What happened
The pilot was operating an airplane in the traffic pattern with the specific intention of warming up the engine oil prior to undergoing an annual inspection. Conditions on the ground had changed significantly just before the flight began; a rain storm had recently passed over the area, leaving the unpaved dirt strip wet and soft.
During the landing roll, the right main landing gear sank into the muddy surface of the runway. In response to the sinking gear, the pilot applied the left brake with significant force. This asymmetric braking action caused the aircraft to pivot sharply, resulting in the nose section collapsing onto the ground.
The investigation
The physical evidence indicated that the wet conditions on the dirt strip played a critical role in the incident. The softness of the ground allowed the right main gear to penetrate the surface during the landing roll. The subsequent application of hard braking on the left side created a torque that forced the nose down.
Findings
The primary factors contributing to this accident were the wet and muddy conditions of the unpaved runway and the pilot's decision to land under those circumstances. The sinking of the right main gear was a direct result of the ground's inability to support the aircraft's weight due to saturation from the recent storm.