Front & Center

Shelley Yak, director of the FAA William J Hughes Technical Center explains how the FAA Technical Center is tackling the TBO challenge

The FAA’s move to Trajectory Based Operations (TBO) continues to change the way NextGen air traffic management capabilities are tested at the William J Hughes Technical Center in Atlantic City, New Jersey, the agency’s leading-edge, premier air transportation system laboratory.

Verification and validation of a new air traffic management capability never has been more challenging due to the rising level of complexity and reliance on software distributed through various parts of the National Airspace System (NAS) to create new capabilities. In contrast to traditional single system test programmes, new capability deployments are increasingly the result of successful verification of multiple software-driven functions operating in co-ordinated fashion across multiple systems.

Validation determines whether a new capability will fulfill its intended purpose when placed in the NAS. Verification determines whether the finished product meets the specified requirements. Verification and validation employ complementary iterative processes and provide a disciplined approach to assess a product, system, or service throughout its lifecycle.

At its core, TBO is an air traffic management (ATM) method for strategically managing and optimising flights by using time-based management, information exchange between air and ground systems, and the aircraft’s ability to fly precise paths in time and space. It is inherently a gate to gate management concept with 4-Dimensional trajectories as the key operations management construct. Along with supporting concepts, such as an integrated weather picture, the key philosophical element of TBO is time-based metering.

Time-based trajectories mean that a single flight has “reservations” at each juncture as it traverses the airspace, including handoffs from one facility to the next, with target times for departure, arrival, and each step in between. The implication of TBO is operational integration to an extent never imagined. A single commercial flight moves through the system on a negotiated trajectory, which requires each intermediate system and actor to support that schedule, working cooperatively with other systems, actors, and facilities.

The TBO-centred operational integration concept has huge implications for the test organisation, particularly regarding validation. A single system improvement, for example, an upgrade to a terminal automation system, could well satisfy every user requirement within its own domain but not satisfy the combined operational need of the whole family of stakeholders. This makes end-to-end testing imperative.


To meet the challenge, the FAA is enhancing its integrated testbed for management of every phase of flight, from surface operations to en route. Many of these highly integrated test capabilities are already available at the Technical Center, but the requirement for TBO to function seamlessly will drive collaboration with outside facilities, such as NASA, MITRE Center for Advanced Aviation System Development and industry test facilities.

Operational integration implies a significant change in operational culture on the part of air traffic controllers and flight deck crews. Presently, each air traffic control facility views its responsibility as the smooth, safe, and timely movement of assigned traffic through its airspace. TBO changes this dynamic by requiring not only the expeditious movement of traffic, but the coordination of traffic according to a previously negotiated schedule. This will occasionally mean a locally less-efficient trajectory through a particular facility’s airspace in service of a potentially more efficient trajectory and/or a better overall result across the system.

More broadly, effective operational integration, validation and verification of TBO requires (1) purposeful awareness of the intricacies of interrelated capabilities and systems; (2) full understanding of the role, needs, and contributions of all stakeholders; and (3) acute awareness of the operator’s role — both present and future. This level of complexity requires the ability to maintain both an awareness of interrelated capabilities, current operations and a perspective on envisioned changes within a global context and are necessary precursors to achieving ‘complexity consciousness’ – a key concept that underlies effective deployment of NextGen enterprise capabilities.

“in the verification and validations world, it is our responsibility to be aware of all the moving parts and to ensure NextGen enterprise capabilities work together harmoniously”

A similar attitudinal change is required of the flight crew. Although airline pilots are always proud of bringing in their flights early, under TBO the metric will be meeting the predetermined times at each meter fix. Continual stakeholder involvement with well-established feedback is important in developing a culture of ‘complexity consciousness’.

This new awareness means changing the focus from the time when an aircraft takes off and lands to emphasise time all along its scheduled flight and is a considerable human factors and stakeholder engagement challenge. In the TBO era, proper system-level validation must determine if flight crews use of the tools and procedures meet the stricter time demands of TBO.

Support for this effort will require a larger integration of flight simulators. A substantial contribution will come from the Technical Center’s own suite of medium-fidelity cockpit simulators and include high-fidelity simulators located at the FAA Mike Monroney Aeronautical Center in Oklahoma City and various other federal and industry facilities. Perhaps most important is the participation of high-fidelity training simulators provided by the airlines. These will be critical to achieving end-to-end operational validation and a highly effective way to receive high-quality stakeholder input to assess operational suitability and crew capability.

It is quite a challenge to maintain awareness of all the moving parts of the NAS: its systems, services, and stakeholder considerations. Equally daunting is the challenge of keeping up with the rapid pace of operational improvements, which we achieve through the integration of enterprise capabilities consisting of air and ground technologies, procedures, airspace redesign, and new policies.

In the verification and validations world, it is our responsibility to be aware of all the moving parts and to ensure NextGen enterprise capabilities work together harmoniously and achieve their intended operational benefits. We’re ready to take on TBO for the next chapter in ATM.


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