Cosmo,
you are reading far more into the original question than is actually there. To aid you I have copied the entire question below.
Hi guys,
I have a question regarding the take-off on a wet runway. I
know the ASDA will be longer due to a lower friction on the runway. That is
because the energy is applied on the wheels and they could skid over the
runway.
But how does a wet runway affect the start of the take-off? Since the energy is not applied on the wheels but on the plane itself, the lower frictioncoefficient should have no influence on the wheels. Still it seems that the aircraft needs more runway for the first part (before V1)
I would say that the runway friction coefficient should only affect the braking (ASDA) part, can anyone clarify?
thanks.
Now if you can manage to set aside your dismissive attitude for a moment you might help us by pointing out where exactly the OP includes either FAR 25 aircraft or paved surfaces.
You might also explain how your statement that
But anyway, grass has to move out of the way, wet or dry. Wet grass is apparently heavier.
Differs significantly from my original statement that
the wheels must push the water out of the way in order to move forward. This requires energy. The fact that some of the available energy is being used to push water aside, means that there is less energy available to accelerate the aircraft. So the distance required to accelerate to a given speed is greater.
In response to your question
Are you seriously thinking that 0-3 mm water will have anything other than a very theoretical minuscule effect on acceleration?
I can only say that it is not a matter of what I think. The people who decided that a factor of 1.3 must be applied to wet grass clearly thought that 3 mm of water would make a significant difference. I suspect that they knew far more about this subject than you or I do.