A Technology Partnership for the New Millennium

Future Flight Image in a Diamond Shape

1.10 Pavement Testing Facility

 The introduction of heavier aircraft with new gear configurations makes it essential that researchers gain a more accurate characterization of paving materials so they can increase design reliability and better estimate the effects of the larger aircraft. The next generation of large civil aircraft is expected to include models that will weigh up to 1.7 million pounds and have complex, multiple-wheel, multiple-truck landing gear systems. The first of this generation of aircraft, the Boeing B-777, which entered commercial service in June 1995, has two six-wheel landing gears and a gross weight of up to 535,000 pounds. The six-wheel gear loads applied to airport pavements by the B-777 are quite different from the loads of the current generation aircraft. Although current pavement design standards have worked well, they may not accommodate the dramatic changes associated with the next generation of airplanes currently being planned.

The FAA is developing new standard procedures capable of producing pavement thickness designs for all aircraft weights and landing gear configurations that might come into operation in the foreseeable future. The FAA's plan includes short-term research to meet the immediate needs arising from the introduction of new-generation aircraft, while pursuing long-term goals for improving the efficiency of airport pavement operations. The short-term research under way includes verification of design procedures based on current layered elastic analysis technology. The FAA's longer-term objective is to develop new design procedures. Essential to the development of these new design procedures is a comprehensive testing and validation program using full-scale pavement sections and dynamic simulated aircraft loading.

Pavement Test Facility

The creation of FAA's National Airport Pavement Test Facility was made possible through a Cooperative Research and Development Agreement between the FAA and the Boeing Company. The cost of the construction and the first year testing is $21,000,000; the FAA and Boeing are sharing this cost. Subsequent costs will be the responsibility of the FAA.

  • The test facility is capable of full-scale loading representing new generation, heavy civil transport aircraft. This load may comprise up to 75,000 pounds (34,020 kg) per wheel on two landing gears with six wheels per gear (a total of 12 wheels). It can handle single, dual tandem, and trident loading configurations, and will have the capability to change wheel spacing and gear spacing, with a maximum tire size at 56 inches (142 cm) overall diameter and 24 inches (61 cm) maximum width.
  • The test pavement is 900 feet (270 m) long and 60 feet (18 m) wide. This width allows two gear configurations to be tested simultaneously. For example, a six-wheel B-777 gear can be tested in one lane and a four-wheel B-747 gear can be tested in the other lane. This direct comparison of two different gears is particularly important in finding a resolution for computing aircraft classification numbers for worldwide aircraft-airport compatibility.
  • A total of nine test sections have been constructed of three subgrade materials (in a range of 3 percent to 20 percent California Bearing Ration) for the first series of tests. There are three asphalt sections with an aggregate base, three asphalt sections with an asphalt-stabilized base, and three concrete sections with a cement-treated base. Test speeds, between 5 and 15 miles per hour, will represent worst-case pavement response. The facility will accommodate lateral wander patterns typical of airport runway operations. Pavement response sensors will measure strain, deflection, pressure, moisture, and temperature.
The preliminary operations plan calls for a comprehensive series of tests, designed to measure pavement response at different wheel and gear configurations. Tests will be performed to the point of pavement failure, with the expected failure rate of one test section per year. Pavement test-section reconstruction will be scheduled at 18-month intervals. The test vehicle can be programmed to skip, or "fly over," a failed section or sections.

Full-scale testing will provide the information urgently needed to investigate the performance of airport pavement that is subjected to the complex gear loads of the new generation of aircraft. The resulting technical data will help validate new design standards and assure compatibility between aircraft and airports throughout the world. The data will also provide an improved scientific basis for further development and refinement of the International Civil Aviation Organization's pavement loading standards for aircraft.

FAA POC:
Gordon Hayhoe
(609) 485-8555
gordon.hayhoe@tc.faa.gov

NASA POC:
Tom Yager
757 864-1304
t.j.yager@larc.nasa.gov

 
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