[NSRCA-discussion] Weather Vane

[James Oddino]

Hi Jim,

You have the picture.  The airplane is essentially hovering  
horizontally with zero ground speed in any direction just before  
touch down.  I don't call that crabbing.  And yes I did twiddle the  
ailerons and the throttle all the way down.  As I see it, as soon as  
I steer with ailerons the airplane starts side slipping, and as I  
recall from your explanation, an airplane will weathervane if it is  
side slipping.  I believe this is what we all experience when landing  
in a cross wind and why we believe the airplane starts to crab all by  
itself.  Make sense?

Jim O


On Oct 25, 2007, at 6:38 PM, Jim Alberico wrote:

>
>
>>
>>> If you didn't crab into the wind and the airplane is
>> aligned with the
>>> runway but drifting sideways, you'd have to time the
>> touchdown to land
>>> on the runway.
>>
>> At touch down the plane isn't crabbed. It is perpendicular to
>> the runway headed into the wind, and it got there without me
>> touching the rudder.
>>
>
> :-D
> LOL.  It's crabbed 90 degrees, then.  So-calling crabbing has no  
> physical
> meaning except for reference to some straight ground track.  Here  
> we'd have
> to assume the reference is the line running down the runway  
> centerline.
>
>>> Either way, without cross-controlling, you're going to put
>> side loads
>>> on the landing gear when you touch down.
>>
>> There is no side load on the landing gear as there is no
>> velocity vector along the runway.
>>
>
> At those high wind speeds, that makes sense.  ...but, I bet you  
> twiddled
> with the ailerons and throttle all the way down.  :-)
>
>
> Jim A
>
>
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