Both Emergency Medical Services (EMS) helicopters were on approach to the Flagstaff Medical Center (FMC) helipad to drop off patients. During the flights, the N407MJ pilot had established two-way communications with his communications center and provided position reports, and the N407GA pilot had established two-way communications with FMC's communications center (which was his company's communication center and which also monitored and advised all traffic at the helipad) and provided position reports. The FMC communications center transportation coordinator advised the N407GA pilot that N407MJ would also be dropping off a patient at FMC. The coordinator also advised N407MJ's communication center that N407GA would be landing at FMC, but the N407MJ's communication center did not inform the N407MJ pilot nor was it required to do so.

Established arrival and departure procedures for the FMC helipad required pilots to contact the FMC communications center at the earliest opportunity or at a minimum of 5 miles from the helipad. According to the FMC communications center's staff, N407MJ's pilot did not make the required contact with the communications center at any time during the flight.

About 3 minutes before the collision, N407GA dropped off a medical crewmember at the local airport (about 5 miles south of the medical center) to reduce the weight on the aircraft and to improve aircraft performance during landing at the medical center. According to witness information, flight-track data, and a surveillance video, N407GA approached the helipad from the south, along a direct line from the airport to the helipad. However, according to helipad arrival and noise abatement guidelines, N407GA should have approached the helipad from a more easterly direction. N407MJ approached the helipad from the northeast, and it is likely that the pilot would have been visually scanning the typical flightpaths, as described in the noise abatement guidelines, that other aircraft approaching the medical center would have used. Thus, if the N407GA helicopter had approached from a more typical direction, the pilot of the N407MJ helicopter may have been more likely to see and avoid it.

At the time of the collision, both pilots were at a point in the approach where their visual attention typically would have been more focused on the helipad in preparation for landing, rather than on scanning the surrounding area for other traffic. The helicopters collided approximately 1/4 mile east of the helipad. There were no communications from either helicopter just prior to or after the collision.

Neither helicopter was equipped with a traffic collision avoidance system, nor was such a system required. Had such a system been on board, it likely would have alerted the pilots to the traffic conflict so they could take evasive action before collision. No radar or air traffic control services were available for the helipad operations to ensure separation. However, if N407MJ's pilot had contacted the FMC communications center, as required, the FMC transportation coordinator likely would have told him directly that another aircraft was expected at the helipad. If the pilot had known to expect another aircraft in the area, he would have been more likely to look for the other aircraft.

Nevertheless, the pilots were responsible for maintaining vigilance and to see and avoid other aircraft at all times. Under 14 Code of Federal Regulations Sections 91.111 and 91.113, all pilots are responsible for keeping a safe distance from other aircraft and for maintaining vigilance so as to see and avoid other aircraft. Advisory Circular 90-48C, "Pilots' Role in Collision Avoidance," amplifies the see-and-avoid concept by stating that all pilots should remain constantly alert to all traffic movement within their field of vision and that they should scan the entire visual field outside of their aircraft to ensure that conflicting traffic would be detected.

Examination of the wreckages revealed that N407MJ's tail rotor contacted the forward fuselage of N407GA, and N407GA's main rotor blades contacted and separated N407MJ's tail boom. The recovered wreckages showed no evidence of any preimpact structural, engine, or system failures.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:

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