History of Flight
On July 25, 2014, about 1646 Pacific daylight time, a Eurocopter EC-130 helicopter, registration N154GC, and a DeHavilland DHC-6 airplane, registration N190GC, collided at Boulder City Airport (BVU) in Boulder City, Nevada. The helicopter was operated by Papillon Airways Inc. (doing business as Papillon Grand Canyon Helicopters and Grand Canyon Helicopters) as an aerial sightseeing flight under 14 CFR Part 135. The airplane was operated by Grand Canyon Airlines (GCA) as a repositioning flight under 14 CFR Part 91. Both companies are part of the same parent company, Papillon Airways. Neither the two pilots on board the airplane nor the pilot and six passengers aboard the helicopter were injured. The helicopter sustained substantial damage. Day visual meteorological conditions prevailed.
The helicopter pilot stated that he was inbound from the south and planned to land on Spot 2, a dedicated helicopter arrival and departure location. He followed the company-designated arrival procedure, flying a descending pattern north along taxiway Alpha and then west along taxiway Delta to Spot 2. Spot 2 was a 50-foot painted square on the ramp, about 50 feet north of the centerline of taxiway Delta. The pilot communicated his positions and intentions on the BVU common traffic advisory frequency (CTAF).
The helicopter pilot first saw the airplane when turning from north to west near the junction of taxiways Alpha and Delta. The airplane was moving south towards taxiway Delta along a taxi line east of Spot 1, about 600 feet east of Spot 2. The airplane crew announced their intention to taxi to runway 15 via taxiway Delta. The helicopter pilot reported that the last time he saw the airplane before the accident was as he overflew the intersection of taxiway Delta and the taxi line just east of Spot 1, at which point the airplane was turning westbound onto taxiway Delta. The helicopter pilot queried on CTAF whether the airplane crew had him in sight and heard a double click, which he interpreted as acknowledgment. Believing the airplane was behind him and in sight, he continued his descent along taxiway Delta toward Spot 2. About 8 to 10 seconds later, as the helicopter came abeam of Spot 2, the pilot began a right pedal turn to land. At that moment, he saw the airplane's wings and nose through his chin windows and felt an impact. He stopped the turn and descent, transitioned to the ramp, and landed on Spot 2.
The airplane crew was unaware of the collision and continued taxiing and departing from BVU. Shortly after departure, company personnel recalled the airplane after learning of the collision. The airplane was equipped with a cockpit voice recorder (CVR), which was sent to the NTSB for readout.
Aircraft Information
The helicopter was a single-main-rotor, single-engine turboshaft aircraft manufactured in 2010, configured for aerial tours with seven passenger seats and a single pilot in the left front seat. The airplane was a high-wing, twin-turboprop aircraft manufactured in 1970, configured for aerial tours with 17 passenger seats and operated by a two-person crew.
Personnel Information
The helicopter pilot held a commercial pilot certificate with helicopter instrument and instructor ratings, with about 1,102 total flight hours, all in helicopters, including about 9 hours in the accident model. His most recent flight review was July 22, 2014, and his second-class medical certificate was issued December 2, 2013. He had been recently hired and the accident occurred on his first day of revenue service.
The airplane captain was an 11-year employee and instructor pilot, who had been on duty for 8 of the 9 days before the accident. He began his duty day at 0507 and the collision was his sixth flight of the day. In his written account, he stated the crew completed the before takeoff checklist prior to taxiing. He did not report stopping on the ramp before turning onto taxiway Delta, nor did his report include awareness of the helicopter beyond describing closest proximity.
The first officer was on his second day as a pilot for Grand Canyon Airlines. His written report did not include awareness of the helicopter or whether the airplane stopped on the ramp.
Communications
BVU had a recorded CTAF. The helicopter (call sign Papillon 31) first reported at 1644:10, south of the substation at 2,800 feet, flying towards the ponds. At 1644:55, the airplane (call sign Canyon View 90) reported taxiing from the east apron to runway 27 via taxiway Delta. At 1645:08, the helicopter pilot announced he was over the ponds, coming over Alpha for a westbound Delta approach. At 1645:39, the airplane crew announced taxiing Delta Bravo for runway 15, indicating a westward taxi on Delta. According to the captain, that call was made as the airplane turned westbound onto Delta; he looked out the left window but saw no helicopters. At 1645:45, the helicopter pilot radioed "Canyon View Papillon 31 right above you for Spot Two," with noticeable breathing and changed cadence. The next communication was at 1647:51, when the airplane crew announced taking runway 15. The first officer handled radio communications; the captain was taxiing. The first officer was aware of the inbound helicopter; the captain was not.
Airport Information
BVU elevation was 2,200 feet, with runways 9/27 and 15/33. The ramp was oriented east-west, about 750 feet north of runway 9/27. Taxiway Delta marked the southern ramp boundary; taxiway Alpha connected runway 27 with Delta; taxiway Bravo paralleled runway 15/33. The airport website provided helicopter arrival/departure procedures. The FAA airport/facilities directory noted a large number of Grand Canyon tour aircraft operations and helicopters crossing active runways and taxiways.
Wreckage and Impact Information
The most significant damage occurred where the inboard trailing edge of the helicopter's right horizontal stabilizer contacted the leading edge of the airplane's vertical stabilizer at about two-thirds span. Additional damage was found on the underside of at least one helicopter main rotor blade and the top of the airplane's vertical stabilizer.
Additional Information
Federal Aviation Regulations (FAR) 91.113 states that vigilance shall be maintained to see and avoid other aircraft, and that aircraft on final approach or landing have right-of-way over others in flight or on the surface. The FAA Pilot's Handbook notes that even if entitled to right-of-way, a pilot should yield if another aircraft seems too close.
Three days after the accident, GCA's Flight Operations published a Read and Initial File designating taxiway Delta between Alpha and Bravo as a Hot Spot, requiring extra vigilance and that pilots of departing airplanes come to a complete stop, report position, and scan for traffic before taxiing onto taxiway Delta.
According to a GCA representative, external visibility from the DHC-6 cockpit was somewhat limited, potentially impeding the captain's visual detection of the helicopter. Subsequently, the operators began a program to familiarize pilots with each other's aircraft and procedures, emphasizing cockpit visibility.
In January 2016, Papillon Airways' Chief Operating Officer/Director of Operations provided an undated document presenting an accident summary, safety improvement steps, and a root-cause analysis. The analysis listed relevant facts: the airplane first officer saw an inbound helicopter after Papillon 31's CTAF call; the captain did not hear the call or see the helicopter; the airplane had taxied onto taxiway Delta before announcing it. The NTSB could not independently verify the captain's lack of awareness as stated in that report.