Runway and taxiway safety measures have evolved from the “silver bullet” mind-set of technology fixes to a mix of technological, procedural and analytical initiatives optimized at a particular airport for a particular runway.
At the tarmac level, boosting runway safety is a continuous hands-on process between the airport operator, airlines, FAA and other businesses in the movement area. At Boston’s Logan International Airport, recent interventions include changes to the basic layout such as removal of some taxiways and building of new ones to reduce runway crossings, installing advanced ground surveillance systems and associated safety aids and developing new procedures for controllers.
Similar efforts are underway in Dubai at the Al Maktoum International Airport, where there is a push to include open standards on safety equipment to spawn innovation in the integration of various tools.
Most incursions are not dangerous in and of themselves, but often point to larger issues in human factors, airport and procedural designs. The most recent statistics from the FAA show an increasing number of incursions at the more than 500 towered airports in the U.S., with the bulk of the incidents categorized by the FAA as “C” or “D”, meaning the aircraft at risk had “ample time” and/or distance to avoid a collision or where there were no immediate safety consequences, respectively. Category A and B incursions, where an accident was narrowly avoided or evasive actions were needed, are very rare events. The FAA’s safety target this year is fewer than 20 A and B incursions in 50 million operations.
XSight Systems is expanding its automated foreign object debris system, installed in Boston, to take on additional functions, including bird harassment. Credit: XSight Systems
A recent Cat. C incursion illustrates the norm and how technology can help. A Boeing 787 landed in San Diego last April and did not fully clear the runway before stopping. The Airport Surface Detection Model X (ASDE-X), a surveillance system that fuses ground radar and other sources to drive safety logic that issues alerts, flagged the problem to controllers, who ordered a Boeing 737 on the same runway to abort its takeoff roll before a serious encounter could occur. Errors can also occur when air traffic control procedures are mismatched with new developments in aircraft.
Last April, two pairs of Airbus A380s were involved in Cat. C incursions in the same location at the Los Angeles International Airport five days apart. In both cases, one A380 that had just landed was incorrectly instructed to use a taxiway that did not provide the required separation from a second A380 taking off on the runway that parallels the taxiway.
Boston Logan, which opened in 1923, has not recorded a Cat. A incursion since 2005, but has seen an increasing number of relatively less risky Cat. C events over the past five years. Given its age, the airport has a complex configuration that the operator, the Massachusetts Port Authority (Massport), and the FAA are detangling in parallel with new or upgraded technical and procedural interventions.
According to the FAA’s Aviation Safety Information Analysis and Sharing (Asias) database, Boston recorded a rate of 33 incursions per million operations in 2010-14, higher than the overall average of 26 incursions per million operations for all U.S. towered airports. The rate for airline and air taxi operations, at 28 incursions per 1 million operations, was approximately twice that of the nationwide average, according to Aviation Week’s computations.
Attempting to drive that number down is a local Runway Safety Action Team effort between Massport, airlines and the FAA. Input from the national level is coming through the FAA’s Comprehensive Review and Assessment (CARA), which, with a runway safety action team, is developing targeted interventions in terms of layout geometry, technologies—including an optimal mix of existing and new Runway Status Lights—and air traffic control procedures. “We see [CARA] as a road map or vehicle to get us to that next stage of improvements,” says Flavio Leo, Massport’s deputy director of aviation planning and strategy.
Runway Status Lights (RWSL) use input from ASDE-X to control lights along the runway centerline at the departure point and at intersections and the runway end. The lights turn red when the runway is occupied. FAA incursion reports do not list any RWSL “saves” for Boston, but an incident in Dallas-Fort Worth in December shows the value. An Embraer 175 had been cleared for takeoff on Runway 17R, but the pilots reported that the RWSL embedded in the runway centerline had lit up red and they halted. It turns out that a Bombardier CRJ900 waiting to cross the runway had taxied over the “hold” line before stopping, potentially impinging on safety margins with the departing E-Jet.
Boston was also a site for testing of another ASDE-X-driven technology known as enhanced final approach runway occupancy signal (eFaros), which causes the precision approach path indicator (PAPI) lights that give pilots a reading of approach slope to flash if the active runway is not safe for landing.
“When we look at concerns like incursions, there is not a single cause or solution,” says Leo. Because of its runway configuration and network of legacy taxiways connected to those runways, part of the solution has been to remove taxiways, adjust intersections and build a new taxiway between two parallel runways. Leo says Massport is discussing with the FAA how to “further optimize” the RWSL system, for which the airport paid construction costs; the FAA paid for the lights, software and safety logic. Through CARA, the airport is also considering changes to the geometry, technologies and air traffic control tower procedures.
Boston has also been a pathfinder for other technologies directly related to runway safety, including Automatic Dependent Surveillance-Broadcast (ADS-B) tracking for ground vehicles and automated foreign object debris (FOD) detection.
The airport has 75 vehicles equipped with ADS-B transponders to provide the airport control center with vehicle locations. In the vehicles, drivers have tablets that show the same information on a moving map, boosting situational awareness. “We know exactly where our assets are for snow management,” says Leo. Boston as of the end of February had received more than 100 in. of snow.
A FOD detection system built by Xsight Systems has been operational on Runway 9/27 at the airport for more than one year, the first of its kind to be installed at a U.S. airport. Selected through a competitive bid, Xsight’s FODetect comprises 68 electro-optical and millimeter-wave radar sensor packages collocated with the runway edge lights placed at 200-ft. intervals along the 7,000-ft. runway. The system is designed to scan the entire runway surface for FOD at 1-min. intervals between operations, sounding an alert in the airport operation center if an object is detected where one should not be. Operators see an icon on a map denoting the FOD and can take control of the articulating and zooming cameras to obtain more information on the object, and if needed, dispatch a crew to inspect or shut down the runway. Airport staff will generally inspect a runway visually by vehicle at least once per shift, or three times per day. The FAA is running a test through June comparing what is being found by FODetect versus the legacy method, and the airport continues to analyze the cost-benefit case.
“We are finding stuff,” says Leo, leaving out the details. “It’s quick, and we can validate it,” he says of the system, noting the airport is still in “learning mode” with the new technology and that the legacy searches of all runways continue. “We tend to very rarely dial back on one thing if we’re doing something else,” he says. “We’re treating it as an additional layer of safety.”
Arik Fux, Boston office leader for Xsight, says the system costs $5-6 million to install per runway, but costs can be covered by the FAA’s Airport Improvement Program or passenger facility charges. In Boston, Massport and the FAA each paid half the cost, says Leo.
Operationally, Boston may get ideas from Tel Aviv, where an Xsight FOD system at Ben Gurion Airport is used to resolve whether to shut down a runway after a crew reports a bird strike. “If they don’t get an alert from the system on remains on the runway, they will continue to keep the runway open,” Fux says, adding that the runway had previously had to be shut down after every reported strike.
An added function set to go live on a new FODetect system at the Seattle-Tacoma International Airport later is a bird deterrent that uses speakers to selectively harass birds spotted by the system.
Clever surveillance designs are also the forte of Canada’s Searidge Technologies, a developer of “intelligent” video-based surveillance and surface management systems. New runway safety projects include two “focus sites” for a remote situational awareness and zone occupancy system, one at Al Maktoum and another at an unannounced airport in the United Arab Emirates, and a video security system at the Aspen-Pitkin County Airport in Colorado. Operational since last summer, the Al Maktoum system uses remote video and airport surveillance information to generate surface traffic status and predictions for aircraft as well as stop lights for vehicles crossing active taxiways, both measures that boost situational awareness and can reduce incursions.
In Aspen, Searidge designed a thermal camera system to create virtual “hot spots” that will alert airport security when passengers or pedestrians cross into active movement areas, says Alex Sauriol, executive vice president for airport and ATM solutions for Searidge. Sauriol says the airport was having issues with passengers deplaning via stairs and walking into critical areas while taking pictures of the surrounding mountains.
Sauriol says the surface management system at Dubai is unique in that it has “open standards” that would allow other companies to potentially use its sensor data for other safety projects. Open standards are not typical elsewhere, he says, leading to disconnects. “What’s not happening is that we’re not acting cohesively,” he says of the industry. “There’s not a formal standard for how to bring technologies together to improve runway safety. Right now, if one company installs runway lights and another company wants to use those lights for an alerting function, they can’t,” he says.