Vision On

There has been much debate about the concept of remote tower services but the Swedish experience suggests they are ready for the real world, writes Fearghal O’Connor

In his entire working life as a tower controller, Mikael Henriksson claims to have seen just three key developments.

“We got sunshades for the tower windows, we got thicker glass for the noise and we got flycatchers. But with remote tower services the air traffic control tower is now moving from the propellor age to the jet age.”

Henriksson has been operational project manager for Swedish air navigation service provider LFV since it began testing remote tower technology in 2010. He detailed his experiences at a recent conference at Dublin Airport, entitled “Unpacking SESAR Remote Tower Services”.

“When a controller sits in position and looks to their right they actually see what is going on behind them, which takes a little getting used to,” Henriksson told the conference.

That’s because although the high quality cameras at the airfield capture a 360 degree view, the images are displayed to the controllers in the Remote Tower Centre (RTC) using a 225 degree array of screens, he explains.

“For some this was strange. But our operational experience has been that you adapt easily and we equally saw benefits. It is more convenient, you have a better overview and without moving your head you can actually see a large area. You just need to look left and right to see all around and behind you,” he says.

LFV Image 2BInitially, the Swedish air traffic controllers bemoaned the fact that they could not use the type of visual separation they were accustomed to using while standing in a tower.

“Okay,” joked Henriksson to his colleagues, “let’s use screen separation instead.”

But the joke sparked a thought for Henriksson. After sitting down with a pen and paper he proved that controllers could in fact use the screens for visual separation because of the high quality image resolution. To help achieve this, LFV recruited one of the best image quality specialists in Swedish television.

Requirement

An important requirement for the team was to ensure that there was no more than a one second delay on the image as broadcast in the RTC. The team has now got that delay down to below 0.8 seconds. This is quite an achievement given that it involves 14 cameras, including infrared, shooting 60 frames per second. These images must then be compressed, sent down a 150 kilometre line, decompressed and presented on the RTC screens with absolutely no flicker,

“You cannot have an image for a controller where something appears to be moving. We worked a lot with image quality, performance and processing. We discovered a lot of things that can fool the cameras but that can be adjusted.”

While a huge amount of planning went into getting the very best image quality from the setup, sometimes practical operational experience threw up important solutions to key problems, says Henriksson.

The cameras used are equipped with filters to deal with a range of different reflections. But the LFV team discovered that by using a sun filter they could trick the camera into improving its compression rates in misty conditions, making it easier to see aircraft on the screen. The use of the filters also made it easier to identify the type of cloud cover, the Swedish controllers found.

Another curious discovery also started as a joke.

“My colleague was complaining that he missed using his binoculars in the tower. So when nobody was looking I took a pair of binoculars from the tower and I stood inside the RTC looking through the binoculars at the screen. We realised that with the right type of binoculars with a narrow focus angle works perfectly because of the quality of the image on the screen.”

“Every day we have more ideas when we are working with these screens,” he says.

The system was handed to the operations team in LFV at the end of 2012 and during the following year the team put it through a huge amount of system verification. During spring 2013 LFV ran a ten-week passive evaluation, meaning that it ran a normal operation in the tower alongside the new system, following which a validation report was produced. That raised some new issues that needed to be dealt with.

LFV Image 3BThe Swedish aviation regulator has been involved since 2011 and the project team has delivered more than 200 detailed documents to them that when stacked on top of each other come to a height of over one metre. The team finished its own validation of the technology in 2013 and has been waiting ever since for final approval to allow the technology go fully operational, which it hopes to achieve this autumn.

Basic System

The team made a conscious decision to keep the system as basic as possible for the approval process, even though it was involved in developing a whole range of more advanced tools that could in the future greatly enhance the technology. For example, the team has already developed a working “sliding window” system that allows controllers in the RTC operate on two different remote airports. Nevertheless, it was decided from the beginning that key to the success of the project was to win approval for a basic setup that did not require a whole raft of new regulations.

“We have never ever been closer to operational rollout for this technology – we are just waiting. It was a complex proposal but we have gained a lot of experience. For me, I have been involved with this project since 2010 and so I am eager for it to finally get up and running. But I fully respect that this is a period of learning. The regulator needs to be confident with this complex system. But we have learned a lot and so have they.”

Other stakeholders also need to be confident that the system works and they have not been shy about showing up at Henriksson’s door.

“As soon as we had something to show we had visitors. The Swedish Air Traffic Controllers Association and the trade unions have been directly involved in the projects. The door has also been open to airport managers, pilots, airport staff. When you actually go inside that operational environment you really feel that it is operating.”

The whole project moved up a gear during the most recent phase of advanced validation that saw the RTC take full operational responsibility for the first time, with a controller in the tower at the airport only there as back up.

LFV lead imageB“The guy in the tower was only goalkeeping,” he says. “One thing we realised during this phase was that the airports and airlines couldn’t tell whether we were running from the tower or the RTC because we were providing the exact same service. During this period, at times we would operate from the tower and at other times we would operate from the RTC just to see if anybody noticed the difference. Nobody noticed. We provided the exact same service from both without the need for any special call signs or anything like that.”

As of today more than 100 of our controllers have been in the facility, they have worked with the technology and they have felt the environment. A key advantage of the new working environment for the controller is that a range of different systems feed into one display meaning weather information, flight information and other key data can be displayed directly.

“The goal of this is to reduce the workload of the controller so that he can focus on the new presentation, allowing him to have access to information directly rather than having to find it in different systems,” says Henriksson.

Key to the success of the project was the decision to comply fully with existing regulations. This means tower controllers can work the new system with their existing rating and licence after taking a number of days training to learn the specifics of the RTC system. From an operational standpoint the complexities remain in the background.

“You can’t put that in the face of the controllers so we had to make a new integrated alarm system and combine that with extensive fallback procedures and this is something we are very proud of. It is very effective.”

Although regulations for now are likely to restrict the remote system to use at airports with less than 50,000 movements per annum, Henriksson says that his team does not see any operational limitations, in its own environment at least, for the amount of traffic that can be handled. How long it will be before regulators and the industry at large is as convinced remains to be seen but the Swedish team appears upbeat.

“It is a controversial project so of course there were a lot of people who says it would never work,” says Henriksson. “But when controllers come into the new environment after a while they start to see things that they would love to have back in the tower. There was one guy who was 100 per cent against it from day one. But then he came into the centre and after five minutes he says to me ‘I’m a true believer’. It was great validation to hear that from someone who had been so opposed.”

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