History of Flight
The helicopter, a Eurocopter AS-350-B2 registered as N213EH, departed Anchorage, Alaska, at 0742 Alaska daylight time on April 15, 2008, en route to multiple communication sites near Chickaloon. The flight was conducted under Title 14 CFR Part 135 visual flight rules. The pilot was the sole occupant at departure; later, at the Anchorage telecommunications facility, three State of Alaska technicians and equipment were boarded. The flight then proceeded to a second communication site, where one technician was left. The helicopter subsequently flew to a highway rest area to pick up another technician and his 15-year-old stepson. After departure from the rest area, the helicopter crashed about three-quarters of a mile away, at approximately 0923 ADT.
The helicopter was reported overdue by the operator to the FAA at 1540 ADT after failing to return. Search efforts were hampered by blizzard conditions. The wreckage was located on April 16 at about 0750 ADT in hilly, tree-covered terrain near the Glenn Highway.
Injuries
The pilot and four passengers were on board. The pilot (right front seat), two passengers (right rear and center rear seats) were found deceased in the helicopter. A third passenger (left rear seat) had exited the helicopter and was found deceased outside. The fourth passenger (left front seat), a 15-year-old juvenile, was found alive but incoherent, with a head injury and hypothermia; he was transported to a hospital. He was the sole survivor.
Aircraft and Pilot Information
The helicopter was a Eurocopter AS-350-B2 equipped with a Turbomeca Arriel 1D1 turboshaft engine. It had accumulated 4,983.7 flight hours at the time of the accident. Maintenance was conducted under an Approved Aircraft Inspection Program; no mechanical discrepancies were noted in the logs. The most recent inspection occurred 11 flight hours prior.
The pilot held a commercial helicopter certificate with instrument rating and a flight instructor certificate with instrument helicopter rating. His total flight experience was approximately 3,747 hours, of which about 1,889 were in the accident make and model. He had flown 47.3 hours in the preceding 90 days and 9.6 hours in the preceding 30 days. His most recent second-class medical certificate, issued March 5, 2008, had no limitations. Training records showed no deficiencies.
Meteorological Information
Visual meteorological conditions prevailed. An automated weather station at Sheep Mountain Airport, 4.5 miles west of the accident site, recorded at 0850 ADT: wind 250 degrees at 3 knots, visibility 2 statute miles, ceiling 400 feet overcast, altimeter 29.42 inches of mercury, temperature 27°F, dew point 23°F. Weather cameras at Tahneta Pass and Sheep Mountain showed marginal VFR conditions in the accident area, with visibility 1–2 miles in light snow and ceilings 300–500 feet above terrain. The technician left at the second communication site reported good weather initially but observed bad weather approaching from the southwest by 1400 ADT.
Wreckage and Impact
The helicopter impacted on the steep west embankment of a dry ravine, about 30 feet from the top and 80 feet from the bottom, with an incline of 35–50 degrees. The terrain was covered with willow brush and 3–5 feet of snow. The fuselage came to rest facing southeast, parallel to the embankment, in a level attitude. The impact crater and crush lines indicated a steep vertical descent. All three main rotor blades exhibited damage; the yellow blade had a sharp downward bend and splayed trailing edge. The tail boom was bent downward, and both tail rotor blades were broken near the hub. The fuel tank was ruptured. The floor-mounted fuel flow control lever was found in the forward (emergency) position, and the emergency fuel shutoff lever was in the aft (off) position. However, the linkages and cables were trapped in the wreckage, preventing movement.
Post-Accident Examination
Examination of the engine and transmission at the manufacturers' facilities revealed a 7 mm misalignment of the module 5 drive nut, indicative of an overtorque event, and free turbine blade shedding indicative of an overspeed event (designed to occur above 150% NF). The fuel control unit bench-tested normally. The engine-to-transmission drive shaft was twisted and shortened, with the splined end separated from the engine output. The direction of twist was consistent with an opposing torque load forward of the shaft. Three complete drive train separations were found: the main drive shaft, the tail rotor drive shaft coupling, and the tail rotor driveshaft key. No pre-impact anomalies were found in the freewheel unit, main transmission, or hydraulic flight control system. The first and second stage compressor turbine wheels showed no evidence of overheating. No evidence of an in-flight main rotor blade strike was found.
Medical and Pathological Information
The pilot's cause of death was attributed to multiple traumatic injuries. Toxicology tests conducted by the FAA's Civil Aeromedical Institute were negative for alcohol and drugs.