Research that may lead to more widespread use of “green” runway pavement materials is underway at the FAA National Airport Pavement & Materials Research Center, in Egg Harbor Township, NJ. Engineers at the new facility use a custom-designed heavy vehicle simulator to test asphalt and other pavement materials at high tire pressures and temperatures.
The pavement-specific complex is part of the William J. Hughes Technical Center, which conducts research on a variety of other aviation topics, including air traffic control, communications, navigation, airports, aircraft safety and security. The Technical Center is the primary facility supporting the NextGen system.
Project: Airfield Pavement Research
Location: FAA National Airport Pavement & Materials Research Center
Part of: William J. Hughes Technical Center — Egg Harbor Township, NJ
Facility Cost: $3.8 million
Construction: Aug. 2013 - May 2015
Building Contractor: Eagle Construction
Key Elements: 6 pavement test strips, each 300 ft. long (4 outdoors; 2 indoors)
Key Equipment: Remote-controlled heavy vehicle simulator by Dynatest U.S.
Simulator Size: 130 ft. long, 16 ft. wide, 14 ft. tall; 240,000 lbs.
Simulator Cost: $4.2 million
Key Benefits: Facilitates testing of environmentally friendly airport pavement materials & related products such as airfield markings, rumble strips, etc.
Until recently, the FAA had not recommended the use of environmentally friendly pavement materials for airfield projects, because research regarding the effects of aircraft tire pressure and heavy gear loads on them had been limited. Thanks to current efforts at the agency’s new facility, the use of green materials and pavement products that can be modified to enhance durability, workability and strength may become more common in the future.
There are two main ways to ensure that a product or component functions as it was designed and built to perform: destructive and non-destructive testing. Engineering labs often opt for computer-simulated (non-destructive) tests due to their lower costs, time requirements and other constraints. But they can only show how a product is intended to perform during actual use.
Products with critical health and safety implications, however, require destructive testing. Cars with crash dummies as passengers get smashed, critical devices are set on fire or exploded, and testers run engines and motors at full throttle until they fail. Determining how much pressure runways can withstand and still be within safe limits is one of tasks engineers perform at the new FAA center.
Construction of the test facility began in August 2013 and was completed in May 2015 at a total cost of $3.8 million.
An integral component is a $4.2 million vehicle simulator that was designed specifically for testing airfield pavement and was delivered to the center in November 2013. The multi-wheeled testing vehicle is 130 feet long, 16 feet wide, 14 feet tall, and weighs 240,000 pounds. Despite its size, no drivers or researchers ride in or on it. Engineers operate the large equipment via remote controls.
“The heavy vehicle simulator has an automated heating system that allows engineers to replicate and analyze the damage that heavy commercial jets can cause to the top asphalt layer during summer months,” explains the FAA’s Navneet Garg, Ph.D. “The vehicle was designed to simulate heavy commercial aircraft wheel loads and tire pressures, and can show how repetitive aircraft operations affect pavement performance.”
FAA engineers operate the simulator on a variety of “real-world” surfaces, including four outdoor pavement strips, each 300 feet long. Two indoor areas of the same size allow for testing in a more controlled environment.
Using the remote-controlled vehicle, engineers can simulate 20 years of aircraft traffic in just a few weeks, Garg notes.
FAA engineers also use the simulator to test the performance of airfield paint markings and rumble strips.
Previously, a lack of research regarding environmentally friendly airport pavement materials prevented the FAA from recommending their use; but change is in the works. “The FAA is seeking ways to expand the use of green materials, along with materials that can be modified to enhance pavement durability, workability and strength,” says Garg. “This will help airport operators save money by lowering the costs of initial construction, maintenance and repairs, and will provide a longer pavement life.”
Extensive testing is required, given the rigorous conditions airfield pavements must endure. “On new generation aircraft like the Boeing 787 and Airbus 350, tire pressures can range from 220 to 250 psi (pounds per square inch), while runway pavement temperatures can reach 140 to 150 degrees Fahrenheit as far north as New York City,” explains Garg. “The FAA’s specially designed vehicle simulator has an automated heating system that allows engineers to replicate and analyze the damage that heavy commercial jets can cause to the top asphalt layer when runways are hot. The vehicle simulates the behavior and weight of aircraft tires, so that researchers can learn and can show how repetitive aircraft operations affect pavement.”
For testing purposes, engineers use a single- or dual-wheel load module that extends down from the carriage to apply the desired amount of load against the runway test pavement. The data obtained from taxi tests will be used to develop standards and specifications for using various technologies such as warm mix asphalt, stone matrix asphalt and recycled asphalt pavement on airfield surfaces.
Research indicates that a fully loaded airplane can cause the most damage while taxiing from the gate to the end of a runway for takeoff. Wide-body jets such A380s can exert between 55,000 and 65,000 pounds of weight per wheel on airfield pavement.
“The heavy vehicle simulator uses hydraulic actuators that allow FAA lab engineers to accurately apply ‘real-world’ forces and pressures in tests that produce very precise results, thereby saving time and money,” says Jeffery Gagnon, manager of the FAA’s Airport Pavements Research and Development Team.
“New airport runways are occasionally being built,” he comments. “But old ones are being completely rebuilt or overlaid for many good reasons beyond wear-and-tear — including the availability of new materials and changes in aircraft landing gear design, wheel loading and traffic levels.