Originally Posted by
gearlever
I was recently asked by a mate about Vp, the hydroplaning speed.
Yes, most of us know Horne's equation Vp = 9 x square root tire press (psi) = ... kts.
Let's say the tire pressure is 220 psi, so Vp is about 135 kts or less (tire tread).
How does it influence take off calcs?
How is it implied in modern performance data tools (wet/contaminated runway)?
Thx
Hydroplaning is not much of an issue on modern grooved (or porous friction coated) runways as long as the surface is not completely saturated from extremely heavy rain like one might get in a tropical storm or such. We have performance manuals (sometimes paper, sometimes computerized) that take account for other types of runway contamination. The data is generally conservative as long as the contamination and/or braking action reports are accurately reflect the current conditions.
Occasionally one might operate to a runway that is either not grooved or has substantial rubber deposits. Those case should be handled with appropriate caution.