I am using the servo torque formula, in which there is mention of maximum servo deflection. At first, I used 90 degrees as my servo was positional rotation servo. But then I found out in internet that they were using some other values. So what's about this servo angle? Is there any formula for it to calculate? About the control surface deflection angle, I found out that it depends on the way I connect my servo arm with control horns. Is this completely true? If not, is there something I need to consider?
The issue with servos is that they are used to turn rotary into linear motion. The pushrod moves a lot when it is at 90 degrees to the output arm, and not at all when it is inline.
Most installations want approximately proportional movement, so they only want a servo to rotate about 90 degrees (i.e. 45 degrees either side of the centre).
In practice, most servos can rotate about 120 degrees but the normal signal from the transmitter only causes them to rotate about 90 degrees. You can set the transmitter to use the extra travel if you really want, but it's usually not a good idea.
Here's a good video from RCModelReviews on linkage geometry: https://www.youtube.com/watch?v=U3AHgk0SUoI&ab_channel=RCModelReviews