Thank you again Lane for posting those documents.
Problem is on a few in the discussion even understand the topic. For many it is a emotional affair riddled with fear their favorite gameshape will be somehow ruined.
I did not read the report but did look over the graphs from Lane's post. Here is what those graphs are telling us about the Spitfires Longitudinal stability in various conditions of flight.
Negative stability is divergent. Co-efficient of moment and Co-efficient of lift have an inverse relationship in a stable airplane. You can look at the Co-efficient of moment against Co-efficient of Lift plots in the other report Lane posted and see the slope is positive.
What does that mean in plain english. As the wing approaches CLmax, the Coefficient of Moment is well into the negative values and wants to push the nose down. Therefore, the pilot must pull the stick back to keep the nose up.
In a positive slope, as the wing approaches CLmax, the Coefficient of Moment is high in the positive values and wants to push the nose up. Therefore, the pilot has to push forward on the stick to keep the nose down.
This is confirmed behavior in our test flight document below.
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