With every passing year, the number of aircraft in the sky keeps growing. Global air traffic is expected to double in the next 15 years, so safety is at the top of the agenda for the world’s aviation authorities, and the International Civil Aviation Organization (ICAO) is planning for a future in which airports will have to accommodate more flights without a commensurate expansion of infrastructure.
There are many safety concerns to address, but chief among them are runway excursions, as Brian DeCouto, implementation support officer – safety, air navigation bureau at ICAO, explains.
“Runway excursions continue to be a high priority simply because of the frequency of events,” he says. “They represent the most significant source of aviation accidents worldwide; about 40–50% of the accidents reported to ICAO every year. Although statistically the majority of runway excursions are survivable, the fatality risk remains significant and it only takes one major event to spike the number of fatalities.”
Figures collated by ICAO for its Global Runway Safety Action Plan show that between 2008 and 2016 there were 382 runway excursion events, of which 140 were classified as serious incidents. This compares with 80 incursion accidents during the same period, of which 73 were of a serious nature. The number of runway safety-related accidents remains high, although only 4% result in a fatal accident.
Cause and effect
The Global Runway Safety Action Plan lists many causes of runway excursions. These encompass many internal factors, such as inadequate standard operating procedures, inadequate training of flight crews, insufficient controls to ensure regulatory compliance, and ineffective airport safety policies. Flight crew errors, such as failure to go around after destabilisation during an approach, are part of the problem. To some extent, these can be addressed through training, audits and moves to harmonise standard practices in different jurisdictions. Harder to manage, however, are the risks posed by external factors.
“For unstable approaches, the air traffic controller must ensure aircraft are correctly handled and vectored appropriately to enable pilots to fly a stable approach and avoid as far as possible making late runway changes,” says Paul Adamson, former head of airports network manager at Eurocontrol, who has been officially seconded to ICAO. “Weather conditions can be a key factor; for example, if the aircraft is landing with a tailwind.”
Some threats to runway safety are beyond the influence of the flight crew or air traffic control, although they need to respond to them. Meteorology is the most obvious and, perhaps, most significant of these. Storms, poor visibility, wind and icing are all major risk factors influencing runway excursions. So, too, is poor aircraft braking action due to contaminated runways. In fact, according to the Flight Safety Foundation, ineffective braking due to runway contamination is the third-most common factor in runway excursions.
The effect of this categorising the many potential risk factors that could lead to excursions is that ICAO has been able to determine how to effectively mitigate them through standards and training programmes, as well as through new processes and technology.
For example, the Global Runway Safety Action Plan, which is linked to the ICAO Global Aviation Safety Plan, has a new approach to addressing imperfect runway assessment and reporting methods on factors that have contributed to the problem of runway excursions caused by meteorology and runway contamination.
“The plan was developed last year after an analysis of runway safety risks, which concluded that excursions and incursions are two major high-risk categories,” notes DeCouto. “The action plan lists many contributory factors, among which are meteorology and contaminated runways. That is why we developed the Global Reporting Format (GRF) for runway surface conditions.”
A global response
The GRF, which is scheduled for deployment in 2020, draws on international best practice to provide a system for reporting runway surface conditions in a standardised manner. With such a system in place, flight crew will be able to accurately determine appropriate aircraft take-off and landing performance in any conditions.
The system relies on operators undertaking on-site assessments of runway surface conditions whenever meteorological risk factors are present. They can then report a Runway Condition Code (RWYCC) with a value of zero to six, plus a description of the runway surface based on universally accepted terms and definitions. The code is based on the effect of the runway conditions on aircraft braking performance.
“The GRF relies on trained airport staff who can go out to visually assess the contaminants on the runway and allocate the runway a categorisation ranging from zero, which means a less-than-poor braking action on, for example, wet ice, up to six, which is a good braking action on a dry runway,” explains Adamson. “Pilots can translate this categorisation into the aircraft’s braking capability.
“The intention is that everything will be done in a standardised way everywhere in the world, so the reports cannot be misunderstood. The system is simple in its structure and approach, it has been discussed through many panels and fora, and the development process has been rigorous.
The challenge is now its implementation.”Part of the challenge will be getting the information to everyone who needs it – whether it is at a small airport in the Hebrides or the safety teams at busy international hubs. Even if that is done effectively, however, the GRF is only part of the solution.
“Everything is interconnected. For example, to help avoid unstable approaches, the ATC should recognise if an aircraft is too high or too fast on its final approach,” Adamson says. “Another example is, the runway must be properly lit to guide pilots.”
– Brian DeCouto, ICAO
The destination is in sight
Coordinating the industry around the GRF is a mammoth task, but ICAO is looking at short-term and long-term solutions to ensure that runway excursions – and other safety risks – are well managed in an age of higher air traffic.
“There are so many stakeholders,” says DeCouto. “So many people need to do their part to have a significant impact on the number of runway excursion events. Air traffic controllers, airports, airlines, civil aviation authorities, ground handlers and others need to be involved.
“We encourage airports to establish multidisciplinary runway safety teams to meet and discuss runway safety risk factors and come up with mitigation strategies. We need to improve training and standards. Irregular oversight by individual states is an issue, so we are encouraging states to establish national runway safety programmes.”The next big challenge will be to link the reporting of runway conditions directly with aircraft performance. The harmonisation of different friction-measuring devices and their linkage to performance is a long and ongoing process, but bringing together runway surface friction data and other factors across different states, regional authorities and international organisations will be a huge step forward.
“Research is going on to correlate the braking capability of an aircraft with runway surface conditions but understanding the relationship between an aircraft braking and runway surface conditions is a complex topic,” explains Adamson. “It involves so many parameters – the relationships between use of wheel bakes, including autobraking, flap deployment, the reverse thrust and the aerodynamics.”
As that process develops, however, other technologies such as engineered materials arrestor systems (EMASs) will become more common. These consist of high-energy absorbing materials at the end of a runway that can rapidly slow down an aircraft in the event of a runway excursion.
“The long-term actions outlined in the runway safety action plan include that manufacturers should continue to develop technologies to address the problem of excursions,” says DeCouto. “These include overrun awareness systems and real-time monitoring systems for unstable approaches.”
Long-term planning is key to ICAO’s vision, as airport infrastructure strives to match growing demand.
“Runways are hard to plan and build, as the UK has found out recently, so the industry will try to squeeze more traffic into existing runways,” notes Adamson. “We need to anticipate opportunities and obstacles to realise this higher runway throughput.”
