Many airports in major European cities are under pressure to increase their capacity and straightforward site expansion is not always feasible. Another factor operators need to take into consideration is that more traffic likely brings more noise that may disturb residents living near the airport.

To tackle both of these issues, SESAR Joint Undertaking (JU) members have developed staggered threshold approach procedures for closely spaced parallel runways, and new tools to improve efficiency for air traffic controllers dealing with both departing and landing planes.

SESAR JU founding member EUROCONTROL has been developing and validating the concepts with SESAR members DSNA and Thales using a suite of simulation software that generated real-time scenarios based on Charles de Gaulle Airport in Paris, France.

The static pairwise separation for departure concept is intended to help increase the number of aircraft taking off, while the staggered threshold concept focuses on planes that are landing. Staggered thresholds have been used to increase efficiency in the management of separation minima (the rules applied by air traffic controllers to keep aircraft a minimum distance apart) in relation to wake turbulence. The arrival staggered threshold concept is applicable at airports with closely spaced parallel runways.

ATC separation delivery tools for dependent parallel approaches

For planes landing on parallel runways, staggered thresholds allow for decreased wake turbulence separation minima by using the height difference between the glide slopes of each aircraft when it is coming in to land. Aircraft landing paths are organised by weight, with heavier planes using different and lower glide slopes to the lighter ones.

“In simple terms, larger aircraft types produce stronger wake than smaller ones,” says Frederic Rooseleer, runway performance expert at EUROCONTROL. “This needs to be carefully considered during take-off and landing, and that is why wake turbulence minima standards are today specified and applied to protect successive traffic when approaching and landing onto the same runway or closely spaced parallel runways.”

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Medium and light aircraft will be less exposed to wake turbulence created by the heavier jets, by being allotted to the upper glide slope on the parallel runway using the staggered threshold. Meanwhile, the heavy and super-heavy aircraft land by using the lower glide slope on mixed runways that also run departures.

“Larger aircraft types produce stronger wake than smaller ones.”

To support air traffic controllers in arrival separation management, a tool developed in collaboration between EUROCONTROL and Thales is used to optimise approach and runway throughput. Optimised runway delivery (ORD) helps to enable greater safety and efficiency on final separation.

Another tool for Optimised Separation Delivery (OSD) on departure has also been developed through using extensive operations data. It is able to predict the ground roll before take-off for aircraft and the subsequent climb rate. It may seem obvious, but the more predictable something is, the easier it is to manage.

The new combined operational solutions have the potential to provide substantial advantages for operators in peak traffic periods for both departures and arrivals, helping to boost runway capacity by as much as 10%. These techniques also enable noise from approaching aircraft to be reduced in case one of the thresholds is moved forward to create the necessary stagger

“In this case, the aircraft noise footprint is brought closer to the airport,” explains Rooseleer. “For the nearby population, you can notice a difference in terms of reduced exposure to noise for approaching aircraft. Alongside this, these approaches have the potential to reduce CO2 emissions as reducing the flight time or by reducing delays thanks to the extra capacity.”

Optimising separation delivery with dynamic indicators for departing aircraft

For aircraft taking off, air traffic controllers have been validating a dynamic departure indicator (DDI) tool, which has also drawn on machine learning in its development. The solution has been designed to organise departure separations and any necessary restrictions for outbound flights in terminal control areas.

“It is possible for air traffic controllers to safely cut the time between providing take-off clearances to increase efficiency.”

The DDI factors in an aircraft’s overall performance with its speed and climb capabilities to then calculate the safe spacing required between departure traffic. DDI provides the controller with easy access to all the information that is needed for operations.

During SESAR JU’s validation tests, it was confirmed that it is possible for air traffic controllers to safely cut the time between providing take-off clearances to increase efficiency without any negative effects.

Data in this project will be used by other airports across Europe seeking to optimise runway operations and in turn expand available capacity.

In 2020, the dual threshold procedure – variant for single runways – is planned to be tested in a real-world environment at a site in the Netherlands. Should they prove successful, it is then hoped to further validate the procedures at other operational sites across Europe.

On their own, the two procedures will already make a visible contribution to improving operations efficiency at airports, which can be further used with other processes and technologies being developed. This combination will make a substantial difference in improving airport safety and throughput. The ultimate plan is to help optimise air traffic operations for airports throughout Europe.

“These enhanced approach procedures are part of a set of airport performance solutions,” adds Rooseleer.

Inside a new project to boost airport throughput

The procedures form part of the larger SESAR 2020 project PJ02 – EARTH – Increased Runway and Airport Throughput. The project was conceived to address the challenges associated with capacity at major European airports such as adverse weather and other ambient factors, noise, as well as the surveillance minima and runway occupancy time.

“Thanks to the gain in runway throughput, airport operators are better able to react to unforeseen circumstances.”

“During peak periods at major airports, we have found that runway throughput can be improved by up to 5% due to separation minima being lessened for some aircraft pairings thanks for example to the use of a second runway aiming point (SRAP) onto single runway. And greater gains can be achieved when operated in combination of RECAT-Pair-wise scheme,” adds Frederic Rooseleer.

“Alongside this, our analysis for predicting aircraft speed behaviour and optimised separation indicators using the machine learning techniques tests have found that it’s possible to achieve an increased and stable landing throughput across headwind conditions when using time-based separation.

“Thanks to the gain in runway throughput, airport operators are better able to react to unforeseen circumstances and adverse conditions, reducing delays and increasing resilience as a result.

“As SRAP allows landing further onto the runway, it can also benefit the runway traffic occupancy time and reduce the taxi-in time to the terminal, depending on the runway and airport layout.”

With airports getting busier, SESAR JU members are developing technologies that are intended to make it possible to increase safety and efficiency alongside the rising number of aircraft landing and departing.