NTSB: Disney, Shuttle key factors in Southwest-Cirrus separation incident

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Air traffic controllers in Florida considered an unresponsive Cirrus SR22 en route from Mississippi to the Orlando area on 27 March to be a threat to national security, spurring them to ask a Southwest Boeing 737-700 inbound to Orlando to investigate.

"The controllers at Central Florida TRACON (terminal radar approach control) considered the Cirrus to be an emergency due to the length of time the airplane was NORDO (a no-radio flight) and considered the Cirrus a potential threat to the Disney World complex and the NASA space centre, where a space shuttle was on a launch pad at the Kennedy Space Centre," says the US National Transportation Safety Board (NTSB) in a newly released factual report on the incident. "The controllers cited [an FAA rule] that tasks [air traffic control] in part, to provide support for National Security and Homeland Defense."

As such, the operations manager at the Central Florida TRACON "considered the fly-by a prudent action and had conducted similar actions in the past," the report continues. Controllers earlier had been in contact with the domestic event network (DEN), an around-the-clock "FAA sponsored recorded telephonic conference call network that includes all of the US air route traffic control centres (ARTCC) and other Governmental agencies," says the NTSB.

The controller's request and the Southwest pilots' action violated minimum separation rules for instrument flight rules (IFR) operations, prompting the NTSB to launch an investigation and the FAA to suspend the controller.

"By placing this passenger aircraft in close proximity to another plane, the air traffic controller compromised the safety of everyone involved. This incident was totally inappropriate," FAA administrator Randy Babbitt had said in late March.

The two aircraft came to within 30m vertically and 0.09nm horizontally during the encounter, says the NTSB. The minimum required IFR separation between the two aircraft is 305m vertical or 3nm horizontally.

The Cirrus pilot, out of radio contact for more than an hour after using improper frequencies, eventually regained communications and landed uneventfully, as did the Southwest 737.

While the Southwest pilots maintained visual separation with the Cirrus during the encounter at 11,000ft, elements of the factual report reveal shortcomings with the procedure that would appear to have increased the risk of the fly-by.

Investigators say the Southwest pilots "did not brief the manoeuvre or contingencies" before accepting the request to perform the fly-by. The pass involved a closure rate of 60-94kt between the aircraft, says the NTSB, during which the autopilot on the Cirrus made a left turn that the Southwest pilots did not anticipate.

The Cirrus pilot, unaware of the 737 approaching from behind, told investigators "the sight of the jet" and nearly simultaneous aural traffic alerts from his Skywatch on-board traffic alerting system was "startling".