Braking of an Aircraft Tire on Grooved and Porous Asphaltic Concrete

The Federal Aviation Administration is engaged in an experimental program to determine the effectiveness of various surface treatments to eliminate aircraft hydroplaning when landing on wet runways. The surface treatments included saw-cut grooves, reflexpercussive grooves, and porous friction overlays in the asphaltic concrete runways. Experiments were conducted on a 1.25-mile long track that included a 300-ft test bed containing concrete with 40-ft sections of various surface treatments. Test speeds between 70 and 150 knots were achieved by the use of a jet-powered pusher car that also supported a dynamometer and tire-wheel assembly. The test tire was similar to one that is used on a Boeing-727 aircraft. The results showed that the porous friction overlay, the reflex-percussive grooves, and the saw-cut grooves of various spacing provided similar friction levels under wetness conditions that were either "wet" or "flooded." However, for the "puddled" condition (intermediate wetness between wet and flooded), the saw-cut grooves spaced at 1.25 in. provided the maximum improvement in friction level over a nongrooved or nontreated surface. Thus, although hydroplaning is delayed to a speed higher than 150 knots for all the surface treatments included in the program, the selection of a particular type of surface treatment can be based on whether the rainfall intensities in a region create predominantly wet, puddled, or flooded water conditions on the runway.