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Date: Sat, 28 Aug 2010 18:24:05 -0400
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Subject: Re: Pitot tube and AoA
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John -

The Jim Frantz AoA system (now sold by, I think, Advanced Flight Systems)=
 uses pitot and static information, so you would get erroneous AoA reading=
s with a plugged pitot tube.

Specifically, the system depends on the relationship between the different=
ial pressure across the wing from top to bottom (lets call that DeltaP) an=
d the dynamic pressure which we recall is the difference between pitot and=
 static pressure (lets call that Q).  It turns out that the quotient Delta=
P/Q is proportional to angle of attack if you pick the right point along=
 the chord (which is why the instructions tell you to put the pressure por=
ts in certain places).  Therefore, if your pitot tube is plugged, DeltaP/Q=
 will be off and so will the alpha readout.

Now, if you're using a different system such as a Dynon, all bets are off.=
  I don't know how that is mechanized.

- Rob Wolf


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<font color=3D'black' size=3D'2' face=3D'arial'>
<div>John -</div>


<div>&nbsp;</div>


<div>The Jim Frantz AoA system (now sold by, I think, Advanced Flight Syst=
ems) uses pitot and static information, so you would get erroneous AoA rea=
dings with a plugged pitot tube.</div>


<div>&nbsp;</div>


<div>Specifically, the system depends on the relationship between the diff=
erential pressure across the wing from top to bottom (lets call that Delta=
P) and the dynamic pressure which we recall is the difference between pito=
t and static pressure (lets call that Q).&nbsp; It turns out that the quot=
ient DeltaP/Q is proportional to angle of attack if you pick the right poi=
nt along the chord (which is why the instructions tell you to put the pres=
sure ports in certain places).&nbsp; Therefore, if your pitot tube is plug=
ged, DeltaP/Q will be off and so will the alpha readout.</div>


<div>&nbsp;</div>


<div>Now, if you're using a different system such as a Dynon, all bets are=
 off.&nbsp; I don't know how that is mechanized.</div>


<div>&nbsp;</div>


<div>- Rob Wolf<br>
<br>
</div>


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