HNSA Crest with photos of visitors at the ships.
6A1. General Electric drive set. The later fleet type submarines use the diesel-electric drive for main propulsion.

The primary source of power is four main diesel engines. The engines are used to drive four main generators which in turn supply the electric power to drive the four main propulsion motors. Each of the two propellers is driven by two main propulsion motors through a reduction gear. (See FigureA-9.)

When submerged, the diesel and generators are not used. Power for the motors is supplied by two sets of storage batteries. These batteries are charged by the auxiliary and main generators during surface operations.

The electric propulsion machinery installed in each 1,500-ton class submarine includes the following (See Figure 6-1.):

a. Four direct-current generators: each rated 1,100 kw, 415 volts, 750 rpm. Each generator is cooled by a surface air cooler and generates power for driving the propulsion motors and charging the storage batteries. Each generator is driven by a directly connected diesel engine.

b. Four direct-current propulsion motors: each rated 1,375 hp, 415 volts, 1,300 rpm. Two of these motors are used to drive each propeller, through a reduction gear, at 280 rpm. Each motor is equipped with an air cooler.


c. Two reduction gears: each is single reduction with two pinions driven by two main propulsion motors and a slow speed gear connection to the propeller shaft. Input is 1,300 rpm, output is 280 rpm. This reduction gear is not used on the latest type submarines which are equipped with slow-speed main motors.

d. One auxiliary generator: direct current, rated at 300 kw at 1,200 rpm, and driven by a directly connected diesel engine. It is used to supply current to the auxiliary power system and for battery charging.

e. The electric propulsion control: includes equipment required for the control and operation of the four main motors when being supplied with power generated by one or more of the main generators or by the storage batteries. The equipment also provides for controlling the charging of the storage batteries by the auxiliary or main generators. Main power cables, capable of carrying the heavy currents involved, connect the storage batteries with the various main generators and motors.

In these circuits, there is control equipment consisting of switches, resistance units, and protective devices designed to permit flexibility of control.

Each unit of the electrical propulsion machinery listed above, the accessory equipment, and the diesel engines, are discussed in the following sections of this chapter.


Main engines. Four main engines are employed to drive the main generators. There are two in each engine room. (See figureA-9.)

Each engine is of the 2-cycle diesel type;

  the two on the port side are arranged for left-hand rotation, those on the starboard, for right-hand rotation. The general characteristics of the General Motors engine are shown in the following table:

Drawing illustrating the general arrangement of main propulsion equipment.
Figure 6-1. General arrangement of main propulsion equipment.

Model number16-278A
Brake horsepower1,600
Rated engine speed750 rpm
Cylinder arrangementV-type
Number of cylinders16
Bore and stroke8 3/4 X 10 1/2
Starting systemAir starting

The diesel engine differs from the internal combustion engine in that it has no spark plugs or ignition system, and relies on heat of compression to ignite the fuel which is forced into the cylinders under pressure and atomized. The two types of main engines used are the Fairbanks-Morse 38D81/8 and the G. M. 16-278A. A description of the G. M. Engine follows.

The cylinder block is the main structural part of the engine. It is fabricated from forgings and steel plates welded together, combining strength with light weight. The upper and lower decks of each cylinder bank are bored to receive the cylinder liners. The space between the decks and the cylinder banks forms the scavenging air chamber. Removable hand-hold covers close the openings in the sides of the cylinder blocks and provide access to the interior of the engine for inspection or repair.

The cylinder liner is made of alloy cast iron, accurately bored and finished. It is removable and can be replaced when worn.

The engine cylinders are fitted with individual alloy cast iron cylinder heads. Each head is fitted with four exhaust valves, the unit injector, the rocker lever assembly, an engine overspeed injector lock, the cylinder test and safety valves, and the air starter check valve.

The pistons are made of alloy cast iron. The bored holes in the piston pin hubs are fitted with bronze bushings. Each piston is fitted with seven cast iron rings, of which five are compression rings, and two are oil control rings. These rings are of the conventional

  one-piece cut-joint type. The connecting rods are made from an alloy steel forging.

The crankshaft is of heat-treated alloy steel with eight crank throws spaced 45 degrees apart, and with nine bearing surfaces.

The camshafts, which control the action of the valves, and the accessory drive shaft are driven by gears from the crankshaft. The accessory drive furnishes power to the blower and the water pumps. The camshaft drives the oil pump, the tachometer, and the engine speed governor.

A diesel engine burns a mixture of fuel oil and air. A blower is provided on each engine to furnish air to the cylinders, and to remove burnt gases from the cylinders. This function is known as scavenging. The scavenging blower consists of a pair of rotors revolving together in a closely fitted housing and furnishes a constant, uniform supply of air at the rate of 5,630 cubic feet per minute. The blower is mounted directly on the engine at the forward end and is driven by the accessory drive shaft.

Fuel for each engine is drawn from the clean oil tank by the fuel oil pump, forced through a filter, and delivered to the injectors. The pump is mounted on the blower end of the engine and is driven directly by one of the camshafts.

The governor, which controls the engine speed, is of the self-contained hydraulic type. It is provided with a power mechanism to regulate the fuel injectors, thus increasing or decreasing speed. The governor is set to allow a maximum engine speed of 802 rpm.

The engine is cooled by a fresh water cooling system. The fresh water is circulated by the fresh water pump, which is of the centrifugal type, and is mounted on the blower end of the engine.

The purpose of the sea water cooling system is to conserve fresh water by cooling it after its passage through the engine, thereby


permitting its constant reuse for cooling purposes. The sea water pump, adjacent to the fresh water pump, is also of the centrifugal type.

The engine is started by air, which is furnished by the high pressure (3,000-pound) air system. Air is admitted through the starting air valve at 500 pounds' pressure to the engine cylinder, causing the engine to start. When the engine begins to run under its own power the air is shut off.

Each engine is fitted with a flexible coupling, providing direct connection to the generator it drives.

6B2. Lubrication. Each main engine is provided with a pressure oil system for lubrication.

The lubricating oil pressure pump on each engine draws oil from the sump tank through a check valve and forces it through an oil strainer and cooler. From the oil cooler, the lubricating oil is delivered to the

  engine lubricating oil system and to a branch line that supplies the generator bearings.

The generator bearing scavenging oil pump draws oil from the generator bearings and returns it to the engine oil pan.

The lubricating oil enters the engine at a connection on the control side of the camshaft drive housing. A regulating and relief valve adjusts the pressure of the oil as it enters the engine.

From the engine inlet connection, the oil flows to the main lubricating oil manifold, where it is distributed to the main bearings, piston bearings, connecting rod bearings, camshaft drive gear and bearings, and the valve assemblies. The excess oil drains back to the oil sump. Oil is supplied by another branch to the blower gears, bearings, and rotors.

The lubricating oil pressure pump, mounted on the camshaft drive housing cover, is a positive displacement helical spur gear type pump.


6C1. Description of main generators. The main generators are two-wire, direct-current, separately excited, shunt-wound, multi-pole, totally enclosed, and self-ventilated machines. The armature shafts are supported on a bearing at each end, except in the Elliott machine which employs a single bearing at the commutator end. The bearings are force lubricated by the oil supply from the main engine lubricating system.

The maximum speed of a main generator is dependent upon the type of main engine. Maximum speed with a G. M. Engine as a prime mover is 750 rpm; with a Fairbanks-Morse engine, 720 rpm. Direct flexible coupling to the engine is accomplished through the flanged end of the generator armature shaft.

With the exception of the cooling units on Allis-Chalmers machines, the construction of all main and auxiliary generators is similar. However, in the latest Allis-Chalmers machines, the encircling cooling arrangement has been replaced by a system similar to that

  employed on the other types. The main generators are rated at approximately 2,650 amperes at 415 volts and 1,100 kw.

6C2. Cooling systems. The cooling systems of the various machines operate on the same principle. The hot air is cooled by forcing it through water-cooled cores. The older Allis-Chalmers machines, however, do not employ the duct work used on the other type machines. The cooling unit on these generators fits the contour of the machine and is made in two sections, each half section covering one-fourth of the outer surface of the generator. Water tubes are set in grooves on the inner surface of the shell to absorb the heat from the circulating air.

The other type machines have the water tubes mounted in cores, similar to an automobile radiator. This assembly is located in the air ducts of the cooling system through which the air passes.

Circulating of air is by means of the ventilating fan attached to the armature


shafts of all machines. Air is delivered from the cooler into the commutator and housing. It is then drawn through the field coils and through the commutator ends, under the commutator into the armature, and then through ventilating ducts in the armature core.

6C3. Description of the auxiliary generator. The 300-kw direct-current auxiliary generator is a two-wire shunt compensated (G.E. and Elliott) or differential compound (Allis-Chalmers) machine. The generator is self-excited, but the switching is arranged so that separate excitation may be obtained from the battery. The rating limits of the machines are approximately 345 volts at 870 amperes and 300 kw at 1,200 rpm.

The generator is connected to the auxiliary diesel engine through a semi-rigid coupling. The commutator end of the armature shaft is supported on a sleeve bearing which is force lubricated from the engine lubricating system. The opposite end of the shaft is carried by the engine bearing. The generator armature thrust is taken by thrust faces on the ends of the sleeve bearing.

In construction, auxiliary generators differ only in minor detail from the main generators. They are produced by the same manufacturers and with the exception of size, weight, and number of some of the components, auxiliary and main generators are identical.

6C4. Description of main motors. The main motors are of the two-wire, direct-current, compensated compound type with shunt, series, and commutating field windings. Separate excitation for the shut field is provided by the excitation bus which receives power from either battery.

The motors are totally enclosed, water-tight below the field frame, split and water-proof above. Cooling is accomplished by a fan attached to the armature shaft which circulates the air through cores cooled by circulating water.

Each end of the armature shaft is supported on a split sleeve bearing. The bearings are lubricated from the oil supply in the reduction gear units.


Various combinations of armatures in series or in parallel, including all four motors in series for dead slow operation, may be obtained for either surface or submerged operation through the main control cubicle.

Motor speed control is accomplished by controlling the generator speed and shunt field, thus varying the voltage supplied during surface operation, and the motor shunt field when submerged. Reverse operation is accomplished by reversing the direction of the flow of current in the motor armature circuit.

Main motors used in a gear drive installation are classed as high-speed motors and are each rated for continuous duty at approximately 1,375 hp, 415 volts, 2,600 amperes, 1,300 rpm.

6C5. Lubrication. Oil under pressure is supplied to the motor bearings by a gear-driven lubricating oil pump which is attached to the reduction gear units of each pair of motors. However, when the propeller shaft speed is operating at a slow speed, a standby pump is placed in operation and supplies sufficient oil pressure for both reduction gears and main motor bearings. Oil-catching grooves and return drains into the housing prevent leakage of oil along the shaft into the windings. The air chamber between the bearing and the interior of the motor serves to prevent formation of a vacuum around the shaft and permits drainage of any possible oil leakage before it reaches the interior of the motor. A safety overflow is provided in the housing oil reservoir to prevent possible flooding of the winding, if the drain should become clogged. After passing through the bearing, the oil passes out of the housing through a sight flow and returns to the lubricating oil sump. When the flow of oil at the sight flow glass appears to be appreciably reduced, or, if the oil pressure falls below 5 psi, the standby pump must be placed in operation. The standby system is also used to force the lubricant to the bearings before starting the motors after a shutdown period.

6C6. Cooling system. The main motor cooling units are similar to the main generator


units with one exception. The Allis-Chalmers cooling units on the older main motors are made in three sections which cover approximately 90 percent of the outer surface of the motor frame. The remaining surface is covered with a dummy section to secure the necessary clearance for the motor arrangement in the motor room. This arrangement is such that each motor has its cooler sections placed on different portions of its outer surface.

6C7. Description of the double armature propulsion motor. On the latest type submarines, main motors and reduction gears have been replaced by two 2,700-hp double armature motors, directly connected to the propeller shafts, one to the starboard, the other to the part shaft.

The motors are of the two-wire, direct-current, compounded, compensated type with shunt and series field windings and commutating poles. Separate excitation for shunt fields is provided by the excitation bus which receives power directly from the battery in the control cubicle. The motors are totally enclosed with a water tube air cooler mounted crosswise over the motor frame. Mechanical air filters are located in the air ducts between the coolers and vent blower. When the motors are operating in the SLOW position, neither cooling air nor circulating water is required.

The motor frame is split at an angle of approximately 11 degrees from the horizontal center line to permit easy removal of the armature. The motor is watertight below this joint and waterproof above.

The armature is mounted on a hollow forged steel shaft which is flanged at the after end for coupling to the propeller shaft. Each end of the shaft has a bearing journal for a force-lubricated, split sleeve bearing, mounted in a pedestal, separate from the frame. In addition to the radial bearing, the forward end of the shaft is fitted with a collar for a Kingsbury thrust bearing which takes the propeller and motor thrust load.

For surface operation, using the various combinations of armatures and taking power from the main generators, the motors develop

  power ranging from 20 hp to 2,700 hp per propeller shaft at speeds ranging from approximately 67 rpm to 282 rpm.

For submerged operation, using various combinations of armatures and taking power from the batteries, the motors will develop power ranging from 30 hp to 1,719 hp per propeller shaft, and will give a speed range from 42 to 219 rpm.

6C8. Main control equipment. Fundamentally, the construction of main propulsion control equipment produced by General Electric (See Figure 6-2), Westinghouse, and Cutler-Hammer is similar. Individual components may vary somewhat in design; their locations and method of installation in the assembly may differ; cables and conduits will be found routed differently; but, each assembly as a whole performs the same function and is operated in a similar manner.

6C9. Split type main propulsion control equipment. (See Figure 6-3.) The split type control equipment is installed on some of the later type submarines on which double armature, slow speed, directly connected propulsion motors are used. This equipment performs the same functions as the standard control cubicle, and with minor exceptions is operated in the same manner.

The two halves of the control panel are essentially the same. Each half is mounted in a steel frame that is joined to form a single unit and shock mounted to the hull. The starboard control panel consists of the generator levers for the No. 1 and No. 3 generators, starting with reversing levers for the starboard motor, a bus selector, and a forward battery lever. The port control panel consists of the generator levers for the No. 2 and No. 4 generators, starting and reversing levers for the port motor, a bus selector, and after battery lever.

6C10. Functions. The control equipment performs the following functions:

1. Start, stop, reverse, and regulate the speed of the main motors for both surface and submerged operation.


Drawing illustrating the General Electric main propulsion control cubicle.
Figure 6-2. General Electric main propulsion control cubicle.

2. Provide for series, parallel, or series-parallel connection of the motor armatures.

3. Provide for uniform speed control of the main motors throughout the entire range of propeller speed from about 42 to 219 rpm submerged to about 280 rpm on the surface.

4. Provide for operating the main motors from one or both main storage batteries and from any combination of the main generators.

5. Provide for charging one or both storage batteries with main generators individually or in combination. Main generators not being used for battery charging may be used for propulsion power.

6. Provide for driving the starboard motors from the starboard generators and the port motors from the port generators entirely

  independent of each other except for a common excitation bus.

7. Provide for operation ahead on one propeller shaft and astern on the other at any speed within the designed operating range.

8. Provide, by means of shore connections, for charging the main battery from shore or tender.

6C11. Simplified circuit description. The main control cubicle circuit consists essentially of two buses, the motor bus and the battery bus, to which the main power units are connected by means of their associated contactors in order to provide the various operating combinations. The motor bus is the one to which the main motors are connected for any of the running conditions by means


Drawing illustrating the split type of main propulsion control cubicle.
Figure 6-3. Split type of main propulsion control cubicle.
of their starting contactors.

The motor bus can be split for operation of the motors on each side independently of the other sides (BUS TIE OPEN), closed for parallel operation of both motor groups (BUS TIE CLOSED), connected to the battery bus for battery operating of the main motors (BATTERY BUS), and lastly, for series operation of all motors the positive side of one motor bus can be cross-connected to the negative side of the other motor bus, so that by proper closing of the motor contactors, all four motors can be placed in series for slow-speed operation on the battery bus (SLOW).

Either or both batteries are connected to the battery bus by closing their respective contactors which, in turn, are controlled by one operating lever.

6C12. Principal parts. The principal parts of the equipment are as follows:

1. One main propulsion control panel and operating bench with necessary instruments, rheostats, and operating levers.

2. One aft contactor group comprising:

    a. Port and starboard motor reversing switches.
  b. Port and starboard motor starting contactors.
  c. Bus selector switches.

3. One forward contactor group comprising:

  a. Port and starboard main generator contactors.
  b. Forward and aft battery contactors.
  c. Motor bus tie contactors.

All parts are mounted in a number of steel frames which in turn are joined to form a single unit. The assembly is supported on rubber shock mounts that are welded to the hull.

6C13. Operating levers. There are 10 levers for manual operation of the contactors in the various switch groups. These levers are provided with lock latches and are connected mechanically to the contactor camshafts through a series of bell cranks and rods. The purpose of the levers is as follows:

a. Two reverse levers. These levers are


used to change direction of rotation of the main motors by reversing the current flow through the armature. One lever is for the two starboard motors and the other for the two port motors. Each lever has three positions, OFF, AHEAD, and ASTERN.

b. Two starter levers. Each of the starter levers for the two port and starboard motors has a STOP position and five operating positions, SER. 1, SER. 2, SER. 3, PAR 1, PAR 2. The starter lever is used for cutting in resistance in series with the armature, thus keeping the starting current down to a minimum. As the motor picks up speed, the resistance can be cut out of the circuit when the armature is at running speed and the current reaches a normal value, putting it across the line voltage. The starter levers have three series positions and two parallel positions. The motors are always in series with each other when the starters are in any of the series positions, the voltage of the line being divided between each of the motors. When the starters are in either parallel position, the motors are in parallel, each motor receiving the full line voltage. The SER. 3 and PAR. 2 positions are the only running positions of the starter levers.

c. Four generator levers. One lever is provided for each of the four main generators. The levers have one OFF position and two operating positions, MOTOR BUS and BAT. BUS.

Note. On Westinghouse controls, the operating positions are GEN. BUS and BAT. BUS.

The function of these levers is to place

  any one or all generators on the battery bus for charging the batteries, or any one or all generators on the motor buses for propulsion. An extra mechanical latch on each lever prevents accidental movement from the OFF position.

d. One battery selector lever. This lever has an OFF position and three operating positions, AFT BAT, FWD BAT, and BOTH BAT. Placing the lever in the AFT BAT position will place the after battery on the battery bus. Placing it on the FWD BAT position will place the forward battery on the battery bus. In the BOTH BAT position, both batteries are in parallel with each other and on the battery bus. The battery bus is a common connection which is supplied with current from either one or both batteries and which in turn supplies current to the motor bus for motor propulsion when the bus selector is in battery position. In addition, any or all of the generators may be placed on this bus to charge either one or both batteries as desired. When the battery bus is used only for charging, it is necessary to have only the battery selector and the charging generator on the battery bus; the bus selector can be in the OFF position.

e. One bus selector lever. The bus selector has five positions, BUS TIE CLOSED, BUS TIE OPEN, OFF, BAT BUS, and SLOW. The function of this lever is to keep the port and starboard motor buses in an open or closed position, to connect the battery bus with the motor bus, and to close the necessary contactors to operate all motors in series.


6D1. Description. Approximately 40 auxiliary motors of various capacities are located throughout the ship for operation of compressors, blowers, pumps, and other miscellaneous equipment. Current for operation of these motors is supplied by the auxiliary generator, the main batteries, or a combination of both, through two auxiliary distribution switchboards. The forward distribution

  switchboard, connected to the forward battery, feeds all auxiliary machines in and forward of the control room, while the after distribution switchboard, powered by the after battery or the auxiliary generator, feeds all auxiliary machines aft of the control room. A bus-tie circuit connects the two switchboards, making it possible to feed one switchboard from the other in the event of an emergency.

During normal operation, the bus-tie circuit is left open and the power for both switchboards is taken from the batteries with the auxiliary generator often floating on the line. The batteries are thus paralleled through the battery selector on the main control panel. With the circuit so connected, the auxiliary generator will contribute current not used by the auxiliary load toward charging the batteries. This circuit arrangement is also used when the auxiliary generator is secured.

6D2. Auxiliary motors. Auxiliary motors are direct-current motors designed to operate on a voltage ranging from 175 volts to 345 volts. Their horsepower rating type of winding, and other data are stamped on the name plate attached to each motor. Auxiliary motor frames are enclosed to provide protection against dripping water and are vented to permit the escape of hot air which is forced out by a fan attached to the armature shaft. Magnetic disc brakes are used on motors that must stop after the current is shut off.

6D3. Motor-generator sets. The following are two types of motor-generator sets:

a. Lighting motor-generator sets. These machines are used on some ships to deliver current for operation of the lighting system as well as for the I.C. motor-generator sets that require a lower voltage than that delivered directly by the battery or auxiliary generator. The 175-345 d.c. motor receives its power from the battery or auxiliary generator and through a common shaft driver the 120-volt generator. It is controlled by a speed regulator.

Note. On some ships lighting motor-generator sets have been replaced by lighting feeder voltage regulators.

b. I.C. motor-generator sets. I.C. motor-generator sets are d.c.-a.c. machines equipped with speed and voltage regulators to produce a 60-cycle current for certain interior communication systems. The d.c. motor receives its power from the lighting motor-generator on ships so equipped, or directly from the battery or auxiliary generator on ships that do not use lighting motor-generator sets.


6D4. Main storage batteries. Each ship has two main storage batteries consisting of two groups of 126 cells each. The forward battery is installed below decks in the wardroom country and the after battery is located in the crew's space.

6D5. Battery installations. The installation in each battery tank consists of 6 fore and aft rows of 21 cells each. The two center rows are on one level. The rows alongside the center are slightly higher and the outboard rows are the highest. Above the two central rows of cells are installed panels of hard rubber that serve as a working deck or flat.

All cells are connected in series by means of intercell connectors while end cells in each row of batteries are connected by means of end cell connectors.

Both positive and negative forward battery disconnect switches are manually operated from a station at the after end of the forward battery room.

The after battery disconnect switches, also manually operated, are located near the after end of the crew's quarters. These disconnect switches are used only in an emergency to isolate the battery.

6D6. Battery ventilation. Each battery is fitted with an exhaust ventilating system in order to remove battery gases. The intakes for the air required to operate this system are located at opposite ends of each compartment. The free air in the compartment is drawn through the filling vent connection of each cell. The cells are connected by soft rubber nipples to exhaust headers of hard rubber which extend fore and aft for each row of cells.

The headers are in two sections and are connected to cross headers which unite in a common exhaust duct. The exhaust duct from each battery is led up to and through the deck to the inlets of two fans which are mounted on the hull overhead in the respective battery rooms.

Each of these four fans is rated at 500 cubic feet per minute at 2,700-revolutions per


minute. Each fan is independently driven; the motor is controlled from the maneuvering room. The motors used on late type submarines are rated at 1.25 hp (continuous), 2,780 rpm, 175-345 volts, 5.0 amperes.

Starting and speed regulation are accomplished by armature resistance. A fused tumbler switch for each motor is mounted in a separate case and connects both the armature circuit and the field circuit to the supply lines. Each armature circuit includes armature resistance, sections of which may be short-circuited by a 20-point dial switch to provide speed control. In regulating the battery ventilation by means of armature resistance and adjustments, care must be taken (when two blowers are being used for one battery) to set the pointers on both rheostat knobs to approximately the same point. The power supply is obtained through a fused switch marked BATTERY VENTILATION on the after distribution switchboard in the maneuvering room.

A damper is provided in the duct between the inlets of the two fans to allow the fans to be operated singly or together. When a single fan is used, the damper must be set in order to close the inlet to the idle fan, thereby preventing free circulation of air through both fans. Each pair of fans exhausts into the ship's exhaust system.

6D7. Air flow indicator. An indication of the quantity of air passing through the ventilation system is given in the maneuvering room by means of two air flow indicators. Each of these indicators is provided with a scale marked in cubic feet per minute.

6D8. Air flow through individual cells. The flow of air through cells of each battery compartment is equalized by means of adjusting regulators which are installed as an internal part of each filling vent cylinder. Proper adjustment of these regulators has been determined and set at a navy yard and must not be altered by ship's personnel.

Note. Do not permit the soft rubber nipples to attain a twisted position. A twisted or partially collapsed nipple will materially affect the ventilation to the respective cell or cells.


6D9. Lighting system. The lighting system is composed of the ship's service lighting system and the port and starboard emergency lighting systems. Each is a separate distribution system.

Power for the ship's service lighting system on late type submarines is obtained from the batteries through two lighting feeder voltage regulators and a lighting distribution switchboard. On earlier ships, power for this system was supplied by lighting motor-generator sets.

On some ships, a battery selector switch has been incorporated in the lighting distribution switchboard and permits selection of either battery or the shore connection as the source of power.

The feeders from the lighting distribution switchboard run the length of the ship on both sides and serve all regular lighting circuits through fused feeder distribution boxes. Final distribution to lighting fixtures and low-current outlets is through standard lighting distribution boxes with switches and midget fuses for each outgoing circuit.

The starboard emergency lighting system is directly powered through two cutout switches which are connected to the positive and negative end cell terminal connections of the forward battery. These switches are connected to 13 lighting units, a circuit to the auxiliary gyro, and the forward and after marker buoy circuits. A branch junction box provides a connection to the gyrocompass control panel for the alarm system.

The port emergency lighting system is directly powered through cutout switches connected to the after battery. The arrangement of this system is similar to that of the starboard emergency system except for the location of the circuits and the lack of a gyrocompass alarm connection.

Each lighting unit consists of two 115-volt lights, a protective resistor, and a snap switch, all connected in series, as they always operate directly on full battery voltage.



6E1. Circuits. The interior communication systems in a submarine provide the means of maintaining contact, transmitting orders, and relaying indications of the conditions of machinery to other parts of the ship.

The majority of the systems are electrical and automatic in operation. Some, such as the motor order telegraph system, are manually operated, but include an electrical circuit for the actual transmission of the order to another part of the ship. Some of the systems operate on alternating current; still others, such as the tachometer and sound-powered telephone systems, operate on self-generated current.

The I.C. systems of a modern fleet type submarine usually consist of about 24 circuits. With few exceptions, they are supplied with power through the I.C. switchboard located in the control room.

Following is a list of important I.C. circuits and their circuit designations:

  • Telephone call system: circuit E
  • Engine governor control and tachometer system: circuit EG
  • Battle telephone systems: circuits JA and XJA
  • Engine order control system: circuit 3MB
  • Dead reckoning tracer system: circuit TL
  • Collision alarm system: circuit CA
  • General alarm system: circuit G
  • Diving alarm system: circuit GD
  • Low-pressure lubricating oil and high-temperature water alarm system: circuit EC
  • Shaft revolution indicator systems: circuit K
  • Gyrocompass system: circuit LC
  • Auxiliary gyrocompass system: XLC
  • Motor order telegraph system: circuits 1MB and 2MB
  • Marker buoy system: circuit BT
  • General announcing system: circuit 1MC
  • Submarine control announcing system: circuit 7MC
  • Rudder angle indicator system (selsyn): circuit N
  • Bow and stern plane angle indicator system: circuits NB and NS
  • Auxiliary bow and stern plane angle indicator system: circuits XNB and XNS
  • Main ballast indicator system: circuit TP
  • Hull opening indicator system: circuit TR
  • Underwater log system: circuit Y
  • Bow plane rigging indicator
  • Target designation system: circuit GT

In addition, the following circuits, which are not part of the interior communication systems, are supplied through switches on the I.C. switchboard:

  • Circuit Ga-1: torpedo data computer
  • Circuit 17Ga-1: torpedo data computer
  • Circuit 6Pa: torpedo firing
  • Circuit 6R: torpedo ready lights
  • Circuit GT: target designation system

6E2. Systems requiring alternating current. The following systems require alternating current for operation:

  • Self-synchronous operated motor order telephone and indicator systems (for main propulsion orders)
  • Self-synchronous operated diving plane angle indicators (bow and stern planes)
  • Self-synchronous operated rudder angle indicator system
  • Hull opening and main ballast tank indicator systems
  • Hydrogen detector
  • Lubricating oil (low-pressure) and circulating water (high temperature) alarm systems

  • General announcing systems (alarm signals and voice communication)
  • Torpedo data computer
  • Self-synchronous operated underwater log system
  • Self-synchronous operated propeller shaft revolution indicator system
  • Target designation system
  • Engine governor control system (direct current on latest classes)
  • Torpedo data computer (Ga-1)

6E3. Systems requiring direct current. The following systems require direct current for operation:

  • Marker buoy system
  • Engine order indicator system (alternating current on older submarines)
  • Searchlight
  • Auxiliary gyrocompass
  • Torpedo data computer (17Ga-1)
  • Torpedo firing
  • Torpedo ready lights
  • Engine governor control system
  • Auxiliary bow and stern plane angle indicating systems
  • Resistance thermometer systems
  • Gyrocompass system

6E4. Interior communication switchboard. The I.C. switchboard is usually located on the starboard side of the control room. The switchboards on the latest type submarines are equipped with snap switches and dead front fuses with blown fuse indication mounted directly below or on either side of each switch requiring fuses. Earlier type submarines used knife switches with fuses mounted immediately below each switch.

a. Source of power. The alternating-current power supply to this switchboard is obtained from the I.C. motor-generators which are 250-volt d.c. motors and 120-volt a.c. generators.

6E5. Torpedo fire control system. The torpedo fire control system employs several

  electrical devices that assist in solving the fire control problem and firing the torpedo tubes. The devices that perform these functions are the torpedo data computer, the gyro-angle indicator regulators, and the torpedo ready and firing light systems.

The torpedo data computer is located in the conning tower and is energized by circuits Ga-1 (115-volt alternating current) and 17Ga-1 (115-volt direct current).

The gyro-angle indicator regulators for automatically setting the gyro angles on the torpedoes in the tubes are located at the forward and after tube nests and are controlled by separate fire control circuits from the torpedo data computer. The regulators are supplied with 115-volt direct current through circuits 17Ga-3 and 17Ga-4.

In addition to the above, the following circuits are provided:

  • An underwater log repeater circuit to the torpedo data computer
  • A gyrocompass repeater circuit to the torpedo data computer

6E6. Torpedo ready light, torpedo firing, and battle order systems. The torpedo ready light, torpedo firing, and battle order systems provide a means of informing the fire control party when the tube is ready to fire, or directing the tube crew to stand by a tube to fire, or firing the torpedoes remotely from the conning tower and simultaneously indicating to the tube crew by means of an audible and visual signal that the tube has been fired, and lastly of indicating that the tube has been fired, by a visual signal in the conning tower. It also indicates to the fire control party in the conning tower, by means of a visual signal, that the gyro-angle indicator regulators are matched.

6E7. Torpedo ready light and battle order system. A forward and after transmitter in the conning tower is used to transmit torpedo orders to an indicator at each tube nest. When power is turned on in the conning tower, the READY AT TUBE and the


STANDBY pilot lights on the corresponding indicator in the torpedo room are lighted. When the gyro retraction spindle switch contacts are closed, an amber GYRO SPINDLE IN light in the indicator in the conning tower for that tube is lighted. When the tube interlock switch contacts are closed, the amber READY AT TUBE light for that tube in the indicator in the torpedo room is lighted. When the operator turns the indicator switch for that tube, it lights a green READY light for the tube in the transmitter in the conning tower. When the gyro mechanism of the tube nest is matched upon closing the manual contact of the gyro setting mechanism contact maker, a red angle SET light in the transmitter in the conning tower is lighted. When a particular tube standby switch in the conning tower is turned to STANDBY at the transmitter, the   corresponding green STANDBY light for that tube in the indicator in the torpedo room is lighted. Upon pressing the firing contact maker, the tube is fired through operation of the pilot valve solenoid. Simultaneously a red FIRE light in the indicator is lighted and a buzzer is operated at the tube nest.

6E8. The torpedo firing system. The torpedo firing system (Circuit 6PA) is energized from the 120-volt direct-current bus on the I.C. switchboard.

Separate fixed and portable contact makers (firing keys), for independently controlling the forward and after groups of firing solenoids, are located at the torpedo ready light and firing panels in the conning tower. A key, mounted on the gyro-angle regulator indicators, operates a light on this panel to show that the regulator is matched.


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