Last February, a controller at San Francisco International Airport mistakenly cleared an Embraer 175 to land on Runway 28L while an Airbus A320 was waiting to depart at the end of the same runway. A surface surveillance system safety net caught the error and alerted the controller, who commanded the E175 to go around. A catastrophe was averted, but barely: The two aircraft had come within less than 100 ft. of colliding.
The incident became one of four “Category A” runway incursions—the type with the most potential for loss of life and limb—that have occurred so far this year. The classification is the result of a laborious process in which an FAA panel ranks individual incursion events as Cat. A (the worst) through Cat. D (the most benign) and attributes the events to pilots, controllers, vehicle operators or pedestrians. The FAA defines an incursion as the incorrect presence of an aircraft, vehicle or person on a runway.
The ranking system and preventatives are getting a second look as the most severe types of incursions—Cat. A and B events—appear to be occurring at the same or possibly higher rates for the past several years despite the introduction of a wide range of corrective measures. Among the technological preventatives are ground surveillance systems like ASDE-X (Airport Surface Detection Equipment-Model X) and airport surface surveillance capability (ASSC)—the type of system that saved the day in the San Francisco incursion—and runway status lights, banks of red lights that alert a pilot not to proceed when a runway is occupied. ASDE-X is now operational at 35 large airports, ASSC will expand to nine airports, and runway status lights will be operational at 20 airports by year-end. Procedural preventatives typically include aids to boost situational awareness, including airport diagrams on moving map displays in the cockpit.
NEW TAKES ON AN OLD PROBLEM:
Safety advocates say incursion classification system too narrowly defined
Airlines using electronic flight bags and adopting more common sense procedures as preventatives
FAA putting larger focus on human factors in designing and deploying incursion barriers
“The categories are not designed on who to blame, but what collection of mitigations are available for that type of event,” says Chris Devlin, senior principal systems engineer at Mitre Corp.’s Center for Advanced Aviation System Development. At an NTSB runway incursion forum in Washington in September, Devlin said safety data over the past two decades shows a “significant” reduction in the rate of runway incursions in 2000-08, but since then, “it’s not clear if there’s been a reduction or not.”
He joins a broader chorus of safety advocates calling for additional data collection surrounding the most serious incursions and a more comprehensive classification system. “We’re chasing a few events each year trying to understand the true risk in the system,” says Devlin. “My argument is that risk actually exists on a continuum, and we need to start looking at runway safety as part of this continuum.”
Analysts are faced with several problems when trying to gauge runway incursion trends and predictions. Given the low number of Cat. A and B events—generally fewer than 20 per year—it can be difficult to decide if performance has been improving or worsening over time. Devlin says a weighted Bayesian curve fit of the data since 2008 suggests virtually no change in rate, while an exponential curve fit suggests the numbers are on the upswing. The total number of reported and verified incursions has been growing since 2011. There were 1,560 last year, based on the FAA’s fiscal year (October through September), and 1,219 this year through the end of August. One caveat to consider when discussing incursion rates—an incursion must be reported to be counted.
Making a judgment based on the sheer number of events also can be problematic. James Fee, the FAA’s manager for runway safety, says the number of incursions has increased over the past decade in part because of culture changes initiated by the FAA. The agency in 2008 launched a voluntary safety reporting program for controllers, the Air Traffic Safety Action Program (ATSAP). Pilots, flight attendants and other aviation workers have similar programs that offer immunity from FAA penalties when employees voluntarily submit a report on an accident or incident, providing there was no criminal activity, substance abuse, alcohol or intentional falsification involved. In 2008-14, the FAA said it had received more than 73,000 ATSAP reports resulting in more than 200 safety improvements to the air traffic control system.
The number of reported and verified runway incursions in the U.S. has been growing since 2011. Credit: FAA
Fee, speaking at the NTSB forum, said in the past decade 66% of all runway incursions were attributed to pilot deviations (pilots not adhering to FAA rules or ATC instructions); 19% were tied to vehicle or pedestrian deviations and 15% to ATC. General aviation aircraft are involved in 80% of all incursions. For the more severe Cat. A and B incursions, 67% were attributed to ATC and 33% to pilot deviations. Many of the ATC events resulted in “fly-overs,” as was the case in the San Francisco incident in February.
The FAA and industry recently reviewed more than 700 Cat. A, B and C incursions to assess what prevented them from becoming accidents, says Fee. The primary cause of incursions (63%) was ATC clearing an aircraft to land or depart on an occupied runway—an error that can cause a “fly-over” event. It was found that one of the leading contributing factors was misjudging the closure rate or separation rate between two aircraft. Of the 361 pilot deviations studied, the top cause was failing to hold short of an active runway; the largest contributing factor was miscommunication. In 20% of the ATC incidents, go-arounds were used as the “barriers,” or preventatives; in another 40%, the FAA could not tell “which barriers were in place or which were the most effective,” says Fee.
Based on the problem of fly-overs, the FAA has begun requiring tower controllers to use “memory aids” to help them recall exact “actions, items, places and sequences,” says Mike Moreau, the FAA’s central service area runway safety program manager. Memory aid toolboxes, which can be as simple as a pad of paper with a check mark next to an aircraft’s call sign or as sophisticated as a touch-screen tablet, have to cover six operational scenarios: runway closed or inactive; runway crossing taking place; vehicle, personnel or equipment on an active runway; land and hold-short operations; line-up-and-wait commands; and landing clearances issued.
The requirement also applies to contract towers. Serco, an operator of 59 contract towers in the western U.S. and Alaska, and one non-federal control tower in California, created what it calls the tower traffic management board (TMB) in response.
“It’s a poor man’s radar,” says David McCann, senior program manager for Serco. “Many of our facilities have radar, but there is an FAA requirement to have the runway incursion avoidance memory aids in place.” TMB is a magnetic dry-erase board with a diagram of the airport printed on it. Controllers use color-coded magnetic chips on the board to indicate an aircraft or vehicle on the runway, taxiways or approach paths. “Each is unique to a facility and has standard operating procedures for that facility,” says McCann. “They’re all geared toward quick recognition by the controller so they can figure out what‘s going on and get back to looking out the window. In the past, you’d have a legal pad and write down the numbers as they call you. That’s not very efficient.”
Airlines are also deploying their own customized solutions while sharing insights with rivals through the FAA’s InfoShare gatherings twice per year.
Delta Air Lines says its rate of runway incursions over the past four years has been “flat,” meaning no appreciable increases or decreases. “We don’t take that lightly,” says Patricia DeMasi, manager of Aviation Safety Action Programs (ASAP) for the carrier. “We watch the industry trends and have a heightened awareness because of that.” ASAPs are part of a broader safety management system structure within airlines.
Key preventive measures include options for electronic flight bags (EFB) in the cockpit. Included are own-ship position on airport moving maps, depictions for closed areas, Delta-specific airport familiarization pages and a capability so pilots can create a highlighted overlay of their expected or assigned taxi route.
Along with using ASAP reports to flag potential problems, Delta is working with its flight operational quality assurance (FOQA) service provider to set up a “trigger” to “highlight possible incursions that our FOQA team can follow up on,” says Josh Migdal, Delta’s senior air safety investigator. “Human factors is a big piece we’re looking at.”
Southwest Airlines would not discuss its incursion rate trends but noted that over the past four years 21% of its runway incursions resulted in a go-around, and 1% caused a rejected takeoff. Causal factors included cockpit distractions, loss of situational awareness, similar call-sign confusion and timing of the before-takeoff checklist, says George Hodgson, manager of ATC systems for Southwest.
Preventive measures include airport “cover pages” in pilot documents that detail special areas of concern at airports. At the Hollywood Burbank Airport in California, a new cover page describes a new hold point to help with incursion problems the airport was having for one runway. In the cockpit, pilots are instructed to confirm ATC instructions between each other and to “suspend discretionary tasks” when needed.
United Airlines has determined that causal factors for its runway incursions largely revolve around situational awareness and communications. “Situational awareness starts with a taxi plan, threats and being aware of their present position,” says Jerry Tsujimoto, United’s senior investigator for flight safety investigations. The carrier uses a VVM (verbalize, verify and monitor) aid to keep both pilots from being “heads-down” at the same time looking at EFBs or other documentation during taxi. Pilots are graded on their understanding of runway incursion prevention measures and on their performance in handling complex airport layouts in simulator training.
The FAA is putting more focus on the human factors aspect on the continued occurrence of runway incursions. The agency’s nine-person human performance team, comprising experts in fatigue, human factors and health and wellness, will be developing the tools needed “to achieve a high level of human performance in the National Airspace System,” says Sabrina Woods, an FAA human factors scientist on the team.
Woods says access to all available data has been a roadblock in coming up with the most effective runway incursion mitigations. “We’re building mitigations on one-quarter or one-half of the story and hoping the outcome of that safety action is moving the safety needle,” says Woods. “We are uncertain if corrective actions are solving the problem; we are not even sure we are asking the right questions.”
The problem, she says, is that analysts do not have access to information about the same incident from multiple databases, including ATSAP, ASAP, the NASA aviation safety reporting system and others. “All the mitigations we create and all the devices we develop to carry out the mitigations are based on what can sometimes be incomplete data,” she says. “It’s not because the data does not ; it’s because our level of accessibility is not there yet.”
Redefining The Runway Incursion Problem
FAA and industry take a fresh look at how to avoid runway incidents
Oct 13, 2017 John Croft | Aviation Week & Space Technology