Evaluation of Trapezoidal Shaped Grooves

Performance. Researchers also determined the ability of the trapezoidal-shaped grooves to evacuate water from the surface of the runway. Researchers elected not to repeat the performance test that was conducted at MCAF Quantico, as it was assumed that both types of grooves would evacuate water in the same fashion regardless of the pavement type. Rubber contamination and groove closure would obviously have a negative affect on the ability of the grooves to disperse water, so it is assumed the trapezoidal-shaped grooves would continue to dissipate water quicker than the standard grooves since they maintained a wider opening. The airport manager of ORD reported that he noticed a significant difference in the amount of water vapor created by a jet blast from a departing or landing aircraft as it passes over the different groove sections. He reported that when the aircraft passed over the trapezoidal-shaped grooves, the amount of mist or water in the air decreased. Researchers concluded that this was a result of less water being held in the trapezoidal-shaped grooves, so as the jet engines of the aircraft passed over the trapezoidal-shaped grooves, there was less water for the jet engines to pull from the pavement and throw into the air. The standard grooves, however, must have contained more water and, thus, provided a large source of water that could be vaporized. Researchers took note of this observation but did not consider it as part of this evaluation effort. Friction Characteristics. During one visit to ORD, researchers were able to conduct friction measurements of the runway area where the trapezoidal-shaped grooves were installed using an FAA-owned and -operated SFME. The SFME that was used for this evaluation was a Sarsys Saab 9-5 Wagon Surface Friction Tester (SFT). This model SFME, like the RFT used at MCAF Quantico, is approved for use by the FAA and is listed in FAA AC 5320-12C [1]. Data collection runs for this project were conducted at 40 mph. Data collection for the longer test sections toward the threshold of Runway 10 started 100 ft from the beginning of the test section closest to the threshold of Runway 10, and ended 100 ft beyond the end of the last test section, for a total of 1850 ft. Testing was done with the vehicle aligned 10, 15, and 20 ft from the center of the runway. This allowed data collection from different parts of the runway that experience different amount of exposure to traffic and rubber. Data collection for the shorter test section towards the threshold of Runway 28 also started and ended 100 ft from the end of the test section, for a total of 950 ft. Testing was also done with the vehicle aligned at 10, 15, and 20 ft from the center of the runway. Figures 50 through 55 show the data collected from the SFT during the test runs at ORD. Figures 50 through 52 show data collected for the test runs on the longer test section, closest to the threshold of Runway 10, at 10, 15, and 20 ft from the runway centerline. Figures 53 through 55 show data collected for the test runs on the shorter test section, closest to the threshold of runway 28, also at 10, 15, and 20 ft from the runway centerline. For all runs, the runway surface was dry and the SFT used its own self-contained wetting system. The locations of the standard and trapezoidal-shaped grooved areas are shown in the figures by the letters “T” for trapezoidal and “S” for standard.

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