N3960MPiper PA-12 · 1947

On May 14, 2022, about 1430 Pacific daylight time, a Piper PA-12 airplane, N3960M, was substantially damaged when it was involved in an accident near Enterprise, Oregon. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot reported that shortly after departure from runway 30 at Enterprise Municipal Airport (8S4), Enterprise, Oregon, about 700 ft agl, the windshield was sprayed with oil. He turned and entered the downwind leg of the traffic pattern and attempted to land on runway 30. He reported that he was too high during the approach and aborted the landing. On the second attempt to land on runway 30, the oil spray was getting worse, and he stated that he “flew the plane onto the ground” east of the airport. The airplane impacted the ground resulting in damage to the fuselage.

Postaccident examination of the engine revealed a loose crankshaft plug within the crankshaft. The pilot reported that about 50 flight hours before the accident, the airplane’s windshield was sprayed with oil when his friend was flying the airplane after an annual inspection during which the crankshaft plug was removed and reinstalled. The airplane landed safely, and it was determined that the expansion plug from the end of the crankshaft separated, causing oil to exit through the propeller spinner. The mechanic who performed the annual inspection reinstalled the expansion plug and the airplane operated about 39 hours before the accident flight.

The FAA conducted an interview with the mechanic and it was determined that improper tools and technique were used when reinstalling the expansion plug. On both occasions, no record of reinstalling the expansion plug was added to the maintenance records.

The Lycoming Service Instruction No. 1583, “Front Expansion Plug Replacement,” (SI1583), provides detailed instruction and tooling required for the replacement of the front expansion plug.