NTSB Identification: ERA09LA238
14 CFR Part 91: General Aviation
Accident occurred Thursday, April 09, 2009 in Clermont, FL
Probable Cause Approval Date: 07/28/2009
Aircraft: Byron J. Moore Zealot, registration: N61ZT
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot stated that he was in cruise flight at 1,800 feet when the motorized glider experienced a total loss of engine power. He attempted an engine restart with negative results and made a forced landing. The current owner stated that he purchased the motor glider about 4 months before the accident. The engine had been removed by the previous owner, rebuilt, serviced, installed on the glider, and placed in storage. A Federal Aviation Administration inspector disassembled the engine after the accident. Prior to disassembly, the oil tank indicated that it was full of oil. Disassembly of the engine revealed the rotary valve disc drive gear had failed due to insufficient lubrication. There were about 2 ounces of oil drained from the oil bath reservoir. The engine manufacturer's installation manual indicated that if the vent plug in the engine case is not removed when servicing the engine with oil. The oil reservoir can indicate it is full of oil, and an air bubble can form which will prevent oil from filling the chamber. This will result in significant heat, and cause catastrophic failure of the drive gear due to insufficient lubrication. The previous owner stated that he did not remove the vent plug when he serviced the oil after the engine was rebuilt and installed on the motor glider.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

A loss of engine power due to oil starvation as a result of the previous owner's improper servicing of the engine oil.

Full narrative available

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