Navigation Systems
Flux Gate Compass
The directional gyro compass system provides primary heading data to the RMI, automatic flight control, and flight director system. The airplane has a dual installation with two independent systems designated as COMP 1 and COMP 2. The systems consist of two directional gyro compasses, two flux valves, and a dual remote compensator. COMP 1 compass heading goes to the pilot's HSI and the copilot's RMI. COMP 2 provides compass heading to the copilot's HSI and pilot's RMI.
These instruments are not only convenient for monitoring the difference between COMP 1 and COMP 2 headings but they also provide one heading display to each pilot after any failure of either COMP 1 or COMP 2. The two compasses and a dual remote compensator are installed in the nose electronic compartment and two flux valves are installed in both the left and right wing tip. The switches 1ocated on both the pilot'sand copilot's instrument panels are utilized for system operation. Two gyro slave control switches, one marked SLAVE/DG, the other INC/DEC, allow selection of automatic (slaved mode) or manual (free gyro mode) operation of the COMP 1/2. When the gyro slave control switch is moved to SLAVE (slaved mode) position, the automatic fast synchronizati on cycle is initiated which moves the gyro at a rate of 50 degrees per minute.
When the gyro is aligned with the earths magnetic field (actual magnetic heading), the system returns to the normal slaving rate of 2.5 to 5.0 degrees per minute. In the slaved mode, the system is fully operational within 3 minutes. The compass flag on the HSI automatically retracts when the slaving cycle is completed and the heading card is aligned with the magnetic heading. The RMI function is the same as the HSI. The slaving conditions can be monitored by the compass annunciator on the HSI. The compass annunciator slowly oscillates between (+) and dot (.) when the system is correctly slaved. The system may be operated in the free gyro mode by placing the gryo slave control switch in the DG position. In this position, the HSI heading card can be rotated clockwise or counterclockwise by toggling the manual slave switch to the INC or DEC marked position. Manual operation gives accurate short term heading reference when heading information is unreliable.