Home >> Hobbies >> Aviation

Mounting Servo Recommendations for a Plane

When you are building a radio controlled airplane, there's a lot to think about. These airplanes are not toys, but rather fully functional machines. All the control surfaces are moved by servos, so getting them "just right" is critical. You do not want a control surface to fail in mid-flight because of an improperly mounted servo. Furthermore, every servo has a certain weight. You must balance out the plane with the weight, so the plane's center of gravity is not affected. Seasoned builders understand all the factors, and pass on some tips to novices.

Placement
- You do not want to upset the airplane's natural lifting center of gravity. Do not mount the servo near the tail, nor too near the engine. To determine the correct placement, the airplane's manufacturer usually provfides the data on where to place the servo. If the airplane is from a drawn blueprint, ask the designer where the servos are placed.
Mounting
- Make sure to mount the servo on a solid fuselage framing surfaces, instead of on weak members. Avoid mounting the servo on a weak mounting point. The whole mechanism could tear out during flight. Instead of the lever arm turning the control surface, the entire servo could turn instead.
Testing
- Before covering the airplane, test the servos first. Plug in the radio, and swing all servo arms through their entire range. Pay close attention to the lever arms and the linkages going to the control surfaces. Look for any signs of binding, such as the lever arm hitting a frame member, or the control linkage rubbing up against a frame member. If all moving parts are not free, take steps to correct the problem. You may have to shift the servo to another position a little bit to free things up.
Proper Torque
- Veteran builder Paul Johnson recommends proper screw torque for the mounting screws. He states that too many people over-tighten the mounting screws, so the rubber mounting grommets are completely mashed down. This is wrong, because the grommets have to absorb vibration. Rather, Johnson says to tighten the screws just enough so the grommets become a little bulged out, but no more. Grasp the servo and move it from side to side after tightening the screws. If it does not move, the servo is secure.

Aviation