SEA98LA066

The pilot reported that on takeoff, immediately after becoming airborne, the airplane banked left and 'I fought for control.' The pilot reported the airplane then 'apparently veered to the north of the runway', then 'seemed to begin to climb [and] then we were down.' The airplane impacted the ground and came to rest about halfway down the runway, to the north (right side) of the runway. Based on aircraft, occupant and fuel weights reported by the pilot, the airplane was computed to be approximately 52.5 pounds (4%) above maximum gross weight at takeoff. Based on reported temperature of 72 degrees F and field elevation of 3,426 feet, density altitude was estimated at approximately 5,000 feet at the time. At this combination of pressure altitude and temperature, the airplane's Continental C75 engine is capable of producing approximately 65 brake horsepower (BHP), approximately 13% less than its sea-level rating of 75 BHP.

On April 22, 1998, approximately 1615 mountain daylight time, an Ercoupe 415-D, N2777H, crashed during an attempted takeoff from the Colstrip, Montana, airport. The airplane was substantially damaged in the occurrence, and the private pilot-in-command and one passenger received minor injuries. Visual meteorological conditions existed and no flight plan had been filed for the 14 CFR 91 local personal flight.

The attempted takeoff was from Colstrip's runway 24, a 5,100 by 75 foot asphalt runway. In her NTSB accident report, the pilot stated that she performed a visual check of the flight controls before takeoff, and that preflight checks of the magnetos and carburetor heat were normal. The pilot reported that on takeoff, the airplane "seemed a bit underpowered." She stated that because of this, she kept the airplane on the runway until the airspeed was between 65 and 70 MPH, as opposed to its normal rotation speed of about 55 MPH. She reported that immediately after becoming airborne, the airplane "banked to the left...[and] I fought for control. She reported that the airplane then "apparently veered to the north of the runway", and that the airplane then "seemed to begin to climb [and] then we were down." The airplane came to rest approximately halfway down the runway, on the north side of the runway.

The pilot reported that the accident airplane's loading was as follows: airplane empty weight 911.5 pounds; pilot weight 241 pounds; passenger weight approximately 180 pounds; and 20 gallons of fuel (120 pounds.) Based on the reported weights, the airplane gross weight at the time of the accident was computed to be 1,452.5 pounds. The aircraft's maximum gross weight is 1,400 pounds. A copy of the engine logbook, supplied by the pilot with her NTSB accident report, indicated that the aircraft was powered by a Continental C75 engine rated at 75 brake horsepower (BHP) at sea level and 2,275 RPM.

The Colstrip airport is 3,426 feet above sea level. The pilot reported that the temperature at the time of the accident was 72 degrees F. Based on a pressure altitude of 3,400 feet and temperature of 72 degrees F, density altitude at the time of the accident was computed to be approximately 5,000 feet. According to altitude performance data presented in the Continental A & C Series and O-200 Aircraft Engine Operator's Manual (Teledyne Continental Motors Form No. X30012, January 1975), at 2,275 RPM and density altitude of 5,000 feet (pressure altitude of 3,400 feet and temperature of 72 degrees F), the C75 engine produces approximately 65.3 BHP, equivalent to approximately a 13% reduction in power available compared to sea level standard day conditions.