Sounds like I may be in the minority here. I sort of like using gyros in airplanes. I'll tell you why, but first maybe I can expand on what a gyro does.

First off, there are lots of gyro devices in the world, but the ones we use in our models are more accurately known as "rate gyros". The rate gyro senses "rate of rotation" of the airplane in the axis for which it is installed. If you orient the gyro so it senses roll rate, then the gyro sends a signal to the aileron servo each time it senses motion in the roll axis.

Note: this means that the gyro sends no signal as long as the model is in steady level flight nor does it send a signal in a steady bank. It only acts for the time the airplane is rotating in roll. And the faster the airplane rolls, the greater the gyro input and the further the servo will move to oppose the roll motion. The upshot of this is the airplane will feel larger and more steady to the pilot. It also means that the airplane will not be as sensitive to gusts. The wings will stay much more level and will resist any quick little uncommanded motions as you are coming in to land.

If you orient the gyro to sense yaw and connect the plugs to the rudder servo, it will help to prevent your plane from veering off the runway on takeoff or landing. As Campgems said, this really works well on a tailwheel model where the yawing action is very quick. Campgems pointed out also that the yaw gyro can be a nuisance in flight if it is set to such a high gain that it causes the rudder to resist your intended turns.

When people talk about gyro gain, they are referring to how big a signal the gyro sends for any given airplane motion. With low gain, the gyro sends a small signal to the servo. With higher gain, the gyro sends a larger signal to the servo for the same amount of airplane motion. With low gain you may not even notice that the gyro is working. With higher gain the airplane becomes very steady, but may give you some of the problems that Campgems mentioned. If your gain is set very high, you may find that your model will waggle its tail (for a yaw gyro) when flying at high speed. That waggling is feedback, just like the annoying hum you used to hear in your high school PA system during assemblies.

The dark side of a gyro? Don't ever hook it up backwards. You'll be into the ground so fast you'll wonder what happened. Very early in the flight test program of the full scale F-117 a gyro was installed backwards and the pilot barely got off the ground before crashing. I don't know all the details there, but it was a stunning reminder of what one little error can do.

One last thing: You will hear mention of "heading hold gyros". They're designed strictly for helicopters, although some folks have experimented with them in airplanes. They are complex and difficult to use. Best leave them alone until you become a very sophisticated flyer.

Dick Fischer