Introduction
A twin-engine turboprop airplane operated by an airline transport certificated pilot on a scheduled air taxi flight experienced a runway excursion during landing at a remote airport. The airport is located with rising hilly terrain to the east.
Accident Sequence
The pilot reported that during the approach for landing, he observed the airport wind sock indicating an easterly wind of about 25 knots. While descending to 500 feet, approximately mid-base, the airplane encountered moderate turbulence and an increased rate of descent. The pilot added engine power to arrest the descent. As he turned toward the runway, the airplane encountered three to four rolling oscillations with bank angles up to 90 degrees while descending toward the runway.
According to a company mechanic who traveled to the scene, the airplane struck the runway about 1,200 feet from the approach end with the left wing and left elevator, while yawed about 45 degrees to the left of the runway centerline. The airplane then slid off the left side of the runway.
Aftermath
After the collision, the pilot evacuated the passengers. He then noticed that the airport wind sock was indicating a tailwind. The Airport/Facility Directory contains the following remark for the airport: "Unattended. Easterly winds may cause severe turbulence in vicinity of runway."
The official probable cause was determined to be the pilot's inadequate evaluation of the weather conditions and his inadvertent flight into adverse weather conditions. Factors in the accident were terrain induced turbulence and a tailwind.