Tracking all Movement: MKE first with ASDE-X system

March 8, 2004


All Movement

By Jodi Richards, Associate Editor

MKE first with ASDE-X system
Milwaukee's General Mitchell International Airport (MKE) air traffic control is using an advance in technology allowing air traffic controllers to better monitor activity on the runway and taxiway. The Federal Aviation Administration-funded program involves utilization of ASDE-X, airport surface detection equipment Model X, from Syracuse, NY-based Sensis Corporation. Over the next three years, the system will be deployed to at least 21 airports across the U.S. with the intent of reducing runway incursions.

Marc Viggiano

Marc Viggiano, Sensis Corporation president of air traffic systems division, describes a runway incursion as a loss of separation between two aircraft, or an aircraft and a vehicle or person. "And it's not surprising that as airports get busier, and we try to get more aircraft in and out of airports, keeping them apart on the ground is a problem," he says.

Sensis Corporation has been in business for some 19 years. It has two divisions: air defense systems and civilian air traffic control systems. "The defense business is really how the company was started," he explains. "We started as experts in radar and systems integration and then applied that technology to the civilian world."

According to Viggiano, "The ASDE-X program is an FAA program that's primarily focused on safety, although the technology does have a number of capacity and efficiency benefits."

Applying The Technology
ASDE-X combines multiple sensors to gather data. It then takes that data and fuses it together for display on a color screen in the tower. "It's an integrated system," says Viggiano. "Instead of just relying on a single radar, [ASDE-X] uses a radar, a transponder multilateration sensor, as well as an ASDE (airport surface detection equipment) sensor and the existing airport radar. It takes all those sources and fuses them together to make sure that you can do a good job of reliably detecting the aircraft and also providing a positive identification by its flight ID."

ASDE-X uses multiple sensors to provide ATC with accurate displays.

The ASDE-X system is comprised of several pieces of hardware and software. "The sensors themselves that actually detect the aircraft are the most visible, external part of the system," says Viggiano. "The SMR (surface movement radar) antenna is the part of the system that detects the aircraft. It will see somebody whether your transponder is turned on or not. It will even see unequipped snowplows, small GA aircraft, and large animals." This antenna is mounted on top of the control tower, or possibly on a stand-alone tower. It stands some one-foot tall, is 24 feet in length, and spins at 60 rotations per minute.

The transponder multilateration is another piece, which is a cooperative surveillance system that provides position and identification of all transponder equipped aircraft. Says Viggiano, "They are small cabinets, that can be mounted outdoors, the size of a small dormitory refrigerator, and a little antenna that looks like a cell tower antenna, which doesn't move. It's stationary and typically mounted on an existing structure." Generally, he adds, there are about eight of those sprinkled around the airport.

Data from the sensors are then fed back over a communications system, typically telephone lines or existing networks, explains Viggiano. The communications are fed back to the equipment room, which is usually in the control tower. All the processing takes place there, while the surface movement radar tower can be located several kilometers from the control tower.

According to Viggiano, the radar is only looking at the movement areas, - runways and taxiways. "So if you have a snowplow on the runway, the radar will pick it up, however it won't tell you what it is. It will be a blob." Although, an external antenna, called a Veelo, can be mounted to a vehicle. "For example, if you want to keep track of your snowplows, fire trucks, or tugs, you put one of these units on it and it will show up on the same [ASDE-X] system - not only where it is, but who it is."

The number of sensors at a given airport depends on the physical layout of the airport, Viggiano explains. "It's a function of its actual geometry - not just how big it is, but also where the runways are." A site survey is done to determine the needs and appropriate locations for the sensors.

Milwaukee's Appeal
MKE was an excellent location for testing the system, according to FAA officials. "I think that one reason that Milwaukee was selected," says Wanda Adelman, FAA air traffic manager, "is because of the climate. We've got really warm and really cold and a lot of the fog that comes off the lake. [There are] many days that we can't see the runway because of the fog, rain, and clouds, so it's a good place to be able to test in all types of different weather."

MKE has been the test site for surface radar as it's been developed over the past decade, according to Adelman.

Externally mounted antenna

She says on low visibility days, without ASDE-X, if an aircraft is arriving, ATC has to wait until the aircraft lands and then taxis off the runway and the pilot tells ATC that it is off the runway before controllers can clear the next departure for takeoff.

"With the ASDE-X, you can see the arrival coming in on the ASDE-X display. Once they're past the threshold, you can put the next aircraft into position and hold and then you can see the arrival taxiing off the runway, onto the taxiway, and you can verify that your runway is clear, even though you can't see it out the window, you can see it on the display."

Tony Molinaro, FAA spokesperson, says it's hard to say for sure what impact the system will have on reducing runway incursions. "It's hard to measure safety in those areas. But one of the major goals of the FAA is to improve safety at all facilities in the airport. And this is one of those systems that really focuses on ensuring a safer environment. Will it eventually result in fewer runway incidents? We expect so, but it's too early to see what that affect is yet."

According to Viggiano, the FAA plans to deploy ASDE-X at 34 airports across the nation, and the first 21 are already contracted at a total value of some $100 million. He expects these airports to be equipped with the system by the beginning of 2007.

The cost of deploying the first system at MKE was some $27 million, says Viggiano, which includes training users, software, hardware, research, development, and testing of the equipment.

Viggiano says one of the biggest advances in technology that has allowed a system like this to become available is the use of multilateration. However, he is quick to add that "beyond the technology, it's a recognition that maximizing the safe utilization of airport runways is a key resource that we have to pay more attention to and make sure we get the maximum out of it that we can in a safe way."

Future Upgrades
Like any other technology, airport surveillance systems are always being improved upon. Viggiano says Sensis has "a fairly steady stream of upgrades coming. One that's getting a lot of interest right now is taking the same basic principle and applying it to aircraft that are 30 or 60 miles away from the airport. So you can get radar coverage where in the past you had only procedural voice control."

Another advancement Viggiano sees is the ability to have a datalink from ASDE-X to the cockpit. "So a pilot not only knows where he is but sees all the other people around him on a display in the cockpit."

The FAA is also engaged in researching other technologies, including AMASS (airport movement area safety system), designed for larger facilities. "It's another screen in the tower that tells a controller how close his airplanes are," says Molinaro. "The difference [between AMASS and ASDE-X] is that AMASS also offers oral alert - the computer will alert the controller if two planes are getting too close on the runway." He adds that the two systems may some day be merged together.

Lights Play New Role in Runway Safety

A simulation study is underway at NASA Ames SimLabs to investigate safety effects of standardizing the use of
aircraft lighting during taxi operations.

The Aircraft Landing Lights to Enhance Runway Traffic Safety (ALLERTS) project addresses a recommendation of the Runway Incursion Joint Safety Implementation Team to develop Standard Operating Procedures for aircraft taxi operations specifically related to aircraft lighting.

The purpose of the ALLERTS project is to investigate the safety effects of using aircraft exterior lighting to convey messages in the airport environment. Two specific procedures are being explored: the use of landing lights to indicate that aircraft are cleared to depart and the use of all exterior lights to indicate that aircraft are crossing the active runway. The objective being to determine whether standardizing the use of aircraft lighting will reduce runway incursions and accidents, and increase pilot situational awareness.

The experiment is being conducted in the B747-400 flight simulation at SimLabs' Crew-Vehicle Systems Research. In each simulation, pilots are instructed to taxi, depart, or land, and researchers gather subjective and performance data on the crew. In half of the scenarios, they encounter another aircraft that makes an error which could result in an incursion or accident if not detected by the subject crews.