Airspace Concept Evaluation System (aces) Capabilities December 5, 2008

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2.1Current Functionality

To support these capabilities, this build provides the models and data sets as listed in the table of contents. In addition, a brief description of the visualization scenario tool is also presented, to provide a more complete picture of the simulation functionality from the user-interface perspective. Agent management control and data collection components are covered in the architectural description.

2.1.1Aircraft

All aircraft are individually modeled. The aircraft model fidelity, however, depends on the flight environment. See Appendix A for the list of supported aircraft.

For the en route environment, a 4 DOF (true airspeed, heading angle, roll angle, flight path angle plus secondary variables: latitude, longitude, altitude, and weight/fuel), medium fidelity aircraft model can be utilized for propagating aircraft in the en route environment and for providing predictive trajectories. This 4 DOF model produces smooth and accurate aircraft maneuvers.
Aircraft fly their designated flight plan until redirected by en route ATC. In the terminal environment, the flight time is specified by the terminal ATC and a low fidelity aircraft model computes (with a simple table lookup) the fuel burn in the TRACON area A medium fidelity aircraft model, using the BADA 3.6 (refer to Appendix A), computes the fuel burn in the En Route area. Individual approach trajectories are not explicitly simulated. ACES 6.0 is enabled with Surface Traffic Limitation Enhancement (STLE) which allows more complex analysis. When a simulation with higher-fidelity approach trajectories is required, the user may use this capability. Refer to Section 2.1.13 for more detail..

At the airport, a queuing model provides aircraft flow into and out of the airport. Similarly, see section 2.1.13 for using a higher-fidelity model for aircraft flow into and out of the airport.

2.1.2ATCSCC

ACES includes a model of the Air Traffic Control System Command Center (ATCSCC). The key functions of the ATCSCC model are the prediction of future congestion events throughout the NAS, dissemination of information on predicted congestion events to appropriate Air Traffic Service Providers (ATSPs) and airlines, and a limited set of system level responses to system level congestion problems. Specifically, the capabilities are:

The ATCSCC predicts the air traffic density of the entire NAS throughout the day-in-the-NAS timeframe. Utilizing the flight plans for both active and planned flights, the ATCSCC model predicts the density of traffic at each en route sector throughout the day, providing a long-term (8 to 24 hour) prediction of traffic densities through out the NAS.
The ATCSCC issues congestion alert messages to the Air Traffic Service Providers (ATSPs) as well as to the airlines (through the AOCs) when predicted density exceeds capacity. Using the air traffic density predictions and comparing them to the NAS capacities, the ATCSCC distributes alert messages to all interested parties when demand exceeds capacity.

2.1.3En Route

The en route environment modeling can be divided into two distinct areas: the Traffic Flow Management (TFM) and the Air Traffic Control (ATC). It is important to note that each individual aircraft trajectory is modeled and can be altered by ATC as needed. The key functions of the en route traffic flow management modeling are the facility (ARTCC) response to predicted congestion within a 30 - 60 minute range.

Specifically, the en route TFM capabilities are as follows:

The En Route TFM analyzes the predicted congestion event and decides on appropriate level of facility response. The TFM model determines if the congestion problem can be handled internally by absorbing delay within the facility or if the congestion problem is large enough that it must be propagated to adjacent facilities with the introduction of TFM constraints.
The En Route TFM provides adjacent up-stream facility with required TFM constraints and responds to adjacent down-stream facility TFM constraints. If congestion requires TFM constraints to be put on an adjacent up-stream facility, the specific TFM constraint information is communicated to the adjacent up-stream facility.

The key en route ATC functions are to respond to TFM constraints and maintain aircraft separation through conflict detection and resolution.

Specifically, the en route ATC capabilities are as follows:

The En Route ATC detects conflicts between aircraft in the ARTCC airspace. The conflict detection time horizon is sufficiently high to provide adequate time for resolution. To perform conflict detection between aircraft in the ARTCC ATC, select CD&R option on ACP editor from the MultipleRunManager GUI. The upcoming release of ACES will integrate an alternative higher-fidelity CD&R modeling called the Advanced Airspace Concept (AAC). Since AAC has its own conflict detection algorithm, AAC option cannot be enabled on ACP editor.
The En Route ATC develops and implements a resolution plan for conflicts between aircraft in the ARTCC airspace and provides aircraft with the necessary maneuvers to avoid conflict.
The En Route ATC responds to TFM restrictions. While resolving conflicts and maintaining separation, the en route ATC also ensures that TFM restrictions from adjacent down-stream facilities are met.
The En Route ATC delivers conflict free aircraft to adjacent down-stream facilities (ARTCC or TRACON).

2.1.4En Route Congestion

The en route traffic congestion assessment and resolution function generates and propagates flight restrictions and resultant delays through the NAS-wide network of airports and ARTCCs. ACES en route delay is originated by traffic flow limitations due to:

Airport/runway system capacity
En route sector traffic capacity.

ACES 6.0 enhances the congestion assessment and resolution function by the introduction of dynamic sector capacity. In previous builds, TFM did not consider future sector capacity configuration changes when planning traffic flow throughout the NAS. It only considered the current sector capacity limits and used these limits to “project” sector capacity limits. This manner of calculation leads to sub-optimal traffic flow management throughout a simulation. For example, the total number of flight delays may be greater during a simulation than when using a more optimal TFM schedule. The Dynamic Sector Capacity (DSC) feature provides TFMs with the capability to consider future sector capacity changes when planning traffic flow throughout the NAS. With DSC, a more realistic sector capacity change scenario may be modeled for a given sector, thereby providing the TFMs with a more accurate depiction of what the actual capacity is for a given sector at a given point in time (which may potentially be in the future). With DSC, there is no longer a need for the TFM to “project” the capacity of a sector based on its current limits when performing its periodic sector congestion forecasting activities.

The capabilities applicable to the ATCSCC, ARTCC TFM, ARTCC ATC and flight models are:

ATCSCC Model: Implement Monitor Alert
- Update Traffic Density (Flight and Sector) Data
- Assess NAS-wide Sector Traffic Overload with dynamic sector capacity functionality:

Upon periodic activation, the ATCSCC TFM begins an assessment of sector congestion, starting at the current simulation time. For the point in simulation time being evaluated, the ATCSCC TFM performs the following for each sector in the NAS:

Compute the projected traffic density in the sector based on planned flight trajectories.
Obtain the planned capacity for the sector (based on dynamic sector capacity) at the specific time being evaluated. (If there is no planned capacity change for the sector, this will be the default capacity.)
If the projected traffic density is higher than the planned capacity, issue a sector congestion alert to the appropriate ARTCC TFM.

After congestion evaluation at a specific point in simulation time, ATCSCC TFM increments the simulation look-ahead time by 15 minutes, and if the look-ahead is less than or equal to 4 hours, the ATCSCC TFM will repeat the congestion evaluation for each sector as described in steps “a” through “c” above.

ARTCC TFM Model: Conduct Congestion Resolution Planning
- Assess ARTCC Exit Boundary Crossing Restrictions

The ARTCC TFM model initiates en route traffic congestion assessments in response to receipt of exit boundary crossing time restrictions. ARTCC TFM model determines delay requirements for exit boundary-constrained flights, assign internal and external delay, and assign ARTCC entry boundary crossing time requirements. ARTCC TFM model allocates internal delay among sectors and assign sector boundary crossing time requirements.

Assess ARTCC Sector Traffic Overload with dynamic sector capacity functionality.

The ARTCC TFM model initiates en route traffic congestion assessments in response to receipt of sector congestion alerts. The ARTCC TFM model determines projected instantaneous aircraft counts (IACs) for the subject sectors, identifies overloaded sectors based on comparisons of projected sector IAC loadings and IAC thresholds, determines external flight delay required to resolve sector congestion (but uses previously-assigned internal delay to the extent possible to minimize disruption to planned exit constraints), and assigns ARTCC entry boundary crossing time requirements. If delays are initiated for a sector, the ARTCC TFM will assign a delay to each flight which will enter the sector if and only if the scheduled sector capacity at the time the flight will enter the sector will be exceeded based on the dynamic sector capacity functionality.

Disseminate Boundary Crossing Restrictions

The ARTCC TFM model issues inbound boundary crossing time restrictions to upstream TFM agents and outbound boundary crossing time restrictions to its ARTCC ATC agent.

ARTCC ATC Model: Implement Congestion Resolution
ATCSCC Model: Modify Trajectory

The ATCSCC model updates the flight predicted trajectory due to a flight maneuver and issue notifications describing the updated predicted trajectory.

Flight Model: Conduct Maneuver

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