Every day between two and three thousand aircraft fly across the North Atlantic, with the UK – and NATS – acting as the gateway to Europe.
Up to 80% of all Oceanic traffic passes through the Shanwick Oceanic Control Area (OCA), which is airspace controlled by the United Kingdom. With this in mind, we created a data visualisation showing a day of traffic from August last year and the oceanic airspace structures that help to make it all work.
NATS controls the Shanwick OCA – made up of 700,000 square miles of sky – from our Prestwick Centre in Scotland. On a typical summer’s day we handle around 1,400 flights across the North East Atlantic, working to safely and efficiently shepherd them from the ocean to their final destinations, whether that’s in the UK, Northern or Southern Europe or further afield.
Controlling without radar
As you can see, the traffic is all fairly uniform, following very clearly defined routes. That’s because Oceanic airspace is unusual in that aircraft are not controlled using radar – radar is limited to about a 250 mile range – so we rely on pilots giving reports – either via satellite or High Frequency radio – at regular intervals and we use these reports to maintain separation between other aircraft.
In Oceanic airspace routings and reporting are based on latitude and longitude. Every ten degrees of latitude pilots make a report giving present position, height and the next two positions that they are intending to route. The controller can check that the flight is routeing in accordance with his clearance and amend or deal with any requests as required.
Traditionally, pilot reports were made using radio on High Frequency to operators in Shannon, Ireland. However developments over the past 10-15 years mean that now 80% of pilots can make these reports via satellite links from the cockpit direct to the controller. Controller–pilot data link communication systems enable the sending and receiving of text based messages, thus cutting out the requirement to make verbal reports.
In radar airspace there is either 5 Nautical Mile (nm) or 3nm separation minima laterally between aircraft, however in Oceanic it is 60nm laterally and for aircraft following on the same route it is based on time – essentially 10 minutes apart. For aircraft crossing another aircraft at the same level it is increased further to 15 minutes. Therefore it’s vital we get accurate reports from pilots to ensure that separation is safely maintained at all times.
The North Atlantic Tracks
A major factor in the routeing of flights over the Ocean is the wind direction. There are huge jet streams over the Atlantic, predominantly flowing west to east at up to 150mph at between 30,000 feet and 40,000 feet.
Due to the amount of traffic flying at the same time and position of those jet streams, many flights want to fly at the same place at the same time. If we allowed all the flights to fly exactly where they wanted, we would actually reduce the capacity of the airspace because of the need to increase the separation between aircraft that cross each other.
Therefore we use a system to rationalise the traffic that sees them following one after the other, almost like roadways in the sky. This rationalisation is what we call the ‘tracks’ – something that you can see very clearly in the visualisation.
Every night, Airline Operators send their preferred routeing for all their flights to the Prestwick Centre based on winds, cost, airspace restrictions etc and we then take the area where most of the traffic wants to route and design a set of routes using latitudes and longitudes and label these from Alpha upwards.
The operators are then advised that night and if they wish to route within the area where the tracks have been designed for the following day they must follow the track structure. This system works well as it gives the airlines the opportunity to shape where the ‘tracks’ will be and also allows them to flight plan well in advance of the following day.
How technology is changing
Due to the demand within the Ocean and the fact that it can be quite restrictive due to the large separation requirements it is an area that is constantly evolving and looking for improvement.
On many occasions Oceanic airspace is at the cutting edge of new technology or big changes of procedures. For example, changing separation from 2000 feet to 1000 feet was first brought in on the Atlantic before being introduced some time later round the rest of the world.
Oceanic airspace is also the first to be using satellite technology for communication and controlling purposes, with Automatic Dependent Surveillance-Broadcast (ADS-B) and Automatic Dependent Surveillance-Contract (ADS-C) tests being trialled some time ago and now being used on a daily basis.
All of the changes in technology will deliver a much greater degree of predictability which means the aircraft will be able to fly more optimal routes carrying less fuel and therefore operating more efficiently.
Facts and stats
The Shanwick OCA is the busiest of all North Atlantic Airspace regions. It is often referred to as ‘the gateway to Europe’ and around 80% of all North Atlantic Air Traffic passes through it, demonstrating the strategic importance of our Prestwick Centre and UK airspace.
The visualisation shows Transatlantic traffic over a 24 hour period taken from a day in August last year and includes 2,524 flights, of which 1,273 pass through the Shanwick OCA. At our busiest periods in the Summer, traffic can peak at 1,500 flights a day passing through the Shanwick OCA.