Directional control after touchdown...

Newps wrote:

Cessna's have dihedral too. May not be exactly the same but it's there.

Yes, but very little. High-wings have more inherent stability since the
CG is below the CP.


I don't see how you get a 5 kph difference with 18m altitude difference.


Did I read that wrong? The chart said the wind went from 15 kmh to 20 kmh.

That was a representative example, but didn't apply as we are taking
from about 1m to about 2m, not from 2m to 18m. It is the general
formula that I was looking at which can be used for any wind speed and
altitude difference of interest.


It states that the relationship is to the 1/7th power of the altitude.
Since it takes 1m as the reference altitude for a wind increase factor
of 1.0, an altitude of 18m has an increase factor of 18 to the 1/7th
power. This is 1.51 which indicates that the wind at 18m is 51%
faster than at 1m. Comparing 1m to 2m which is approximately correct
to compare a Bo wing to 182 wing, the increase factor is 2 to the
1/7th power which is 1.1. Thus the wind velocity at 2m is 10% greater
than at 1m. So, if the wind at 1m is 20 MPH then the wind at 2m would
be expected to be 22 MPH. If the wind at 1m is 40 MPH it would be
expected to be 44 at 2m.

That's a lot of words to prove that the difference is irrelevant for the
purpose of this discussion. No way anybody tells the difference from 20
- 22 mph or 40 - 44 mph.

4 MPH is the difference between stalling at not stalling if you are
already flying only 2 MPH above the stall.

Whether that is relevant depends on the circumstances, no doubt. I
never said anything different. I'm simply correcting your statement
that wind speed is constant with height above the ground - which it isn't.

Having a 10% higher headwind when touchdown in a 182 vs. a Bo or Piper
is significant with respect to landing and takeoff distance. Check your
POH if you don't think a 10% difference in wind makes a performance
difference.

Matt