What happened
During the initial departure from the departure airport, the aircraft performed an unplanned right turn as the pilot increased thrust. The pilot aborted the takeoff to conduct an engine run-up, after which the flight proceeded normally. No further issues were noted during the subsequent takeoff or the cruise portion of the flight.
Upon arrival at the destination airport, the pilot began the landing sequence in the traffic pattern. While reducing power, the left engine unexpectedly increased to 60 percent power. The pilot notified the tower of engine surging and difficulty maintaining control of engine speed. After adjusting the throttles, the engines appeared to respond correctly, allowing the pilot to proceed with the approach.
During the flare phase of the landing, the left engine surged again to 65 percent power despite the throttle being set to idle. This sudden thrust caused the aircraft to veer sharply to the right, leading to a drop of the right wing and a subsequent impact with the ground. There were 0 fatalities and 0 injuries reported in this incident.
Findings
Post-accident inspection of the engines showed no mechanical defects that would explain the surging or the uncommanded power increases. However, testing of the fuel pumps and fuel control units indicated that the flight idle fuel flow rates were higher than the manufacturer's specifications. The left engine flowed 237 pounds per hour and the right engine flowed 312 pounds per hour, both exceeding the standard 214 pounds per hour limit. Excessive flight idle fuel flow can create asymmetrical thrust, which contributes to unexpected power surges when throttles are at idle.