What happened
On June 11, 2014, a Piper J3C with registration N61903 departed Lille Marcq-en-Barœul, France, bound for Burgos, Spain. After a brief stop at Dieppe Saint-Aubin, the aircraft continued toward Le Havre Octeville for refueling. While cruising at approximately 900 ft, the engine began to sputter and subsequently failed. The pilot attempted an emergency landing in a wheat field, but during the landing roll, the aircraft overturned and came to rest on its back.
The investigation
The investigation focused on the fuel system and the engine's performance. The aircraft was equipped with a primary 12-gallon tank and a secondary 12-gallon tank installed in the left wing via a Supplemental Type Certificate (STC). This secondary tank allowed for gravity-fed fuel transfer to the primary tank via a selector.
Investigators examined the fuel quantity indicator, noting significant friction in the float rod due to deformations. Ground tests of the engine, conducted at 1,700 rpm in a cruise-like attitude, demonstrated that the engine functioned normally but eventually failed after several minutes due to a lack of fuel. While the transfer mechanism was found to work via gravity, the investigation also noted that the STC used for the secondary tank was technically not applicable to the aircraft's Continental C-85 engine configuration.
Findings
- The engine stopped due to fuel starvation.
- The pilot may have failed to initiate the fuel transfer from the secondary tank, or the transfer may have been initiated too late to replenish the primary tank sufficiently.
- The pilot noted that the fuel level in the primary tank had dropped significantly, but during the transfer process, he did not observe an increase in the fuel gauge reading.
- The secondary tank's vent cap was positioned with the vent facing rearward because the pilot found the original forward-facing position difficult to close; however, the impact of this orientation could not be definitively determined.
- There was a discrepancy in the aircraft's configuration, as the STC for the auxiliary tank was not intended for use with a C-85 engine.