Incident Overview
A local sightseeing flight along a ridge line encountered a sudden windshear while maneuvering around a cloud build-up. The windshear caused the aircraft to nose over into an approximately 75-degree vertical dive. Just prior to colliding with trees, the pilot regained some control, and the aircraft struck the terrain at an approximately 45-degree attitude.
Meteorological Conditions
In the mountainous area, a katabatic wind often flows downslope as solar heat is radiated from the terrain, cooling the surface. Additionally, trade winds cross the ridges obliquely, resulting in eddies that produce off-ridge flow. When these eddies and katabatic gusts coincide, a windshear can occur.
Sequence of Events
The flight was proceeding along the ridge line when the pilot maneuvered to avoid a cloud build-up. At that point, the aircraft entered windshear, which abruptly pushed the nose down into a steep dive. The pilot managed to partially recover, but the aircraft struck trees and terrain at a nose-down attitude.