Eurocopter EC 130 B4 N154GC and Dehavilland DHC 6 300 N190GC accident near Boulder City, Nevada

Probable cause

The airplane flight crew’s failure to exercise the necessary vigilance and precautions and yield the right of way to the landing helicopter, which resulted in the airplane colliding with the helicopter. Contributing to the accident was the helicopter pilot’s decision to continue his descent without positively determining that the airplane did not pose a collision hazard.

NTSB analysis

The commercial helicopter pilot was operating on his first day of revenue service for the aerial tour company and was returning to the nontowered airport at the completion of a tour with six passengers. The pilot complied with the published arrival procedures, including flying the prescribed route and making the appropriate radio position callouts on the airport's common traffic advisory frequency (CTAF). Concurrent with the helicopter's arrival, the captain and first officer of an aerial tour airplane were beginning the taxi-out for departure of the positioning flight. The airport arrival procedures, layout, and wind conditions resulted in the two aircraft having to use the same portion of taxiway Delta, in the same direction, for their respective operations.

The helicopter pilot reported that he first saw the airplane when the helicopter was turning westbound and descending over Delta; at that time, the airplane was taxiing southbound on the ramp toward Delta. The helicopter pilot announced his location and intentions and continued descending along Delta. When the airplane reached Delta, the first officer announced on the CTAF that the airplane was planning to proceed westbound on Delta. The captain reported that he looked but did not see any helicopters and that he then proceeded to turn westbound onto Delta, which placed the airplane directly into and under the helicopter's flightpath and prompted the helicopter pilot to radio that he was "right above" the airplane and repeat his landing intentions. The helicopter pilot continued the descent based on his hearing a "double-click" on the CTAF, which he interpreted as the airplane flight crew's acknowledgement that they saw and would avoid the helicopter. Shortly thereafter, the helicopter collided with the airplane; damage patterns indicated that the two aircraft were aligned in nearly the same direction (westbound) at the time of impact.

Because the helicopter was approaching from the airplane's left, along taxiway Delta, and was close in, it should have been readily visually detectable by the captain. Given that the first officer was aware of the inbound helicopter and should have been aware of its location and intentions based on the radio calls, the airplane's flight crew should have recognized the high potential for conflict and operated the airplane in a manner to ensure that a collision would not occur. In addition, the helicopter, as the landing aircraft, had the right of way over the departing airplane. The simplest and most effective method to prevent any conflict would have been for the airplane flight crew to stop on the ramp and not proceed onto taxiway Delta until the helicopter was positively determined to no longer pose a collision threat. However, there was no evidence that the airplane stopped before it turned from the ramp onto taxiway Delta. The evidence indicated that the airplane taxied out just ahead of and below the descending but faster moving helicopter, which significantly reduced the helicopter pilot's ability to avoid the airplane.

Text from the NTSB. Open the NTSB docket for WPR14LA313 for the full record.