What happened
At 1245 central daylight time, an amphibious Cessna 206 (registration N753) departed from Runway 20 at Swan River, Manitoba, while en route to Dauphin. The aircraft, operated by the United States Department of the Interior for waterfowl data collection, was carrying a pilot and one observer. Shortly after takeoff, the engine began to lose power accompanied by vibrations.
At an altitude of approximately 75 feet, the pilot determined there was insufficient runway remaining to land back at the airport. To avoid obstacles such as roads and ditches, the pilot initiated a right-hand circuit to return to the runway. However, as engine power continued to decline, the pilot executed a forced landing in a plowed field roughly a quarter-mile west of the runway.
Upon impact, the aircraft overturned. The landing gear configuration and impact forces caused the float tips to dig into the ground, leading the propeller to strike the floats and eventually separate from the engine. During the roll-over, a fuel leak developed at the left wing root, which ignited and destroyed the aircraft. Both the pilot and the crew member escaped the wreckage with minor injuries.
The investigation
The investigation focused on the engine's failure and the subsequent fire. Because the aircraft was destroyed by fire, investigators could not analyze fuel samples directly from the aircraft's tanks. However, a sample from the local fueling station was found to be clean.
Engine teardown at the manufacturer's facility revealed that the fuel manifold's steel shaft was coated in rust, indicating contact with water. Further analysis by the TSB Engineering Laboratory confirmed that corrosion particles from the manifold screen had migrated to the No. 1 fuel injector, causing a restriction. Additionally, investigators noted that the fuel nozzles for 100 LL and Jet B at the Swan River station were identical in size and shape, which presented a risk of misfuelling.
Findings
- Water contamination in the fuel caused deteriorating engine power during the takeoff phase.
- A restriction in the No. 1 fuel injector, caused by corrosion from the manifold screen, led to the No. 1 cylinder failing to fire.
- The aircraft was destroyed by fire following a fuel leak triggered by airframe damage during the forced landing.
- The decision to leave the landing gear extended increased drag and contributed to the aircraft pitching forward during the landing.
Safety action
- To mitigate the risk of misfuelling, the Jet B fuel nozzle at the Swan River airport fueling station was replaced with a larger, oblong nozzle.