DFW Pioneers Runway Safety with New Perimeter Taxiway

Author: 
Kathy Hamilton
Published in: 
March-April
2009

When Dallas/Fort Worth International Airport (DFW) opened one of the nation's first perimeter taxiways in December 2008, years of work in airfield design came to fruition.

Along with changing airfield configurations, perimeter taxiways top the Federal Aviation Administration's list of short-term initiatives to reduce runway incursions. As the third busiest airport in the world, DFW offered a unique setting for a perimeter taxiway. With about 1,900 daily flights departing and arriving on seven active runways, air traffic controllers at DFW orchestrate as many as 1,500 runway crossings every day. With every runway crossing, there's potential for something to go wrong - a potential that increases exponentially with an increase in traffic.

As early as 1992, DFW's executive vice president of Operations, Jim Crites, began kicking around the idea of a perimeter taxiway that would allow airplanes to taxi around DFW's seven active runways rather than cross them. Working at that time as an operations research analyst for American's DFW hub activities, Crites was acutely aware of the runway incursion potentials, as was his friend, Ronnie Uhlenhaker, FAA Southwest Region Air Traffic Support Team manager.

"Ronnie and I pondered the feasibility of eliminating runway crossings," explains Crites. "This would make it possible for the airport to safely operate at capacity, and air traffic control would be simplified, likely resulting in enhanced airfield operation efficiency. There had to be a way."

Why Not?

While Uhlenhaker and Crites considered the possibilities, arguments against perimeter taxiways also mounted. Most were based on the lack of technology available to realistically analyze air traffic ground activities and airport air space.




Facts & Figures

Project: Perimeter Taxiway

Location: Dallas/Fort Worth International Airport

Owners: Cities of Dallas and Fort Worth

Operator: DFW Airport Board

Research & Planning: NASA Ames Research Center, FutureFlight Central; FAA William J. Hughes Technical Center; Ronnie Uhlenhaker, FAA Southwest Region Air Traffic Support Team manager; Jim Crites, executive VP of Operations, DFW

Design/CM Team Leader: Kellogg, Brown and Root

Primary Contractor: W.W. Webber, Ltd.

Cost: $67 million for first quadrant

Funding: 75% FAA; 25% DFW

Testing & Design: Approximately 2 years

Construction: 2 years

Benefits: Enhanced airfield safety, reduced fuel consumption and emissions, passenger convenience, 30% - 35% increase in airport operating capacity

"A computer-based model is only as good as its ability to represent the real world," says Crites.

A related argument contended it would be impossible to eliminate the risks associated with aircraft departing and arriving over a perimeter taxiway.

But Crites and Uhlenhaker were determined, literally drawing their first plans on a cocktail napkin. "We 'modeled' the paths of aircraft by waving our hands in the air," recalls Crites. "Even though our methods were crude, we became convinced that a perimeter taxiway at DFW would work."

Historic Partnerships

DFW's long history of partnering with the FAA helped the project progress. Crites credits Bob Baker, the former executive vice president of American Airlines, for developing that relationship and "setting the stage" to present the idea to the FAA. The duo also had the collective ear of pilots, air traffic controllers and DFW executives.

The airport began exploring the benefits of a perimeter taxiway in 2001 using computer simulations. Then, Crites and Uhlenhaker found a way to design and virtually test the concept with real human pilots and air traffic controllers.

The team worked closely with air traffic controllers and pilots to learn their perspectives about DFW's runway safety issues to help persuade FAA and NASA to participate in designing and testing the perimeter taxiway concept. "Ronnie, having been an air traffic controller, worked closely with his colleagues to gain their perspectives," explains Crites. "I rode in the jump seats with pilots and asked them to talk to me - and show me - the problems."

In 2003, DFW partnered with the FAA and NASA to do the first virtual reality testing of a perimeter taxiway. Experts from the FAA William J. Hughes Technical Center (located near Atlantic City) supported NASA's research team as they performed real-time, human-in-the-loop testing at the NASA Ames Research Center, FutureFlight Central, in Moffett Field, CA.

Using airport data and the personal testimonials Crites and Uhlenhaker had collected, NASA developed a replica of the DFW airfield for air traffic controllers and pilots to perform virtual testing of the perimeter taxiway.

"It was like really being there," recalls Crites. "It wasn't like a computer model; it was total emersion. The air traffic controllers and pilots actually saw and controlled what was happening."

During testing, aircraft were continually added to the simulation to predict how air traffic controllers would choreograph a growing number of arrivals and departures. Crites describes the results: "When we ran the simulation without the perimeter taxiway in the model, neither the pilots nor the controllers felt capable of handling conditions beyond a 30% increase in traffic. Even at 30%, the air traffic 'control tower' was chaos."

Adding the perimeter taxiway to the simulation produced the expected results: "The air traffic controllers and the pilots cruised through easily," recalls Crites. "The results of this testing put us over the top. With the addition of a perimeter taxiway, DFW would be able to safely boost its capacity by 30% to 35%."

 

Concept to Construction

A team led by Kellogg, Brown and Root worked closely with the FAA to design the taxiway, and preliminary schematics were complete in 2005.

"The perimeter taxiway design was fairly standard, except for having to account for all of the imaginary surfaces, or air spaces, around the airport," notes Rick Jones, P.E., KBR's design team leader. "DFW required the perimeter taxiway to be waiver-free - aircraft have to be able to use it without crossing any of the airport's imaginary surfaces."

Construction of the southeast quadrant of the perimeter taxiway began in 2006 and ended in December 2008. FAA funded 75% of the $67 million project; DFW funded 25%.






Ronnie Uhlenhaker, FAA Southwest Region Air Traffic System Support Team manager (left) and Jim Crites, DFW executive vice president of Operations, celebrate the completion of the first quadrant of DFW’s new perimeter taxiway.

Dec. 4, 2008: Grand opening of the DFW perimeter taxiway, with keynote speaker, airport CEO Jeff Fegan.

"The taxiway construction presented its own challenges," says Jim Ivy, construction manager for the CM team assembled by KBR. "To begin with, the primary contractor, W.W. Webber, had to break ground right at the beginning of one of the region's wettest seasons."

W.W. Webber's project manager, Byrne Stewart, agrees: "We had to work around nearly constant rain. Further complicating our schedule, we were working at the ends of two runways, and one runway had to be open at all times. Added to this, our work within runway safety zones was limited to carefully scheduled 48-hour windows."

It was the cooperation of KBR's construction management team and Airport Operations, he adds, that made it possible for the project to proceed on schedule.

Benefits Abound

Crites espouses perimeter taxiways for all airports with closely spaced dual runways. "The FAA wants to use DFW's perimeter taxiway as a standard for design," he says, adding that a perimeter taxiway can be a more cost-effective solution than an additional runway.




DFW International Airport opened the southeast quadrant of its new perimeter taxiway in December 2008. Design of the northeast quadrant is in the works, pending feedback about the performance of the completed quadrant.

In addition to the safety advantage realized by eliminating runway crossings, there is also an associated reduction in radio communications - about 21% fewer transmissions and 25% shorter conversations. Other benefits include reduced fuel consumption, restored airport traffic capacities and reduced noise.

Because they require significantly less concrete, perimeter taxiways are estimated to cost about 10% less to construct than runways. Permitting for perimeter taxiways is also relatively simple when compared to runway permitting.

The bottom line, Crites adds, is safer service and greater passenger convenience.

With the southeast quadrant of DFW's perimeter taxiway complete, design of the northeast quadrant is in the works, pending feedback about the performance of the first quadrant. So far, however, airport data as well as feedback from pilots and air traffic controllers indicates that the perimeter taxiway is an overwhelming success.

Subcategory: 
Runway/Ramp

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