Incident Overview
During the cruise portion of a cross-country flight, the pilot/owner informed air traffic control that the airplane’s left engine had lost power and he could not maintain altitude. The controller suggested a nearby airport, but the pilot requested and proceeded to a different airport with a 9,003-foot-long runway.
Approach and Maneuver
After twice circling the approach end of the runway to the left while descending, the pilot flew down the runway well above a normal glide path. A witness reported that the airplane never touched down, and track data showed that the airplane’s ground speed increased while over the runway. Airport surveillance video captured the airplane pitching up and banking left at the departure end of the runway. It continued into a left, descending turn until it impacted the ground about ¼ mile west of the departure end of the runway.
Post-Impact Examination
The wreckage was destroyed by impact forces and a postimpact fire. The left engine’s propeller blades were feathered and showed no indications of powered rotation at impact, while the right engine’s propeller blades displayed damage signatures consistent with powered rotation at impact. A postaccident examination of the left engine revealed severe detonation damage of the No. 4 cylinder piston. Examination of the left engine fuel servo disclosed a significant amount of sand-like contamination in the servo inlet filter, identified as polyethylene terephthalate (PET), a thermoplastic polymer commonly found in fuel system components. The right engine’s fuel servo was also contaminated with the same substance. Additionally, the right engine’s spark plugs and one of its cylinders displayed signatures consistent with a lean fuel-to-air ratio.
Probable Cause
The probable cause was the pilot’s loss of airplane control during a single-engine go-around. A contributing factor was fuel system contamination, which resulted in detonation and a total loss of left engine power. The investigation was unable to determine how or when the PET was introduced into the fuel system due to postimpact fire damage.