Accident Overview
The pilot reported that during the takeoff roll, at the halfway point, the airspeed was 45 knots. Due to insufficient remaining runway, the pilot chose to continue the takeoff. The commercial-rated passenger, who was the previous owner of the airplane, noticed the engine rpm decreased to 2400 or less during the roll. At the end of the runway, the pilot applied aft pressure on the control yoke, and the airplane became airborne. Upon retracting the landing gear, the airplane rolled right and the nose pitched down. The pilot observed trees and power lines before the airplane collided with the ground, and a post-crash fire ensued.
Pre-Departure Events
A witness stated that the pilot and two other individuals attempted to turn the airplane around by hand before departure, but were unsuccessful. The pilot then entered the airplane, released the parking brake, and exited. Another attempt to move the airplane by hand also failed. Subsequently, the pilot and passenger entered the airplane, the pilot started the engine, turned the airplane around using engine power, and taxied to runway 06. The witness observed the airplane during its takeoff roll. The airplane traveled about 400 to 500 feet before reaching the witness's location, with an estimated ground speed of 15 to 20 knots. The witness saw the airplane make an abrupt pitch up at the end of the runway, and the tail down ring contacted the ground. The airplane became airborne, rolled to the right, and disappeared from view.
Runway and Performance Data
The runway was measured by the FAA to be 1,383 feet long and 80 feet wide. According to the Aircraft Owner's Manual, the takeoff roll on a hard surface runway would be 790 feet, and 808 feet on a soft surface. Examination by the FAA revealed that the airplane traveled 819 feet on the takeoff roll before encountering a dirt section of the runway. Two skid marks were present in the dirt: the left skid mark measured 417 feet long, and the right skid mark measured 388 feet long. Ten feet past the left skid mark, a tail strike mark appeared on a stone with a blue color; the bottom of the accident airplane is blue in color.
Post-Crash Examination
Examination of the airplane revealed that the post-crash fire destroyed the parking brake valve. The No.1 engine induction tube was damaged and separated from the No.1 cylinder intake port; both induction tube bolts were missing. One half of the No.1 intake gasket and one bolt with a locking star washer and a plain washer were located in the right side of the lower engine cowling. The bolt with locking star washer and plain washer was encased with molten aluminum, and the locking tabs on the washer were not flattened. A follow-up examination by the FAA revealed thread damage on the No.1 cylinder induction tube bolt holes, and improper sized threaded bolts had been installed in the No.1 and No.3 cylinder induction tube bolt holes.
Engine Testing
Testing of an IO-360 engine at the engine manufacturer showed that with a separated induction tube from a cylinder intake port at 2,650 rpm, the engine rpm remained relatively constant. Engine rpm settings below 2,650 rpm revealed that the engine would falter and rpm would decrease.