How do we make our airspace ten times safer?

The Single European Sky ATM Research (SESAR) project is bringing many changes to air traffic management (ATM) and it has lofty goals. Improving ATM processes is intended to up capacity, reduce delays on the ground and in the air, increase safety by a factor of ten, reduce the environmental impact of the aviation sector and bring down the cost of ATM for airspace users.

SESAR will mark some fundamental changes in the way traffic flows are managed in the sky and at airports, and requires a lot of work in terms of developing both the technology and the skills of the people who will operate the new systems. Safety is, of course, of prime importance.

"The most radical change to ATM will be the move away from the concept of airspace and towards trajectory-based operations," says Eric Perrin, team leader for safety at EUROCONTROL. "That is a shift from tactical ATM and will reduce the number of conflicts before take-off. There will be more direct routing, more closed-loop instructions, fewer vectoring instructions and a reduction in holding stacks over an airport.

"There is a battery of tools to support ATM controllers and there will be changes in pilot flows, which is very important for safety, but the cornerstone is a change in the way information is used," he adds.

Information flow

The use of information will be handled by system-wide information management (SWIM), which serves as an intranet for ATM. Early information sharing and coordination is one of the most important parameters for safety, and SWIM will control information flows for aircraft, airports, air traffic controllers and air navigation service providers, airline and military operation centres, ground vehicles, flow management centres and weather service providers.

SWIM will replace the systems that have evolved independently to manage information flows, which have so far relied on sub-system and service-specific functionality. The current model means ATM information systems are insufficiently integrated and the flow of key data can be slowed down as it passes through the different cogs of the machine. The new information infrastructure will connect all ATM stakeholders, aircraft and ground facilities in a seamless loop.

The implementation of SWIM will impact passengers by reducing delays and congestion. It will also improve environmental performance by making the most accurate information on weather, air congestion, ground conditions and so on readily available, reducing unnecessary reroutes or taxiing on the ground.

The result will be less fuel burnt and resources used more efficiently. Crucially, SWIM will also improve safety through better and more efficient decision-making. Pilots, controllers and dispatchers will all have the same information in near real time, meaning they can react more quickly to changing circumstances.

Less room for error

"The move from voice radio to data link means there is less room for erroneous interpretation of directions, although we do lose the 'party line' function, which means it is harder for the flight crew to develop a mental picture of the information," explains Perrin. "There will, however, be an improvement in the accuracy of ground-based trajectories. With better trajectory prediction on the ground, it will be easier to sort out potential conflicts."

There are many elements of SESAR that are intended to improve safety. For instance, airborne collision avoidance system (ACAS) alerts can be automatically resolved by ATM services. There are also changes to the way altitude data is captured to minimise false ascents, and runway throughput and weather-based operations will be upgraded to reduce inaccuracy and minimise an aircraft's runway occupancy time. A suite of new tools to improve airport surface movement and reduce runway incursions will also be introduced.

"Basically, we are moving to 4D trajectories with better ground tools to detect conflicts. The only potential negative safety impact will be that we are reducing physical separation, which means the wake of the aircraft could be stronger, but we are looking closely at that," says Perrin.

Transition to SESAR

There are clear safety goals woven into the fabric of SESAR, and the switch to a new ATM model is a prime opportunity to look closely at all the risks to see how they can best be mitigated. Everything is under review, from runway incursions to controlled flights into terrain (CFIT) - accidents involving an airworthy aircraft under pilot control that is intentionally flown into the ground or an obstacle.

"The design target for SESAR is to keep the number of accidents the same, even if the volume of traffic increases. This can be done with better tools on the ground to support air traffic controllers. In fact, there are many potential routes to maintain the current safety levels despite an increase in traffic. The complex thing is the transition," says Perrin.

"SESAR involves a higher level of automation, but the human element is still pivotal," he stresses. "Engineers, pilots and controllers all play essential roles, and they are so critical that all aspects relating to human strengths and weaknesses are part of the development process. People and technology are on an equal footing."

The transition process involves a series of incremental improvements in technology. It is not, however, purely technological. It is important that the ATM system can revert to the existing standard model if SESAR fails. As a result, comprehensive training is vital for everyone involved.

"You need training on the new tools, but you have to keep the former ATM skills in place in case you need to revert. There are more than 200 ATM changes in SESAR, so any delay will have an impact on safety. We must also look at developments in adjacent airspace as we need contingency plans to revert to the old way of doing things if the occasion arises," notes Perrin.

"The process of reaching the SESAR end state is a long one and we have to maintain safety throughout the transition," he continues. "We have a set of risk modelling tools at EUROCONTROL to help us do this. It is not about meeting a deadline. Since the financial crisis started, we have not attached any dates to the three steps involved in SESAR. Instead, it is all about capability. SESAR is a big animal and we have never before carried out such a big safety assessment in the area of ATM."

A tenfold safety improvement

One of the goals of SESAR is to increase safety by a factor of ten. This seems at once highly desirable and incredibly difficult. Improvements of that magnitude in any endeavour are very hard to achieve, so the people behind the project are careful to define what the target means in order to get a realistic perspective on whether efforts to improve ATM are delivering on that goal.

"There is a long debate about what that target means. A tenfold improvement does not refer to reducing the number of accidents by a factor of ten - the number of accidents is already low. It means reducing the risk of collisions, runway incursions and CFIT. The challenge is to turn that goal into design components for SESAR, so we use a lot of risk-modelling scenarios to help us do that. We have to take a sensible approach to it," says Perrin.

Charting progress

As it stands, the European ATM master plan has been accepted and the target for safety has been sensibly interpreted as keeping the number of accidents stable in the face of increasing passenger numbers and air traffic volumes.

"The next milestone is dealing with step one of the overall concept," explains Perrin. "We have a rigorous engineering approach and we aim to reach the stage where the product is up to the pre-industrialisation phase. This means that we are happy with the information collected about SESAR's ability to achieve the desired performance through the design. We will then look at the certifiability of the products before moving to the industrialisation phase for things like 4D trajectories and the ground tools.

"After that, we move to steps two and three, which will deliver operations that are entirely performance and trajectory based," he continues. "The safety people are heavily involved at every stage, assessing whether SESAR is effective enough to achieve its safety targets and looking at how the design could be improved.

"We are part of the design process, which shows that SESAR has a much broader approach to safety assessment than before. Safety is fundamental, not an afterthought."