What happened
The flight initially proceeded without incident to La Belle Municipal Airport, where the crew performed an uneventful landing. During the subsequent departure intended to return to the original departure airport, the certified flight instructor noted a discrepancy with one of the fuel gauges. After landing at a nearby airport to inspect for leaks, the instructor found no leakage and confirmed both tanks contained sufficient fuel.
Upon departing again to complete the return to the original airport, oil spots appeared on the windshield approximately 15 minutes into the flight. Shortly after this observation, the engine lost power. The instructor maneuvered the aircraft for a landing in a field while maintaining a speed of 85 mph. During the landing roll with flaps retracted, the aircraft collided with a berm and became airborne. It then contacted a second berm, becoming airborne again briefly before impacting the ground and coming to rest upright. There were no fatalities, though the student remained in the aircraft until the instructor obtained assistance.
The investigation
Mechanical examinations of the fuel system, fuel vent system, air induction system, exhaust system, and engine assembly showed no evidence of preimpact failure or malfunction. Investigators identified a crankshaft fracture caused by overstress. Testing of the ignition system components, fuel injection system, and both magnetos revealed no evidence of preimpact failure, though a discrepancy was noted with the condensers of both magnetos. The fuel selector valve and flexible fuel lines also showed no signs of preimpact failure. Additionally, testing of the fuel from the fueling facility showed no discrepancies that would cause engine power loss.
Findings
- A crankshaft fracture occurred due to overstress.
- Discrepancies were noted in the condensers of both magnetos.
- The flight manual specifies that for forced landings on unprepared surfaces, full flaps should be used if possible with a 75 mph glide.