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AFS angle of attack indicator

cojaken

Active Member
I recently had a bug block my pitot on short final and lost airspeed indication.

I landed successfully, but realized afterwards that the AOA might have helped me, if I had looked at it! I have the AOA ports on the wings, not on the pitot tube.

So here’s my question: with a blocked pitot, could I have flown by the AOA or is the airspeed part of the input to tha AOA algorithm?
 
If your AFS AoA is a standalone unit like mine, it has a connection to the pitot tube. From the manual, AoA is a function of the difference between pressure at the upper and lower AoA pressure ports *and* the difference between pitot and static pressure. So, if the pitot tube is blocked the AoA you see almost certainly isn't correct.

HTH

Dave
 
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If you have the ports in the wings as you say, The AoA may be independent of airspeed. But I think only AFS or someone with knowledge of their system can reply with certainty.
 
I too thought it was independent, but Dave is correct. The manual says they are normalizing with dynamic pressure (q=Pitot pressure - Static pressure) when using the wing surface probes, so pitot and static are needed for the AOA solution.

Quote from the AFS AOA manual:
"The result of dividing the airfoil or probe differential pressure Pw by the pitot static differential pressure Pp is a coefficient of pressure (CP). There is a unique variation of CP with angle of attack."​

So if airspeed isn't looking good, don't rely on AOA indication with this setup.

Lenny
 
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