horizon, toward the direction the airplane was heading prior to turning toward the airport. The light conditions would have provided a challenging perceptual environment for the pilot as he looked toward the unlit terrain and peak. It was likely that the pilot’s visual attention was directed toward the airport at that time, while he monitored the other airplane and positioned himself for landing. Both factors would have impeded the pilot’s visual identification of the terrain. Further, the limited cultural lighting in the vicinity of the airport would provide few cues from which the pilot could reliably estimate distance while maneuvering. The reason for the pilot’s nonstandard flight track and flight below pattern altitude is unknown, but it is indicative of the pilot losing situational awareness as he followed the other airplane in the traffic pattern and prepared for landing over unlit and unpopulated terrain.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.