Reliability of Runway Alert System at O'Hare in Question

O’Hare International Airport claimed the title of world’s busiest airport for takeoffs and landings in 2015, but NBC 5 Investigates has found holes in a system designed to prevent accidents on the ground there.

Frequent false targets and duplicate targets are appearing on equipment used by air traffic controllers to detect potential runway conflicts, according to daily operation logs obtained from O’Hare’s control tower.

“The frequency of incorrect alerts has desensitized us to the alert,” wrote one anonymous controller who reported his concerns to NASA. “We are used to it going off for non-critical situations.”

The Airport Surface Detection Equipment-Model X (ASDE-X) uses information from radar, sensors and transponders to allow controllers to detect potential runway conflicts. An alarm sounds if planes get too close to one other or aviation vehicles. In fact, the alert went off in April when a truck missed an incoming plane by 100 feet.

But ASDE-X false-alerted or failed to work properly at least 39 times at O’Hare between April and July of this year, according to the tower’s daily operation logs.

Controllers logged ASDE-X false alerted four times on May 29th.

“Which ones are the false ones and which ones are the real ones? That’s where it really gets to be a problem,” said aviation safety consultant Rob Mark.

The Federal Aviation Administration (FAA) said ongoing construction activity at O’Hare Airport sometimes triggers false alarms. Other aviation sources have suggested so-called “ghost targets” can be caused by reflections from buildings and snow.

“Too many of these ghost signals that cause the controller to keep looking over at their radar scope when they should be looking out the window are not good,” Mark said.

According to the FAA, controllers respond to every ASDE-X alarm and analyze it.

“The FAA continually works to fine-tune its ground surveillance systems to enhance safety within dynamically-challenging environments such as O’Hare Airport,” FAA spokesperson Tony Molinaro wrote in a statement.

NBC 5 Investigates consulted with multiple aviation sources with knowledge of the ASDE-X system at O’Hare. Each considers ASDE-X to be a great tool.

But the ground radar system is facing limitations at O’Hare’s new south runway in the form of coverage gaps or blind spots.

Controllers rely on ASDE-X especially at night or in poor weather.

“The approach end of the new runway is almost three miles away from the tower and when the visibility is bad they can’t see the airplanes and the vehicles on the runway,” Mark said.

The FAA responded in a statement that it can see all ground movement of vehicles that have a transponder. Vehicles without a transponder are not allowed in certain areas, which the FAA said creates a safe separation.

Still, the FAA said it will install an antenna to fill coverage gaps and install additional transponders on remaining FAA ground vehicles in the coming months.

Issues with ground surveillance are happening at a time when runway incursions are increasing at O’Hare. There have been 28 runway incursions so far this year compared to 18 last year, according to FAA records.

The FAA responded by saying incursions are up at O’Hare because controllers and pilots are adjusting to changes in taxi patterns.


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