advantage over road vehicles in such situations, as this type of braking is not affected by aquaplaning, but it requires a considerable distance to operate as it is not as effective as wheel braking on a dry runway. Aquaplaning is a condition that can exist when an aircraft is landed on a runway surface contaminated with standing water, slush, and/or wet snow. Aquaplaning can have serious adverse effects on ground controllability and braking efficiency. The three basic types of aquaplaning are dynamic aquaplaning, reverted rubber aquaplaning, and viscous aquaplaning. Any one of the three can render an aircraft partially or totally uncontrollable anytime during the landing roll. However this can be prevented by grooves on runways. In 1965, a US delegation visited the Royal Aircraft Establishment at Farnborough to view their grooved runway for reduced aquaplaning and initiated a study by the FAA and NASA. Grooving has since been adopted by most major airports around the world. Thin grooves are cut in the concrete which allows for water to be dissipated and further reduces the potential to aquaplane. Types Viscous Viscous aquaplaning is due to the viscous properties of water. A thin film of fluid no more than 0.025 mm in depth is all that is needed. The tire cannot penetrate the fluid and the tire rolls on top of the film. This can occur at a much lower speed than dynamic aquaplane, but requires a smooth or smooth-acting surface such as asphalt or a touchdown area coated with the accumulated rubber of past landings. Such a surface can have the same friction coefficient as wet ice. Dynamic Dynamic aquaplaning is a relatively high-speed phenomenon that occurs when there is a film of water on the runway that is at least 1/10 inch (2.5 mm) deep. As the speed of the aircraft and the depth of the water increase, the water layer builds up an increasing resistance to displacement, resulting in the formation of a wedge of water beneath the tire. At some speed, termed the aquaplaning speed (Vp), the upward force generated by water pressure equals the weight of the aircraft and the tire is lifted off the runway surface. In this condition, the tires no longer contribute to directional control, and braking action is nil. Dynamic aquaplaning is generally related to tire inflation pressure. Tests have shown that for tires with significant loads and enough water depth for