This April 2008 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Aircraft: Cessna 150. Injuries: 1 Minor. Location: Columbia, Calif. Aircraft damage: Substantial.
What reportedly happened: The flight instructor reported that the student pilot had recently purchased the airplane and that they intended to test fly it within the traffic pattern. Prior to departure, the instructor noted that the wind was about 10-15 knots and favored a 2,600-foot turf runway. The instructor initiated a short field takeoff by holding the brakes, using 10° of flaps, and applying full throttle. He recalled that the engine only produced 2,050 rpm, and that he expected the rpm to increase as he released the brakes. During the takeoff roll, the instructor felt that the tall grass slowed the acceleration of the airplane before it lifted off the ground at 55 mph. He lowered the nose to gain airspeed in ground effect, but the airplane did not accelerate. Due to upward sloping terrain with trees and power lines in the flight path, the CFI turned left to avoid the obstacles. During the turn, the angle of bank increased due to a wind gust and the airplane stalled, entered a spin to the left, and hit the ground in a nose low attitude.
Examination of the engine revealed that the number two cylinder top and bottom spark plugs were fouled with carbon deposits. These spark plugs would not have fired, resulting in a loss of power from the number two cylinder. The owner’s manual states that during the initial takeoff phase the pilot should verify full throttle operation and that the engine should run smoothly and turn approximately 2,500 to 2,600 rpm with carburetor heat off.
Probable cause: The flight instructor’s decision to attempt takeoff with an engine discrepancy and subsequent failure to abort takeoff when the airplane did not attain adequate airspeed during the initial climb, resulting in an aerodynamic stall. The partial loss of engine power was a factor.
For more information: NTSB.gov