History of Flight
On October 30, 2010, about 1030 eastern daylight time, an MD Helicopters, Inc. 369E, registered as N765WH, was substantially damaged after colliding with power transmission wires and terrain near Thomas, West Virginia. The helicopter was operated by Winco, Inc. under 14 Code of Federal Regulations Part 133. The certificated commercial pilot was seriously injured. Of the three linemen on board, two suffered minor injuries while one was fatally injured. Visual meteorological conditions prevailed, and no flight plan was filed for the local external load flight.
The helicopter was tasked with transporting linemen between power transmission towers to transfer fiber optic grounding lines. The crew began work at 0820, moving linemen sequentially to seven towers (242 through 248). For each tower, the helicopter hovered near the peak while linemen disembarked, then ascended about 40 feet so the linemen could retrieve equipment from a sling suspended below the helicopter. The process was reversed for pickups.
On the accident flight, a third lineman was carried to assist a worker experiencing difficulty. After all three completed work on tower 248, the helicopter returned to retrieve them and their equipment. Two linemen sat in the rear; one stood on the left skid. The pilot reported that after clearing the tower, the helicopter began shaking violently, then hit something and spun before impacting the ground. A lineman stated the pilot "picked up and powered into" the tower, feeling a pause and the engine bogging down. The pilot could not recall attempting to jettison the external load.
Personnel Information
The pilot held a commercial pilot certificate with a rotorcraft-helicopter rating, accumulating 1,682 total flight hours (all rotorcraft), with 282 hours in the accident make and model. His most recent FAA second-class medical certificate was issued February 15, 2010, with the limitation "must wear corrective lenses." He was hired in March 2010, completed 4.6 hours of external load training on April 28, 2010, and logged 18.7 hours of initial training, followed by 434.7 hours of on-the-job training. On October 27, 2010, he was certified proficient in operations including approach, transfer of linemen, and departure from structures.
Aircraft Information
The helicopter was manufactured in 2009, with its airworthiness certificate issued December 7, 2009. The most recent 100-hour inspection was completed October 23, 2010, at 392 total hours. Mission-related modifications included a safety harness attachment point, a deck plate, and an external cargo hook with electric and manual release systems. A 40-foot synthetic fiber-rope sling with a custom 3-prong grappling hook was used to ferry equipment.
Meteorological Information
At 1051, the weather at Elkins-Randolph County Airport (24 nautical miles southwest) included clear skies, 10 statute miles visibility, calm winds, temperature 5°C, dewpoint 0°C, and altimeter setting 30.13 inHg. The pilot reported calm winds, no gusts, sunny skies, and cold temperatures at the accident site.
Wreckage and Impact Information
The helicopter came to rest on its left side about 100 feet west of tower 248. The tail boom separated approximately 2 feet forward of the tail rotor gearbox. The vertical stabilizer exhibited two parallel concave depressions about 14 inches apart with contact marks consistent with transmission line wires. Both tail rotor blades also showed concave depressions and wire contact signatures. All three conductors on the tower showed damage and paint transfer matching contact with the vertical stabilizer and tail rotor blades.
Main rotor blade grips separated from the hub, and blades were distributed in an arc southwest to northwest of the fuselage. Control continuity was traced from the flight controls to the main rotor and tail rotor, with fractures noted in the tail boom driveshaft. The engine mounts remained secure except the right front. The external load sling (27 feet remained attached to the cargo hook; the remaining 13 feet with grappling hook was found at the tower base). Red fiber transfer marks and abrasions on the tower were consistent with the sling and grappling hook positions.
Tests and Research
A GPS receiver from the wreckage indicated the accident flight lasted about 2 hours 53 minutes. From 1025 to 1030, the helicopter remained within a 0.2-mile area at altitudes between 2,700 and 2,800 feet, ground speed under 3 mph. At 1030:10, altitude was 2,708 feet, ground speed 0.1 mph; five seconds later, speed increased to 5 mph as altitude decreased to 2,702 feet. At the last data point, speed was 6 mph and altitude 2,601 feet.
Additional Information
The operator's Task Analysis documents specified responsibilities. For departure from a structure, risks included obstacle clearance, helicopter performance with additional weight, and inadvertent attachment. Recommended risk reduction included slow, deliberate departure and verification of clearance. Emergency procedures advised performing helicopter emergency procedures per the rotorcraft flight manual and noted that inadvertent attachment might be rectified by slowly moving the helicopter back to the work location. The external load task analysis advised releasing the load immediately if difficulties arose and an emergency landing was necessary.