NTSB Identification: ANC99TA058.
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Accident occurred Wednesday, May 05, 1999 in WRANGELL, AK
Probable Cause Approval Date: 11/30/2000
Aircraft: Bell UH-1B, registration: N97HM
Injuries: 1 Fatal,2 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this public aircraft accident report.
A restricted category Bell UH-1B helicopter was hovering near high voltage wires at a construction site, performing external load lift operations with a 110 feet long steel cable. The construction project was under the direction of the Alaska Energy Authority, a State of Alaska corporation. The State of Alaska construction project manager reported the electrical wires were energized, and the wires were configured to de-energize if shorted. The pilot had extensive external load experience, but had about 1 hour in the accident helicopter make and model. He said he was not aware the electrical wires were energized. The chief pilot was occupying the right seat, and said he was providing 'guidance' during the flight. The chief pilot said he was aware the wires were hot. Just after the long line was hooked to a load of steel beams on the ground, the cable touched the overhead electrical wire, and electrocuted one ground member standing on the load. The construction project operations manager said that the electrical short, caused when the cable touched the wire, was insufficient to trip the electrical power off. The helicopter company's external load manual includes the following: 'The chief pilot will brief all involved personnel concerning procedures for each operation; the flight crew consists (normally) of one pilot; the use of a hand signalman, separate from the ground crew, shall be assigned no other duties during the operation; the pilot may elect to use a continuous visual observation method, wherein he is directly observing the load by looking out the window, out the door, or by use of mirrors. In this case, release and/or signalmen need not be utilized.' The manual also includes: 'Radio contact between the pilot and the hook-up man is highly desirable, and the presence of a radioman in no way alleviates the need for the hand signalman. A signalman should be present at all times in the event of a radio failure. If the pilot is able to observe the hook-up operation by using a skid-mounted mirror, and VHF two-way radio communications are maintained between the pilot and the hook-up man, a signalman is not required.' During the accident, direct radio communication between the ground crew and the pilot was not maintained, and a signalman was not utilized.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot-in-command's failure to maintain sufficient distance from a transmission wire, arcing of the transmission wire, the failure of company personnel to utilize a nonconducting cable, and an inadequate procedure utilized by the construction project manager to ensure adequate fault protection on an energized transmission wire. Factors in the accident were a failure of the helicopter operator to maintain sufficient standards, including flight and ground crew coordination, and a failure to maintain radio communication between the pilot and ground crew. Full narrative available
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