Contributing to the accident, in which the three occupants of the Robinson R44 II helicopter died, were the lack of a published helicopter traffic pattern altitude, absence of radar equipment in the control tower, and “the controller's inadequate task prioritization,” the NTSB said in a report released May 23. The pilot of the airplane, a Cirrus SR22, and a passenger survived when the aircraft’s ballistic parachute deployed.
The 2006 Cirrus, flown by Scott Greaves, then 56 and a 969-hour private pilot, was arriving from Cleveland, Tennessee, and had entered a left downwind leg to Runway 30, with instructions to report midfield. The local controller advised Greaves that there were three helicopters below his altitude, flying in the traffic pattern.
Aboard the helicopter, which entered a vertical descent after the impact, were Christopher D. Parsons, 29, an 832-hour helicopter instructor; William Jenkins, 47, of Morrison, Colorado, a 2,850-hour commercial pilot with 1,538 hours of helicopter time; and Brendan MacFawn, 35, of Cumberland, Maryland, according to news reports.
A flight instructor in another of the operator’s helicopters was following the accident helicopter in the pattern and saw the company aircraft at the point where it would turn downwind from a crosswind leg. “At the same time, the airplane appeared in his field of view as it ‘flew through the rotor system’ of the helicopter,” he told investigators.
The report, citing data from the Cirrus, said the collision occurred at approximately 1,100 feet msl.
“The published traffic pattern altitude (TPA) for light airplanes was 1,300 ft msl. Although several different helicopter TPAs were depicted in locally produced pamphlets and posters and reportedly discussed at various airport meetings, there was no published TPA for helicopters in the airport/facility directory or in the tower's standard operating procedures. According to the Federal Aviation Administration's Aeronautical Information Manual, in the absence of a published TPA, the TPA for helicopters was 500 ft above ground level; therefore, the appropriate TPA for helicopters at the accident airport was about 800 ft msl.”
The absence of an “official” pattern altitude for helicopters “significantly reduced the potential for positive traffic conflict resolution,” it said.
A controller’s task prioritization was noted as a contributing factor because at the moment the accident airplane’s pilot reported that he was three miles out on a 45-degree downwind leg, the controller “was listening to the read back” of an IFR clearance just issued to a business jet on the ground control frequency.
A traffic advisory system aboard the Cirrus did not warn of the impending conflict. The report noted that the system would not detect an “intruder” if that aircraft’s transponder were not responding to interrogations, or if the equipped aircraft “was located directly above an intruder.”
The report examined various stakeholders’ impressions about the proper traffic pattern for helicopters at the airport—where AOPA is based—and noted that as a result of the investigation, official publications were “updated on January 8, 2015, with a recommended TPA for helicopters of 1,106 ft msl/800 feet agl.”