"Simple Things" Needed to Prevent Near Misses at Airports

Air Safety Week, June 19, 2000

Safety Board notes failures of promised high-tech "solutions" while incursions increased

Immediate action is needed to stem the rising tide of runway incursions. A ten-year search for a technological solution has not produced a deployable system to warn of incursions, and it may be time to look to simpler technologies and to procedural changes.

This was the central message emanating from a National Transportation Safety Board (NTSB) June 13 hearing on the subject of incursions. Incursions might be defined as the unauthorized or inadvertent movement of aircraft from taxiways onto active runways, or the loss of separation between aircraft or ground vehicles that could lead to a collision.

"I find it disappointing that there are still few effective measures in place to deal with this dangerous problem and that, once again, the Board finds it necessary to consider new recommendations," NTSB Chairman Jim Hall complained. "The number of runway incursions remains alarmingly high," Hall noted. "We are currently averaging a runway incursion every day somewhere in the United States, and we are just entering the busy summer season, when the number of incursions tends to increase."

The term "incursion" does not do justice to the potential for disaster. Of four recent incursion incidents the Safety Board presented to illustrate its concern, the April 1, 1999 near-collision between a Korean Airlines B747 on takeoff at Chicago's O'Hare International Airport, and an Air China B747 that mistakenly taxied onto the runway, was the most spectacular. The crew of the Air China B747 made a wrong turn from its assigned taxiway and was moving onto the runway as the Korean Air B747 was on its takeoff roll. The computer animation presented by the Board was accompanied by the recorded voice of the tower controller shouting, "Stop!" The urgent command apparently was directed at the Air China crew. The two aircraft, with nearly 400 people aboard, missed colliding by a scant 80 feet.

In a Dec. 6, 1999 incident at Providence, Rhode Island, a United Airlines [UAL] jet taxied onto an active runway and remained there for more than three minutes. In the Safety Board's animation, the frustrated tower controller was clearly fearful of a collision. "Everybody stand by. Radio silence unless I talk to you," she demanded, explaining, "I have a United (airplane) who doesn't know where the hell he is."

In these instances, both of which involved aircrews lost on the taxiways, luck played a role. But Safety Board Chairman Hall groused, "Relying on luck doesn't make for good public policy."

Decade of Disappointment

The Safety Board's evident frustration stems from the lack of progress over the past decade. In 1991, the Board recommended that the Federal Aviation Administration (FAA) develop a technology to prevent runway incursions. The essential idea was to deploy an operational system "analogous to the airborne conflict alert system." The centerpiece of the FAA response was a software package known as the Airport Movement Area Safety System (AMASS). The system was promised as the "high end" solution to incursions at the larger airports. A lower-cost system known as Airport Surface Detection Equipment (ASDE) was envisioned for the less-busy airports.

The FAA's centerpiece effort, AMASS, so far has not produced a single operational system. As sunk costs into AMASS have mounted, the deployment date has slipped and the performance specifications have been reduced. The system as currently envisioned will not warn of incursions, but rather of impending collisions only. From the voluminous correspondence back-and-forth between the NTSB and the FAA, apparently one of the major technical challenges was the problem posed to AMASS by aircraft on approach. The technical focus also shifted from incursions to collisions "due to a high false alarm rate," recalled Dr. Bernard Loeb, Director of the NTSB's Air Safety Office.

"If you don't alert the flight crew, you're not going to avert the problem," Loeb declared.

Indeed, there is a feeling that the U.S. has fallen behind the Europeans in deploying simple or sophisticated technology to prevent incursions.

In the case of the near-collision at O'Hare, the Safety Board believes that AMASS would have provided the tower controller with only about six seconds warning. "Staff believes that even doubling the warning time is not adequate," said Sandy Rowlett of the Safety Board's Operational Factors Division.

AMASS was deemed deficient for a number of reasons. Its symbology does not provide the tower controller with aircraft identification. Further, the fact that it provides alerts to the controller, but not directly to the aircrew, is deemed a major shortcoming. The controller has to detect the warning, identify the nature of the problem and determine the necessary action before attempting to establish radio contact with the flight crew.

"The key is time. The current system doesn't provide enough time. If you provide warning when the airplane is on the taxiway, you get more time," Loeb explained.