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Date:Friday 25 July 2014
Type:Silhouette image of generic DHC6 model; specific model in this crash may look slightly different
de Havilland Canada DHC-6 Twin Otter 300
Operator:Grand Canyon Airlines
Registration: N190GC
MSN: 285
First flight: 1970
Engines: 2 Pratt & Whitney Canada PT6A-27
Crew:Fatalities: 0 / Occupants: 2
Passengers:Fatalities: 0 / Occupants: 0
Total:Fatalities: 0 / Occupants: 2
Aircraft damage: Minor
Aircraft fate: Repaired
Location:Boulder City Municipal Airport, NV (BLD) (   United States of America)
Phase: Taxi (TXI)
Departure airport:Boulder City Municipal Airport, NV (BLD/KBVU), United States of America
Destination airport:?
A landing Eurocopter EC-130, N154GC, and a taxiing DHC-6, N190GC collided at Boulder City Municipal Airport, NV (BLD). Neither the two pilots on board the airplane, nor the pilot and six passengers aboard the helicopter, were injured. The helicopter, operated by Grand Canyon Helicopters as an aerial sightseeing flight, sustained substantial damage. The airplane, operated by Grand Canyon Airlines, was beginning a repositioning flight.

According to the EC-130 pilot, he was inbound from the south, and planned to land on the airport location designated as "Spot 2," which was a dedicated helicopter arrival and departure location. He followed the company-designated arrival procedure, in which the helicopter flew a descending pattern first north along the centerline of taxiway A, and then west along the centerline of taxiway D to Spot 2. Spot 2 was a 50-foot painted square situated on the airport ramp. Taxiway D was 40 feet wide, was oriented approximately east-west, and comprised the southern perimeter of the same ramp. The center of Spot 2 was located about 50 feet north of the centerline of taxiway D. Since Boulder City was not equipped with an operating air traffic control tower, the pilot communicated his positions and intentions via radio transmissions on the common traffic advisory frequency (CTAF).
The helicopter pilot first saw the airplane when the helicopter was making the left turn from north to west near the junction of taxiways A and D. At that time, the airplane was moving south, towards taxiway D, along a taxi line just east of Spot 1, on ramp about 600 feet east of Spot 2. The airplane crew announced their intentions on CTAF to taxi to runway 15 via taxiway D. The helicopter pilot reported that the last time he saw the airplane prior to the accident was as the helicopter overflew the intersection of taxiway D and the taxi line just east of Spot 1. At that time, the airplane was turning westbound onto taxiway D. The helicopter pilot realized the potential for conflict, since the two were now both traveling westbound along taxiway D. The helicopter pilot stated that he "immediately" queried on CTAF whether the airplane crew had him in sight. The pilot heard a "double click" on the CTAF frequency, which he interpreted as acknowledgement by the airplane crew that they had him in sight. Based on this information, the pilot was convinced that the airplane was behind him and that its flight crew had him in sight.

The helicopter pilot therefore continued his descent along the centerline of taxiway D towards Spot 2. About 8 to 10 seconds later, as the helicopter came almost abeam of Spot 2, the pilot began a right pedal turn to traverse to and set down on Spot 2. At the commencement of that pedal turn, the pilot simultaneously spotted the wings and nose of the airplane through his chin windows, and felt an" impact." He stopped the turn and descent, transitioned to Spot 2, descended, and landed on the ramp.
The flight crew of the airplane was unaware that there had been a collision, and they continued with their taxi-out and departure from Boulder City. The airplane was recalled by company personnel once they learned of the collision.

Probable Cause:

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.

Accident investigation:
Investigating agency: NTSB
Status: Investigation completed
Duration: 2 years and 2 months
Accident number: WPR14LA313B
Download report: Summary report
Language: English

Ground collision
Damaged on the ground



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This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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