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Terminal Area Operations in the Airspace Operations Laboratory is focused on the problem of how to support air traffic controllers in safely and efficiently managing arriving and departing aircraft within a few hundred miles of the airport.

Most current aircraft are capable of flying precise trajectories from cruise altitude to the runway. Some aircraft are capable of controlling their speed so as to arrive at a specified point at a precise time. Other aircraft can be given clearances to precisely space themselves behind another aircraft.

The air traffic control systems task is to use all of these capabilities to safely deliver aircraft to airport runways while allowing aircraft to fly fuel efficient, low noise trajectories.

In the Airspace Operations Laboratory we are developing automation, displays and procedures to support air traffic controllers in efficiently controlling aircraft capable of flying these precise trajectories.

Our approach is to develop emulations of the key air and ground automation, develop procedures for controllers and pilots and then evaluate the new concepts in human-in-the-loop simulation. These simulations allow subject matter experts to experience what it would be like to operate a future system in both normal and abnormal situations. One result of these simulations is a better understanding of how the future concept could work and the possible roles and responsibilities of the humans in the system.

Concept for Managing Arriving Aircraft:

The transition to super-density operations (SDO) capability at busy hub airports in metroplex areas in the mid-term timeframe will involve controllers managing traffic on RNAV RNP routes that allow capable aircraft to conduct Continuous Descent Arrivals (CDAs) providing fuel efficient lower noise and emissions operations with high throughput during normal operations.

Precision RNAV RNP routes are used for all departure and arrival runways. These routes have been designed to optimize the vertical profile of both arriving (on CDAs) and departing aircraft. These routes may include altitude windows to vertically separate aircraft in one flow from other flows of arriving, departing or over flying aircraft. These routes also typically include speed restrictions to regularize the flow and improve the ability of ground automation to estimate runway arrival times.

In the mid-term most aircraft are assumed to be equipped with Flight Management Systems (FMSs) capable of flying RNAV RNP/CDA trajectories. Most aircraft are equipped with GPS and broadcast their position, velocity and limited intent data to ground stations via ADS-B out. This information is available to ground automation, improving trajectory prediction accuracy. Some aircraft have FMSs with Required Time of Arrival (RTA) capabilities, enabling air traffic controllers to assign them to cross a fix at a specific time. A small fraction of aircraft are equipped with Flight Deck Merging and Spacing guidance, enabling controllers to assign them to merge behind and then follow another aircraft. Aircraft are generally not equipped with Data Communications capability for clearance delivery and trajectory clearance negotiation.

The air traffic control facilities use a runway-based scheduler to strategically meter arriving and departing aircraft so that the majority of aircraft can usually fly the RNAV RNP/CDA routes with minimal controller intervention. This is accomplished by using successive stages to control of time of arrival. Control for arriving aircraft starts at 300 to 500 nautical miles from the airport, at which point aircraft receive their assigned runway and landing time. Aircraft also receive an advised cruise and descent speed to fly to meet the scheduled time of arrival (STA). This information can be delivered by voice or existing data exchange capabilities such as ACARS. Aircraft may receive a second speed advisory before they initiate their descent and nominally fly their descent CDA in VNAV mode. TRACON routes and airspace provide a maneuver zone before the final approach fix for additional corrections. These may be small speed changes or vectors followed by a return to the RNAV route. Automation can provide advisories for these adjustments.

Current Research:

Our initial simulation evaluated a display concept that graphically depicted to controllers where each arriving aircraft should be if it was to fly the precision RNAV route and arrive at the scheduled time. Figure 1 shows a controller display with two streams of aircraft merging and then landing on one runway. On the right side of the display is a timeline that indicates when each aircraft is estimated to arrive at the runway, as well as the STA assigned by the automation. The circles ("slot markers") in Figure 1 show where each aircraft would be if it flew the RNAV procedure and complied with all of the speed and altitude constraints. The radius of each circle is set to the distance the aircraft would fly in 10 seconds. As the aircraft near the runway and slow, the circles get smaller. For example the display shows that DAL673 is within 10 seconds of its scheduled time; ASQ556, however, is about 25 seconds ahead of schedule. The circles were designed to provide a reference that allows the controller to assess each aircraft's progress and intervene as necessary with a speed or path change to deliver the aircraft on schedule. The results of the simulation are currently being analyzed.

Super-Density Operations screen shot

Future Directions:

Our next simulation will evaluate a concept where the controller is provided with speed and path advisories that will deliver the aircraft to a specified location at the scheduled time.
We plan to use TRAC's fast-time simulation capabilities with controller agent models to examine the amount of initial variability that controllers should be able to cope with while still leaving aircraft on their RNAV RNP/CDA routes. Other sources of variability in this sensitivity analysis will include wind uncertainty, controller timing and pilotage errors. We will use the results from our initial study to estimate the controller variability.

Point of Contact: Everett Palmer, III, Ph. D., NASA Ames Research Center
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Curator: Phil So
NASA Official: Everett Palmer
Last Updated: June 22, 2012