Accident Details
The pilot of a helicopter initiated a maximum power takeoff from a confined parking lot with two passengers on board. The area was bordered by obstructions and people. During lift-off, the pilot increased power to 2900 RPM, lifted off to a 4-foot hover with 33 inches of manifold pressure, then began a max performance takeoff. The pilot reported 'pulling power and turning throttle' for extra RPM with slow forward speed, reaching 36 inches of manifold pressure.
Loss of RPM and Avoidance Maneuver
At approximately 15 feet above ground level, the pilot noted a decrease in RPM. She increased throttle application, then decreased the collective, but was unable to recover the loss of RPM. She made a left pedal turn to avoid obstructions and people. Subsequently, the helicopter touched down hard and was damaged.
Engine Examination
An examination of the engine did not reveal any defects. The flight manual warned that loss of rotor and engine RPM would follow when the engine was overboosted. At 36.5 inches of manifold pressure, the pop-off valve would have activated, which would have resulted in a slight power loss.