Directional control after touchdown...

"Newps" wrote in message
. ..


Bill Denton wrote:
Could it be the ground effect differences between low wing and high wing
aircraft that are contributing to this issue?


No, I noticed that right away after I bought my Bonanza. With my 182 it
was second nature to manipulate the aileron for the wind while taxiing.
In the Bo I don't bother as there's no reason to. I simply hold the
yoke so the controls don't get slammed around in the wind. With a high
wing the wing is out there on a longer lever plus the wheel track is a
little narrower.

I am pretty sure that there is also more wind six feet from the graound than
there is three feet from the ground.

Presumably there are plenty of statistics on the subject, although I have no
idea where to look or would would make a good search argument for and
internet search.

Peter

Peter Dohm wrote:




I am pretty sure that there is also more wind six feet from the graound than
there is three feet from the ground.

You're kidding.




Presumably there are plenty of statistics on the subject,


You'll never find that as it isn't true.

Newps wrote:


Peter Dohm wrote:




I am pretty sure that there is also more wind six feet from the
graound than
there is three feet from the ground.

You're kidding.




Presumably there are plenty of statistics on the subject,


You'll never find that as it isn't true.

It absolutely is true. Wind velocity drops dramatically as it
approaches a surface.

Matt

Matt Whiting wrote:

Newps wrote:



Peter Dohm wrote:




I am pretty sure that there is also more wind six feet from the
graound than
there is three feet from the ground.


You're kidding.




Presumably there are plenty of statistics on the subject,



You'll never find that as it isn't true.


It absolutely is true. Wind velocity drops dramatically as it
approaches a surface.

I better get my digital handheld windmeter recalibrated becxause at 4
feet, the top of the wing on my Bo and six feet, the top of the wing on
a typical Cessna the wind is the same.

"Newps" wrote in message
. ..


Matt Whiting wrote:


You'll never find that as it isn't true.


It absolutely is true. Wind velocity drops dramatically as it approaches
a surface.

I better get my digital handheld windmeter recalibrated becxause at 4
feet, the top of the wing on my Bo and six feet, the top of the wing on a
typical Cessna the wind is the same.

I'm sure Whiting will come back that there's 0.05 MPH difference and that
difference should be taken into account.

Matt Barrow wrote:
"Newps" wrote in message
. ..

Matt Whiting wrote:

You'll never find that as it isn't true.

It absolutely is true. Wind velocity drops dramatically as it approaches
a surface.
I better get my digital handheld windmeter recalibrated becxause at 4
feet, the top of the wing on my Bo and six feet, the top of the wing on a
typical Cessna the wind is the same.

I'm sure Whiting will come back that there's 0.05 MPH difference and that
difference should be taken into account.



Plonk.

Newps wrote:


Matt Whiting wrote:

Newps wrote:



Peter Dohm wrote:




I am pretty sure that there is also more wind six feet from the
graound than
there is three feet from the ground.


You're kidding.




Presumably there are plenty of statistics on the subject,



You'll never find that as it isn't true.


It absolutely is true. Wind velocity drops dramatically as it
approaches a surface.

I better get my digital handheld windmeter recalibrated becxause at 4
feet, the top of the wing on my Bo and six feet, the top of the wing on
a typical Cessna the wind is the same.

I would say so. The following article has a graph shows the
relationship on average between wind speed and height. The difference
between the wind at 1m (about the average height of your Bo wing) and at
2m (about the average height of a 182 wing) is about 10%.

http://www.rpc.com.au/products/windt.../wind_faq.html

Not a huge difference, but not no difference either.

Matt

Matt Whiting wrote:


I would say so. The following article has a graph shows the
relationship on average between wind speed and height. The difference
between the wind at 1m (about the average height of your Bo wing) and at
2m (about the average height of a 182 wing) is about 10%.

My Bo wing is 4'2" at the tip. I know that because I installed a
furnace in my hangar last month. The code calls for the furnace to be a
minimum 10 feet above the wing. I'm 6'2" and coud not walk under the
wing of my 182 as it sat on its big tires. So I would say the top of
the wing tip there would be at most 6'6". Even according to your
generalized graph an 18 meter difference in height brings a 5 kph
difference in windspeed, the difference between about two feet is
trivial and certainly not a factor at all for the subject at hand which
was stability of the airplane because one is a high wing and one is a
low wing.

Newps wrote:


Matt Whiting wrote:


I would say so. The following article has a graph shows the
relationship on average between wind speed and height. The difference
between the wind at 1m (about the average height of your Bo wing) and
at 2m (about the average height of a 182 wing) is about 10%.

My Bo wing is 4'2" at the tip. I know that because I installed a
furnace in my hangar last month. The code calls for the furnace to be a
minimum 10 feet above the wing. I'm 6'2" and coud not walk under the
wing of my 182 as it sat on its big tires. So I would say the top of
the wing tip there would be at most 6'6". Even according to your
generalized graph an 18 meter difference in height brings a 5 kph
difference in windspeed, the difference between about two feet is
trivial and certainly not a factor at all for the subject at hand which
was stability of the airplane because one is a high wing and one is a
low wing.


That is why I said average height of the Bo wing. Most Bonanzas I've
seen have a fair bit of dihedral and the wing isn't anywhere near 4'2"
at the root. I don't know what the average height is, but is sure isn't
4'2".

I don't see how you get a 5 kph difference with 18m altitude difference.
The chart expresses the difference as a factor relative to 1 as it
can't give an absolute wind velocity difference without knowing the base
velocity at 1m which is where the chart starts.

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.

As I said, 10% may or may not be significant in any particular
situation, but to say that the wind doesn't vary with altitude above the
ground as you claimed initially is simply false. I realize that you
never admit you are wrong and won't this time, but that doesn't change
the fact that you are wrong and it doesn't change the physics of wind
flow at various altitudes above the ground.


Matt