N1079U
Bell 212
The public use helicopter was lifting a 20' by 14' by 6" thick platform, weighing about 1250 pounds, on a 100 foot long line. The airline transport pilot had successfully lifted and transported three similar platforms with the accident helicopter just before the accident flight, although he had difficulty controlling the load on two flights, and landed to check the helicopter for damage after the third flight. On the accident flight, the pilot reported a severe jolt to the airframe while the helicopter was approximately 200' AGL, and the load was approximately 100' AGL, followed by an immediate loss of engine power. Ground witnesses noted that the platform swung from right to left, fore and aft, and rose vertically several times. The platform rose one final time, and "slammed down" on the long line, breaking the platform in half. Witnesses said they then saw white vapor coming from the helicopter, the load was jettisoned, and the helicopter descended very rapidly, impacting on a frozen lake. Postaccident examination of the engines disclosed no evidence of any preimpact mechanical anomalies. An inspection of the external cargo hook and its support structure in the belly of the helicopter, revealed a sheared bolt at the top of the hook support assembly, which allowed the assembly to move and change shape. Witness marks indicate that the hook assembly overrode its container ring, and struck the fuel crossover lines, throttle control bell cranks for both engines, and the throttle position push/pull tubes. Both fuel crossover lines were pulled from their respective fuel tanks, and the throttle position bell cranks were found in the engine idle cutoff position, with the crossover lines crushed against them.
HISTORY OF FLIGHT On January 17, 2003, about 1552 New Zealand daylight time, a Bell 212 helicopter, N1079U, sustained substantial damage during an in-flight collision with terrain following a total loss of engine power while maneuvering with an external load, about 40 miles west of McMurdo Station, Antarctica. The helicopter was being operated by the National Science Foundation's Antarctica Mission, as a public use flight when the accident occurred. The helicopter and pilot were provided under contract to the National Science Foundation by Petroleum Helicopters, Incorporated, Lafayette, Louisiana. The airline transport pilot and the sole passenger received serious injuries. Visual meteorological conditions prevailed for the local area flight, and company flight following procedures were in effect. The helicopter departed McMurdo Station about 0855, and made several flights in the vicinity of the accident site during the day. Note: Antarctica does not fall within any standard time zone. McMurdo Station uses the Christchurch, New Zealand, time zone. New Zealand Daylight Time (NZDT) prevailed at the time of the accident. NZDT is GMT/UTC + 13 hours. The National Science Foundation public use helicopter contract with Petroleum Helicopters is administered by the United States Department of the Interior (DOI), Aviation Management Directorate (AM). During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on January 17, about 0900 Alaska standard time, an accident investigator for the DOI-AM, said he received a report that a helicopter crashed while engaged in external load operations in Antarctica. Preliminary reports indicated that the helicopter was at approximately 200' AGL in the process of moving a tent platform floor, when witnesses said they saw the load rotate from the horizontal position in which it had been carried, to a vertical position. The load, which was at approximately 100' AGL then "slammed" down to the horizontal position, and broke in two pieces. The witnesses then reported seeing white vapor emanating from the helicopter. They said the helicopter descended rapidly with the rotors barely turning, and impacted the snow-covered ice of Lake Fryxell. A DOI-AM investigator traveled to Antarctica to conduct the onsite portion of the investigation. According to a written statement provided by the DOI-AM investigator, the accident helicopter left McMurdo Station at 0855 to conduct a series of 100-foot long-line external load operations at Lake Bonney and Lake Fryxell in the Taylor Valley, Antarctica. The weather was VFR, and the winds were easterly at 5-15 knots. The helicopter was piloted by an airline transport certificated pilot, accompanied by a Heli-Tech/Rigger. The mission at Lake Bonney involved moving flooring platforms and boxed tents from a position on the frozen lake to the shore. The distance the flooring was moved varied from 100 yards to approximately one mile. The flooring platforms were rigged to be carried in a horizontal position. According to the pilot and witnesses, the first platform became unstable in forward flight, moving fore and aft, and left and right, under the helicopter. The second platform was "hovered" (moved at a slow pace without entering translational lift/forward flight) from the lake to the shore without incident. During movement of the third platform, the helicopter entered forward flight, and witnesses said the platform rotated from the horizontal position to vertical, and then slammed down to horizontal. The pilot said that although the platform was a hundred feet in the air, it felt like the platform "hit the ground." After setting the platform down, the pilot landed, and had the Heli-Tech/Rigger inspect the helicopter for damage. The mission at Lake Fryxell was to move the largest of the platforms, which was 20' by 14' by 6" thick, weighing 1250 pounds. After picking up the platform, the helicopter again entered forward flight with the helicopter approximately 200' AGL, and the load approximately 100' AGL. Witnesses at Lake Fryxell said the platform rotated from horizontal to vertical as many as three times. On the final rotation of the platform, the platform slammed down, and broke in half. The witnesses said they then saw a white vapor, or smoke, emanate from the helicopter, and the helicopter entered a near vertical descent, and impacted on the frozen surface of Lake Fryxell. The pilot reported the action of the platform severely jolting the airframe. The jolt was followed by an immediate loss of engine power, activation of the engine out annunciator light, and the activation of the main rotor low rpm horn. He jettisoned the platform, and the helicopter impacted the ground. IMPACT AND WRECKAGE AND IMPACT INFORMATION The impact area was the surface of a frozen lake. The surface was rutted and undulating, and the ice quality varied from rock hard to air-infused, crumbling and unstable. Prior to the impact, the helicopter pilot jettisoned the platform, and the helicopter impacted the ice 59 feet ahead of the platform. There was no evidence of forward motion of the helicopter during impact. The landing gear skids spread apart, and the helicopter came to rest with its belly imbedded in the ice. The entire cabin structure exhibited vertical crushing from the bottom up. The tail boom from its midpoint aft, was over a depression in the ice during impact, and separated from the forward portion. The main rotor mast was canted forward about 3 degrees, and the rotor blades rotated freely. There was no obvious damage to the rotor head or main rotor blades. The tail rotor was intact, and one blade was bent 90 degrees at its midpoint. During the on-site inspection, the DOI-AM investigator noted that the fuel pump/fuel control unit, and the oil to fuel heater, were separated from the number one engine. The power pack, consisting of both engines, combining transmission, and accessory gearboxes, was removed from the helicopter and shipped to Pratt & Whitney in Montreal, Canada for disassembly and inspection. The fuselage, main transmission, and main rotor head were shipped to Atlanta Air Salvage, Atlanta, Georgia. The cockpit voice recorder was shipped to the NTSB laboratory in Washington, DC. RECORDER INFORMATION The cockpit voice recorder was examined at the NTSB recorder laboratory. The laboratory technician determined the time from the initiating event to the impact was 16 seconds. No other useful information was available, and no written report was generated. ENGINE AND TRANSMISSION INSPECTION INFORMATION On April 22, 23, and 24, 2003, the two engines, the combining transmission, and the two accessory gearboxes, were disassembled and inspected by the NTSB IIC, and parties to the investigation at the Pratt & Whitney plant in Montreal. Aside from the separation of the number one engine fuel control unit, and the oil to fuel heater, the engines received minimal impact damage. The internal inspection of the engines revealed minimal rubbing in the compressor and power sections of both engines. The mounting flanges of the number one fuel control unit exhibited signs of overstress fracture. The number one engine fuel control rod on the fuel cluster was bent. The adjustment device on the end of the fuel control shaft attached to the rod was bent about 90 degrees forward from the closed throttle position. There was corresponding damage to the bottom of the oil to fuel heater, which is normally positioned above the adjustment device. The oil to fuel heater is mounted to the engine with three bolts. All three bolt holes had been previously repaired with helix coils. All three bolts had pulled out of the engine, stretching and exposing the coils, and separating the heater from the engine. The combining transmission and both accessory gear boxes were disassembled and inspected. No significant damage was found. FUSELAGE INSPECTION INFORMATION On July 29, and 30, 2003, the fuselage, main transmission, and the main rotor head, were examined by the NTSB IIC, and parties to the investigation at Atlanta Air Salvage, Atlanta. During the examination, the fuselage area of the cargo suspension well (CSW) was inspected. This area is in the transition area between the main cabin and the tail boom, and directly below the main transmission. The area is accessed by transmission access panels in the cabin area, and an approximate 24-inch diameter hole in the belly of the helicopter. Located inside this area are the helicopter's main transmission, access to the fuel tanks and assemblies, fuel lines and associated plumbing, throttle control linkages, and the external cargo hook assembly. The fuselage portion of the external cargo hook is comprised of a lift link, which attaches the load hook to the bottom of the main transmission. There is an extension arm which places the hook in the center of the opening, with the load hook protruding about 4 inches below the belly of the helicopter. The edge of the opening is protected by a 3-inch wide metal band faced with a thin rubber bumper. The portion of the hook that is centered in the opening has a thick circular rubber bumper ring, about 10-inches in diameter, to provide a cushion, if the hook comes in contact with the opening. The upper portion of the hook is an A-frame assembly, which extends about 10 inches above the rubber bumper. The actual hook protrudes about 5 inches below the hook's bumper ring. There is a single bolt at the top of the A-frame assembly which keeps the assembly aligned with the extension tube. That bolt was sheared laterally, and the hook assembly had moved out of alignment with the extension tube. There was a rubber transfer mark on the upper portion of the opening boundary ring, and a paint transfer from the boundary ring on the hook's rubber bumper. On the aft wall was a fuel transfer valve connected by 1-inch aluminum fuel lines to the left and right auxiliary fuel tanks. The fuel lines had aft crushing, and had been pulled from their solder joints at the tanks. The crushing damage matched the A-frame of the hook assembly. Co-located with the fuel lines are the bell cranks and push/pull tubes associated with engine throttle position. The bell cranks were rotated to the full aft/up position, and the fuel transfer lines were crushed against them. The full aft/up position is the throttle "idle cutoff" position. The throttle control pushrods on the aft wall coming from the engine deck to the bell cranks, were bent in compression.
The pilot's continued operation of the helicopter with an unstable external load, which resulted in damage to the cargo hook assembly, adjacent throttle controls, and subsequent loss of engine power, precipitating an emergency descent and impact with terrain. Factors associated with the accident were the load oscillations, and the separation of the fuel crossover lines.
Source: NTSB Aviation Accident Database
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