LAX03LA138 · Eurocopter France AS355N

The helicopter's main rotor and tail rotor blades contacted a brush pile during a precautionary landing that was preceded by a discrepancy in the engine/power torque indication gages. The flying pilot (FP) conducted a normal start up and hover taxied the helicopter to a predetermined location for takeoff. He observed a discrepancy between the two engine torque indicator needles, with no other engine, systems, or rotor indications noted, which led him to make the precautionary landing. As the FP hovered the helicopter in a high hover about 10 feet above the ground, he initiated a slow left turn, with the intention of keeping an adjacent brush pile in view. The pilot reported that the initial 45 degrees of the left turn were normal. Unbeknownst to the pilot, the tail rotor had contacted a brush pile. After the tail rotor contacted the brush pile and the tail rotor gear box separated from the tail boom, the helicopter pitch attitude changed to a nose low attitude and the helicopter started to yaw to the left with the yaw rate increasing. The FP attempted to counteract the loss of control with full aft cyclic and full right pedal, with no effect. Ultimately the main rotor struck the brush pile and the helicopter rotated to the left. The helicopter manufacturer does not identify a torque split between the number 1 and number 2 engines as an emergency. The normal procedure for a torque split discrepancy is to utilize the equalizing trim to balance the torque loads. The FP indicated there was very little apparent vibration, and the NFP did not report any vibrations. After the accident it was observed that the tail and tail rotor assembly had separated from the tail boom, and one of the STARFLEX rotor head arms were fractured at a 45-degree angle. Left yaw of the helicopter is consistent with a loss of tail rotor authority, and the change in noise level heard by the crew could be associated with the tail rotor's interaction with the brush pile. Both engines were test run at the Turbomeca factory in Texas, under the auspices of a Safety Board Investigator on September 3, 2003. No discrepancies were noted with the test run.

Verbatim NTSB analysis and probable cause from the NTSB dataset