Dynamic Hydroplaning Speed

From the NASA/FAA relation that depends only on tire inflation pressure: spin-down (a rolling wheel losing traction) Vp = 10.35 sqrt(P) mph = 9 sqrt(P) knots; spin-up (a locked wheel starting through standing water) onset 7.7 sqrt(P) knots, the more conservative case, so hard braking into standing water is worse. A truck tire at 100 psi hydroplanes near 104 mph, a car tire at 32 psi near 59 mph, an underinflated 24 psi tire near 51 mph -- which is why low pressure is dangerous in rain. A screening figure assuming standing water about 0.1 in deep and smooth/worn tread; deeper water or bald tires lower it, good tread raises it. Public domain (NASA TN D-2056 Horne & Dreher; FAA AC 91-6A). A safety screen; road conditions and the driver govern.

spin-down (rolling wheel) Vp = 9 sqrt(P) knots = 10.35 sqrt(P) mph; spin-up (locked wheel) onset Vp = 7.7 sqrt(P) knots; P = tire inflation pressure (psi). 1 knot = 1.1507794 mph.

Dynamic hydroplaning speed per NASA Technical Note D-2056 (Horne & Dreher, 1963) and FAA Advisory Circular AC 91-6A, by name; both public.

NASA TN D-2056 and FAA AC 91-6A are public-domain U.S. Government documents; the relation depends only on the user's tire pressure.

Estimate. AHJ and licensed professional govern.

Field names used by the API: tire_pressure_psi, hydroplaning_speed_knots, hydroplaning_speed_mph

• Spin-down speed Vp = 9 sqrt(P) knots = 10.35 sqrt(P) mph (rolling wheel), P in psiNASA TN D-2056 / FAA AC 91-6A
• Spin-up onset Vp = 7.7 sqrt(P) knots (locked/stationary wheel), the more conservative onsetNASA TN D-2056
• Scope assumes ~0.1 in standing water and smooth/worn tread; a screening figure, not a tread-and-water-depth modelscope of this tile