Gyros are devices designed to stabilize an aircraft. They are typically the size of an average receiver or small ESC. Gyros are connected in between the servos and the receiver, and mix their input with the input from your fingers. These inputs are calculated by the gyro, to counteract forces acting on the plane. The result is that the gyro can react much faster than our eyes and fingers can, to properly adjust an aircraft's control surfaces to produce stable flight.
A common use of a gyro is to prevent a tail-dragging plane from torque rolling to the left during takeoff. Another advantage is that an aircraft with a properly configured gyro can fly more stably in much higher wind conditions than an aircraft without a gyro.
While a properly configured gyro can be a great benefit to your flying experience, an improperly configured gyro can be very dangerous and lead to crashes and other damage. It is crucial that pilots read the complete instruction manual and follow all setup videos to ensure their gyro is installed correctly and configured properly.
Gyros are best installed on an aircraft after you have already maidened the aircraft and flown it a couple of times, to trim its control surfaces and verify your preferred CG position. Only after those factors have been finalized, should a gyro be installed. In agreement with the manufacturer's manual we do not recommend maidening a new aircraft with a gyro installed, even if that gyro is turned off.
Depending on the sensitivity of the gyro, which can be adjusted by a pilot for his or her preference, a gyro can play a large part of the flight stability of an aircraft. That being said, a gyro will not actually fly an aircraft for you, so gyros should not be considered a tool to help a pilot fly an aircraft which he or she is not yet ready for. A gyro is a supplement to an aircraft the pilot must already be able to fly safely. A gyro is not an enhancement to be relied upon to allow a new pilot to fly, for example, a big 90mm 100mph jet when that pilot's experience so far is limited to small 30mph parkflyer trainer planes.
See the other articles in this Gyro section for more detail on the performance and advantages that gyros can offer your RC flying experience.
IMPORTANT** When a gyro is powered on and the aircraft is on the ground, it is normal for your radio's throws/rates and expo to not visually appear to be working. This is because in flight, the gyro is mixing the appropriate amount of throw to correspond with your radio's preprogrammed throws/rates. Also, when configuring any gyro, if too many changes are made to it in a row, and you detect that the gyro's behavior is not consistent with your inputs, we recommend resetting the gyro, by depressing the control button and continuing to hold it down while you plug in the battery. Follow the manual's instructions on how to reset your gyro.