Directional stability decreases with altitude. Lateral stability ?
I found this question in my Fly Around JAA bank : (Principles of flight)
With increasing altitude and constant IAS the static lateral stability (1) and the dynamic lateral/directional stability (2) of an aeroplane with swept-back wing will:
Right answer: (1)increase (2) decrease
I understand that with increasing altitude the air density decreases thus any control surface is less effective. Therefore it makes sense to say that the vertical tail fin is less effective and thus directional static stability decreases.
However I don't understand those 4 points:
- Why dynamic directional stability decreases ?
- Why lateral dynamic stability decreases ?
- Why static lateral stability increases ?
- Why static lateral stability increases while dinamic- decreases ?
Thank you very much to whom will be able to write a clear explaination to that.
Have a good night,
Emmanuel Cordier.