WPR12LA227 · Cessna 150F

The pilot was performing banner tow operations over water, about 500 feet above ground level, in the modified two-seat airplane. The pilot-rated passenger was handling the airplane controls, and 1 hour after takeoff, having performed a series of uneventful laps, the pilot and passenger decided to return for landing. The passenger applied full forward throttle control to initiate a climb, but the engine lost all power. The airplane immediately began to descend, and the pilot took over the flight controls, released the banner, and performed a forced landing into the water.

The airplane sustained substantial damage to the fuselage as it struck the water, separating the right main landing gear from the airframe. The separation of the right main landing gear meant that the airplane most likely came to rest right-wing-low on the sea bed. Due to the design of the fuel tanks’ interconnecting vent lines and the inclusion of a vent port on the left tank only, fuel most likely either un-ported from the left tank while in the water, or transferred between tanks after recovery. As a result, an accurate determination of the fuel tank quantities could not be determined. The pilot and passenger reported that the fuel selector valve was in the “BOTH” position throughout the flight, however it was found in the “RIGHT” tank position after the accident. The location of the valve was such that it was most likely inadvertently kicked to this position as the passenger egressed from the airplane as it was sinking.

Postaccident examination did not reveal any anomalies with the airframe or engine that would have precluded normal operation. The pilot did not use carburetor heat before the accident. While the temperature and dew point were conducive to carburetor icing at the engine’s operating power level, the investigation could not conclusively determine that carburetor ice caused the loss of engine power.

Verbatim NTSB analysis and probable cause from the NTSB dataset