Passage Two

Gyro Compass

Learning Objectives:Basic principles of Gyro Compass (GC)Components of GCWorking procedures of GCRepeater synchronization proceduresRoutine inspection of GC

A human gyrocompass

Vocabulary:indispensable / , indis'pensbl/ adj. gravitational adj. motor and generatordistribution box switch junction boxazimuth /'zim/ n. mode selector switch knob /nb/ n. slew /slu:/ n. vi. identical /ai'dentikl/ adj. sameascertain / , s'tein/ vt. verify, confirm, make surevoltage n. malfunction /ml'fkn/ n. vt. with the exception of except

The gyro compass is an indispensable instrument for navigation as it functions as a true direction finder by seeking and continuously aligning itself with the meridian using the earths rotation and gravitational effects. Most gyro compasses consist of the master compass, the motor and generator, repeater compass, distribution box, switch junction box, alarm system, etc.direction finder seeking and continuously aligning itself with the meridianseek the meridianalign itself with the meridian

When the ships heading direction is given by a magnetic compass or if it is made known in reference to the azimuth of the quay wall, start the gyro compass according to the following procedures:1) Shift the mode selector switch on the switch panel of the power source unit to SLEW. Wait for some time until a red lamp lights (approx. 4 minutes).2) When the lamp turns on, change over the slew switch either to the left or right. Then, turn the compass card according to the true bearing which has already been indicated (for synchronization).3) Thereafter, shift the mode selector switch to RUN (at this time, a green lamp lights).In this case, the gyro compass gets set within two hours. When the ships heading direction is unknown, start the gyro compass by shifting the mode selector switch on the switch panel of the power source unit to RUN (a green lamp lights at this time). In this case, the gyro compass gets set within 4 hours. To stop the gyro compass, shift the mode selector switch on the switch panel of the power source unit to OFF.in reference to: with reference toSperry375 1slew 2start 3)automatic level 4run 5run/slew/get set: be ready (for work) slower direct Run

In terms of repeater synchronization, the following procedures should be acted upon:1Shift the repeater switch to OFF and set the repeater to the reading on the master compass by turning the repeater synchronization knob.2) When the repeater has been set to the reading of the master compass, turn on the repeater switch to confirm that the master compass and repeater give the same readings.3) Should these readings be not identical, repeat the above specified setting procedures.Normally, the repeater switch is kept turned on and is capped so that it will be free from being accidentally touched by the operator.Shouldbe If these readings should not be identical,adjustcovered

Routine inspection of the gyro compass includes:1) Check the repeaters with the master compass to ascertain that the transmission system is functioning properly. If the power supply fails for any reason, be sure to check it and, if necessary, synchronize the repeaters as soon as the power supply is restored.2Check the compass by azimuth observation when possible.3Make sure that the power supply voltage is constantly maintained.4Normal operation of the master compass should involve no noise, vibration or overheating. With this in mind, the operator should observe the performance of the gyrocompass and make the necessary adjustments should any malfunction develop.With the exception of the above-described routine inspection, the gyrocompass seldom requires special maintenance checks. It is desirable, however, to periodically check for loose connections, oil and component wear and to make the necessary adjustments when required.ifif any malfunction should develop,

Gyro Error the difference between the true bearing and the Gyro reading

Expressed in degrees East or degrees WestGyro Least, error EastGyro Best, error West

Home work:Read Part Two of this Chapter, and keep the following expressions in mind:Magnetic Compass Gyro Compass compass bowl binnacle stand nonmagnetic material gimbals compass card cardinal and intercardinal points deviation correcting devices [ semicircular deviation (B.C), quadrantal deviation (D), heeling error (H) correcting devices, flinders bar (F)]deviation, variationsemicircular curves

gravitational effects master compassrepeater compassdistribution boxswitch junction box mode selector switch (SLEW ,AUTOMATIC LEVEL, etc)repeater synchronizationget settransmission system

Preview Part Three: GPS, VDR, AIS and ECDIS