What aircraft was involved and where did it happen?

The accident on 1990-09-02 involved a Bell 47G-3B1, registration N73957, at Canon City, CO.

Helicopter Collides with Power Lines During Downwind to Helipad (N73957)

On September 2, 1990, a Bell 47G-3B1 (registration N73957) was involved in an aviation accident near Canon City, CO. Investigators recorded the probable cause as: THE PILOT'S FAILURE TO MAINTAIN AN ADEQUATE PATTERN ALTITUDE AND THE POSSIBLE EXISTENCE OF ADVERSE WINDS DUE TO THE SURROUNDING TERRAIN. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

A helicopter struck power lines while on downwind approach to a helipad, causing tail rotor separation. The pilot reported windshear at 230 ft AGL, but the existence of windshear could not be verified.

Accident Overview

A helicopter collided with power lines while conducting a downwind approach to a helipad. According to witnesses, the helicopter was traveling perpendicular to an electrical transmission line at approximately 60 knots when it struck the top of a two-wire set at about 30 feet above ground level (AGL). Paint transfer from the tail rotor (T/R) skid was found on the damaged power line.

Tail Rotor Separation

After striking the wire, the tail rotor separated at the gear box mounting flange. Small pieces of the tail rotor blade were found on the ground below the point of initial wire contact.

Pilot Statement

The pilot stated that during the downwind climbing turn after takeoff, while passing over a gully near a 6,200-foot ridge, he encountered windshear at 230 feet AGL. This encounter resulted in a loss of 200 feet of altitude and the subsequent collision with the power lines.

Investigation Findings

The existence of the reported windshear, or a possible downdraft, could not be verified.

1990-09-02: Bell 47G-3B1 (N73957) — Canon City, CO