ATC - Introducing SRAP - Secondary Runway Aiming Point - Avionics Intl.

Eurocontrol Evaluates Feasibility of Secondary Runway Approaches

By Woodrow Bellamy III | November 22, 2019
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Eurocontrol is evaluating the feasibility of "Secondary Runway Aiming Point" arrival procedures to increase runway throughput at busy European airports. Photo: Eurocontrol

Eurocontrol is evaluating the use of new airport arrival procedures, called Secondary Runway Aiming Point (SRAP) approaches, that the agency believes can increase runway throughput by up to 5 percent at some of the busiest airports in Europe.

SRAP is one of the concepts Eurocontrol is evaluating for the Single European Sky ATM Research Joint Undertaking (SESAR JU) project “Enhanced Arrivals and Departures,” which aims to deploy new tools and procedures that can increase the capacity of terminal areas at European airports. Eurocontrol describes SRAP as allowing “light wake” category aircraft to fly a final approach that occurs above the profile of heavier aircraft flying to the primary runway threshold.

The concept would allow a lighter aircraft such as an Airbus A319 to avoid the turbulence generated by the wake vortex of the heavier aircraft, such as a Boeing 777, enabling increased throughput by allowing both aircraft to land on the same runway. Frédéric Rooseleer, implementation support coordinator for airport performance at Eurocontrol told Avionics International that his team used a full motion Airbus A319 flight crew training simulator operated by Lufthansa Aviation Training, to assess the feasibility of SRAP.

Across multiple simulator sessions, the team used a normal three-degree glide slope and an increased glide slope (IGS) along with a visual system that replicated the way runway markings and approach lights would appear when flying the real approach.

Secondary Runway Aiming Point (SRAP) approaches would allow a lighter aircraft to fly above the approach profile of a heavier aircraft while avoiding its wake vortex. Photo: Eurocontrol

“In the flight simulation campaign, a set of visibility conditions were evaluated, ranging from good visibility greater than 10 km to visibility above 2,500 m, excluding the low visibility conditions,” Rooseleer said.

The simulated SRAP approach evaluated was an arrival procedure into Germany’s Munich International Airport. A total of 24 A319 type-rated pilots participated in two variants of the SRAP concept, including one where all the approach lights were illuminated and another where just the runway threshold and approach lights were illuminated for one aiming point that only served the first aircraft in the approach sequence. Once the first aircraft landed, the threshold and approach lights for the next aircraft were switched on.

Eurocontrol used video recordings of flight parameters, including three-dimensional positioning, vertical speed, airspeed, thrust and weight to assess approach and landing performance of each flight crew. Rooseleer said the SRAP concept only has avionics equipage requirements for approaches that use navigation guidance, such as a Ground Based Augmentation System (GBAS) Landing System (GLS) or required navigation performance (RNP) localizer with vertical guidance (LPV) approach based on an aircraft equipped with a satellite based augmentation system (SBAS) receiver. There are other exceptions as well.

“In case of IGS-to-SRAP concept however, combining SRAP with Increased Glide Slope, additional onboard flight assistance functions to pilots may be needed for some aircraft types in order to facilitate energy management and flare when the slope is increased between 3.5 degrees and limited to 4.49 degrees maximum,” Rooseleer said. “On the airport ground infrastructure, both SRAP and IGS-to-SRAP are to be supported with the implementation of specific visual aids, covering a second set of the runway markings, Approach lighting system and Visual Approach Slope Indicators.”

Eurocontrol is currently compiling a full report on the flight simulations to be submitted to SESAR JU by the end of January as part of the consortium’s broader enhanced runway throughput project validation report. Additional trials are planned over the next year, with Eurocontrol aiming to make SRAP a reality by 2023.