Md Helicopters Inc 369E N765WH accident near Thomas, West Virginia

Probable cause

The pilot's failure to clear the helicopter and its external load from surrounding structures and his failure to execute a timely release of the external load, which resulted in an inadvertent entanglement and collision with wires and terrain. Contributing to the lineman's fatal injury was his position outside of the helicopter during the accident.

NTSB analysis

The pilot transitioned the helicopter to pick up three linemen who were working from the peak of a 100-foot-tall transmission tower. Before the linemen boarded the helicopter (two were in the helicopter and one was on the skid), they secured their equipment to the external load grappling hook suspended 50 feet below the helicopter. The pilot positioned the helicopter adjacent to the tower structure between the two sets of electrical conductors, with the grappling hook and the linemen's equipment suspended below. As the pilot attempted to maneuver the helicopter clear of the tower, it paused, and then began to shake before the helicopter contacted wires on the opposite end of the tower and impacted the ground under power. Both of the linemen who were seated in the helicopter before it impacted the ground incurred minor injuries; the lineman standing on the helicopter's skid was fatally injured. The pilot did not attempt to release the external load at any point during the accident sequence, and postaccident testing of the system revealed no anomalies. Postaccident examination of the airframe and engine revealed no evidence of any preimpact mechanical malfunctions or failures of the helicopter. Examination of the power transmission tower and external-load sling revealed evidence consistent with entanglement of the external load with the tower's structure. Immediate compliance with the operator's recommended procedure of jettisoning the external load in the event of an emergency (actual or perceived) would have provided an opportunity for the pilot to have prevented the accident.

Text from the NTSB. Open the NTSB docket for ERA11FA042 for the full record.