Primary finding
Probable cause
the pilot's improper (maintenance) modification and his initiating an operation with known deficiencies in equipment
Investigator assessment
Analysis narrative
The pilot stated that he noted that the airplane had developed an oil leak in the oil cooler. He isolated the leak by capping the oil lines from the engine to the cooler and initiated a flight. He reported that after about ten minutes of flight the oil pressure dropped to zero and he was attempting a forced landing when the engine began running rough and shortly thereafter suffered a total loss of power.
Source record
Factual narrative
On September 14, 1994, at 1825 eastern daylight time, a Mooney M20E, N6944U, registered to Earl R. Sobeck of Dearborn Heights, Michigan, and operated by a private pilot, struck a fence during a forced landing following a total loss of engine power. The accident occurred in an industrial area about seven miles east- northeast of the intended destination of Canton, Michigan. The airplane sustained substantial damage. The pilot reported no injuries. The personal 14 CFR Part 91 flight was operating in visual meteorological conditions. No flight plan was on file. The flight departed Detroit, Michigan, at 1815. The pilot stated that he had made a modification to the accident airplane, which included isolating the oil cooler which was leaking. He accomplished this by capping off the engine fittings to the oil cooler hoses which blocked the lubricating oil between the engine and the oil cooler. He then departed for another airport where he intended to obtain maintenance to repair the leaking oil cooler. He stated that while enroute the engine oil pressure dropped to zero and while he was conducting a forced landing the engine began to run rough and a total power loss soon followed. -