An air tour helicopter pilot flying four passengers on a Part 135 sightseeing trip from Las Vegas to the Hoover Dam deviated from the standard air tour route shortly before impacting terrain in a mountainous terrain 14nm east of the city, according to the US National Transportation Safety Board's preliminary report on the 7 December accident.
The pilot, working for Sundance Helicopters, and the four passengers were killed when the Eurocopter AS350B2 "impacted in a narrow ravine" and burned in mountainous terrain between the city of Henderson and Lake Mead, said the NTSB, adding that weather was reported as "clear with good visibility and dusk light conditions" at the time of the accident.
Radar data obtained from the US Federal Aviation Administration (FAA) showed that the helicopter departed Las Vegas "and followed a normal route" to the east before turning south toward the dam.
"Tour routings are standardized for all the area tour operators," said the NTSB.
Investigators said the helicopter was level at 3,500ft (1,067m) MSL flying at approximately 120kt (222km/h) until about 1min before the accident, when radar data showed the helicopter climb to 4,100ft MSL and turn about 90 degrees to the left.
"The left turn and climb are not part of the normal route," said the NTSB.
Radar data then indicated the helicopter descended to 3,300ft MSL and tracked a northeasterly course for about 20sec, until entering a left turn and then descending. The last radar target received was about 0.12nm from the accident site, according to the report.
The fatal tour accident comes on the heels of the crash of a Blue Hawaiian Eurocopter EC130B4 crash in mountainous terrain on the Island of Molokai, Hawaii on 10 November. The commercial pilot and four sightseeing passengers were killed, with witnesses reporting heavy rain in the area during the time of the accident.
Source: Flight International