Event Description
The airplane was on takeoff when the pilot began to lift off the runway surface. Shortly after, the engine started surging, and climb performance degraded. After reaching approximately 30 to 40 feet above ground level, the pilot determined that the aircraft could not continue the departure and elected to perform an emergency landing on an alternate runway. The airplane subsequently collided with the runway in a 15-degree nose-low attitude.
Prior to departure, the pilot had completed an engine run-up and observed no anomalies with the engine gauges or its performance.
Post-Accident Examination
A post-accident examination of the engine found that the spark plugs, cylinders, and piston heads were heavily sooted. These signatures are consistent with an excessively rich fuel mixture. No other anomalies were discovered that would have precluded normal engine operation.
Fuel Servo Analysis
Examination of the fuel servo revealed black coloration in the throat section and blue staining near the idle valve, consistent with a rich fuel mixture and a continuous fuel leak. During bench testing, several small fuel leaks were noted at the idle valve, fuel diaphragm, and center body seal. Flow tests at high power settings indicated that the fuel servo was operating well over the prescribed maximum flows for that unit.
The fuel servo was approximately 28 years old and showed no evidence of having ever been overhauled. A representative from the engine manufacturer stated that, based on the servo's tested flow, the engine would have been running very rich and most likely could not have produced normal power. The servo manufacturer had issued a Service Bulletin in 1990 that recommends the unit be overhauled at engine TBO or every 10 years.