Incident Description
During the climb after takeoff, at an altitude of approximately 300 feet, the pilot experienced a loss of engine power. The pilot subsequently performed a forced landing on water, ditching the aircraft.
Investigation Findings
The investigation identified a loose rubber seal within the mechanical fuel pump as the cause of the fuel flow interruption. This seal had become dislodged and obstructed the fuel flow exiting the pump.
Further examination revealed that the engineering drawing for the seal did not include an ASTM specification that governs the production and curing of the rubber. Without this specification, the rubber used in the seal was susceptible to swelling when exposed to aviation gasoline.
Fuel Pump Seal Issue
According to the investigation, seals manufactured from rubber not meeting the ASTM specification would swell upon contact with aviation gasoline. With sufficient exposure, the swollen seal could become unseated and migrate into the exhaust side of the pump. Once there, it would restrict the fuel flow to the engine, leading to power loss.