WPR09LA268 · Maule M-5-210C

The pilot reported that he filled the airplane's fuel tanks prior to flight with aviation gasoline, and performed preflight inspections both before the flight, as well as the day prior. During the takeoff initial climb, the airplane experienced a loss of engine power. The pilot attempted to restart the engine, but ultimately force landed in a field adjacent to the airport. The airplane sustained substantial damage to the wings and fuselage during the impact sequence. Post accident examination of the engine did not reveal any obvious anomalies; however, a fuel sample obtained from one of the wings revealed the presence of a residual quantity of automotive gasoline mixed with aviation gasoline. The owner of the airplane stated that he had used automotive gasoline in the airplane on prior occasions, but had given up the practice about 6 months prior to the accident. The use of automobile gasoline in the airplane is explicitly prohibited by the engine manufacturer for reasons including the potential for vapor lock. Additionally, the engine examination showed multiple indications of an excessively rich mixture, which can also result in a loss of power. Whether one or both of these possibilities resulted in the loss of engine power could not be determined. The pilot reported flight control difficulties during the emergency descent; however, impact damage prevented an accurate assessment of the airplane's control rigging.

Verbatim NTSB analysis and probable cause from the NTSB dataset