Thanks for the input!
|Quoting Metroliner (Reply 1):
Whenever I see servo tabs, I think of the elevator + tab as a whole separately from the whole aircraft - no matter if there is equilibrium between the tab and elevator, if there is still a net force exerted on that hinge line, something will change.
|Quoting SlamClick (Reply 3):
The forces are only balanced out when they agree with the position commanded by the control column movement.
|Quoting Lemmy (Reply 4):
So the relatively small force the tab exerts has an easy time of moving the large elevator because it's located as far away from the hinge as possible.
I can see what you are all explaining, but what happens when equilibrium is reached? Is it the transient portion of the deflection that produces the net force
To muddy the waters further, there are other types of tab which act in a manner to either assist or resist the pilot in moving the control surface.
|Quoting Tdscanuck (Reply 7):
cambered airfoil has a non-zero moment at zero angle of attack. Since the angle of attack changed (as well as the camber), the lift produced by the surface changed.
|Quoting Jetlagged (Reply 8):
The elevator deflection changes the lift produced by the horizontal tail, which therefore produces a pitching moment. It doesn't really matter how the elevator gets deflected (whether directly by the pilot, by a hydraulic servo, or an aerodynamic servo). In this case it is held deflected by an aerodynamic moment.
It appears that you are both agreeing that the camber of the tailplane / elevator combination is effected. This in turn, affects the aerodynamic qualities of the tailplane / elevator combination.
If I understand Tds correctly, the camber change produces a net increase or decrease in lift of the tailplane, which then effects the pitch change of the entire aircraft.
If I understand Jetlagged correctly, the camber change produces a net increase or decrease in pitching moment of the tailplane, which then effects the pitch change of the entire aircraft.
I see from both of your explanations, that it was not correct of me to focus on hinge line forces, and the key to it all is the ability to maintain an elevator deflection.
The only bit I don't understand now, is the slight difference in your explanations of the exact type of force responsible for changing the pitch of the entire aircraft. I guess you are saying the same thing in two different ways.
Tds' change in lift, multiplied by the distance from the C of P to the quarter chord of the elevator + tailplane equals Jetlagged's pitching moment.
The issue is much clearer now. Many thanks
[Edited 2008-08-14 07:22:58]