Gyroscopes can be used as devices for direction finding, guidance, and control. If a gyroscope, mounted on its gimbal rings, is set spinning about a horizontal axis, and the outer gimbal ring is rotated in a horizontal plane, then the inner gimbal ring, carrying the flywheel, tilts up out of the horizontal plane in which it,too first lay. After a few oscillations, damped out by friction, the axis of spin of the gyroscope settles down along a vertical direction. Inertial guidance systems make use of very similar phenomena. Once a gyroscope has been set spinning about a chosen axis, any motion that would cause it to deviate from this direction calls into existence a torque that can be used as an error signal to control corrective maneuvers. The same techniques, in essence, can be used for the stabilization of vehicles against undesirable rolling motions. Some ofthe most important applications of gyroscopic phenomena are in aircraft instruments. A free (perfectly balanced) gyroscope can give a constant indication of a chosen reference direction for checking the correct course, and a gravitationally loaded gyroscope can be used to identify the true vertical at all times and so define an artificial horizon against which the pilot can measure the angles of bank and climb.

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