Conflict avoidance: TSB proposes direct-to-pilot warning systems to prevent runway incursions
By Kathy Fox
Board Member, Transportation Safety Board
This article was originally published in English in the March 2013 edition of Canadian Skies magazine.Footnote 1
It's a dark November night at Toronto's Pearson International Airport, and a Learjet 35A is making its way from the general aviation ramp toward its intended departure runway when it is told
«to hold short.» Unfamiliar with the airport's layout, however, the flight crew misidentifies the appropriate runway and does not stop—placing them directly in the path of a landing aircraft. Disaster is averted only when the crew of the landing aircraft spots the intruder and manoeuvers to pass behind it.
Now consider this:
It's a snowy afternoon in Whitehorse, and a pair of sweepers is busy clearing the runway. Meanwhile, a Bombardier regional jet has been cleared for an instrument landing system (ILS) approach to the same runway. Despite being asked to
«report 10 miles back on final approach,» the crew misses the call; minutes later, they touch down without being given final clearance to land—passing over both sweepers while they are turning around on the threshold of the runway.
Airports are busy places, with aircraft and vehicles constantly moving between ramps, taxiways and runways. Sometimes this movement can lead to incursions or conflicts between aircraft, or between aircraft and people or ground vehicles, on active runways. Approximately 400 of these occurrences are reported in Canada every year—an average of more than one a day—and while the vast majority are classified as low risk, approximately half a dozen are classified as
«high risk».Footnote 2
That's why, back in 2010, Canada's Transportation Safety Board (TSB) highlighted the issue of runway incursions on its inaugural safety Watchlist—and it's why the issue remains on the updated 2012 Watchlist. That list, which identifies the issues posing the greatest risk to Canada's transportation system, is based on an analysis of thousands of TSB investigations, safety concerns, and Board recommendations—including the two near misses described above.Footnote 3
The good news is that Canada's aviation industry has been actively addressing this issue. For example:
- Airports have started bringing together runway safety teams—comprised of pilots, snow removal equipment operators, emergency response personnel, runway maintenance crews, and air traffic controllers—to share information and develop procedures to improve safety.
- Phraseology in Canada for authorizing aircraft onto a runway has been aligned with international standards, and pilots must acknowledge instructions to hold short of a runway.
- Aerodrome charts depict hot spots where there is a heightened risk of incursions to raise crew awareness of these areas. Many companies require their crews to be briefed on these areas prior to taxiing.
However, more leadership is still required from Transport Canada and industry, especially because recently available technological defences have not been seriously considered or widely implemented.
One area of particular concern to the TSB is the ground radar systems that monitor surface movements to detect incursions. In 2007, the Board expressed concern that the airport surface detection equipment/runway incursion monitoring and collision avoidance system (ASDE/RIMCAS) in place at Toronto's Lester B. Pearson International Airport—Canada's busiest airport—provided insufficient warning time to avert a potential collision, and that this system could not be enhanced due to the type and age of its software. At the time of writing, the surface movement radar in Toronto had not been replaced, although there are plans to do so.
In Montreal and Calgary, meanwhile, a system that incorporates multi lateration (MLAT) allows targets on the controller's display to be automatically identified, thus providing an effective tool for improving controllers' situational awareness. Like RIMCAS, however, the MLAT system still relies on controllers interpreting warnings and their subsequent radio communication with aircraft and vehicles.
What's needed is more advancement in direct-to-the-pilot warnings, such as flight deck enhancements being developed by aircraft manufacturersFootnote 4 and the runway status light system now undergoing Federal Aviation Administration testing at some airports in the United States. Early reviews of these lights, which are independent of controller action, are very promising. Also effective are stop bars, which provide an additional cue to pilots and vehicle drivers when they are authorized to enter a runway. And while these bars were initially designed for low-visibility conditions, some Canadian airports have implemented them in all weather conditions, as an additional layer of defence. Cost, however, is an issue, as the installation of these options is expensive.
Less expensive, though still not regulated in Canada, and not widespread, are airport markings that have been developed to provide advance warning of an upcoming runway. Specifically, enhanced centerline and hold short marks designed to make hold short positions more conspicuous have become the standard throughout the United States. To date, though, they have not been adopted in Canada.
All of these are good steps, and airports say they are planning even more initiatives. However, until that actually happens—until Transport Canada and industry work together to take full advantage of the procedural and technological defences available to detect and prevent runway incursions—this issue will remain on the TSB Watchlist.
Because, to put it simply, the risk remains too high, especially when the consequences can be catastrophic.