NTSB Factual Report

On June 16, 2001, about 1415 hours Pacific daylight time, a Hughes 369HS, N4467V, collided with a tower and crashed about 1.5 miles northeast of Moffett Field, Mountain View, California. The helicopter was operated by Trinity Helicopters, Inc., Hayward, California. Visual meteorological conditions prevailed at the time of the public utility work-related flight performed under 14 CFR Part 133. No flight plan was filed. The helicopter was destroyed. The commercial pilot was seriously injured, and the passenger received minor injuries. The flight originated from Mountain View about 1410.

According to the pilot, he flew to the tower to pickup a passenger who was performing maintenance on the tower. The pilot placed one skid on the tower and the passenger began boarding the helicopter. Although he had performed this type of maneuver on numerous occasions, on this occasion the wind direction suddenly shifted from a direct tail wind to a right crosswind. Despite his effort to maintain control, the helicopter dynamically rolled over resulting in a main rotor blade striking the tower. Control was lost, and the helicopter fell about 90 feet to the ground. The pilot also indicated that prior to experiencing the loss of control, no mechanical malfunctions were experienced.

The pilot further indicated that the sudden change in the wind direction was not predictable. The pilot estimated that, at the time of the mishap, the wind was from the northwest at 10 knots. There were gusts to 15 knots.

NTSB Probable Cause

The pilot's failure to maintain control while hovering out of ground effect. A factor was the wind gusts.