TSB featured article
This article was published in Flightplan Magazine, Fall 2010
Landing Accidents and Runway Overruns: Reducing the Risks
By the Transportation Safety Board of Canada
Although thousands of safe landings take place around the world each day, somewhere-about twice a month, on average-an aircraft veers off the side or past the end of a runway-sometimes with tragic results. Canada had its own experience with a large aircraft runway overrun in 2005, when an Air France Airbus A340 slid off the end of the runway after landing in bad weather at Toronto's Lester B. Pearson International Airport. Fortunately there were no fatalities. However, there were a number of serious injuries, and the aircraft was destroyed in the post-crash fire.
In March 2010, the Transportation Safety Board of Canada released its Watchlist of nine critical safety issues posing the greatest risk to Canadians. These issues were selected because they've proven tough to solve, with further action needed to significantly reduce the risks. One such issue is the risk to passengers during landing accidents and runway overruns.
The scope of the problem
Runway overruns are a worldwide problem. According to a 2009 report by the Flight Safety Foundation, an international non-profit organization dedicated to improving aviation safety across the globe, there were 435 instances between 1995 and 2008 where aircraft either ran off the end of the runway or veered off to the side 1. This translates to roughly 30 such "excursions" per year and accounts for approximately 29 per cent of total aircraft accidents2.
In Canada, there were 46 overruns involving larger aircraft between 1989 and 2006, 11 of which involved significant aircraft damage and injuries3. An annual occurrence rate of 2.7 in Canada may seem low, when viewed in terms of the total number of landings that take place each year. However, according to a 2008 study commissioned by Transport Canada, Canada's rate of runway overruns per million landings is almost twice the world average, and three times the U.S. rate. That figure jumps to four times the global average when the runway is wet4. And we should remember that the consequences can be catastrophic.
A complex issue
Runway overruns are a complex issue. Crew training, company procedures, weather conditions, and the surrounding terrain are some of the contributing factors. Following the Air France investigation, the TSB recognized the need for numerous defenses, and issued recommendations aimed at improving operational standards, pilot training, and operational procedures. In particular, the Board called for clear standards to limit landings in bad weather, mandatory training for pilots to better enable them to make decisions about landing in deteriorating weather, and the need for crews to establish a margin of error between required and available landing distance before conducting approaches in deteriorating weather.
But even if training and procedures go some distance to preventing overruns, they will not eliminate them entirely.
The Last Line of Defense
In accidents that resulted in significant damage, serious injuries, or fatalities, three key underlying factors related to overrun surfaces have been found: an insufficient runway overrun area, close proximity to urban development, or obstacles such as cliffs or berms. Since 1999, these have been cited as factors in four runway accidents in the U.S., resulting in 12 fatalities and 185 injuries.
So when an overrun does occur, the preferred option is to make sure planes have the room they need-and then some. According to a 1987 study conducted by the U.S. Federal Aviation Administration (FAA) 90 per cent of aircraft that overrun runways stop within 1000 feet (300m) of a runway's end. This figure was re-confirmed in a 2009 study by the Australian Transport Safety Bureau5. Adequately sized runway end safety areas, or RESAs, are one way to provide this.
Currently, Transport Canada requires a 60m buffer strip at the end of Code 3 and 4 runways6, though it recommends an additional 90m RESA after that. This 60m required plus 90m recommended would match the current minimum 150 m standard set out by the International Civil Aviation Organization. ICAO, however, also recommends an additional 240m RESA at the end of the 60 m strip-for a 300m margin of safety.
ICAO Standards and Recommended Practices for Runway Overrun Areas
Sometimes, however, the terrain around an airport makes extending runway overrun areas unfeasible. This is why the Board recommended that, as an alternative to a 300 m RESA, Canada's longest runways be equipped with an equivalent means of stopping aircraft safely, such as an arrestor bed. This promising option uses a layer or "bed" of lightweight, crushable concrete that is designed to break apart under the weight of an aircraft. As the material crumbles, it increases the rolling resistance on the aircraft's wheels, helping to slow the aircraft. Arrestor beds have already been installed at 48 runways ends at 32 airports around the world. Thus far, they have successfully stopped seven aircraft during runway overruns, preventing personal injuries and aircraft damage7.
More Action Required
In Canada, the TSB's recommendation has led to RESA standards being put under review. Although Transport Canada has indicated that it plans to consult the industry, there is no guarantee that the Canadian standards will be changed to meet ICAO's requirement of a 150m overrun area. Such changes, moreover, usually require a lengthy regulation-setting process. Meanwhile, some organizations are already encouraging ICAO to go even further, and enhance the standard to 240 m runway. As such, the Board assessed Transport Canada's proposed action as "Satisfactory in Part."
Prompt or not, however, all of these solutions are expensive. Creating or extending RESAs, or installing special arrestor beds, involves a significant capital investment, one that may be particularly tough given the current economic climate. The TSB realizes this, just as it realizes that runway overruns themselves are a complex issue, one where all the parties involved-aircraft manufacturers, air operators, ANS providers and airports-have a role to play. Doing nothing, however, may be even more expensive: A Flight Safety Foundation study found that, between 2005 and 2007, runway excursions cost the aviation industry $506 million per year in damage, in delays due to downtime, and in litigation.
Clearly, then, action is required. Using their safety management systems, airports with Code 4 runways should thoroughly assess the risks of runway overruns. This will help them quantify the risks and decide on the most effective means to mitigate them. In the meantime, and whatever the defenses that are put in place, the TSB will continue to monitor the situation, pushing for change-and safer landings-for all Canadians.
- SMS Specialties, Report on the Design and Analysis of a Runway Excursion Database, produced on behalf of the Flight Safety Foundation, May 2009. ↑
- Flight Safety Foundation, Reducing the Risk of Runway Incursions, May 2009. ↑
- TSB occurrence database. ↑
- Jacobs Consultancy, Risk and Benefit-Cost Analysis of Procedures for Accounting for Wet Runway on Landing, prepared for Transport Canada, July 2008. ↑
- Australian Transport Safety Bureau, Runway excursions, Part 2: Minimising the likelihood and consequences of runway excursions, an Australian perspective, 2009. ↑
- ICAO runway codes: Code 1: less than 800m long, Code 2: 800m-1199m, Code 3: 1200m-1799m, Code 4: longer than 1800m ↑
- Zodiac Aerospace Fact Sheet http://www.esco.zodiacaerospace.com/downloads/documents/ESCO-ZA_EMAS_Fact_Sheet_012110.pdf ↑
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