What happened
The accident occurred during the initial phase of flight while departing from a small lake. An instructor pilot was on board supervising a student pilot who was acting as the pilot in command for the maneuver. The student executed a flat, step-turn takeoff procedure from the water surface.
During this critical phase, the aircraft's fuel supply became critically low. As the engine operated under these conditions, the fuel pickup mechanism failed to maintain a consistent flow, leading to intermittent fuel starvation. Consequently, the engine stopped and restarted multiple times in rapid succession.
Despite the instructor pilot's efforts to manage the situation and recover engine power, the repeated loss of thrust prevented any successful return to the lake or alternative landing site. The aircraft was unable to maintain altitude and subsequently impacted a line of trees.
The investigation
Examination of the event focused on the fuel system performance during the specific takeoff maneuver. The investigation confirmed that the fuel tanks were at a low level prior to and during the takeoff sequence. This low state contributed directly to the fuel pickup unporting, which is the failure mode where the intake loses contact with the liquid fuel.
Findings
The primary factors leading to the accident included:
- Low fuel quantity in the aircraft tanks at the time of takeoff
- Fuel starvation caused by the pickup unporting during the step-turn maneuver
- Loss of engine power due to intermittent fuel supply
- Inability to recover sufficient thrust to avoid terrain
The sequence of events demonstrates that operating an aircraft with minimal fuel reserves during a high-demand phase like water takeoff can lead to immediate system failure. The specific aerodynamic and hydrodynamic forces involved in a step-turn takeoff likely exacerbated the fuel starvation issue.
Safety message
Pilots must ensure adequate fuel reserves are available before attempting any takeoff, particularly from non-standard surfaces like lakes where drag and power requirements may be higher than on paved runways. Fuel management is critical during low-altitude operations where recovery options are limited.