NTSB Factual Report

HISTORY OF FLIGHT

On August 21, 2006, about 1920 Alaska daylight time, a Canadian registered Eurocopter AS350 B2 helicopter, C-FYUN, was destroyed when it impacted water during an external load operation, about 20 miles northwest of Nuiqsut, Alaska. The helicopter was being operated under contract from Prism Helicopters, Wasilla, Alaska, by the United States Geological Survey (USGS), Reston, Virginia, as a visual flight rules (VFR) public use local flight under Title 14, CFR Part 91, when the accident occurred. The solo commercial certificated pilot received fatal injuries. Marginal visual meteorological conditions prevailed, and company flight following procedures were in effect. The flight's destination was Inigok, Alaska.

During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on August 22, an FAA specialist at the FAA Regional Operations Center (ROC) in Anchorage, Alaska, said the helicopter had been dispatched from Inigok on the evening of August 21, to retrieve an external load at the Fish Creek Well 1 site, about 40 miles northeast of Inigok, and about 20 miles west of Nuiqsut. The specialist said the helicopter pilot did not report arriving at or leaving the Fish Creek site, and had not returned to Inigok. She said the Air Force Rescue Coordination Center (AFRCC) had been notified, but low clouds, fog, and darkness had precluded aircraft from searching the area.

The helicopter's wreckage was discovered by searchers in a shallow lake, about 1100 on August 22.

On August 23, during an interview with the IIC, the Inigok camp manager said the helicopter had returned to Inigok from the Fish Creek site on the day of the accident, with a USGS employee and an internal load. He said the pilot then returned to the Fish Creek site to retrieve an external load which had been prepared by USGS and BLM personnel, and left for his retrieval. The camp manager, who is employed by BLM, said prior to the helicopter leaving to retrieve the external load, he had a discussion with the pilot about deteriorating weather conditions at the Fish Creek site. He said the pilot was advised not to take any chances because the fog was moving in from the north, and to return to Inigok without the external load if necessary. The camp manager said that the varying conditions between the two locations were typical, and that he was confident the pilot would make the correct decision with regard to continuing the mission.

The USGS employee who rode with the pilot on the evening of the accident, told the IIC that when they left the Fish Creek site en route to Inigok, low clouds and fog from the north had already started to move into the area. He said characteristically, in the late morning, the fog and low clouds would move north toward the Beaufort Sea allowing flight operations, and then in the late afternoon or early evening, move inland once again, curtailing flight operations. He said when the fog and low clouds moved in, the ceilings were often less than 500 feet, and visibility less than one-quarter mile.

INJURIES TO PERSONS

The solo pilot received fatal injuries.

DAMAGE TO AIRCRAFT

The helicopter was destroyed by impact with water/terrain.

PERSONNEL INFORMATION

According to company records and FAA documents, the pilot held a commercial pilot certificate with a helicopter rating. He had accumulated about 4178 hours of flying experience, all of which was in helicopters, and about 2978 of those hours were in the same make and model as the accident helicopter. An FAA second class medical certificate was issued September 26, 2005. The pilot completed a biennial flight review on May 29, 2006. He was selected as a replacement pilot to operate out of a remote site supporting Bureau of Land Management personnel, and scientist from the U.S. Geological Survey. The pilot had no previous experience working on Alaska's north slope, and the accident occurred during preparation for closing the remote site prior to winter.

AIRCRAFT INFORMATION

The accident helicopter was a Eurocopter AS-350-B2, Canadian registration C-FYUN. It was operating in Alaska under a U. S. Bureau of Land Management contract, and the flight was being conducted under a joint use agreement with the United States Geological Survey. The helicopter was being maintained under a manufacturer's approved airworthiness inspection program (AAIP). The last inspection was completed on July 11, 2006, and the total time in-service of the airframe at the time of the accident was 17,897 hours.

METEOROLOGICAL INFORMATION

According to witnesses, the weather on the evening of the accident was moving north to south, as was typical for the time of day. During the morning hours the fog and low clouds moved north, onto the Beaufort Sea, and during the evening the fog and low clouds moved inland again. The Fish Creek site was farthest north along the route of flight, and according to the passenger on the flight from Fish Creek to Inigok, the fog and low clouds had started to move into the Fish Creek area prior to leaving for Inigok. The nearest official weather reporting site is located at the Nuiqsut Airport, about 20 miles southwest of the accident site, between the Inigok base camp and the Fish Creek pick-up site. During a 2 hour period surrounding the approximate time of the accident, the visibility at Nuiqsut varied rapidly between 6 miles and one-half mile in rain. The ceiling was consistent at 200 feet above ground level (agl). The winds were not reported.

COMMUNICATIONS

There were no voice communications received from the accident helicopter after leaving Inigok en route to the Fish Creek site. The helicopter was equipped with a global positioning device which transmitted the helicopter's position, altitude, ground speed, and heading to a satellite every 2 minutes. The position report was then retransmitted to a ground station, and monitored by the company. A ground track derived from the position reports did not indicate any unusual characteristics. The track and last position report indicated that the helicopter was proceeding toward Inigok, at an indicated ground speed of 47 knots, an altitude of 302 feet, and a heading of 325 degrees.

WRECKAGE AND IMPACT INFORMATION

The area where the accident occurred is principally a tundra plain, typically less than 100 feet in elevation, with the Beaufort Sea to the north. The area has numerous shallow lakes and arctic marshes. The on-site inspection of the wreckage by the IIC commenced on August 24. The IIC was accompanied by an FAA air safety inspector, investigators from the U. S. Department of the Interior and Bureau of Land Management, and representatives of the operator. Access to the site was via helicopter. The wreckage was located in a shallow lake about 10 feet from the shore, in about 2 feet of water. There were no ground scars on the lake's perimeter adjacent to the accident site. The lake's perimeter near the accident site is predominately marsh. The lake and marsh are surrounded by a vast, flat tundra plain. The Fish Creek site, where the external load was picked up, is about one mile to the north of the accident site, and can be seen from the accident site. The fuselage/cabin area of the helicopter appeared to be complete with the exception of the tail boom, which was floating about 80 feet farther out in the lake. The fuselage was resting on its left rear section, with the nose pointed skyward about 45 degrees to the terrain. Most of the cabin ceiling was missing, and the left side of the cabin was open. The main rotor head and the engine were partially submerged. The three main rotor blade grips were attached to the rotor head, but the blades were fragmented. The first segment of the tail rotor drive shaft from inside the tail boom was separated from the helicopter, and lying in about 2 feet of water near the fuselage, along a line with the separated tail boom. The drive shaft flex coupling was torn apart. The main fuel tank was breached, but there appeared to be a substantial amount of fluid in the tank. Due to the breach, lake water and fuel were mixing freely.

The external load was floating in the lake between the fuselage and the tail boom. The load was comprised of small sheets/pieces of plastic baffling that resembled cardboard, short lengths of PVC pipe, and wood blocks. The load was wrapped in a plastic tarp, which was enclosed in a cargo net. The cargo net had cinch ropes, which were attached to a 15-foot long cable leg, which was attached to the helicopter's external lifting hook. All of the equipment was present. The load was not attached to the helicopter. One of the cinch ropes had been torn in half at a metal thimble. The personnel who prepared the load, estimated the weight of the load to be about 600 pounds. Given the length of the cable, the length of the cinch ropes when pulled tight, and the length of the cargo net, the load would have hung about 30-35 feet below the helicopter. The helicopter's external load lifting hook appeared to be intact.

After recovery, on October 31, the helicopter was re-examined by the IIC in a shop in Palmer, Alaska. Accompanying the IIC were representatives of the FAA, the U.S. Department of the Interior, the engine manufacturer, the helicopter manufacturer, and the operator. During the examination control continuity was established, and evidence of engine rotation was noted. No preaccident mechanical anomalies were noted. At the request of the Canadian Transportation Safety Board (TSB), the hydraulic servos (4), hydraulic pump, and pressure regulator were removed for further examination.

The helicopter's external load lifting hook assembly consists of the hook in a metal framework, suspended below the helicopter on 4 cables, each of which has a swaged eye, which is attached via clevis pins to brackets attached to the airframe. The hook assembly showed no impact damage, however the suspension cable's swaged eyes were bent, and the clevis pin holes in the brackets were elongated.

The tail boom separated from the helicopter at its attachment point to the fuselage. The tail boom was intact, and the tail rotor drive shaft segment nearest the fuselage had pulled apart at the flex coupling. The tail rotor drive shaft cover, where the flex coupling pulled apart, had been spiral cut from the inside for about 18 inches of its length. The tail boom and both tail rotor blades had rope marks in their paint. One tail rotor blade had fragmented near its midsection, but the other tail rotor blade was intact, and had blue fibers trapped under the end cap bolt.

The external load was carried in a cargo net made with white rope containing a black trace. The cinch ropes of the cargo net were larger diameter than the rope used to construct the net, yellow in color, and had a blue trace throughout the rope. The cargo net was damaged with several broken ropes, and one of the cinch ropes had been pulled apart at a thimble. The blue fibers of the cinch rope trace were consistent with the blue fibers found trapped under the end cap bolt of the intact tail rotor blade.

MEDICAL AND PATHOLOGICAL INFORMATION

A postmortem examination of the pilot was performed under the authority of the Alaska State Medical Examiner, 4500 S. Boniface Parkway, Anchorage, Alaska, on August 24, 2006. The examination revealed the cause of death was multiple blunt force impact injuries due to a helicopter crash. Tissue samples were sent to the FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, for toxicological examination. A review of FAA medical records, the autopsy, and the toxicological results, did not disclose any evidence of any preimpact incapacitating medical conditions.

ADDITIONAL DATA/INFORMATION

The hydraulic components of the helicopter noted above were requested for examination by the Canadian TSB in reference to an unrelated case. The report generated as a result of their examination revealed no anomalies that would be relevant to this accident.

The helicopter was fueled from a tank at the Inigok site. An analysis of the fuel in the supply tank showed that the fuel was the proper grade, and was not contaminated.

NTSB Probable Cause

The pilot's failure to maintain clearance from the sling load during cruise flight, which resulted in the load becoming entangled in the tail rotor, and an in-flight loss of control.