Ercoupe 415-D N415JC accident near Waupun, Wisconsin

Probable cause

The pilot’s decision to take off without correcting a misinstalled fuel cap, which resulted in a loss of engine power due to fuel starvation caused by improper venting of the fuel system.

NTSB analysis

During a cross-country flight, the engine rpm dropped and the engine lost power. The pilot attempted to restore engine power without success. The pilot established that the engine was likely starved of fuel and elected to perform a forced landing into a marsh. The airplane sustained substantial damage to the fuselage, empennage, and both wings.

The pilot stated that they departed with about 28 gallons of fuel on board. After the airplane was fueled, the line technician placed the vented fuel cap on backwards. The pilot elected to continue the flight to the destination and address the misinstallation upon arrival.

After the accident all of the fuel tanks were empty; however, law enforcement reported that an unknown quantity of fuel had leaked from the left fuel tank. A postaccident examination confirmed that the vented fuel cap was on backwards on the outboard fuel tank. An examination of the remaining fuel system and the engine revealed no mechanical anomalies that would have precluded normal operations.

The lack of venting from the misinstalled fuel cap likely precluded fuel from flowing from that fuel tank, which resulted in a loss of engine power due to fuel starvation.

Text from the NTSB. Open the NTSB docket for CEN23LA322 for the full record.