FlarePath

What happened

NTSB summary, verbatim

The pilot and passenger were departing downhill in a southwesterly direction from a remote, sloped airstrip located on a mountain ridgeline. According to a witness, the pilot had three trips planned to the airstrip that day, transporting hunters and gear to a nearby village. The witness stated that, upon the pilot’s return to the airstrip following the first flight of the day, he reported to the pilot that, since his previous departure, the winds had increased and were “gusting and changing a lot.” He watched the initial portion of the takeoff roll; nothing appeared abnormal, and he did not watch the remainder of the takeoff. He stated that, during previous departures, the airplane would typically dip out of sight below the departure end of the airstrip before continuing its climb out of the valley. When he did not see the airplane continue the climb, he went to the edge of the ridgeline and saw that the airplane had impacted tundra about 300 ft below the airstrip. A small cluster of trees was present about 2/3 of the way down the left side of the 750-ft-long airstrip. One tree was fractured and displayed fragments of red paint that matched the accident airplane’s paint color. The left horizontal stabilizer displayed a concave dent perpendicular to the leading edge about 1 ft outboard of the stabilizer root. Tree sap and embedded tree fibers were observed in the leading edge of the horizontal stabilizer. Examination of the airframe and engine revealed no evidence of any preimpact mechanical failures or malfunctions that would have precluded normal operation. Review of weather information indicated the presence of north/northeasterly surface wind conditions in the area of the accident site. Another pilot, who responded to the accident site about 45 minutes after the accident, reported that the wind was “unusual” and variable, gusting 10-12 knots from the north before gusting 5 knots from the south and repeating. Based on the available information, it is likely that the pilot encountered gusting tailwind conditions during the takeoff, which resulted in the airplane veering left and impacting a tree, followed by a loss of control and impact with terrain.

Photographs

10the aircraft, and what the investigators found

Wreckage and site documentation · 10 photographs from the docket

Photographs are NTSB docket attachments — works of the US government, in the public domain. Captions are the Board’s own.

Probable cause

the Board's determination

The pilot’s encounter with gusting tailwind conditions during takeoff, which resulted in impact with a tree, a loss of control, and subsequent impact with terrain.

Occurrence sequence

1 stepsNTSB coding · CICTT taxonomy

1 · Initial climb
Collision during takeoff/land
defining event

Findings

6 causal · 0 contributing

CAUSE
Environmental issues › Physical environment › Object/animal/substance › Tree(s) — Effect on equipment
CAUSE
Personnel issues › Task performance › Use of equip/info › Aircraft control — Pilot
CAUSE
Environmental issues › Conditions/weather/phenomena › Wind › Sudden wind shift — Effect on equipment
CAUSE
Environmental issues › Conditions/weather/phenomena › Wind › Tailwind — Effect on equipment
CAUSE
Environmental issues › Physical environment › Terrain › Mountainous/hilly terrain — Effect on equipment
CAUSE
Environmental issues › Physical environment › Terrain › Sloped/uneven terrain — Effect on equipment

NTSB analysis

from the final report

The pilot and passenger were departing downhill in a southwesterly direction from a remote, sloped airstrip located on a mountain ridgeline. According to a witness, the pilot had three trips planned to the airstrip that day, transporting hunters and gear to a nearby village. The witness stated that, upon the pilot’s return to the airstrip following the first flight of the day, he reported to the pilot that, since his previous departure, the winds had increased and were “gusting and changing a lot.” He watched the initial portion of the takeoff roll; nothing appeared abnormal, and he did not watch the remainder of the takeoff. He stated that, during previous departures, the airplane would typically dip out of sight below the departure end of the airstrip before continuing its climb out of the valley. When he did not see the airplane continue the climb, he went to the edge of the ridgeline and saw that the airplane had impacted tundra about 300 ft below the airstrip. A small cluster of trees was present about 2/3 of the way down the left side of the 750-ft-long airstrip. One tree was fractured and displayed fragments of red paint that matched the accident airplane’s paint color. The left horizontal stabilizer displayed a concave dent perpendicular to the leading edge about 1 ft outboard of the stabilizer root. Tree sap and embedded tree fibers were observed in the leading edge of the horizontal stabilizer. Examination of the airframe and engine revealed no evidence of any preimpact mechanical failures or malfunctions that would have precluded normal operation. Review of weather information indicated the presence of north/northeasterly surface wind conditions in the area of the accident site. Another pilot, who responded to the accident site about 45 minutes after the accident, reported that the wind was “unusual” and variable, gusting 10-12 knots from the north before gusting 5 knots from the south and repeating. Based on the available information, it is likely that the pilot encountered gusting tailwind conditions during the takeoff, which resulted in the airplane veering left and impacting a tree, followed by a loss of control and impact with terrain.

CESSNA 180JAMES B. TWETO