Servo Centering By James Goss      Have you ever had a servo such as an aileron or elevator that would not respond as fast as it normally does when compared to the other servos on the plane? I use the aileron as an example because when you are using two aileron servos it is easy to see the difference between the two servos when one is not performing just right. When you release the control stick one aileron centers, but the other one might take its time to return to center. When it does make it to neutral position it keeps on going and stops off center. Each time you operate the stick you may get a different action by the servo, a random response. And then at times the servo may not move at all when the stick is moved. You stop and think for a while because this is really puzzling, what in the world is going on? It's like the servo has a mind of its own and it doesn't want to cooperate with you. How do you troubleshoot something like this?      I have seen this happen many times over the years and I have had several of my own servos to go through this “Adolescent Stage” I call it. There have been many servos thrown away because it appears to indeed be a defective servo. Now don't get me wrong, a servo with internal defects can and will act this way. In most cases it will not be the servo that is at fault, instead it is something much simpler to deal with. Nine times out of ten it is going to be due to added resistance in the wiring between the receiver and the servo. This is more likely to happen with the ailerons because you normally have an extension wire from the receiver to servo. Of course on larger planes you will be using extension cables elsewhere as well so it is even more likely to happen.       If we were able to have a direct wire from the receiver to the servo that was soldered at both ends, this would be ideal. Instead we have to use plug-in extension cables and most of the time they work great. The direct wire would have the least resistance possible, so when plugs are added the overall resistance will be increased. If we have a bad connection at one of the plugs the resistance will become large enough to hamper or impede the signal current if the resistance happens to be in the signal line (white) on Futaba equipment. If in the red line (the positive power supply line) the motor will begin to slow down and also the logic amplifiers may become erratic. Of course the black wire (ground) will alter both the signal and the power supply current because it is common to both.      These bad connections are likely to happen on days when we have drastic temperature changes, but it is not limited to these days only. This is due to the metallic wire expanding and contracting and over a period of time the resistance will build up and become a problem. Also humid days may entice corrosion to occur and with that comes more resistance at the pin connections. This is another good reason to store your planes in a dry storage place. To solve this problem of added resistance in your servo cables may only require you to unplug and reconnect the male and female plugs. Do this several times at both ends of the extension wires and your problem has a good chance of being repaired. At least this is a good temporary field repair that will allow you to get in some flying time. Repeating the plug-in process over and over will allow the pins in the plugs to rub each other and clean themselves. You can also use electronic contact spray cleaner to help remove the corrosion. If you get the cable fixed chances are that in the long run the problem will return.      Of course you don't want to take any chances with your really nice planes. Even if you use the above process and everything seems to be working fine on the ground you may not want to chance it in the air. While in the air the plane goes through a lot of vibrations and turbulence that might reactivate the initial condition. To avoid this you might want to replace the extension with a new cable.