MOJAVE, CA, USA
N6466G
Cessna 150K
The pilot descended into the airport traffic pattern from 4,200 feet AGL with the engine idled, mixture rich, and carburetor heat on. When engine power was added to adjust the landing approach, the engine failed to respond. Because of high surface winds, the pilot was unable to glide to the runway and an off-airport landing was made and the aircraft nosed over. Inspection of the engine revealed carbon buildup under the intake and exhaust valves and low compression. After staking the valves compression returned to normal. The second pilot said they had not cleared the engine during the descent as required by the engine Operator's Manual.
On April 17, 1996, at 0915 hours Pacific daylight time, a Cessna 150K aircraft, N6466G, was substantially damaged during an off-airport landing 1 mile east of the Mojave, California, airport. The airline transport pilot and one passenger were not injured. Visual meteorological conditions prevailed for the instructional flight. The second pilot, who holds a commercial pilot license, told an inspector from the FAA Van Nuys, California, Flight Standards District Office that the flight was part of the training syllabus of a private test pilot school. After descent from 7,000 feet (4,200 feet AGL) with the engine idled, carburetor heat on and mixture rich, the engine failed to produce power when the throttle was advanced during landing approach to runway 25. The first pilot took control of the aircraft at this point; however, because of 20- to 30-knot surface winds, he was not able to glide to the runway. An off-airport landing was made in the desert and the aircraft nosed over. The second pilot stated that they had not "cleared" the engine during descent. The Teledyne Continental Motors Operator's Manual for the O-200 engine, dated January 1975, states on page 19: "If a long glide is made, apply power at short intervals to clear the cylinders and retain engine temperatures in the event that instant power is required." Inspection of the engine by the FSDO inspector revealed heavy carbon buildup under the intake and exhaust valves and low compression. After staking the valves compression returned to normal. The fuel supply was clear and the magnetos and spark plugs sparked normally.
the pilot's failure to clear the engine during an idle power descent, as required by the engine manual.
Source: NTSB Aviation Accident Database
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