A small nylon or plastic arm or wheel that attaches to the output shaft of a servo, the purpose of which is to connect the servo to whatever control linkage necessary. There are usually holes at different points on a servo arm to facilitate adjustments in control surface deflection (the amount the surface moves in relation to the servo) and leverage.
The output shaft and the arm are splined in order to transfer torque from one to the other; this means that the arm can only fit in a number of preset positions (usually about 20). Often multi-armed horns have each arm at a slighly different rotation relative to the spline, allowing the servo arm centre point to be set quite accurately.
Also called the servo arm.
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