Time-Based Flow Management (TBFM) is the term used to describe the system of time-based metering (TBM) technologies and methodologies employed by Federal Aviation Administration (FAA) personnel to tactically adjust capacity and demand imbalances at certain U.S. airports. TBFM is a cornerstone of the Trajectory-Based Operations (TBO) concept, itself a foundational Next Generation Air Traffic System (NextGen) component.
The TBFM technology module used today to plan efficient trajectories and manage traffic from the enroute environment down to the runway threshold is called Traffic Management Advisor (TMA). Like any TBFM system, TMA delivers maximum benefit when the number of aircraft scheduled to land at an airport approaches its capacity. Using TMA to manage a flow of landing traffic can result in significant and desirable operating efficiencies.
Weather is the primary cause of airport capacity reductions and delays in the NAS today. As weather begins to impinge on airport arrival routes, aircraft deviate from their planned trajectories. The resulting ETA fluctuations cause metering operations to become unsustainable, and TMA is shut down at the time it would be most effective. Given that an overarching goal of NextGen is to be able to operate more efficiently in the face of weather constraints, this shortcoming will be even more critical in the coming years.
With respect to weather and TBFM, the fundamental problem is to determine how to transition from the current system to one which can not only be kept running during hazardous weather situations, but will provide the associated capacity improvements and operating efficiencies when and where they are most needed, namely in high density, weather-constrained airspace and key, high demand, weather-constrained airports. Full weather integration into TBFM systems and decision making processes is believed to be a key component of the solution to this problem.
The CONOPS for Weather Integration into TMA/TBFM lays out a number of incremental changes that will result in the integration of weather into TBFM systems and decision making processes. These steps take place in phases over the projected life of TBFM systems, and are structured in such a way as to enable the ongoing, continuous use of TBFM systems even as new capabilities are being introduced.
It is felt that the integration methods described in the CONOPS, along with the layout of the document itself, can potentially serve as models for the critical task of fully integrating weather into other current and future FAA systems and processes, a key NextGen requirement.