My question is how does an aileron work considering it rotates around a fixed point and the actuator arm moves in a straight line. If what is shown in the first picture I have provided is true, then how can the actuator arm move the lever that moves the aileron considering the fact that the lever moves in a circular direction and the actuator arm only moves in a linear direction? If the picture is right doesn't that mean the lever that moves the aileron would have to change length to be able to move in a circular direction since the actuator arm moves in a straight linear direction? Please let me know if you need clarification.
You will see two methods of providing articulation for the hydraulic cylinder to accommodate the vertical shift of the attachment at the aileron as the aileron moves.
In one method, one end of the actuator has a pivoting attachment to the structure and the other end a pivoting attachment to the control surface. The entire actuator moves in a small arc defined by the relative up and down shift of the attachment at the aileron as the aileron moves.
An alternate method is used if you need the actuator to be rigidly attached to the structure (usually because of space considerations that make it undesirable to have an actuator that can articulate up and down itself, or the design of the input linkage requires the actuator to be stationary).
The rigidly attached actuator is connected to the control surface by an articulating link, sometimes called a "Dogbone Link". This actuator operates on a fixed axis, and all of the geometric compliance is accommodated by the two pivot bearings in the dogbone itself.
The actuator extends linearly indeed, and is mounted on both sides with bushings that allow for rotation. As can be seen in above picture, from this site.
So when the actuator extends:
- the end at the actuator arm follows a circular curve;
- the other end stays fixed in one point;
- both ends rotate around their bushings.