Evaluation of Trapezoidal Shaped Grooves

 compare the performance characteristics of the trapezoidal-shaped groove configuration to those of the standard groove configuration in the areas of water dissipation, integrity, longevity, and skid resistance.  determine whether application of the trapezoidal-shaped groove configuration could provide any advantages over the use of the standard groove configuration.  determine if the trapezoidal-shaped groove configuration holds the potential to be acceptable to the FAA as an alternative method for runway grooving. BACKGROUND. The basic purpose of grooving runway pavements is to provide a path for water to escape from under the tire of an aircraft as rapidly as possible to eliminate the potential for hydroplaning. While the standard groove configuration has proved satisfactory to date, there are several issues associated with grooves that allow room for improvement. Runway grooving using rotary saw equipment was first accomplished in the United Kingdom in the early 1960s. The National Aeronautics and Space Administration (NASA) conducted an extensive test program in the mid-1960s to determine the most effective runway groove configuration for minimizing aircraft tire hydroplaning. Cornering tests were performed with aircraft tires up to speeds of 100 knots. A 1/4 in.- by 1/4-in.-square groove spaced at 1 in. center to center was identified as providing the best performance [2]. Based on NASA’s findings, the FAA adopted a 1/4 in.- by 1/4-in.-square groove spaced at 1 1/4 in. center to center as its standard. Personnel from the Airport Safety Technology R&D Team directed an extensive test effort at the Naval Air Engineering Center in Lakehurst, New Jersey, in the late 1970s and early 1980s. A variety of runway surface treatments were tested. Braking tests were performed with aircraft tires up to speeds of 150 knots, beyond the takeoff and landing speeds of many jet aircraft. These tests showed that hydroplaning could still be minimized with grooves spaced greater than 1 1/4 in. Based on the results of this effort, the FAA Office of Engineering and Standards added 1/4 in. to the standard 1 1/4-in. groove spacing. The revision subsequently called for a standard groove configuration of 1/4-in.- by 1/4-in.-square grooves spaced at 1 1/2 in. center to center. This remains the FAA standard to date. The recommendations in the unsolicited proposal were presented at the same time the revisions to the standard were being considered. The recommendation, however, was made not as an alternative to the standard, but rather a new standard to be adopted. As a result, the recommendation was rejected by the FAA Office of Engineering and Standards. Action may have been taken at that time had the contractor proposed a test and evaluation effort instead. The trapezoidal-shaped groove proposal that this evaluation effort is based on was introduced by a different contractor. The most recent proposal that was presented to the FAA provided sufficient background information and data to warrant further consideration, and as a result, it was decided that the FAA would conduct an in depth evaluation of the new trapezoidal-shaped groove configuration.

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