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ModelMuncher avatar image
ModelMuncher asked ModelMuncher commented

Excessive Trim required

One for the FDE Experts ..
I am finding the trim required for level flight is excessive between low and high speeds
for example .. at Low speed .. WELL above stall... I am requiring 100 % UP TRIM
and at High speed .. WELL Below VNE The required trim is 100% DOWN
My weight and balance seems fine and the COL is 25% Exactly and I am Not using Flaps...

could there be a fundamental flaw in the Cl Curve?
or something else glaringly obvious I may have overlooked ..
Could it be the available Trim "Range" and how would I set this ?

I am No newbie when it comes to FDE .. I have created MANY Famous models over the years But this is driving me to despair ! :)

10 |10000

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GrimPhoenix9349 avatar image GrimPhoenix9349 commented ·

In previous sims, this would be suggestive of CG and CL being too far apart, there are known issues with any wing sweep affecting the relationship in MSFS so I would suggest starting there. You don't mention the aircraft, but not all have the CL at precisely 25% MAC.

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ModelMuncher avatar image ModelMuncher GrimPhoenix9349 commented ·
The CG and CL Are in approx the same location depending on Payload but never outside the (quite narrow) Limits .

The aircraft, if it matters .. is the Shorts 330

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GrimPhoenix9349 avatar image GrimPhoenix9349 ModelMuncher commented ·

Okay, so straight wing. And if your CG and CL are on roughly the same point, and everything else is geometrically correct, then you are down to the guesswork which goes alongside this flight model unfortunately. There is probably something in the flight tuning section - hstab lift perhaps? I really am clutching at straws unfortunately - I've been working FDEs in FSX / P3D / X-plane for 15 years or so, this one since release and it still does not make any sense to me nearly two years on. Genuinely sorry not to be much help.

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