Incident Overview
A helicopter on a mission to insert a fire attack crew at a wildfire location struck trees after entering a spin during a right turn to return to a mountain landing zone. The landing zone (LZ) closest to the fire was a small area surrounded by trees. The density altitude at the site was calculated to be 11,968 feet.
Flight Details
The pilot initially landed at a meadow about one mile away, off-loading two firefighters. He then proceeded to the LZ, where he dropped off the remaining firefighter and tools. After returning to the meadow to pick up additional crewmembers, the flight headed back to the LZ. The aircraft overflew the LZ and continued up the drainage before initiating a right turn to return.
Witness Observations
A witness seated in the left front seat reported that during the first takeoff from the meadow, the torque gauge indicated 100 percent, and the helicopter was "hard to get off the ground" with a slow, labored climb. On the return flight, the first firefighter dropped at the LZ observed the helicopter flying slowly about 20 feet above the tree line. He expected the pilot to land with the wind, but instead the pilot flew past the LZ and continued up the drainage.
A surviving witness in the left front seat noted that the torque gauge read 100 percent as the pilot began the right turn. The torque then increased from 100 to 105 and subsequently to 110 percent. The witness asked the pilot if the tail rotor was going to stall but received no response. The airspeed gauge indicated zero. The pilot then began rapidly moving the collective, cyclic, and foot pedals. The helicopter spun twice to the right before impacting trees.
Both a ground witness and a rescue flight crew described the LZ as having a slope and being located in a tight area, with reported winds from the southwest at 2 to 4 knots.
Investigation Findings
On-scene investigation revealed that the compressor blades in the engine were folded opposite the direction of rotation, and tree fibers had been ingested by the compressor impellor—a condition consistent with an operational engine at high power at the time of impact. A subsequent engine teardown found additional tree fibers throughout the gas path, from the compressor section through the combustion and exhaust sections. No other discrepancies were noted with the airframe or engine that would have precluded normal operation.