The present invention generally relates to methods and systems for managing air traffic. More particularly, aspects of this invention include methods and systems for negotiating and processing air traffic trajectory modification requests received from multiple aircraft, and methods and systems for scheduling air traffic arriving at airports.
Trajectory Based Operations (TBO) is a key component of both the US Next Generation Air Transport System (NextGen) and Europe's Single European Sky ATM Research (SESAR). There is a significant amount of effort underway in both programs to advance this concept. Aircraft trajectory synchronization and trajectory negotiation are key capabilities in existing TBO concepts, and provide the framework to improve the efficiency of airspace operations. Trajectory synchronization and negotiation implemented in TBO also enable airspace users (including flight operators (airlines), flight dispatchers, flight deck personnel, Unmanned Aerial Systems, and military users) to regularly fly trajectories close to their preferred (user-preferred) trajectories, enabling business objectives, including fuel and time savings, wind-optimal routing, and direction to go around weather cells, to be incorporated into TBO concepts. As such, there is a desire to generate technologies that support trajectory synchronization and negotiation, which in turn are able to facilitate and accelerate the adoption of TBO.
As used herein, the trajectory of an aircraft is a time-ordered sequence of three-dimensional positions an aircraft follows from takeoff to landing, and can be described mathematically by a time-ordered set of trajectory vectors. In contrast, the flight plan of an aircraft will be referred to as documents that are filed by a pilot or a flight dispatcher with the local civil aviation authority prior to departure, and include such information as departure and arrival points, estimated time en route, and other general information that can be used by air traffic control (ATC) to provide tracking and routing services. Included in the concept of flight trajectory is that there is a trajectory path having a centerline, and position and time uncertainties surrounding this centerline. Trajectory synchronization may be defined as a process of resolving discrepancies between different representations of an aircraft's trajectory, such that any remaining differences are operationally insignificant. What constitutes an operationally insignificant difference depends on the intended use of the trajectory. Relatively larger differences may be acceptable for strategic demand estimates, whereas the differences must be much smaller for use in tactical separation management. An overarching goal of TBO is to reduce the uncertainty associated with the prediction of an aircraft's future location through use of an accurate four-dimensional trajectory (4DT) in space (latitude, longitude, altitude) and time. The use of precise 4DTs has the ability to dramatically reduce the uncertainty of an aircraft's future flight path in terms of the ability to predict the aircraft's future spatial position (latitude, longitude, and altitude) relative to time, including the ability to predict arrival times at a geographic location (referred to as metering fix, metering fix, arrival fix, or cornerpost) for a group of aircraft that are approaching their arrival airport. Such a capability represents a significant change from the present “clearance-based control” approach (which depends on observations of an aircraft's current state) to a trajectory-based control approach, with the goal of allowing an aircraft to fly along a user-preferred trajectory. Thus, a critical enabler for TBO is the availability of an accurate, planned trajectory (or possibly multiple trajectories), providing ATC with valuable information to allow more effective use of airspace.
Generally, trajectory negotiation is a process by which information is exchanged to balance the user preferences with safety, capacity and business objectives and constraints of operators or Air Navigation Service Providers (ANSPs). Although trajectory negotiation is a key component of existing TBO concepts, there are many different viewpoints on what trajectory negotiation is and involves. Depending on the time-frame and the desired outcome of the negotiation, different actors will be involved in the negotiation, and different information will be exchanged. Generally, the concept of trajectory negotiation has been described as an aircraft operator's desire to negotiate an optimal or preferred trajectory, balanced with the desire to ensure safe separation of aircraft and optimal sequencing of those aircraft during departure and arrival, while providing a framework of equity. Trajectory negotiation concepts also allow for airspace users to submit trajectory preferences to resolve conflicts, including proposed modifications to an aircraft's 4D trajectory (lateral route, altitude and speed).
In view of the above, TBO concepts require the generation, negotiation, communication, and management of 4DTs from individual aircraft and aggregate flows representing the trajectories of multiple aircraft within a given airspace. Trajectory management of multiple aircraft can be most reliably achieved through automated assistance to negotiate pilot trajectory change requests with properly equipped aircraft operators, allowing for the negotiation of four-dimensional trajectories between the pilot/operator of an aircraft and the ANSP. Trajectory negotiation has been described as having four phases: pre-negotiation, negotiation, agreement, and execution. See, for example, Joint Planning and Development Office, October, 2008, NextGen Avionics Roadmap, Version 1. In pre-negotiation, the user-preferred trajectories of all relevant aircraft are known or inferred by an air traffic management (ATM) system. Any conflicts between these user-preferred trajectories or with airspace constraints leads to the negotiation phase. In this phase, modifications to one or more user-preferred trajectories may be negotiated between the flight operator and the ANSP to make best of use of the airspace from the ANSP perspective while minimizing the deviation from the operator's objectives for that flight. The agreement phase results in a negotiated 4DT for the aircraft, at least a portion of which is cleared by the ANSP. In the execution phase, the aircraft flies the agreed and cleared 4DT, and the ANSP monitors adherence to this 4DT. Failure of an aircraft to adhere to the negotiated trajectory, or changes in circumstances (for example, an emergency situation or pop-up flight) can result in reinitiation of the negotiation phase. For use in the negotiation and agreement phases, several air-ground communication protocols and avionics performance standards exist or are under development, for example, controller pilot data link communication (CPDLC) and automatic dependant surveillance-contract (ADSC) technologies.
Related to concepts of air traffic management are various types of Arrival Managers (AMAN) known in the art, nonlimiting examples of which include systems known as Traffic Management Advisor (TMA) and En-Route Decent Advisor (EDA), which are part of the National Aeronautics and Space Administration's (NASA) Center-TRACON Automation System (CTAS) currently under development. TMA is discussed in H. N. Swenson et al., “Design and Operational Evaluation of the Traffic Management Advisor at the Fort Worth Air Route Traffic Control Center,” 1st USA/Europe Air Traffic Management Research & Development Seminar, Saclay, France (Jun. 17-19, 1997), and EDA is discussed in R. A. Coppenbarger et al., “Design and Development of the En Route Descent Advisor (EDA) for Conflict-Free Arrival Metering,” Proceedings of the AIAA Guidance, Navigation, and Control Conference (2004). The primary goal of TMA is to schedule arrivals by assigning to each aircraft a scheduled time-of-arrival (STA) at metering fixes. TMA computes the delay needed as the difference between the STA and the estimated time-of-arrival (ETA). The primary goal of EDA is to compute advisories for air traffic controllers (ATCo) to help deliver aircraft to an arrival-metering fix in conformance with STAs, while preventing separation conflicts with other aircraft along the arrival trajectory. EDA primarily makes use of speed adjustments and then, if necessary, adds lateral distance to absorb more delay via path stretches. EDA also incorporates conflict detection and conflict resolution through simultaneous adjustments to both cruise and decent speeds. However, user preferences are not incorporated into the EDA concept.
Several significant gaps remain in implementing TBO, due in part to the lack of validation activities and benefits assessments. In response, the General Electric Company and the Lockheed Martin Corporation have created a Joint Strategic Research Initiative (JSRI), which aims to generate technologies that accelerate adoption of TBO in the Air Traffic Management (ATM) realm. Efforts of the JSRI have included the use of GE's Flight Management System (FMS) and aircraft expertise, Lockheed Martin's ATC domain expertise, including the En Route Automation Modernization (ERAM) and the Common Automated Radar Terminal System (Common ARTS), to explore and evaluate trajectory negotiation and synchronization concepts. Ground automation systems typically provide a four-dimensional trajectory model capable of predicting the paths of aircraft in time and space, providing information that is required for planning and performing critical air traffic control and traffic flow management functions, such as scheduling, conflict prediction, separation management and conformance monitoring. On board an aircraft, the FMS can use a trajectory for closed-loop guidance by way of the automatic flight control system (AFCS) of the aircraft. Many modern FMSs are also capable of meeting a required time-of-arrival (RTA), which may be assigned to an aircraft by ground systems.
Notwithstanding the above technological capabilities, questions remain related to the trajectory negotiation process, including the manner in which parameters and constraints are exchanged that affect the 4D trajectories of a group of aircraft in a given air space, and how to arrive at negotiated trajectories that are as close to user-preferred trajectories (in terms of business objectives) as possible while fully honoring all ATC objectives (safe separation, traffic flow, etc.).
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