Incident Details
The helicopter lifted off during an 80% power check and began a northerly departure. Before achieving translational lift, the rotor RPM dropped to approximately 85%. The torque meter indicated a split, with the #1 engine showing about 55% torque and the #2 engine indicating as low as 39%. The low rotor RPM audio and warning light activated, and the helicopter began to sink. The pilot had insufficient altitude to recover rotor RPM. He landed the helicopter in a clear area in a nose-high attitude with forward speed. During the landing, the skids were damaged (spread), the helicopter rocked forward, the radome was damaged, and the tail boom was severed.
Investigation Findings
An investigation revealed that the #2 engine main fuel control, part number 3244736-8, had an air leak at the P3-TP-PG regulator air diaphragm where a retaining screw was loose. The screw had been safety wired and sealed by the manufacturer but would turn slightly within the limits of the wire. When tightened within those limits, the air leak stopped.