Incident Details
A helicopter pilot was en route to pick up passengers when, approximately 16 miles from the intended destination, he landed in a field due to deteriorating weather conditions. During a cellular telephone conversation with his employer, it was decided that the pilot should reverse course, land at a nearby airport, or return to the helicopter's base. The pilot subsequently took off from the field and attempted to fly directly to an airport but was again unable to follow his desired course due to weather.
As he maneuvered, the weather improved, and ridgelines became visible. The pilot reported flying about 100 feet above the trees and 200 feet below the clouds as he approached a field crossed by a power line. He stated that he chose to land in the field because of a "klunking" noise behind him. "As I entered the approach the noise got worse and the aircraft started to vibrate. The vibrations got very bad as I tried to arrest my descent, so I decided that touching down hard was better than shaking apart."
Flight Path and Weather
Examination of the global positioning system ground track revealed that the helicopter descended at a rate of 1,000 feet per minute during an s-turn across the face of a mountain before it leveled over flat terrain and slowed below effective translational lift in the vicinity of the crash site. The crash site was surrounded by rising terrain, in the lee of a mountain with strong winds. An AIRMET for turbulence was in effect along the route of flight. The helicopter experienced a high sink rate and high levels of vibration prior to ground contact.
According to The Good Aviation Practices publication Helicopter Performance, published by the Civil Aviation Authority of New Zealand (November 2002), "Local terrain, trees, and buildings all influence the flow of wind near them. The mechanical turbulence resulting from this disturbed airflow may become very marked in the lee of the obstruction. A gusting wind situation where windshear is likely to be present will require a greater power margin to deal with any unexpected loss of airspeed and sink."
Aircraft Examination
Examination of the wreckage and a post accident engine run revealed no preimpact anomalies.