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Trajectory Modeler from User Request Evaluation Tool (URET) Disclosure Number: IPCOM000008420D
Publication Date: 2002-Jun-12
Document File: 5 page(s) / 57K

Publishing Venue

The Prior Art Database

Related People

MITRE Technology Transfer Office: SUBMITTER


he User Request Evaluation Tool (URET) Trajectory Modeling function models a 4-D (space and time) flight profile, or trajectory, that represents the predicted path of an aircraft through en-route airspace. The trajectory is generated by integrating flight plan state and intent data with site-specific adaptation, aircraft performance characteristics, and forecast winds and temperatures aloft. For active flights, track report updates are also integrated into the model. These updates provide aircraft position and altitude on a periodic cycle. Upon receipt of each update, the reported position and altitude of an aircraft is compared to the associated trajectory-predicted position and altitude. This process is referred to as Conformance Monitoring. If the reported and predicted position or altitude is out of an operationally acceptable tolerance, or conformance, the trajectory is remodeled. This process is referred to as reconformance. In addition to bringing the trajectory back into conformance, the process takes into account the observed behavior of the aircraft and adjusts remodeled trajectory speeds and altitude transition rates accordingly.

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Daniel J. Brudnicki and Daniel B. Kirk

       The MITRE Corporation Center for Advanced Aviation System Development 7525 Colshire Drive, M.S. W175

McLean VA USA 22102-3481 Fax: (703)883-3348


AERA (Automated En Route Air traffic control) is a continuing Federal Aviation Administration (FAA) program to increase system capacity, safety, and the granting of user-preferred trajectories (e.g., direct routes) to airspace users. A cornerstone of AERA is its trajectory modeler: the model predictions may be displayed graphically to the controller in the AERA Future Situation Display, and are used to provide strategic (up to 20 min.) detection of aircraft-to-aircraft conflicts. This paper provides an overview of the AERA Trajectory modeler, as currently envisaged for field implementation in the late 1990s. It is divided into 4 sections, dealing (in turn) with 1) initial trajectory construction, 2) the maintenance of the trajectory as the flight progresses, 3) sources of modeling error, and 4) the application to Air Traffic Control.

1. Initial Trajectory Construction

This section describes the process of modeling a 4-dimensional trajectory profile. This process is driven by several goals. The first is to be consistent with air traffic control (ATC) clearances and the observed performance of the aircraft. The latter applies to both altitude and speed profiles; if the prediction varies significantly from observed behavior, the model is corrected, provided that the correction does not violate any ATC restrictions placed on the aircraft. Second, the accuracy of a positional prediction is required at all points along the trajectory-up to some lookahead time. (This is opposed to the case in which accuracy is needed at only a single downroute point, e.g., at a meter fix.) Third, robustness of the modeler is a key consideration. It should fail to model a trajectory only in extreme cases. Fourth and last, the modeler must be computationally efficient-the peak number of simultaneous trajectories that will have to be maintained by AERA in a given en route facility is projected to be over 2,000 (cf. Section 4.1).

1.1. Modeler Input

The input data used to model a trajectory are divided into four categories: ATC clearances, site adaptation, aircraft

performance characteristics, and wind and temperature data. ATC clearances include information from the filed flight plan as well as subsequent amendments to it. Site adaptation includes data required for route conversion (e.g., fix locations) and for the application of ATC constraints. Aircraft performance characteristics include such things as climb and descent gradients as a function of parameters such as aircraft type, weight, engine type, outside air temperature, and the altitude range over which the gradient is applicable. Wind, temperature and pressure data is to be provided and used in a gridded fo...