American revolution: the NextGen system8 September 2013
Despite being beset by delays, the US Next Generation Air Transportation System (NextGen) is on course to revolutionise the nation’s airspace system over the next decade. James Lawson talks to Dan Elwell of trade association Airlines for America about the challenge of integrating new and existing navigation and surveillance technologies.
At any given moment, there are around 5,000 planes in the skies above the US. More than 15,000 federal air traffic controllers guide pilots through the system, helping them land safely and on time at their destinations.
But today's national airspace system (NAS) struggles to cope. Employing an antiquated, ground-based navigation system in serious need of updating, it requires constant monitoring and costly maintenance.
"We are still operating with technology that dates back to the Second World War," says Dan Elwell, senior vice-president, safety, security and operations at airline industry association Airlines for America. "These legacy 'navaids' are being rendered obsolete by cockpit equipment capable of navigating by satellite, yet they are still the dominant mode of navigation."
Thankfully, help is on the way. The Next Generation Air Transportation System (NextGen) is the new NAS for North America, to be implemented over the coming decade. As well as assisting airports and Federal Aviation Administration (FAA) air traffic controllers, NextGen offers considerable benefits to airlines too.
According to the FAA, flight delays and cancellations cost the US more than $31 billion annually. The FAA's March 2012 implementation plan stated that NextGen will reduce delays by 38% by 2020, providing $24 billion in cumulative benefits across 2011-20.
"We believe in the promise of NextGen," says Elwell. "This initiative is so vitally important to the US airline industry that we made it one of our top five priorities under a National Airline Policy - a comprehensive proposal that speaks for airline customers and is designed to spur growth and support for the integral role the US airline industry plays in our nation's economy.
"Once fully implemented, NextGen will integrate new and existing technologies, including satellite navigation and surveillance, and advanced digital communications. This will ultimately result in better metering and coordination of the flow of air traffic, reducing congestion, which is especially important during peak travel times," he adds.
NextGen's move to satellite-based tracking will shorten routes and streamline approaches; rather than stacking jets above the destination, delays will be absorbed through speed reductions at cruising altitude. A NextGen-enabled NAS should result in a smoother-running system with a higher network capacity, less prone to delays and able to cope more effectively with bad weather. Most important of all, controllers will monitor and manage aircraft with greater safety margins.
But bringing US airspace into the 21st century isn't straightforward. Rather than a single technology, NextGen is a family of interwoven, interdependent navigational and air traffic management systems.
One such system is automatic dependent surveillance-broadcast (ADS-B). Once fully implemented, ADS-B will give pilots and air traffic controllers the same real-time view of air traffic.
The next-generation network-enabled weather (NNEW) system is another vital strand. According to the US Department of Transportation, 37% of delayed flights in 2012 were caused by bad weather. By delivering a single national weather information system in real time, NNEW will support better air traffic decision-making, with the aim of cutting weather-related delays in half.
Then, there is the system-wide information management (SWIM) initiative. Based on the service-oriented architectures now standard in corporate IT, SWIM will facilitate better information sharing by mandating a common interface for every FAA system; it is also a key component of SESAR, Europe's version of NextGen.
NextGen will also replace much of the information currently passed via voice communications with direct data links to aircraft. For airlines, better sharing of air traffic management (ATM) information like airport operational status, weather information and flight data means more effective decision-making and, thanks to the consistency that comes from working from the same data, improved safety.
The PBN revolution
Finally, there is performance-based navigation (PBN), perhaps the most valuable NextGen element for airlines. Rather than procedures that rely on fixed sensors like VHF omni range (VOR) navigation beacons, PBN sets out flight paths that aircraft follow using enabling technologies such as required navigation performance (RNP) and area navigation (RNAV). That makes for more efficient use of airspace and opens the door for pilots and dispatchers to select their own direct flight path, rather than using today's grid-like 'highway system'.
Using RNP/RNAV with the new PBN procedures, aircraft can fly consistent and controlled approach and departure paths in complex airspace at high-density airports, using shorter, continuous-descent approaches instead of traditional 'stair-step' landing paths. With optimised profile descents, the aircraft essentially glides in idle from cruising altitude to the runway threshold.
Fewer miles flown and lower engine power settings cut fuel use significantly, save time, and result in lower emissions and less noise over sensitive residential areas close to airports. According to the FAA, full NextGen implementation from 2011-20 would result in cumulative savings of 1.4 billion gallons of fuel and 14 million metric tons of CO2.
"NextGen will further reduce aviation's impact on the environment by decreasing fuel burn and CO2 emissions by as much as 12% a year according to the US Government Accountability Office," explains Elwell. "By minimising fuel burn, the airlines will, in turn, conserve fuel, which will help combat high and volatile fuel prices."
With benefits like these, it's easy to see why the airlines welcomed NextGen with open arms and have worked hard to advance the project.
"The FAA has brought the airlines, airports, air traffic controllers and other federal agencies together in the development of PBN and other NextGen programmes," says Elwell. "We are in constant contact with the FAA, and participate in many collaborative efforts alongside it, our airline members and industry partners, such as the NextGen Advisory Committee, as well as its many subcommittees and work groups."
Part of that work has involved proving NextGen's benefits in a number of demonstration projects. For example, Port of Seattle, Boeing, the FAA and Alaska Airlines collaborated on the 'Greener Skies Over Seattle' initiative at Seattle-Tacoma International Airport (Sea-Tac).
Starting in Summer 2009, this showed clearly that the more direct, continuous descent approaches enabled by RNP reduce noise and emissions as well as saving time and fuel.
Based on tests in 2010, Alaska Airlines estimated that the new Sea-Tac procedures could cut overall annual fuel consumption by 2.1 million gallons and reduce carbon emissions by 22,000 metric tons.
Unfortunately, NextGen has been plagued by delays and budget overruns since its inception. Much of this is to do with its incredible complexity and the fact that so many systems are interdependent; until one is working, the others won't work either. The En Route Automation Modernization (ERAM) project is a good example.
This lies at ATM's heart, letting controllers track 1,900 aircraft at a time compared with a current maximum of 1,100. ERAM delays have in turn held back SWIM, data communications and ADS-B, among others. Budget cuts have also added to NextGen's woes.
"NextGen progress has been an issue with and without sequestration," says Elwell. "Sequestration had an additional impact on many NextGen projects, causing further delays, as well as stops and starts. Timelines to achieve set goals have already slipped by several years."
But it's the long wait for the introduction of those time and fuel-efficient approaches that really dismays the airlines. Using RNP at enabled airports outside its home state saved Alaska Airlines more than $17.6 million in 2012.
In fact, the airline considers RNP to be instrumental in helping it to become the most fuel-efficient of all large US carriers, with a 30% drop in consumption per revenue passenger mile since 2004. Though deploying PBN without NextGen's other elements will not achieve the full efficiency and capacity improvements, airlines are keen to see some progress, as Ewell explains.
"The most effective way to advance NextGen is for the FAA to develop, certify and implement those procedures and policies that will enable carriers to maximise their current RNAV and RNP capabilities, which, in the case of RNAV, we've been equipped with for more than 20 years," he says.
To its credit, the FAA has prioritised PBN rollout. With its optimisation of airspace and procedures in the metroplex (OAPM) scheme, the FAA is bringing PBN to major city airports one by one. Development has been sluggish, however, as it takes around three years to design, test, implement, review and modify procedures for a single airport.
"Minor procedural changes to RNAV/RNP procedures still can take 12-18 months, and benefits of more precise navigational procedures await FAA approvals that are far too lengthy," says Elwell.
Airlines must pay a substantial part of NextGen's $18-billion cost and have already invested substantial amounts. But, given the uncertain deployment schedule, they are understandably reluctant to spend more.
"NextGen is a significant investment in the billions," says Elwell. "Airlines have shown their willingness to install NextGen equipment, participate in tests, and train their pilots and employees, but they have yet to see progress."
So, currently there is an impasse. However, spearheaded by Airlines for America, the industry is still firmly behind the NextGen scheme.
"The FAA's delivery of tangible and sustained benefits, an improved process for NextGen procedural approvals and incentives for equipage would justify further investments," states Elwell. "We look forward to continuing our work with the FAA, our member carriers and industry partners to make NextGen a reality for the travelling and shipping public."