Originally Posted by
IRRenewal
A/C manufacturers like showing their product in the best possible light, so I was wondering if the stall speeds in the book could be for an aircraft with a CofG nearer the aft limit.
Is there a way of estimating the change in stall speeds with a CofG change?
Both Part 23 and Part 25 require stall speeds to be for the most adverse (i.e. forward) cg position. I assume that would apply to your data too.
Very roughly, you can turn the cg shift into a tail download and thus into a pseudo-weight effect.
Say the distance from 1/4 chord wing to 1/4 chord tail is 50". Say the cg shift is 5" forward. The increase in nose-down weight moment is 5" * weight. The change in downforce at the tail to balance that is (5" * weight) / 50" i.e. 10% of weight. So if the cg went forward 5", you'd have an increase in tail load equivalent to 10% of a/c weight, so you could say that the stall speed should increase as if the a/c were 10% heavier (i.e. about 5% increase in stall speed). That's pretty crude but should give you a ROM to work with.