the amount of tread so that the dynamic head pressure from the speed is applied to the whole contact patch, the minimum speed for dynamic aquaplaning (Vp) in knots is about 9 times the square root of the tire pressure in pounds per square inch (PSI). For an aircraft tire pressure of 64 PSI, the calculated aquaplaning speed would be approximately 72 knots. This speed is for a rolling, non-slipping wheel; a locked wheel reduces the Vp to 7.7 times the square root of the pressure. Therefore, once a locked tire starts aquaplaning it will continue until the speed reduces by other means (air drag or reverse thrust). Reverted rubber Reverted rubber (steam) aquaplaning occurs during heavy braking that results in a prolonged locked-wheel skid. Only a thin film of water on the runway is required to facilitate this type of aquaplaning. The tire skidding generates enough heat to change the water film into a cushion of steam which keeps the tire off the runway. A side effect of the heat is it causes the rubber in contact with the runway to revert to its original uncured state. Indications of an aircraft having experienced reverted rubber aquaplaning, are distinctive 'steam-cleaned' marks on the runway surface and a patch of reverted rubber on the tire. Reverted rubber aquaplaning frequently follows an encounter with dynamic aquaplaning, during which time the pilot may have the brakes locked in an attempt to slow the aircraft. Eventually the aircraft slows enough to where the tires make contact with the runway surface and the aircraft begins to skid. The remedy for this type of aquaplane is for the pilot to release the brakes and allow the wheels to spin up and apply moderate braking. Reverted rubber aquaplaning is insidious in that the pilot may not know when it begins, and it can persist to very slow groundspeeds (20 knots or less). Reducing risk Any aquaplaning tire reduces both braking effectiveness and directional control. When confronted with the possibility of aquaplaning, pilots are advised to land on a grooved runway (if available). Touchdown speed should be as slow as possible consistent with safety. After the nosewheel is lowered to the runway, moderate braking should be applied. If deceleration is not detected and aquaplaning is suspected, the nose should be raised and aerodynamic drag utilized to decelerate to a point where the brakes do become effective. Proper braking