Beneficial Capabilities
Air traffic service (ATS) data communications provide benefits in terms of increased airspace capacity and improved operational efficiency while also enhancing the existing high level of safety.
• Increased airspace capacity. In continental/domestic airspace, capacity is primarily increased through basic controller-pilot datalink communications (CPDLC) that reduce controller and flight crew workload as well as voice frequency congestion associated with routine communications. More specifically, basic CPDLC offers information exchange between the controller and flight crew for vertical, crossing constraint, lateral offset, simple route modification, and speed change clearance request and delivery. Effective strategic management of predictable and accurate aircraft trajectories in the future is also expected to increase continental/domestic airspace capacity; for example, delays due to convective weather will be mitigated by the ability to quickly supply complex route modifications to a large set of affected aircraft before departure. In oceanic, polar, and remote airspace, capacity is primarily increased through manual and automated reports that enable reduced aircraft separation by reliably providing surveillance data for separation assurance, flight plan conformance monitoring, and trajectory planning purposes.
• Improved operational efficiency. Operational efficiency is primarily improved through trajectory-based operations (TBO) that decrease aircraft fuel consumption and/or flight time, particularly in the face of constraints that would otherwise increase those parameters. Parallel integration of ATS provider ground automation, aircraft operator ground automation, and avionics (aircraft automation) and of controller, dispatcher, and flight crew operations enable TBO for rapid and accurate trajectory definition, coordination, and monitoring. TBO can be used, for example, to reduce flight time through user-preferred complex route modifications for in-flight aircraft as seen with Dynamic Airborne Reroute Procedures (see Figure 1) and to perform environmentally-friendly fuel-saving optimized profile descents as demonstrated by Tailored Arrivals (see Figure 2).
• Enhanced safety. Safety is primarily enhanced through accurate machine-to-machine exchange of precise data, such as complete three- or four-dimensional complex routes and latitude/longitude coordinates that resolve duplicate waypoint identifiers. These exchanges prevent gross navigational errors that could otherwise be caused by the flight crew manually transcribing detailed information.
NextGen
The FAA stated in the recently-released 2012 update to its NextGen Implementation Plan that “NextGen is a comprehensive overhaul of our National Airspace System [NAS].” This overhaul is highly dependent on effective use of ATS data communications to provide beneficial capabilities, particularly TBO, that are not possible or practical with voice communications. While supplementing and even replacing voice communications with data communications offers certain benefits when and where appropriate, such replacement alone is simply a costly way to duplicate today’s voice communications functionality without providing any additional capabilities. For example, ground automation generating and sending a complete optimized closed-loop route to the avionics is much more effective than the controller sending a series of open-loop vectors that simply duplicate voice communications to the flight crew.
As a critical component of NextGen, the FAA is currently developing and implementing the Data Comm program for ATS data communications in the NAS. According to the Trajectory Operations Task Group report to the RTCA NextGen Advisory Committee, “Data Comm is crucial to achieving the maximum benefits from TBO, serving as a basic ‘building block’ for this important NextGen capability.” Boeing fully supports the Data Comm program plan, which calls for initial operating capability for terminal services (specifically revisable departure clearances) in 2015 and for enroute services in 2018. Considering the FAA’s termination of their previous ATS data communications program in 2004, maintaining – and even accelerating – these dates is essential to industry’s continued confidence and involvement.
Data Comm Program
The FAA plans to support two data communications standards within the Data Comm program. Significantly, both of these standards support the ability of the navigation avionics, namely the flight management computer (FMC), to automatically extract data from and insert data into messages that are routed by the data communications avionics. This functional integration of navigation avionics with data communications avionics is commonly referred to as ‘FMC-integrated datalink’ (and more colloquially as ‘FMC autoloading’). FMC-integrated datalink is an essential element of end-to-end integration of ground automation and avionics in support of TBO because it allows the flight crew to command the FMC to load a complex route clearance sent by ground automation with only a few keystrokes (see Figure 3A and Figure 3B).
Without FMC-integrated datalink, however, flight crew workload increases and gross navigational errors can occur when the flight crew must manually enter a complex route clearance character by character. FMC-integrated datalink is also important because it reduces flight crew response time in support of Required Communications Performance, which is performance-based, technology-agnostic communications expressed in terms of end-to-end transaction time and measured in terms of time, continuity, availability, and integrity.
In order of introduction, the two data communications standards that the FAA plans to implement in the NAS are Future Air Navigation System (FANS) 1/A and Aeronautical Telecommunications Network (ATN) Baseline 2 (B2).
• FANS-1/A. FANS-1/A is a robust, mature ATS data communications solution that has been in use since 1995, is approved by the International Civil Aviation Organization, is widely deployed around the world both in aircraft and at ATS providers, and offers FMC-integrated datalink in support of early TBO. Given that Boeing calls its implementation ‘FANS-1’ and Airbus calls its own implementation ‘FANS-A’, industry often uses the generic term ‘FANS-1/A’ to encompass all implementations. FANS-1 equipage is available on all in-production Boeing commercial airplane models as well as on multiple out-of-production Boeing and McDonnell Douglas commercial airplane models.
• ATN B2. ATN B2 is a nascent ATS data communications solution that RTCA SC-214 and EUROCAE WG-78 are jointly defining as the global focus for converged operations in continental/domestic and oceanic, polar, and remote airspace. ATN B2, for which the initial specifications are currently due to be completed by the end of 2013, will also offer FMC-integrated datalink in support of advanced TBO. Although Boeing is concerned that the 2013 ATN B2 specifications may not be sufficiently stable or mature for actual implementation, it will continue to actively participate in RTCA SC-214, EUROCAE WG-78, and other relevant industry forums to ensure the realization of beneficial ATN B2 capabilities as soon as the various stakeholders’ business cases permit. One issue in particular that requires attention is expanding supported ATN B2 subnetworks beyond only the terrestrial, line-of-sight VHF Digital Link Mode 2 subnetwork in order to enable converged operations in oceanic, polar, and remote airspace where use of a beyond-line-of-sight subnetwork is necessary.
Boeing supports the FAA’s plan to offer FANS-1/A services followed by ATN B2 services in the NAS because this approach:
• provides an excellent means to rapidly leverage existing stakeholder investments in FANS-1/A, a highly capable system that supports early TBO;
• focuses on a single technology in order to achieve the earliest initial operating capability while incurring the lowest technical, schedule, and cost risks;
• supplies practical operational experience with FANS-1/A in continental/domestic airspace that can be leveraged toward maturing ATN B2 specifications and procedures while avoiding multiple costly upgrades to future ATN B2 aircraft and ATS provider systems;
• allows a graceful transition from existing FANS-1/A aircraft and ATS provider systems to future ATN B2 aircraft and ATS provider systems as the associated stakeholders’ business cases drive their respective investments in ATN B2; and
• offers a clear migration path from early TBO supported by FANS-1/A to advanced TBO supported by ATN B2.
Non–FMC-Integrated Datalink
Based on the reasons described above, Boeing believes that the FAA should avoid implementing ATS data communications without FMC-integrated datalink because such an implementation could only replicate current voice communications functionality without offering any additional capabilities. Although Europe’s non–FMC-integrated Link 2000+ implementation (which is a subset of ATN Baseline 1 functionality) was determined to be a short-term solution for frequency congestion and other capacity-related issues there, Link 2000+ is not appropriate for NextGen because introduction of non–FMC-integrated datalink would jeopardize deployment of TBO and accrual of the corresponding benefits through a ‘lowest common denominator’ effect. More specifically, if aircraft both with and without FMC-integrated datalink would participate in the Data Comm program, then the collective inability of aircraft without FMC-integrated datalink to perform TBO would largely prevent other stakeholders from realizing TBO benefits because the fundamental NextGen transformation from clearance-based air traffic control to trajectory-based air traffic management would be severely hampered.
Additionally, despite the European implementing rule for Link 2000+, it is an unsuitable objective for harmonization because a significant area of FANS-1/A airspace over Canada and the North Atlantic – which has its own pending mandates for FANS-1/A equipage – exists between the United States and Europe. Another reason why Link 2000+ is an inappropriate target for harmonization is that Europe is already planning its transition from Link 2000+ to ATN B2 starting as early as 2018.
Summary
Boeing fully supports the Data Comm program plan to offer FANS-1/A services and then ATN B2 services in the NAS in order to realize as quickly as practical the increased capacity, improved efficiency, and enhanced safety benefits that those FMC-integrated ATS data communications standards provide, particularly from TBO. The most critical event for realization of NextGen benefits from ATS data communications is enroute initial operating capability in 2018 (or earlier) as currently planned. Any decision that would jeopardize this event – including risky acceleration of deploying unstable and immature ATN B2 services – should be closely questioned.
Furthermore, Boeing opposes the suggestion that the FAA also offer Link 2000+ services. FANS-1/A does now and ATN B2 will in the future enable TBO and provide the associated benefits, while Link 2000+ does not support any capabilities that are not already available using voice communications. In other words, Link 2000+ is simply not a transformative NextGen air traffic management technology as FANS-1/A is and as ATN B2 will be.
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