Amateur-built RV7A N667AZ accident near Hanover Park, Illinois

Probable cause

A partial loss of engine power shortly after takeoff due to water contamination of the fuel system.

NTSB analysis

The pilot was conducting a personal cross-country flight when the airplane had a partial loss of engine power shortly after takeoff. Engine operation did not improve after the pilot's corrective actions and a forced landing was completed to a soft field where the airplane nosed over upon touchdown. The fuselage, both wings, and the empennage were substantially damaged during the accident.

Postaccident fuel samples taken from each wing tank sump did not exhibit any contamination. A fuel sample collected from the fuel supply line connected to the fuel injector servo inlet contained a small amount water contamination. The electric fuel pump was used to obtain an additional fuel sample, which also contained water contamination. The fuel filter, which was not equipped with a drain sump, had evidence of water contamination. Besides the water contamination found in the fuel system, the postaccident examination did not reveal any anomalies that would have precluded normal engine operation during the flight.

The pilot reported that the fuel samples he obtained from each wing tank sump during his preflight inspection were not contaminated. The pilot would have been unable to identify water contamination downstream of the fuel tanks, because the experimental airplane was not equipped with a drainable fuel filter. A review of maintenance documentation revealed at least one instance of water and particulate contamination being found in the fuel filter and the fuel injection servo finger screen. Based on the available evidence, it is likely that the partial loss of engine power shortly after takeoff was due to water contamination of the fuel system.

Text from the NTSB. Open the NTSB docket for CEN18LA181 for the full record.