Introduction
On June 23, 2008, about 1045 Alaska daylight time, a Eurocopter AS-350BA helicopter, registration N357CH, sustained substantial damage when it collided with snow-covered terrain on the Matanuska Glacier, approximately 40 miles east of Chickaloon, Alaska. The helicopter was conducting an external load operation at 8,950 feet msl under Title 14, CFR Part 133. It was operated by Last Frontier Air Ventures Ltd., Sutton, Alaska. The commercial certificated pilot and the sole passenger were not injured. Visual meteorological conditions prevailed, and VFR company flight following procedures were in effect.
Accident Sequence
The director of operations reported that the pilot was inserting an external load of about 400 pounds of equipment at a remote camp for the National Outdoor Leadership School (NOLS). The pilot stated that during the insertion, he descended into the helicopter's own main rotor vortex, then collided with the snow. In a written statement, the pilot detailed that he planned to transport 14 passengers and their gear from the toe of the glacier to the top. His first flight carried three passengers and internal cargo; during the landing approach, he aborted, pulled maximum power, and the main rotor rpm dropped to about 365 with 81-83% torque, accompanied by a low rotor speed warning horn. He landed on the second approach without issue and returned to the toe.
For the external load, the pilot prepared a net attached to a 50-foot long line. He selected a NOLS student, who had U.S. Air Force experience but was not a trained employee of the operator, to assist with connecting the line and to disconnect it if needed. After landing at the toe, the pilot remained at the controls while the student attached the line and boarded. The pilot lifted into an out-of-ground-effect hover (HOGE) to assess power, requiring about 70% power to maintain hover. He flew to the top of the glacier with the external cargo net and established a 75-foot hover while pulling maximum power. He then reduced power to lower the net to the snow. The pilot reported reducing power too much, causing a rapid descent. He felt a small vibration reminiscent of entering a vortex ring, which then smoothed out, but the helicopter descended quickly. He applied power but did not release the external load. The helicopter collided with the snow and rolled onto its right side. Neither the pilot nor the student was injured.
Performance Data
Using GPS data from the operator and NOLS students, the accident location was about 8,950 feet msl. Based on the helicopter's weight, fuel, occupant, and cargo weights provided by the pilot, the gross weight was approximately 4,286 pounds, below the maximum gross weight of 4,630 pounds. According to the HOGE performance charts in the helicopter's flight manual, at 4,286 pounds, the helicopter should have been capable of a HOGE altitude of about 9,500 feet msl.
Additional Information
The operator did not submit a Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1.