Incident Summary
A helicopter pilot conducting a reconnaissance flight to survey a hilltop landing site in mountainous terrain experienced a loss of airspeed and an increased rate of descent during the approach. Despite application of full power and a turn into a valley, the helicopter struck a tree, touched down on sloping terrain, and rolled over.
Approach Details
The pilot first performed a high reconnaissance pass over the intended landing site, then initiated a low reconnaissance approach. The estimated wind was from 210 degrees at 10 to 15 knots with light turbulence. The approach was flown on a heading of 200 degrees at an airspeed of approximately 40 knots and a descent rate of 200 feet per minute.
When the helicopter was about 150 feet from the hilltop and approximately 50 feet above it, the airspeed dropped to zero and the rate of descent increased. The pilot immediately applied full power and turned to the right, down a valley, but could not arrest the descent. The helicopter subsequently struck a tree, touched down on sloping terrain, and rolled over.
Terrain and Performance Factors
The elevation at the site was about 9,200 feet, with a density altitude of approximately 10,040 feet. The helicopter's hover ceiling out of ground effect was about 8,500 feet; in ground effect, the hover ceiling was approximately 11,800 feet. No further details regarding aircraft performance or environmental conditions were provided in the source.