Hi Bob Rich,

Can you please explain controllability maneuverability?
Just a bit confused in how COG position effects longitudinal stability the more aft the COG moves the weaker the moment becomes the more destabilizing moment becomes what happens to controllability does it decrease because there is weaker moment there ? between the control surface / tailplane.

I have seen in your text it says that Stability and maneuverability are opposites i'm just not clear on Maneuverability and controllability ?


Cheers
Linc

An aft centre of gravity reduces stability for the reasons you have given above. Since an aft centre of gravity is closer to the elevator hinge, the arm of the elevator is also reduced so the elevator becomes less effective requiring a larger deflection to produce the same response. In other words, controllability, especially in pitch and yaw will be reduced. When stability reduces, controllability also reduces.

It is interesting to note that a highly manoeuvrable aircraft like the Pitts Special, is actually less stable [more willing to change its attitude]. It takes more frequent and larger control deflections to control it. i.e. in spite of the fact that it is able to do a lot of extreme manoeuvres, it is actually less controllable.

Bob

Thanks Bob that clears things up thank you

Cheers
Linc