Delta 767 taxiway landing prompts ASDE-X review recommendation

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Federal safety regulators are urging the US FAA to perform a technical review of airport surface detection equipment-model X (ASDE-X) to determine if the capability exists "system-wide" to detect improper operations, after a Delta Air Lines Boeing 767 landed on a taxiway at Atlanta Hartsfield International airport.

In a safety recommendation notice, issued today, the National Transportation Safety Board (NTSB) says that, at those installation sites where the technical review determines it is feasible, the FAA should implement modifications to ASDE-X "to detect improper operations, such as landings on taxiways, and provide alerts to air traffic controllers that these potential collision risks exist".

The recommendation stems from a 19 October 2009 incident involving a Delta 767, N185DN. Operating from Rio de Janeiro, the aircraft landed at about 0605 eastern daylight time on "taxiway M" at Atlanta airport, 200ft north of - and parallel to- runway 27R. The taxiway was unoccupied, and the flight crew was able to stop the aircraft safely and taxi to the gate. None of the 11 crewmembers and 182 passengers was injured.

Night visual meteorological conditions prevailed, says the NTSB. Following its investigation the agency determined that the probable cause of the incident was the flight crew's failure to identify the correct landing surface due to fatigue.

Contributing to the cause of the incident, says the NTSB, were the flight crew's decision to accept a late runway change; as well as "the unavailability of the approach light system and the instrument landing system for the runway of intended landing; and the combination of numerous taxiway signs and intermixing of light technologies on the taxiway".

Atlanta is equipped with ASDE-X, which includes conflict detection and alerting technology that detects potential collision risks in the approach corridor and airport surface and alerts controllers of these potential hazards.

As presently configured, however, ASDE-X detects and alerts controllers of potential collision hazards on runways and situations in which aircraft appear to be landing on or departing from closed runways but not a situation in which an aircraft appears to be landing on a taxiway. Therefore, the system did not emit an alert when the Delta 767 lined up with and landed on Atlanta's taxiway M.

The NTSB says the circumstances of the incident suggest that automated assistance would have augmented the tower controller's visual observations and possibly assisted him in detecting the flight crew's misidentification of the taxiway as a runway.

At the NTSB's request, ASDE-X manufacturer Sensis performed a preliminary technical review and found that software modifications could possibly enable ASDE-X to detect a potential taxiway landing at Atlanta at a distance of up to 0.75 mile from the runway threshold and 15 seconds from touchdown and provide an alert to controllers.

"Such a warning would afford air traffic controllers the opportunity to assess the situation and provide instructions to a flight crew that would prevent a taxiway landing or potential collision with aircraft or vehicles that may be on the taxiway," says the NTSB.

Because the Sensis review was preliminary and only evaluated the ASDE-X installation at Atlanta, "a more thorough evaluation of the system should be conducted to determine whether ASDE-X logic can be modified system-wide to detect taxiway landings", concludes the NTSB in its recommendation to the FAA.