Accident Details
On June 23, 2008, at approximately 1910 central daylight time, an Air Tractor AT-502B (registration N5005G) was substantially damaged following a collision with terrain after a partial loss of power during initial takeoff from Bethany Memorial Airport (75K) in Bethany, Missouri. Visual meteorological conditions prevailed. The flight was an aerial application operation conducted under 14 CFR Part 137 without a flight plan. The commercial pilot was not injured. The airplane was departing at the time of the accident.
The accident pilot reported that another pilot had indicated the engine was not responding properly. To assess the engine's performance, the accident pilot decided to fly the airplane. After loading approximately 430 gallons of applicant, the pilot began the takeoff roll. Around midfield, the tail wheel raised, but with about 560 feet of runway remaining, the engine began "rolling back." The pilot raised the nose at the departure end, clearing the airfield fence before the airplane settled back to the ground. The airplane continued through a field toward a residence. The engine momentarily regained power, but the airplane collided with a garage and a residence, rolled inverted, and slid 50 yards before coming to rest.
Engine Examination
The engine was removed and shipped to Pratt & Whitney Canada. Under the supervision of the Transportation Safety Board of Canada (TSB), an examination revealed that the engine displayed signs of rotation at impact. Examination of accessories showed the fuel control unit (FCU) bellows had deformation consistent with power reduction and erratic engine performance in the high power range. Additionally, an adjustment was noted on the FCU lever adjustment, indicating possible maintenance corrections for low power. The FCU itself was impact damaged and could not be tested. A separate examination of the FCU bellows by Honeywell under FAA supervision detected no anomalies. The bellows was then returned to Pratt & Whitney Canada and, under TSB supervision, tested in a "slave" FCU with no anomalies detected.