4425 HYDROGRAPHIC MANUAL , PaGE 342 



If the gyrocompass stops at sea, it is easier to set all repeaters in agreement on one 

 heading and switch the master compass in, than it is to set each repeater separately. 



There are two reasons for starting the gyrocompass several hours before leaving 

 port: first, so that it may warm up to running temperature and to check its performance; 

 and second, to give the master compass time to seek the true meridian. If it is started 

 when it is within 2° or 3° of the true meridian, it should be close enough for all practical 

 purposes in an hour or two. 



On the working gi'ound the gyrocompass shall be kept running in readiness for 

 use at any time. 



4425. Maintenance of Gyrocompass 



The gyrocompass needs no attention as long as it functions properly, except the 

 periodic cleaning and oiling prescribed by the manufacturer. With each gyrocompass 

 a large oiling and cleaning chart is supplied which should be mounted near the master 

 compass. The cleaning and oiling is usually required at intervals of 3 or 4 weeks and 

 may be done when the ship is in port and the gyroscope is stopped. All the exposed 

 parts should be cleaned with a chamois skin or camel's hair brush even though no dust 

 can be noticed. A few drops of oil should be added in the oil cups as directed. The 

 oil vials on each side of the rotor must be dramed and refilled with new oil from a medi- 

 cine dropper to get the correct amount. It is important to have the oil level at the 

 marks on the vials but not above them. Qnly that grade of oil prescribed by the 

 manufacturer shall be used. If the oil turns green it should be changed more frequently. 



443, Compass Auxiliaries 



Several auxiliaries are used in connection with the ship compasses in navigation 

 and position finding. Of these, the gyro pilot and the photoelectric pilot are modern 

 inventions, but the azimuth circle and pelorus are old and well known. 



4431. Gyro Pilot 



The gyro pilot, or "Metal Mike" as it is frequently called, is an auxiliary for 

 automatic steering used in conjunction with the gyrocompass. The gyro pilot consists 

 of two units: the pilothouse unit at the steering station and the steering engine unit. 



The pilothouse unit is connected' with the master gyrocompass. It provides three 

 alternative methods of controlling the rudder: fully automatic gyro steering, hand 

 steering by the gyro pilot wheel, and manual steering with the automatic control 

 disengaged. To change course the gear lever is moved from automatic steering to 

 gyro pilot wheel steering and the vessel is brought on the new course by the use of this 

 wheel. The rudder indicator must be observed closely because the pilot wheel should 

 not be turned faster than the rudder will follow. One turn of the wheel gives approxi- 

 mately 8° of rudder. Changes in course of less than 10° are made by simply turning the 

 gyro pilot wheel one spoke for each K° change. The pilothouse unit may be adjusted 

 by hand dials to improve the automatic steering performance in various weather 

 conditions. 



In automatic steering the steering engine unit is operated by a contact maker actu- 

 ated by the master gyrocompass. The slightest departure of the ship from its course 

 due to yawing, wind, or waves is counteracted by an automatic movement of the 

 rudder in the opposite direction to bring the ship back on course. 



