On elevator control surfaces that have an anti-servo based trim surface, where the trim surface moves in the same direction as the elevator movement, but with a greater degree of deflection relative to the elevator movement (such as on the stabilator of a cherokee), how is overcontrolling (which apparently is the reason for having this setup) prevented with this mechanism? If the stabilator lacked the anti-servo tab, would movements with the yoke be more sensitive in general?
Trim tabs
- Thread starter ZUM
- Start date
chris
Well-Known Member
The surface area of the stabilator is a lot greater than that of a regular elevator. If both are positioned at the same distance away from the CG, then the stabilator (i.e. the control surface with a lot more surface area) will provide a much greater force (remember, lift depends on area). This can cause over-controlling of the a/c, which is undesirable.
To prevent this, an anti-servo tab is incorporated into the design. Its purpose is to oppose the movement of the stabilator, and thus, prevent overcontrolling. It does this by moving in the same direction as the stabilator (push forward on yoke, stabilator deflects down, and servo tab also deflects down). As the servo tab deflects down, it produces a force which tries to deflect the entire stabilator up, which opposes the intial input by the pilot.
Hope this helps.
To prevent this, an anti-servo tab is incorporated into the design. Its purpose is to oppose the movement of the stabilator, and thus, prevent overcontrolling. It does this by moving in the same direction as the stabilator (push forward on yoke, stabilator deflects down, and servo tab also deflects down). As the servo tab deflects down, it produces a force which tries to deflect the entire stabilator up, which opposes the intial input by the pilot.
Hope this helps.
