On May 15, 2000, a Maule M-4-220C (registration N91480) was involved in an aviation accident near Gettysburg, PA. Investigators recorded the probable cause as: The pilot's failure to secure the fuel drain after pre-flight inspections, which resulted in a fuel leak and subsequent engine fire during the run-up. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
White smoke and subsequent flames were observed from the engine cowling during a routine pre-flight engine run-up, prompting immediate shutdown procedures.
What happened
The pilot was conducting a standard engine run-up procedure when the engine experienced a backfire. Shortly after this event, white smoke became visible emanating from the underside of the engine cowling. Recognizing the potential hazard, the pilot immediately turned off the fuel selector switch and exited the aircraft. Upon exiting, the pilot observed that the underside of the engine was engulfed in flames.
The investigation
A subsequent examination of the airplane revealed the root cause of the incident. Investigators found that the fuel drain located under the engine was left in the open position. This failure to secure the fuel drain likely allowed fuel to leak or spray during the run-up, which ignited upon contact with hot engine components or electrical sparks, resulting in the visible smoke and subsequent fire.
Findings
The primary contributing factor was the fuel drain being in the open position during the engine run-up. This oversight led directly to the fuel leakage that caused the fire under the cowling. No other mechanical failures or environmental factors were cited as causes for this incident.
Probable cause
The pilot's failure to secure the fuel drain after pre-flight inspections, which resulted in a fuel leak and subsequent engine fire during the run-up.