Background
On July 13, 2018, at 1021 Pacific daylight time, a Cessna 172R airplane, registration N24442, was substantially damaged when it crashed near Deer Park, Washington. The flight instructor and two student pilots, one receiving instruction and the other observing, were fatally injured. The flight was operated under Title 14 Code of Federal Regulations Part 141 as an instructional flight. The aircraft departed Felts Field Airport (SFF) in Spokane, Washington, about 0955, intending to remain in the local area.
Accident Sequence
After departure, the flight proceeded to the Clayton practice area, about 15 nautical miles northwest of the airport. Radar data showed the aircraft entering the practice area at 1010 and executing various turns and climbs, reaching altitudes up to about 7,450 ft mean sea level. At 1020:53, the airplane was at 7,000 ft msl with an estimated ground speed of 77 knots. It then made a sharp 90° right turn, followed by another 90° right turn 14 seconds later. The last recorded data at 1021:18 indicated a ground speed of 117 knots. The accident site was about 740 ft southwest of the last radar return. Witnesses reported the airplane banked hard, then descended in a steep dive. During the descent, the wings separated from the fuselage before ground impact.
Aircraft and Wreckage
The Cessna 172R had a gross weight of about 2,400 lbs at the time of the accident, within the flight envelope. The aircraft’s never-exceed speed (Vne) was 160 knots, maximum structural cruising speed (Vno) 126 knots, and design maneuvering speed (Va) 97 knots. The wreckage was distributed over a 400 ft distance. Both wings had separated in flight; outboard sections were found at the start of the debris field. The main wreckage contained the inboard portion of the left wing. Examination of the wings showed signatures of overstress and torsional forces. The engine was found partially buried; postaccident examination revealed no preimpact mechanical anomalies or foreign object ingestion. Control cables exhibited overstress fractures.
Medical and Toxicology
Autopsies determined the cause of death for all three occupants as blunt force injuries. Toxicology testing detected ethanol in muscle and liver tissue of both the flight instructor and student, but the presence of putrefaction indicated the ethanol was likely from postmortem production. No drugs were detected.
Additional Findings
Examination of windscreen fragments revealed bird feather material consistent with American white pelican, which was sighted in the area during July 2018. However, no avian DNA was found on airframe swabs, and the presence of feathers did not necessarily indicate a bird strike as the cause of the accident.