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.