A A  A B C D North Pole E q u a t o r 10-54 Figure 10-94.  Once spinning, a free gyro rotor stays oriented in the  same position in space despite the position or location of its base.  Figure 10-93.  Gyroscopes.  A gyroscope with this configuration, two rings plus the  mounting bracket, is said to be a free gyro because it is free  to rotate about two axes that are both perpendicular to the  rotor’s spin axis.  [Figure 10-93D]  As a result, the supporting  ring with spinning gyro mounted inside is free to turn 360°  inside the outer ring.  Unless the rotor of a gyro is spinning, it has no unusual  properties; it is simply a wheel universally mounted. When  the rotor is rotated at a high speed, the gyro exhibits a couple  of unique characteristics. The first is called gyroscopic  rigidity, or rigidity in space. This means that the rotor of  a free gyro always points in the same direction no matter  which way the base of the gyro is positioned.  [Figure 10-94] Gyroscopic rigidity depends upon several design factors: responding to the force by moving about the horizontal axis,  the gyro moves in response about its vertical axis. Stated  another way, an applied force to the axis of the spinning gyro  does not cause the axis to tilt. Rather, the gyro responds as  though the force was applied 90° around in the direction of  rotation of the gyro rotor. The gyro rotates rather than tilts.  [Figure 10-95]  This predictable controlled precession of a  gyroscope is utilized in a turn and bank instrument.  This characteristic of gyros to remain rigid in space is  exploited in the attitude-indicating instruments and the  directional indicators that use gyros. Precession is a second important characteristic of gyroscopes.  By applying a force to the horizontal axis of the gyro, a unique  phenomenon occurs. The applied force is resisted. Instead of  Improved attitude and direction information is always a goal  in aviation. Modern aircraft make use of highly accurate solid- state attitude and directional devices with no moving parts.  This results in very high reliability and low maintenance.  Solid State Gyros and Related Systems 4.  Bearing friction—any friction applies a deflecting  force to a gyro. Minimum bearing friction keeps  deflecting forces at a minimum. 3.  Radius at which the weight is concentrated— maximum effect is obtained from a mass when its  principal weight is concentrated near the rim, rotating  at high speed. 2.  Angular velocity—the higher the rotational speed, the  greater the rigidity or resistance is to deflection. 1.  Weight—for a given size, a heavy mass is more  resistant to disturbing forces than a light mass.