ASAS Interval Management, Real Time Simulations

Automatic distance

Peak hours? The on-ramp traffic lights makes merging onto the motorway easier. Long queues at the till in the supermarket? An extra till opens up. Or better yet: we use the self-scanners so we don’t need a cashier at all. We are always developing new means and methods to use our time and space more efficiently. This also applies to the aviation sector. More and more air traffic means we need to develop new ways to ensure a smooth operation in the air. Interval Management is the answer to increase efficiency.

The Dutch aviation sector (KLM, Amsterdam Airport Schiphol, LVNL), together with the Department of Infrastructure and Environment have jointly committed to develop a new concept for the Schiphol terminal airspace operations. This concept consists of fixed arrival routes and continuous descent operations. It is expected that the current night operation at Schiphol will gradually be expanded into daytime off-peak hours, provided that new support tools become available to manage the inbound traffic.

New technological solutions will open new doors
For Schiphol operations a new handling concept is developed with fixed arrival routes and continuous descent approaches. The aviation sector agrees that fixed arrival routes are desired from the edge of the TMA to the runway related to predictability and enabling continuous descent approaches. Fixed arrival routes, like standard instrument departures have the tendency to negatively affect capacity and Schiphol can afford no loss of capacity. Therefore, research is done for innovative ways to handle the incoming traffic, to make high capacity combined with fixed arrival routes possible.  

Flight Deck Interval Management is precise and predictable
One of the pillars under the SESAR concept is Flight Deck Interval Management (IM). With IM, aircraft exchange flight information via ADS-B and use this information to control an ATC assigned time interval with a lead aircraft. It is assumed that this close loop control provides the accuracy and predictability that is required to maintain peak hour capacity. For the Schiphol terminal airspace IM may be an enabler to expand fixed arrival route operations and CDOs into peak hour operations. 

How does the IM Concept of Operations work?
For Schiphol, IM operations start with Amsterdam Area Control (ACC) using an Arrival Manager (AMAN) and other tools, such as the Speed and Route Advisor (SARA), to build up a properly spaced sequence of aircraft to the designated runway. From this planned sequence, aircraft pairs can be determined. Each pair consists of an IM aircraft and a lead or target aircraft. The target aircraft may initially be on a different route. 

The aircraft receives an IM Clearance
Prior to entering the TMA at the IAF, the IM aircraft will receive an IM Clearance. The IM Clearance, communicated over radio, includes:

  • the target aircraft identification and route;
  • ATC assigned spacing interval;
  • the point where to achieve this interval. This point lies 10 km before runway.The flight crew acknowledges reception and enters the data into the on-board equipment. The flight crew assesses feasibility of the IM Clearance and initiates the IM operation. Upon reaching the final approach segment, the spacing interval is achieved with an accuracy of approximately 10 seconds and the IM operation is terminated. The flight crew will from thereon fly speeds either in accordance with the final approach procedure or as instructed by the Schiphol Approach controller. 

The results of initial IM-fast-time simulation studies
KDC IM research exists of 4 phases. In the first phase Schiphol requirements were fixed. During the second phase of the development of the IM-concept Schiphol IM-fast-time-simulations were performed to evaluate the IM-performance. The outcome of the study is positive: IM separation can generate the required performance in the Schiphol TMA environment, allowing high-density operations on fixed arrival routes. 

The results of the IM-real-time simulations
The third phase of the IM concept for Schiphol progressed with IM real-time simulations (RTS) to assess controller acceptance and workload and to evaluate the IM procedures and IM support tools. The RTS study was performed at NLR’s ATC Research Simulator (NARSIM). A number of aspects were varied during the RTS. These variations included: 

  • the traffic density (26, 32 and 36 landings per hour per runway);
  • level of FIM equipage (5%, 50% and 95%);
  • wind conditions (light, moderate). 

Furthermore, a number of non-normal events were tested, e.g. an incorrect target aircraft selection.  

What were the main conclusions of the RTS? 

  • All controllers readily accepted and appreciated the IM Concept of Operations and were able to safely and efficiently manage the arrival traffic in all scenarios, including non-normal events, with the newly developed HMI.
  • Perceived controller workload was generally well within predefined targets in all scenarios. 

The next step: IM-flight trials
KDC and the Dutch aviation sector continue to develop the Schiphol IM-concept. The next step is to develop an on-board IM-system and run a series of flight trials to test this system in real life. The objective is to demonstrate technical feasibility of the on-board IM system.  

The development of a preliminary version of the IM system has been put in motion. The system, with algorithms developed by NASA, will be built in NLR’s Citation II test aircraft. Flights tests will take place in the first quarter of 2017.

Scenarios will be tested in which the IM aircraft and target aircraft fly the same fixed approach route. Also a scenario will be tested in which two planes initially fly different approach routes which merge onto the same route. System development and testing are supported by an international team of experts from LVNL, KLM, NLR, TU Delft, Boeing, Rockwell Collins, NASA and EUROCONTROL. After this test flight, the plan is to develop and test the actual IM avionics.

Parties involved
LVNL, KLM, NLR, TU Delft, Boeing, Rockwell Collins, NASA, EUROCONTROL

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