Airbus AS350 N207CH accident near Juneau, Alaska

Probable cause

The pilot's decision to depart into an area of degraded visual meteorological and flat light conditions, which resulted in a loss of visual references and subsequent controlled flight into terrain.

NTSB analysis

After another company pilot returned to base due to deteriorating weather conditions en route, the instrument-rated commercial helicopter pilot flew to a remote glacier to pick up passengers. Upon departing from the glacier, the pilot encountered deteriorating visibility and flat light conditions. She decided to turn back to the departure point and land to wait for conditions to improve; however, during the turn, the helicopter impacted the featureless, snow-covered terrain and came to rest inverted.

The pilot reported no preimpact mechanical anomalies that would have precluded normal operation with the helicopter, and the accident is consistent with the pilot's failure to maintain clearance from terrain while operating in poor visibility and flat light conditions, which obscured features of the terrain and resulted in a loss of visual clues regarding the helicopter's distance from the ground.

The operator assigned different weather minimums to each of its pilots depending on their experience level. The accident pilot was classified at the highest experience level and was permitted to fly in conditions as low as 1/2 mile visibility, cloud ceilings 300 ft above ground level (agl), and from remote sites with the potential for white out conditions. The estimated conditions reported from the landing site shortly before the accident included 1 1/2 miles visibility with fog and ceilings about 1,500 ft agl, though previous observations indicated that fog had begun developing about an hour before the accident occurred and that conditions had continued to deteriorate since that time. Though the reported weather conditions were above the minimums specified by the company's operations manual, it is possible that the pilot felt pressure to complete the flight given that she was classified as more experienced; it is also possible that the pilot and/or operator felt pressure to conduct the flight because there were no formal procedures in place in the event that passengers were required to remain on the glacier for an extended time due to a contingency such as weather conditions that prohibited flight.

Text from the NTSB. Open the NTSB docket for ANC17LA025 for the full record.