What happened
On 17 October 2000, an MDHC 369E helicopter, registration ZK-HFT, was conducting a charter flight to inspect road damage near the Homer Tunnel. After completing the inspection and beginning the return journey toward Queenstown, the aircraft was flying approximately 500 feet above the ground in the Upukerora Valley when the pilot and passenger experienced a sudden bump and a simultaneous loss of power.
Recognizing the descent was not caused by turbulence, the pilot immediately transitioned the aircraft into an autorotation. Despite attempts to use the relight button and performing maneuvers to maintain rotor speed, the engine failed to restore power. During the subsequent landing in a clear area, the pilot executed a hard flare to reduce the descent rate. This maneuver caused the tail rotor to strike the ground, which subsequently severed the tail boom of the MDHC 369E. The helicopter remained upright following the impact, and both the pilot and the passenger escaped without injury.
The investigation
Investigators examined the aircraft, the engine, and various fuel and component samples. The engine, an Allison 250-C20B, was disassembled, but the inspection of the compressor, turbine, and fuel burner-can revealed no mechanical defects or abnormalities. Fuel samples from the aircraft and the operator's supply met all required specifications, and no significant contamination was found.
While the investigation could not definitively identify the cause of the power loss, investigators considered the possibility of snow ingestion. Although the aircraft had been clear of active snow for several minutes, the recent flight through rain and sleet, combined with a descent into warmer air, could have caused accumulated snow on the air intake to melt and be ingested into the engine. However, the investigation also noted that the aircraft had been on the ground for only brief periods, making significant snow buildup unlikely.