What happened
On August 25, 2020, an Eurocopter AS350 B2 helicopter, registration N160SH, was performing a Part 135 air taxi flight near Ninilchik, Alaska. The pilot was transporting workers between various mining sites near the Johnson River Tract in the Alaska Range.
After dropping off passengers at a low-elevation drill pad and a high mountainside helipad, the pilot returned to the mountainside site to pick up departing workers. During the second approach to the helipad, when the aircraft was approximately 25 feet from the landing site at a very slow forward airspeed, the engine experienced a flameout. Witnesses reported seeing a puff of smoke and hearing loud alarms as the engine lost power.
Following the loss of power, the pilot attempted an autorotation to a level area approximately 600 feet below the helipad. Realizing the intended site could not be reached, the pilot applied aft cyclic and increased collective to cushion the impact. The helicopter landed on its skids facing downslope and began to slide. The left skid struck a rock, causing the aircraft to roll over and continue moving down the mountain. The impact caused the tail boom to separate. The aircraft sustained substantial damage to the tail section, fuselage, and main rotor blades. The pilot sustained one minor injury and there were no fatalities.
The investigation
The investigation included an examination of the airframe and the Honeywell LTS101-700D2 turbine engine. The airframe showed no discrepancies other than impact damage.
The engine was sent to the Honeywell Engines division for testing. On February 18, 2021, the engine was run on a test cell for 1 hour and 14 minutes with five starts; it demonstrated normal fuel flow metering, control, and power turbine governor performance. On February 23, 2022, further testing of the overspeed system was conducted. The engine successfully demonstrated the ability to detect overspeed, activate the overspeed solenoid, vent pneumatic control pressure, and command minimum fuel flow, as well as the ability to recover to normal operation once speeds dropped. No abnormal operation or uncommanded shutdowns were observed during these tests.