Accident Sequence
The pilot was attempting to land on a grass runway when a waterline traversing the approach end prompted an application of engine power to extend the touchdown point. During the power application, the engine hesitated and backfired while the airplane was in a near-stall phase of flight approximately 3 to 8 feet above the runway. Following the momentary hesitation, the engine accelerated, and the airplane entered a left-banked turn. This resulted in the left wing contacting the ground, and the airplane subsequently impacted terrain.
Investigation Findings
A functional test of the engine's fuel servo revealed that it exceeded its upper service flow limits. Examination of the servo identified an obstruction of its diaphragm with diaphragm material. After the obstruction was removed, a second functional test showed the fuel servo operated within service flow limits. Additionally, scoring of the idle metering plates was noted during the investigation.