History of Flight
On September 7, 2022, at about 1555 Pacific daylight time, a Bell 205A-1 helicopter, registration N66HJ, sustained substantial damage during an accident near Cougar, Washington. The pilot reported minor injuries. The helicopter was being operated as a public aircraft firefighting flight under contract with the Bureau of Land Management and under the operational control of the US Forest Service, responding to the Kalama Fire on Mount St. Helens.
The pilot stated that earlier that day he conducted water drops and crew relocation activities using the north end of Merrill Lake for about two hours. After refueling at Southwest Washington Regional Airport, he returned to the lake. Winds had shifted to a more northerly direction, so he chose to dip from the northwest corner of the lake, using an approach similar to one used the previous day. He flew oval approaches from the fire to the lake.
During the final dip, while hovering about 130 feet above ground level and lowering the bucket into the water, the pilot experienced severe airframe vibrations, a strong sensation of sinking, and an uncommanded left yaw. He lowered the collective, received caution lights and a low rotor RPM horn, and attempted to guide the helicopter toward the shoreline. The helicopter landed hard and flat, coming to rest partially submerged on its right side. The pilot egressed after shutting down the helicopter.
Personnel Information
The pilot held a USDA/USDI Interagency Helicopter Pilot Qualification Card issued on June 3, 2022, with authorization for external load, water/retardant bucket, Helitack/PAX transport, low level and reconnaissance, and mountainous terrain. He reported 6,100 total flight hours, with 2,774 in rotorcraft and 89 hours in the accident make and model. His other rotorcraft experience included Bell 206 and Airbus Helicopters AS350 (H125).
Aircraft Information
The helicopter was a Bell 205A-1 operated by Kachina Aviation, which provided fire-suppression services. It was powered by a single Ozark Aeroworks T5317B turboshaft engine. The helicopter was equipped with a 240-gallon Bambi Bucket set to 90% capacity.
Meteorological Information
A High Resolution Rapid Refresh (HRRR) model sounding for the time of the earlier flights indicated a surface elevation of 1,982 ft msl, temperature about 21.3°C, dewpoint about 7.6°C, and 4-knot winds from 200°. A weak cold front passed through the area before the accident. An updated model showed that at accident time, winds were from 326° at 14 knots, increasing to 17 knots through 4,232 ft. The models did not account for wind induced by the fire.
Wreckage and Impact Information
The helicopter came to rest on its right side on the north end of the western shore of Merrill Lake, at an elevation of about 1,550 ft msl. The tailboom was bent forward and underneath the main cabin, partially detached about 2 ft forward of the horizontal stabilizer. The vertical fin had diagonal crush features and a cut consistent with tail rotor blade contact. Both main rotor blades remained attached; the white blade was bent upward with a severed leading-edge spar, and the red blade had a slight upward bend at the tip. The main driveshaft fragmented, puncturing cowlings. The fuel system was intact with clean fuel. The bucket was found about 20 feet away, released from the cargo hook. The cinch strap was severed at the 90% cinch ring, and the dump valve seam was torn.
Tests and Research
The engine was examined and found intact with water intrusion throughout. Disassembly revealed damage to compressor blades, impact marks on the compressor housing, and debris in the combustion section. A shiny 5 mm-wide fragment at the root of the 2nd stage power turbine rotor appeared to match aluminum honeycomb from the main rotor blades. The NTSB Materials Laboratory analyzed debris and found primarily high chrome steel, iron, chrome, and nickel, with smaller amounts of other materials. The fuel control unit and power turbine governor tested nominally. Data from the engine MGT gauge showed temperature cycles consistent with water pickup and dump operations. On the accident flight cycle, MGT suddenly dropped from 710°C to 150°C 15 seconds before data ended.