In addition to the standard noise abatement challenges all airports face, Denver International (DEN) has an additional layer of complexity: a stringent noise compliance agreement with its county that dates back to 1989. Each of the agreement's 101 points includes a $500,000 annual penalty; so noise infractions could potentially cost DEN more than $50 million every year.
Given the high stakes, DEN jumped ahead in the official nationwide sequence to implement new procedures of NextGen, the FAA program that is modernizing the National Airspace System with satellite-based navigation, optimized routing and widespread infrastructure improvements. DEN and its local system siblings, Centennial Airport and Rocky Mountain Metropolitan, began adopting the program's efficiency measures in January 2010.
Previously, DEN had racked up three $500,000 noise violations with the county. Using NextGen procedures, the airport resolved its long-standing community noise issues and has maintained a clean violation record with the county for the last three years.
Project: Implementing NextGen Procedures
Location: Denver Int'l Airport
Stakeholders: FAA; National Air Traffic Controllers Association; Denver Airport Authority
Localized Effort Launch: Jan. 2010
FAA Metroplex Design Launch: April 2015
Est. Implementation of Holistic Denver Metroplex Procedures: 2017
Other Denver Airports Affected: Centennial Airport; Rocky Mountain Metropolitan
Key Benefits: Improved safety; decreased fuel consumption/aircraft emissions; noise abatement; enhanced traffic efficiency
"Right off the bat, we were saving $1.5 million" recalls Mike McKee, DEN's airport noise abatement manager. The decision to proceed with more NextGen efforts was clear - despite not being selected as one of the 12 U.S. airport metroplexes prioritized for improvements via the federal program.
"The FAA was targeting the locations where they had the biggest air traffic issues to try to resolve with their limited resources," explains McKee. "I think (the FAA) probably viewed Denver International Airport and the airspace to go along with it as being pretty efficient, all things being equal, compared to other airports."
But DEN wanted to do better. With more NextGen changes, the airport is improving traffic flow and has already decreased go-arounds for arriving aircraft. This, in turn, improves the airport's on-time performance record, saves its carriers millions of dollars in fuel costs and decreases aircraft emissions.
Airport officials consider the overall results nothing less than exceptional.
"I have no qualms about saying it," reflects McKee. "We are absolutely the most successful NextGen implementation in the country, and yet we were the one that did it on our own."
Optimizing Flight Patterns
McKee cites increased traffic in the Denver airspace as a key impetus for early adoption of NextGen. As flight volume grew during the mid-2000s, local FAA personnel began encountering challenges handling traffic efficiently using legacy procedures that relied on conventional radar and controller discretion, he explains.
"We started to see difficulties crop up in certain areas where controllers were having to vector traffic out of the arrival stream - just to keep it out of the way - and bide time to find (flights) a spot in the landing sequence," McKee recalls.
Stair-step descents became common for aircraft flying into Denver-area airports. After passengers heard the engines throttle back and felt the nose pitch down slightly, the aircraft would power back up and climb ... only to be throttled down once again. Air traffic controllers directed the series of up and down movements to ensure that flight paths of arriving and departing aircraft would not cross one another.
"That approach is very inefficient," McKee comments. "Every time the aircraft would level out and have to increase power, it would burn about three times as much fuel as compared to an idle descent."
Not to mention the noise. And emissions.
In contrast, NextGen's Optimized Profile Descents are designed to be more formatted and predictable. Landing patterns are set before aircraft enter local airspace, with less reliance on human judgment from the control tower. A network of regimented procedures are designed to allow aircraft to safely pass each other upon arrival and departure, with required separation built in both vertically and horizontally to largely bypass the previously used air traffic controller dynamic. Aircraft following DEN's new procedures often descend on idle power almost all the way down, notes McKee.
"With NextGen being so predictable, you can build those crossings in and make sure the departing aircraft continue climbing, and descending aircraft continue descending," he explains. "They don't have to level out, because you know they are going to miss each other and provide adequate separation."
DEN worked with a variety of industry stakeholders to evolve its legacy traffic control approach into a model with NextGen efficiencies. The collaborative design process produced 15 standard terminal arrival routes (STARs) and 15 required area navigation (RNAV) departure procedures.
"When you get to that level, you are not going entirely away from radar, but you are referencing more GPS satellite navigation, which is much more precise," McKee explains. "The computer is flying the aircraft much more than in the past, and it is flying those procedures very efficiently and predictably, so that it will do it the same way every time. That gets you to a point where you can start, to some extent, to narrow the airspace that is needed to protect either side of a route, because now you know the aircraft are going to stay on those desired routes more predictably. There is still some dispersion and some drift, but it is much more precise than the old way of doing it."
Beyond that, the airport's use of required navigational performance (RNP) is making RNAV more accurate, repeatable and predictable in order to narrow down areas in need of protection.
"When you are flying multiple strings of aircraft to multiple runways, and you have parallel final approaches that are coming in next to each other, RNP enables you to do a lot of things with that traffic that you couldn't do before," says McKee. "We can get creative with it, because in the past, we would have had constraints due to the large blocks of airspace we had to protect."
In fact, the Denver area is at the cutting edge of required navigational performance development, with DEN serving as a demonstration site where FAA is proving new concepts to maximize airspace efficiency. As of late August, DEN had implemented 16 RNAV arrival procedures and 16 RNAV departure procedures. Within that initial group, it implemented 12 RNP arrival procedures - one for each end of the airport's six runways - and all have been used in earnest since October 2013.
The combined result of all of these measures is a dramatically, yet predictably, shorter distance from descent to the runway, McKee reports. "With NextGen here, we have seen a 35% reduction in go-arounds," he specifies.
And when pilots don't have to repeat landing patterns, airlines save time and fuel.
"When it comes to savings in general, it all starts with fuel burned, because noise and emissions are really just a derivative of that," McKee explains. "If you're not going around, you're not burning as much fuel. You're also not creating as much noise, and you're not generating as many emissions. It is all proportional."
Importantly, DEN's improvements in noise abatement, scheduling efficiency and fuel burn/emissions have required very little cash outlay, notes McKee. "The investment was almost nothing," he reflects. "We had controllers, air carriers and managers working on their own time. They eventually donated hundreds of thousands of dollars of their time to this effort. It was an amazing collaboration."
United Airlines, for instance, provided simulator time to verify that new NextGen procedures or changes to existing procedures would prove "flyable" for its pilots and aircraft. The carrier also helped ensure that noise and emissions were minimized prior to implementation.
"One of the guiding principles of NextGen arrivals is to be at idle power during the descent," says Ron Renk, United's chief technical pilot for navigation. "The simulation exercises help identify areas where the design of the procedure may not be producing that desired result.
"United strives to be a good steward of the environment and a good citizen of the communities we serve," Renk continues. "We always keep that in mind as we work with the FAA on initiatives to modernize our National Airspace System."
Building on the localized effort that developed several new performance-based navigation and RNAV performance procedures to enhance safety and efficiency at DEN, FAA began the design phase of the Denver Metroplex Project this past April. The design team, which includes representatives from the FAA, National Air Traffic Controllers Association and other key industry stakeholders, will work together to develop new arrival and departure procedures for DEN and its satellite airports. McKee will collaborate with the team to ensure that the designs include noise abatement practices.
From an environmental perspective, the design will be evaluated using the process defined by FAA Order 1050.1F, Environmental Impacts: Policies and Procedures, which details the agency's policies and procedures for implementing the National Environmental Policy Act. Designers will also check for compliance with other relevant federal laws.
From a safety perspective, system evaluation tools will be used to ensure that designs are developed within standardized safety criteria and adhere to standard separation minimums. Individual procedures will also be tested in flight simulators to ensure safety and operability. Officials expect the designs to be developed and ready for environmental modeling by April 2016.
Southwest Airlines has committed to supporting FAA and industry efforts to develop performance-based navigation procedures across the National Airspace System, including required navigational performance approaches, RNAV Standard Instrument Departures and STARs.
"Cooperation between carriers and the FAA is vital for the success of NextGen across the system," says Rick Dalton, director of air space and flow management for Southwest. "Through collaboration, the outcomes can benefit the industry as a whole, as well as the communities the airlines serve. We remain a committed part of a collective effort to transform the National Airspace System with PBN and remain very interested in the work that continues at Denver."