Starting a Gyro Compass
At power-up and prior to entering the settle mode, the system performs the automatic ‘bite‘ procedure to determine if the equipment is operating within specified parameters. The CPU also initializes the system hardware and communication channels. During this procedure the gyro wheel is checked for movement. If it is stationary, the system opts for a cold start, if it is rotating a hot start is programmed. During a cold start, if no heading data is input to the system when requested, the gyrocompass selects Automatic.
From start-up a gyrocompass needs time to settle on the meridian. The time taken depends upon the make, model and the geographic location of the compass. The duration also depends upon whether the gyro wheel is already rotating or not. If the compass has been switched off, it will take much longer to bring the compass into use. Inputting the ship’s heading to reduce the initial error factor can reduce the time period.
Cold starting the gyro compass:
After an initial period, during which the bite is active, the following sequence is initiated and the settle indicator lamp will be lit.
• Two bleeps prompt the operator for a heading input. If heading data is not entered within 5 min, the gyro switches to an ‘auto level‘ process.
• Assuming heading data has been input, the yoke will be offset based on this data. It will be slewed from the meridian, either clockwise or anticlockwise.
• The gyrowheel is brought up to speed within 14 min.
• The yoke is slewed back and forth to level the ballistic. This action takes about 4 min.
• Again assuming heading data has been input, the gyrocompass will settle within 1 hr and the settle indicator lamp goes out. If no heading data was entered, the compass will automatically settle within 5 hrs.
Other inputs to the gyrocompass are as follows:
• Heading: It is in the range 0 to 359°. If the entered heading is in error by more than 20° from the true heading, the compass takes 5 hrs to settle.
• Initialize and Synchronize Step Repeaters: An operator selects a repeater and when requested uses the keypad’s left or right arrow switches to scroll the display to the repeater’s current position. After 10 s the system steps the repeater to the compass heading. It is essential to repeat and double check this procedure because there must be no alignment errors in a repeater system.
• Speed Input: Using the left or right arrow keys, an operator inputs a speed.
• Latitude Input: Using the arrow keys, an operator inputs latitude in degrees north or south of the equator.
Ref: Beyond Discovery website
