Port Alsworth

The commercial pilot was conducting a cross-country flight to a family residence in the turbinepowered, single-engine airplane. The pilot was familiar with the route, which traversed a mountain pass and remote terrain. Before departing on the flight, the pilot communicated with a family member at the residence via text messages and was aware the weather was windy but that the mountain tops were clear. There was no record of the pilot obtaining a preflight weather briefing from an official, accesscontrolled source, and the pilot indicated to a friend before departure that he had not accessed weather cameras. Weather forecast products that were available to the pilot revealed possible turbulence at low altitudes and icing at altitudes above 12,000 ft along the route of flight, and weather cameras along the planned route and near the destination would have indicated deteriorating visibility in snow showers and mountain obscuration starting about 1.5 hours before departure. The airplane departed and proceeded toward the destination; radar data correlated to the accident flight indicated that the airplane climbed from 4,600 ft to 14,700 ft before turning west over the mountains. Text messages that the pilot sent during the initial climb revealed that the mountain pass he planned to fly through was obscured, and he intended to climb over the mountains and descend through holes in the clouds as he neared the destination. Radar data also indicated that the airplane operated above 12,500 ft mean sea level (msl) for about 30 minutes, and above 14,000 msl for an additional 14 minutes before entering a gradual descent during the last approximate 20 minutes of flight. Review of weather information indicated that cloud layers over the accident area increased during the 30 minutes before the accident, and it is likely that the airplane was operating in icing conditions, although it was not certified for flight in such conditions, which may have resulted in structural or induction icing and an uncontrolled loss of altitude. The airplane wreckage came to rest on the steep face of a snow-covered mountain in a slight nose-down, level attitude. The empennage was intact, the right wing was completely separated, and the forward fuselage and cockpit were partially separated and displaced from the airframe with significant crush damage, indicative of impact with terrain during forward flight. Page 2 of 10 ANC17FA004 There was no indication that the airplane was equipped with supplemental oxygen; pilots are required to use oxygen when operating at altitudes above 12,500 ft for more than 30 minutes, and anytime at altitudes above 14,000 ft. It could not be determined if, or to what extent, the pilot may have experienced symptoms of hypoxia that would have affected his decision-making. The airplane wreckage was not recovered or examined due to hazardous terrain and environmental conditions, and the reason for the impact with terrain could not be determined; however, it is likely that deteriorating enroute weather and icing conditions contributed to the outcome of the accident.

The commercial pilot of the float-equipped airplane was transporting passengers to a lodge at a remote lake. When the airplane did not arrive at the lake, a search was initiated, and two days later the wreckage of the airplane was located on the side of a box canyon about the 2,400 foot elevation level. The canyon is oriented approximately east-west, and the wreckage was distributed along a 100 foot debris field on the north flank of the canyon. Ground scars and wreckage distribution were consistent with the airplane impacting terrain in a steep left bank while executing a turn to reverse direction. No evidence of any preimpact mechanical anomalies was discovered.

The captain and the first officer were landing a short takeoff and landing (STOL) cargo airplane on a private, dirt and gravel surface runway. The airplane was configured for landing with 40 degrees of flaps. During the landing approach, variations in indicated airspeed and ground speed indicated windshear conditions. About 100 to 200 feet above the ground, the airplane encountered a downdraft and began to drift to the right of the runway centerline. The captain said she increased engine power and applied full left aileron and rudder, but could not gain directional or pitch control of the airplane. The right wing struck trees, short of the runway threshold, increasing the airplane's right yaw. The captain said that as the airplane neared the ground, she pulled the engine throttles off. The airplane struck the ground with the right main landing gear and right front portion of the fuselage. The airplane then pivoted to the right, 180 degrees from the approach heading. The owner of the airport reported that wind conditions from the east may produce downdrafts in the area of runway 05. He indicated that at the time of the accident, the wind was blowing from the east about 15 knots. The first officer reported the captain appeared to be attempting to maintain a stabilized approach angle by varying the pitch attitude of the airplane. A review of company training literature revealed that the airplane is especially sensitive to slight wind shear, and wind gusts as low as 5 knots when operating at low airspeeds. Pilots are cautioned that when flying the aircraft at low speeds, a large application of the aileron control may be required to maintain wings level. During gusty wind conditions, the threshold airspeed should be increased by one-half the gust factor, and any lateral displacement should be corrected rapidly. If a wing is allowed to drop beyond corrective action of full aileron, power should be increased immediately to regain level flight.

The plane was observed to enter a valley with mountains on both sides. While the pilot was maneuvering the airplane to the left to reverse direction, it collided with terrain. Witnesses reported the plane's engine sounded normal and that the weather was good with clear skies, unlimited visibility and light wind. A pilot who flew over the accident site minutes after the mishap reported the area was devoid of turbulence. This was a part 135, on-demand, lodge/hunting guide operation. All three occupants were killed.

The pilot continued the air taxi flight into adverse weather conditions and struck a mountain. The pilot, sole on board, was killed.