Mcdonnell Douglas Heli Co 369FF N527SH accident near Fossil, Oregon

Probable cause

The pilot's failure to maintain clearance from a power pole to which he was connecting wire-pulling ropes.

NTSB analysis

The pilot of the helicopter was pulling a rope along a line of wood power poles, and placing the rope within the lowest traveler (pulley) attached to each power pole. The placement of the rope into the traveler required maneuvering the helicopter in close proximity to the pole, while the rope was attached to a long-line that was shorter than the distance from the top of the pole to the traveler that the rope was being placed in. The pilot had already placed the rope in the traveler on the first pole of the line, and had just completed the placement of the rope into the traveler on the second pole, when he began to maneuver the helicopter in order to proceed to the next pole. At the beginning of that maneuver, the pilot inadvertently allowed the helicopter to come close enough to the pole that he had just finished working on for its main rotor blades to come in contact with the pole. Immediately thereafter, all five of the main rotor blades separated from the helicopter, whereupon the helicopter's tail boom separated from its fuselage. The helicopter then fell to the down-sloping terrain near the base of the pole. No pre-accident anomalies were found with the helicopter's airframe, engine, or flight control system.

Text from the NTSB. Open the NTSB docket for WPR10FA012 for the full record.