Aireon real-time surveillance consigning OTS to history

NATS and NAV CANADA trials of Aireon’s satellite-based ADS-B system to track aircraft flying through NAT oceanic airspace are starting to show significant potential benefits for their airline customers.

Satellite-based ADS-B technology is allowing the air navigation service providers to progress from the traditional, procedural form of control where aircraft report their position every 14 minutes, to one which is virtually real-time, with track updates every few seconds.

“That transformation means we’ve been able to begin reducing aircraft separations and for airlines to begin flying at the speed that best suits them,” said Andy Smith, NATS’ head of strategic oceanic engagement. “That’s in addition to the clear safety benefit of having real-time surveillance and conformance monitoring (i.e. knowing that an aircraft is complying with the clearance they’ve been issued), something we believe will significantly reduce the estimated risk of a collision.”

Smith reported that in terms of the trial itself, of the 113 million ADS‐B reports received in April, all arrived within the target eight second update rate, with some as low as 3‐4 seconds. The average time it took for those position reports to reach a controller was 0.17 seconds against a target of two seconds.

“That’s truly incredible given the journey that data makes from the aircraft, through Aireon’s satellite network, then to its ground station before reaching our ATM system.  But of course that’s only half the story. What’s more important is what that data is now allowing us to do.”

The high update rate, low latency, real-time surveillance means the ANSPs have been able to safely reduce the distance between aircraft (14nm nose to tail, down from 40nm) and offer airlines that were previously assigned fixed speeds and heights the opportunity to take advantage of more flexible flight paths and optimum trajectories. “That is reducing fuel use and greenhouse gas emissions, and helping them maintain their operating schedules,” said Smith.

He said that between 15 April – 27 May, around 12,000 flights flew their optimum speed for a total of 620,000 minutes which could one day allow the ‘streaming’ of aircraft into busy airports from further out in order to reduce the amount of stack holding on arrival.

These reduced separation standards signify the end of the Organised Track Structure (OTS) which was designed to add additional oceanic capacity with a series of set routes designated each day, taking into account the location of the jet stream, to permit aircraft to efficiently cross the North Atlantic.

“Being able to reduce separation standards and offer greater flexibility on routes, speeds and levels means 62 per cent of traffic now doesn’t need to use the OTS at all, compared with 50 per cent in 2015,” said Smith.

“That’s a trend we will now see accelerate as we continue to unlock all of the service improvements available to us through Aireon and our deployment of our new standards. Over the coming years, we estimate that 90 per cent of airspace users will be assigned their requested trajectories, something that will support the progressive reduction and eventual removal of the OTS.”

Smith reported that the next project milestone will be the reduction of the lateral separation minima from 23nm to 19nm and then to 15nm this autumn.