[simpits-tech] AOA sensors

[Francois Mavel]

Hi Craig,

an AOA sensor is just like a flag flying in the air stream.
you only scale the angle between the airflow and the aircraft longitudinal 
axis.

Hope it will help,
Francois

>Yes, the syringe concept is sweet; on paper. ;)  It's near impossible >to
>have leak free sliding seals.  My altimeter case doesn't really seem >to 
>have
>a 100% air tight seal around the barometric adjustment knob.  I think >the
>mechanics of making a bellows that could pull below 20 in Hg would be >real
>challenge as the 15 psi atmospheric pressure on the sides would tend to
>collapse the bellows. To pull from ambient to 28 in hg would require 
> >roughly
>a 15:1(29.92:2) volume increase of the Altimeter and piping dead >space.  
>The
>altimeter volume is about 1 cup(1/16 gallon) so the bellows or syringe 
> >would
>have to have about a gallon capacity! :O
>
>I read up a bit on vacuum regulators and I think I can do a simple mod >to
>one of the eBay pressure regulators I have.  It involves porting the 
> >vacuum
>source to the regulator's exhaust port...pretty simple change.  I'll >try 
>it
>at work as I've no vac pump at home.
>
>BTW, I made a mistake here:
>
>"So with one vacuum signal and one pressure signal you could drive the
>Altimeter(vac), ASI(vac and press), and AOA Indicator(vac). Where vac =
>barometric pressure and pressure = pitot dynamic pressure."
>
>I meant VVI, not AOA Indicator would have the same vac signal.  I >think 
>the
>AOA uses two pitot pressures, I'm not sure exactly how this works.
>
>Craig R.


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