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XFLR5 Question: Zero Moment angle

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Aerowerx

Well-Known Member
Joined
Dec 1, 2011
Messages
6,091
Location
Marion, Ohio
A question for everyone familiar with XFLR5...

What I typically do is create a design and adjust the location of the wing and/or masses to get a moment of 0.0 at an AoA of 0.0 degrees with a certain airspeed. This would be using a static analysis.

After this I do a dynamic stability analysis.

My question: Why does the speed and AoA turn out different for the dynamic stability? I would think that if the plane is statically "trimmed" at a certain air speed, then the dynamic stability should have the same trim. That is, after the oscillations die out the AoA and airspeed should be the same as in the static analysis. But what it does is end up with a "speed to balance weight" and "zero moment AoA" that is sometimes quite different.

Sometimes the zero moment AoA ends up so far off that there is a negative lift, at which the analysis gives up.

Anyone else see this? What am I doing wrong?
 
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