NTSB Factual Report

On April 7, 2001, about 1440 Eastern Daylight Time, a Cessna 150D, N974CA, was substantially damaged during a precautionary landing in Slanesville, West Virginia. The certificated private pilot received minor injuries. Visual meteorological conditions prevailed for the personal flight. No flight plan had been filed for the flight that was conducted under 14 CFR Part 91.

The pilot reported that he had purchased the airplane, and taken delivery of it in Tulsa, Oklahoma, on April 6, 2001. He left Tulsa in the afternoon, destined for Woodbine, New Jersey. At his first fuel stop, he replaced the nose landing gear tire and bearings due to dry rot and a flat spot on the tire. He spent the night in Mount Vernon, Illinois. On April 7th, he resumed his eastward flight. After he departed Mt. Vernon, he made two additional stops to refuel during the day. His last refueling stop prior to the accident was Fairmont, West Virginia, which he departed from about 1400.

The pilot said that he was in cruise flight at 5,500 feet, operating above some scattered clouds, with an outside air temperature of about 55 degrees Fahrenheit. He further stated:

"...About 50 minutes into the flight I developed a sudden power reduction from 2500 to 1000 RPM for about 5 to 7 seconds then with no pilot input engine regained full power. I proceeded to check fuel selector, carb heat, mags, throttle and mixture positions...At no time did any of my inputs seem to effect to resolve the problem. The engine would at times run rough and then loose power regaining same at different intervals."

The pilot reported that he checked his GPS for the closest airport, which he observed was 20 nautical miles away. Based upon the condition of the engine, and the distance to the nearest airport, he elected to perform a precautionary landing in a field below him. He positioned the airplane over the field, and set up for the landing.

The pilot further stated:

"...During my rapid descent the engine ran rough at times but settled during the base and final leg to the field. So as not to be high on short final I flew low and slow through a break in the tree line which bordered the field. Flaps were fully extended and I touched down at a relatively low speed. At 250 to 300 ft into the roll out the nose gear touched down and dug into the soft ground causing the plane to nose in and flip on its back.

After the accident, the airplane was removed to a local airport for further examination. According to the report from the inspector with the Federal Aviation Administration (FAA), who conducted the examination:

"The engine started immediately, but would not remain running. If the primer was repeatedly pushed, the engine would continue to run...."

"The carburetor bowl was drained and some sediment was found in the fuel. Inspection of the carburetor revealed that the mixture control sheath had slipped out of the retaining clamp. When the mixture control was moved, the cable flexed but the mixture valve did not move. The mixture valve [was] in idle cut off all the time. The cable was reattached and the engine ran normally, reaching approximately 2,400 static rpm....The clamp system was metal to metal; The Cessna 150 Parts catalog shows that a rubber lined Adel type clamp is required.

In a follow-up telephone interview, the FAA inspector reported that the contamination in the carburetor bowl was loose and in an area from where fuel was supplied to the main carburetor jet. However, no contamination was found in the main fuel strainer, and the source of the contamination in the carburetor bowl was not determined. There were no marks on the mixture control cable housing to indicate it was forced from the clamp. The looseness of the mixture control cable housing allowed the mixture control valve to move towards the idle cut-off position.

The airplane had accumulated 38 hours since its last annual inspection on May 24, 2000. The pilot also reported that the airplane had not flown for period of time prior to him taking delivery of it.

NTSB Probable Cause

a loose mixture control cable housing which resulted in an intermittent running engine, and the pilot's subsequent decision to perform a precautionary landing. A factor was the soft terrain.