CHI98FA286

The pilot said that after takeoff, and over the departure end of the runway, the engine began to run rough and lose power. The pilot said that he leaned the mixture. It seemed to help, but then the engine began to run rough again. The pilot turned back toward the airport with the intent of landing on the grassy field near the runway. Then the engine quit. The pilot stretched his glide so that he could clear trees on the edge of a corn field. The pilot tried to force land the airplane in the corn field. The airplane touched down in the corn and flipped over. Examination of the airplane revealed no anomalies. According to the Department of Transportation/Federal Aviation Administration/CT-82/44 Publication: Light Aircraft Piston Engine Carburetor Ice Detector/Warning Device Sensitivity/Effectiveness, June 1982, Carburetor Icing Probability Chart; the temperature (72 degrees Fahrenheit) and dew point (52 degrees Fahrenheit) at the time the airplane lost power, places the probability for carburetor icing in the 'serious icing at glide power' area of the chart.

History of flight

On July 31, 1998, at 1130 central daylight time (cdt), a Monocoupe 70, NC6740, operated by a commercial pilot, sustained substantial damage when on takeoff, the airplane's engine lost power. During the subsequent forced landing, the airplane nosed over into a cornfield. Visual meteorological conditions prevailed at the time of the accident. The personal flight was being conducted under 14 CFR Part 91. No flight plan was on file. The pilot reported minor injuries. The flight originated at New Holstein, Wisconsin, and was en route to Oshkosh, Wisconsin.

The pilot said that he had flown from Oshkosh to the New Holstein Airport earlier that morning. Before taking off from New Holstein to return to Oshkosh, he noticed that the engine was running rough. The pilot examined the engine and noticed that he had a loose exhaust stack. After repairing it, the pilot ran the engine and noted that everything worked fine. The pilot taxied out and took off. Just after takeoff, and just over the departure end of the runway, the airplane's engine began to run rough and lose power. The pilot said that he leaned the mixture.

It seemed to help, but then the engine began to run rough again. The pilot said he turned back toward the airport with the intent of landing on the grassy field near the runway. Then the engine quit. The pilot said that the propeller was still turning, but the engine had stopped making power. The pilot said that he stretched his glide so that he could clear some trees on the edge of a corn field. The pilot tried to force land the airplane in the corn field. The airplane touched down in the corn and flipped over.

Personnel information

The pilot possessed a commercial pilot certificate with single- engine land, multi-engine land, single-engine sea, and instrument ratings. The pilot claimed to have approximately 5,000 total flight hours, 40 of which were in the accident airplane.

Aircraft information

The airplane was a restored Monocoupe Model 70, manufactured by the Mono Aircraft Corporation in Moline, Illinois, on July 28, 1928. According to the pilot, the airplane "dropped off the face of the earth in 1930." It was located again in a mini-warehouse in South Lake Tahoe, California, in 1987. The pilot purchased the airplane and began restoring it to a flyable condition. The pilot said that he "flew it for the first time a couple of years ago."

The airplane was powered by a Velie 5-cylinder carbureted radial engine. According to the pilot, the engine had 40 to 50 hours total time.

Wreckage and impact information

The NTSB on scene investigation began on July 31, 1998, at 1415 cdt.

The airplane was located 150 feet into a corn field, located one mile east of Orchard Road, a north-south running paved road. The airplane was resting inverted and oriented on 325 degree magnetic heading.

The airplane rested on the south edge of a flattened area in the corn, 54 feet long, and 23 feet wide, and oriented on a magnetic heading of approximately 150 degrees. Corn stalks, approximately 15 feet preceding the flattened area, were sliced off on a gradually descending angle of 25 degrees. An 18 inch wide and 13 inch long impression in the ground was located 45 feet from the north edge of the flattened area.

The airplane rested at the south edge of the flattened area. The airplane's spinner was crushed inward and twisted counter- clockwise. The airplane's main undercarriage was bent upward to the right, and twisted forward. The propeller showed minor torsional bending and chordwise scratches. The engine, firewall and engine mounts were pushed inward and bent down approximately 22 degrees from the longitudinal line. The remainder of the airplane was undamaged. The smell of fuel was prevalent at the accident site. Control continuity to the ailerons, rudder and elevator was confirmed. Examination of the engine, engine controls and other airplane systems revealed no anomalies.

Tests and research

Weather conditions reported at Fond Du Lac, Wisconsin, 19 miles southwest of the accident site, at the time the airplane lost power, were clear skies, 10 miles visibility, temperature 72 degrees Fahrenheit, and dew point 52 degrees Fahrenheit. According to the Department of Transportation/Federal Aviation Administration/CT-82/44 Publication: Light Aircraft Piston Engine Carburetor Ice Detector/Warning Device Sensitivity/ Effectiveness, June 1982, Carburetor Icing Probability Chart; these conditions places the probability for carburetor icing in the "serious icing at glide power" area of the chart.

Additional information

Fuel records showed that the airplane was serviced with 20 gallons of fuel prior to departing Oshkosh, Wisconsin, that morning. The pilot said that the flight to New Holstein was approximately 40 minutes in duration. The airplane's engine burns approximately 5.5 gallons per hour.

Weight and balance information was recovered from the airplane. The maximum gross weight as specified in the airplane's weight and balance form is 1,350 pounds. A typical weight and balance center of gravity, as a percentage of mean aerodynamic chord averages 30.3 percent.

Weight Arm Moment Basic Airplane 924.0 65.0 60,075.0 Oil (2 gallons) 15.0 40.0 600.0 Fuel (25 gallons) 150.0 74.0 11,100.0 Pilot 210.0 80.0 16,800.0

Gross Weight 1,299.0 68.2 88,575.0

A party to the investigation was the Federal Aviation Flight Standards District Office, Milwaukee, Wisconsin.

The airplane was released and returned to the owner.