Hydroplaning speed
Thread Starter
Hydroplaning speed
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
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
Last edited by gearlever; 21st Oct 2019 at 22:02.
Join Date: Jun 2019
Location: VA
Posts: 210
Likes: 0
Received 0 Likes
on
0 Posts
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
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
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.
Thread Starter
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.
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.
So may I assume Vp is considered in up to date performance charts/computer programms for contaminated runways?
Kind regards
Join Date: Jun 2019
Location: VA
Posts: 210
Likes: 0
Received 0 Likes
on
0 Posts
See: AC 25-31 for more information and references.
gearlever, A more detailed reference is at https://www.easa.europa.eu/sites/def...dment%2023.pdf
AMC 25.1591 starts at page 958
I doubt that aquaplaning is an issue during takeoff as the physical aspects tend to reduce tire drag.
Spray / impingement drag might be of greater concern.
Also note that 9 x root P may not apply to all types of tire ( radial ply ?); the critical speed could be as low as 7 x root P.
See https://babel.hathitrust.org/cgi/pt?...iew=1up&seq=44 via https://en.wikipedia.org/wiki/Aquaplaning for a range of speeds.
AMC 25.1591 starts at page 958
I doubt that aquaplaning is an issue during takeoff as the physical aspects tend to reduce tire drag.
Spray / impingement drag might be of greater concern.
Also note that 9 x root P may not apply to all types of tire ( radial ply ?); the critical speed could be as low as 7 x root P.
See https://babel.hathitrust.org/cgi/pt?...iew=1up&seq=44 via https://en.wikipedia.org/wiki/Aquaplaning for a range of speeds.
Join Date: Nov 2019
Location: unknown
Posts: 3
Likes: 0
Received 0 Likes
on
0 Posts