9 x sqrt of tire pressure in psi=hydroplane speed
Dynamic hydroplaning is a condition where the tire is lifted completely above the surface of the runway. As little as one-tenth inch of water combined with the “NASA critical speed” of the tire is the causal factor.
Viscous hydroplaning can occur at slower speeds and rather than the water lifting the tire from the pavement, the tire slips on a thin film. This occurs on smooth runways.
Reverted Rubber (Steam) Hydroplaning
Encountering an emergency during takeoff or landing often causes the pilot to “lock” the brakes. If this occurs on a wet runway, the tire track area heats up due to friction causing some of the rubber to “revert back” to a gummy state, trapping water. The water turns to steam and steam pressure lifts the tire from the runway.