T5 Analysis results inverted scales(?)

Berk YurteriBerk Yurteri asked 11 hours ago

Hi André,
I’m using the T5 analysis to verify static yaw and roll stability, and the yaw stability scale seems to be inverted. Could you please help me with it? In the image you can access from this link (https://imgur.com/a/ZXkvmjX), you’ll see one plane with a 100-in. tail arm (blue) vs. another with a 60-in. tail arm (red). To me, it makes no sense that the 100-in. one would be more unstable than the 60-in. one. Sorry in advance if I’m reading the graph wrong.
Best Wishes,
Berk

André Deperroistechwinder Staff replied 8 hours ago

Hi Berk,
The graph seems to show that the yawing moment with the long lever arm, i.e. the blue curve, is stronger than the moment due to the shorter lever arm which makes sense.This would translate into higher “call-back” moment, not lesser. Stability should be measured using the spiral and Dutch roll modes, so I’m not sure that I understand the concern.
André