Clermont, FL, USA
N61ZT
Byron J. Moore Zealot
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.
On April 9, 2009, at 1145 eastern daylight time, an amateur built, experimental light sport, Moore Zealot motor glider, N61ZT, registered to a private owner, operating as a Title 14 Code of Federal Regulations Part 91 personal flight, experienced a total loss of engine power in cruise flight near Clermont, Florida. The pilot made a forced landing to a rough, dry lakebed. The fuselage, both wings, and the empennage received structural damage. Visual meteorological conditions prevailed and no flight plan was filed. The private pilot reported no injuries. The flight originated from Grass Roots Airpark (06FD), Mascotte, Florida, at 1120. The pilot stated he was in cruise flight at 1,800 feet when the motor glider experienced a total loss of engine power. He attempted an engine restart with negative results. The pilot initiated a forced landing to a residential street. He abandoned the approach due to obstructions on the street and landed in a dry lakebed. The motor glider was equipped with a Rotax 582 engine. The engine was examined and disassembled by a Federal Aviation Administration (FAA) inspector on April 10, 2009. Prior to the engine being removed from the airframe for disassembly, the externally mounted oil tank for the rotary shaft lubrication system indicated it was filled to the proper level. Disassembly of the engine revealed the "destruction of the rotary valve disc drive gear due to insufficient lubrication." Approximately 2 fluid ounces of oil was drained from the rotary valve shaft "oil bath," when the shaft assembly was removed from the engine case. Information obtained by the FAA inspector from the Rotax Installation Manual, and Rotax Service Center Technicians, substantiated that it is possible for the rotary valve shaft lubrication system externally mounted oil tank to contain a full quantity of oil, without the rotary valve shaft "oil bath" chamber within the engine case actually being full of oil. This can occur in Rotax 582 engines mounted on an airframe in the inverted position (spark plugs down), if the rotary valve shaft oil is added without removing a vent plug in the engine case to vent the system during oil servicing. If the vent plug is not removed, an "air bubble" can form in the rotary valve shaft "oil bath" chamber, preventing oil from filling the chamber. The oil tank will indicate full, but insufficient oil will have been introduced into the rotary valve shaft "oil bath" chamber. The current registered owner stated he purchased the motor glider from the original builder 4 months before the accident. The engine had been removed by the previous owner and builder on July 1, 2008, and sent to an overhaul facility to be rebuilt. The engine was returned and reinstalled on the motor glider in August 2008. The motor glider was placed in storage for about 6 years. The current owner and an airframe and power plant mechanic completed a condition inspection on March 25, 2009, and no oil had been added. The motor glider had flown 2 hours and 30 minutes since he purchased it. The FAA inspector located the previous owner of the motor glider. The previous owner stated he did not remove the vent plug during oil installation after the engine had been overhauled.
A loss of engine power due to oil starvation as a result of the previous owner's improper servicing of the engine oil.
Source: NTSB Aviation Accident Database
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