A helicopter gyroscope serves to limit the left and right motion, or yaw, of the helicopter tail. This helps to keep the helicopter balanced and prevent it from spinning out of control. The motion is detected by a magnetic sensor and is sent to the tail rotor. Modern radio-controlled helicopters use crystal yaw detectors or non-mechanical gyros to balance the tail and preserve battery power.
Radio-controlled helicopters require a yaw control section because the reactive torque is constantly changing. Any change in the engine speed or rotor blades can cause the helicopter to become unbalanced and spin out of control. The gyroscope manages these changes and keeps the helicopter flying with minimal difficulty. Flying a radio-controlled helicopter without a gyroscope requires copious amounts of effort and can take the fun out of flying.
As of 2014, the gyroscopes found in radio-controlled helicopters are actually accelerometers. They create a signal during acceleration that becomes stronger as acceleration increases. The accelerometers produce the same results as the original gyroscopes, but they create the results in a different way. They are much smaller and use less battery power than the original gyroscopes. This type of gyroscope is known as the MEMS, or micro electric-mechanical system, gyroscope.