The Directional Gyroscope Type (Gyro) C-12 consists of two major assemblies: a base and case assembly and a partial gyro assembly. The case of the Gyro is mounted on the base by means of four vibration isolators. These isolators have specific resonant frequency and damping characteristics that eliminate undesirable jitter. The case serves as a housing for the partial gyro assembly. The base for the Gyro serves as a mounting base and as a housing for electrical circuitry. The partial gyro assembly consists of the synchro stator assembly, a gyroscope subassembly, and a spindown brake to accomplish the gyroscopic functions of the Gyro. The partial gyro assembly is hermetically sealed in the case of the base and case assembly in a helium and nitrogen gas environment. The C-12 directional gyro provides the basic heading stabilization for the C-12 Compass System. It consists of a hermetically sealed case containing the gyro proper, and a base assembly containing earth rate power supply, drift bias circuit, slaving amplifier stage, and gimbal error corrector.

The sealed gyroscope rotor is mounted in an inner gyro gimbal which, in turn, is supported by coaxial ball bearings. These bearings have middle races which rotate in opposite directions with respect to one another, and are periodically reversed to average out the dynamic friction of the bearings. This results in less bearing torque and lower drift rates, thus improving overall gyro performance. The bearing outer races are mounted on the outer gimbal which is free to rotate about the vertical axis.North and south magnet assemblies, mounted on the outer gimbal, produce a torque about the inner axis with the proper magnitude to compensate for the rotation of the earth. Torque is also produced about the inner axis by the slaving motor mounted between the gyro and the outer gimbal. Direction and magnitude of the torque produced by the slaving motor is such that the gyro unit will rotate about the vertical axis to maintain the required gyro heading. A leveling torque motor, controlled by a tilt switch mounted on the gyro unit, provides torque about the outer axis in the proper direction to level the gyro unit. A spindown brake is provided to prevent outer gimbal rotation when electrical power is removed from the Gyro. The brake also reduces nutation when the gyro is started.