12th of March 2021, Blog #590
Updated: Mar 12
A Cessna 208 B Grand Caravan was scheduled to operate a scheduled air taxi & commuter flight as an FAA Part 135 flight from Chevak Airport to Bethel Airport, both in the state of Alaska, USA. On board a pilot and four passengers.
The aircraft in its final position (Source; kathrynsreport.com © Unknown)
The weather at the nearest weather station at the time of departure (Cape Romanzof, Alaska, USA approximately 19 nautical miles from Chevak Airport) was recorded as;
- Wind : 140º at 34 knots, gusting 42 knots
- Ceiling : broken at 700 ft AGL
- Altimeter : 30.31 inHg
- Temp. : -8ºC
- Dewpoint : -10ºC
- Visibility : 0,5 miles (800 metres in fog)
After the passengers had boarded the appropriate checklists were completed and the engine was started. The pilot intended to take off from 02 and after making the necessary call on the Unicom frequency started to back taxi on runway 20.
The wind at the time, as observed by the pilot, was 120º at 20 knots, which is the maximum demonstrated crosswind for a Cessna 206 (based on public source information). The runway was covered in snow and ice as the aircraft taxied down runway 02 for a departure off runway 20. A strong wind gust hit the aircraft and the aircraft started to slide to the left side of the runway. The pilot corrected for the deviation and the aircraft started to move back toward the runway centre line. At that time the aircraft was hit by a “violent gust of wind” and began to slide again. The pilot applied the right brake and right rudder while leaving in the full right aileron, but the airplane had zero braking action on the snow and ice-covered runway. When the aircraft continued to slide the pilot applied engine power to increase the rudder authority and get the aircraft under control again, the aircraft did not respond to the inputs from the pilot and continued to slide to the left. The aircraft left the paved area of the runway and the left-hand mainwheel impacted a snowbank. This stopped the aircraft abruptly and made it tip on the left wing tip. The aircraft ended in a nose-down attitude, banked to the left at about a 40° angle.
The aircraft, after being repaired, in flight on the 23rd of January 2023 (© tangoscar) Damage to the aircraft was limited to the left wing and aileron, although this damage was substantial.
The National Transportation Safety Board (NTSB) investigated the accident and conclude that the probable cause(s) of this accident was:
"The pilot’s loss of directional control during the back taxi for departure in strong crosswind conditions which resulted in a runway excursion."
The snow-and-ice-covered runway was identified as a contributing factor by the NTSB. The NTSB accident report, which served as a source for this blog, can be accessed by clicking on the .pdf file below;