Accident
On August 25, 2020, about 0709 Alaska daylight time, a Eurocopter (Airbus) AS350 B2 helicopter, registration N160SH, was substantially damaged during an accident near Ninilchik, Alaska. The commercial pilot sustained minor injuries. The helicopter was operating as a Title 14 Code of Federal Regulations Part 135 air taxi flight.
Pilot Statement
The pilot reported that he was operating at the Johnson River Tract mining camp in the Alaska Range mountains west of the Cook Inlet. He was transporting workers to and from various mining sites about 3 miles from the main camp. On the morning of the accident, he conducted a preflight and sumped fuel from the helicopter's main fuel tank and airframe fuel filters. All samples were clear and bright. The fuel level was about 40%, corresponding to about 55 gallons of Jet A. No known discrepancies existed. He had flown the helicopter most every day for the previous 2 months and was very familiar with it.
The pilot departed the main camp about 0655 with 4 passengers. He disembarked 2 at a low-elevation drill pad, then flew to a high mountainside helipad at about 2,750 ft msl, cut into a rocky steep slope, and disembarked the other 2 passengers. He flew to a nearby site and waited for the off-going workers. He departed and made another approach to the helipad. When the helicopter was about 25 ft from the landing site, at very slow forward airspeed, the engine "flamed out" and the helicopter yawed right. The pilot continued the right turn, lowered the collective, and attempted to autorotate to a level area about 600 ft below the helipad. Realizing the helicopter could not reach that site, he slowed by applying aft cyclic and increasing collective to cushion the touchdown. The helicopter landed on the skids facing down the mountain and slid. The left skid impacted a rock, the helicopter rolled over, and it continued down the mountain, resulting in the tail boom separating. It came to rest on its left side on a drill pad under construction about 200 ft below the helipad. The tail section, fuselage, and main rotor blades sustained substantial damage. Mining workers at the helipad called for assistance, hiked down, and assisted the pilot.
Engine Examination
The helicopter was recovered and examined. The Honeywell LTS101-700D2 turbine engine was secure on the airframe and intact. No airframe or engine anomalies other than impact damage were observed. The engine was shipped to Honeywell Engines for further examination.
On February 18, 2021, the engine was run on a test cell for 1 hour 14 minutes with five starts. It demonstrated the ability to meter and control fuel flow, and the power turbine governor operation and performance was demonstrated. No abnormal operation was observed.
On February 23, 2022, the engine was run on a test cell for 1 hour 9 minutes with four starts to test the overspeed system. Three tests demonstrated the overspeed system's ability to detect overspeed, activate the overspeed solenoid, vent pneumatic control pressure, command minimum fuel flow, and keep the engine operating at minimum flow. It also demonstrated the system's ability to deactivate once input speed dropped below the reset value, and the engine's recovery to normal operation.