Originally Posted by
Keith.Williams.
Isn't the relationship between weight and angle of attack at any given EAS also a factor?
Let's suppose the lighter aircraft has 4 degees of alpha and a heavier one has 8 degrees. If they both hit an instantaneous upgust that increases alpha by 2 gegrees, the light aircraft experiences 1.5 g (due to 6 deg / 4 deg) while the heavy one only experiences 1.25 (due to 10 deg / 8 deg).
All of the above ignores the effects of different inertias of course and assumes that zero lift alpha = zero degrees (to keep the arithmetic simple).
I think that as a result of those (over) simplifications you are double accounting.
If you really do have zero lift alpha=0 deg (unlikely, too) then if one aircraft is at twice the AoA of the other for level flight, then it weighs twice as much. So your 6/4 factor and your 10/8 factor are simply an expression of the relative size of the delta lift due to the gust, and the weight of the aircraft. And that factor can be expressed independent of the trimmed alpha or the zero lift alpha; indeed, all that matters is that the delta alpha due to the gust remains on the linear lift0curve slope for both the heavy and light aircraft.
That is, if you assume that the gust creates a delta alpha on both a/c, creating a delta lift due to gust of G for both, then the total lift on the light aircraft is w+G and on the heavy is W+G where w and W are the light and heavy weights. Diving by the weight of each, we get accelerations of 1+G/w or 1+G/W respectively. It doesn't matter what the trimmed alpha or zero lift alpha is.