Summary
The pilot reported an in-flight engine malfunction that led to a forced landing on a road. During the landing roll, the aircraft struck a road sign, resulting in substantial damage. A subsequent examination of the engine revealed oil leakage and turbocharger wear.
Event Description
While in cruise flight, the engine manifold pressure dropped, followed by a loss of oil pressure. The pilot decided to divert to a nearby airport. During the descent, the engine began to fail, prompting the pilot to force land the airplane on a road. While setting up for the landing, the engine seized. During the landing roll, the airplane's right wing struck a road sign, causing substantial damage to the airplane.
Post-Event Examination
An initial examination showed oil adhering along the full length of the bottom fuselage. The oil originated at the engine right side exhaust pipe. An examination of the engine revealed that the right hand turbocharger impeller blades were worn at the tips, with some blades fractured. There was also excessive play noted in the compressor assembly.
Turbocharger Analysis
The turbocharger was examined at the NTSB Materials Laboratory. The examination determined that the impeller's aluminum bearings were heavily worn and distorted. There was no sign of overheating in the bearings. Attempts to conduct Rockwell hardness tests were made, but accurate readings could not be obtained due to the softness of the metal. Further examination showed damage to the oil seal at the impeller shaft.