Ship control does not, in general, present any startling innovations, although certain individual components are of interest.  
          The items of interest are the gyro sextant, the gyro compass, the column type depth gauges, and the periscopes.  All but the column type depth gauges are subject of other reports not yet available.  
March, 1946
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          Ship control arrangements consist of a chariot bridge at the top of the conning tower fairwater bulwarks of which house retractable radio, radar and RDF masts, a small conning tower, a control room, and a maneuvering room.  
          Navigational instruments consist of azimuth circles, barometers, (including barographs), several different types of binoculars including a pressure proof type for the bridge pelorus stand, chronometers, clinometers, ship's clock, gyro compass and repeaters, an optically distant reading magnetic compass, depth gauges, leads and fittings, a pit log, sextants including a gyro sextant, echo sounding equipment, meteorological thermometers and stop watches.  
          The ships are fitted with demountable bells, fixed chart board, chart locker, megaphones and a hand fog horn.  
          Two periscopes are provided, both operated from and used in the conning tower.  One of these is a fixed eye level type.  
  Ship Control:  
          The only navigational equipment permanently fitted on the bridge is the TBT stand, a pressure-proof rudder angle indicator and a pressure-proof gyro repeater.  It is possible to steer from the bridge, however, as the steering station in the conning tower can be moved to the bridge and connected by portable cable down the conning tower hatch to the terminal box in the conning tower.  Searchlight and signal lamp cable also has to be extended down through the hatch to the conning tower.  There are normally four persons on the bridge when surfaced.  
          The ship's horn is operable from the bridge.  There is also a voice tube from the bridge to the conning tower and control room.  
          The conning tower is a small oval compartment in which is located the two periscope operating stations, the periscope hoists and the turning gear for the fixed eye level periscope, an indicator showing the height of the periscope  
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  above the surface of the water, torpedo firing keys and TDC, a steering stand, engine order telegraphs, rudder angle indicator, plane angle indicator, shaft r.p.m. indicator, log repeater and dead reckoning analyzer indicator, gyro compass repeater, depth gauges, fathometer, loud speaker amplifier and microphone, sound powered telephone, voice tubes to multiple locations, diving alarm contact maker, and torpedo fire control panel.  
          When surfaced, there are normally three persons in the conning tower.  Under battle station conditions, there are four.  
          The control room is a compartment amidships within the pressure hull of the vessel.  In it are located a steering station, the normal plane control stations, (in certain vessels, an auxiliary plane control station), chart board and locker, engine order telegraphs rudder angle indicator, plane angle indicators, shaft r.p.m. indicator, log and DRAI, gyro compass and repeater, depth gauges including a snorkel extension indicator, clinometer, trim indicator, the screen for observing the optically distant reading magnetic compass, loud speaker amplifier and microphone, sound powered telephones, voice tubes, hull opening indicator panel, compartment clear indicator panel, vent valve indicator panel, a mechanical trim and drain order transmitter, and an alarm contact maker.  
          When surfaced, there are five persons in the control room.  At battle stations, there are ten.  
          The maneuvering room and engine room are in one compartment, separated by a water-tight (not pressure tight) bulkhead.  Control is not centralized, for when the vessel is operating on diesels, control is in the engine room, while when operating on main motors, control is in the maneuvering room.  
          The engine room is fitted with a control stand for each engine, engine order telegraphs, shaft r.p.m. indicators, rudder angle indicator, a loud speaker, alarm bell and light flasher, and compartment clear contact maker.  There are normally four persons in the engine room.  At battle stations, there are six.  
          The maneuvering room is fitted with a control board for each main motor, engine order telegraphs, shaft r.p.m. indicators, rudder angle indicator, loud speaker and microphone, sound powered telephone, alarm bell, compartment clear contact maker, and salinometer.  There are normally two persons in the maneuvering room.  At battle  
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  stations there are three.  
          Certain of the items mentioned in the foregoing are of common types and need not be mentioned further, except to say that they are all of a high quality.  Items in this category include barometers and barographs, binoculars, chronometers, clocks, sextants, etc.  
          Other items are described in the appropriate "S" group heading and will not be further discussed here.  Such items include communications and signal systems components.  
          A third group includes some items which have been forwarded to certain agencies for exploitation, on which separate reports will presumably be made although they are not available at the moment of writing.  These include the gyro sextant, echo sounding equipment, periscopes & gyro compass.  
          The periscope hoisting motor is an IMO hydraulic motor operating through a worm gear to drive a pair of cable drums.  The cables lead up to the overhead, across to the sides of the well, and down to an equalizing yoke at the foot of the periscope.  
          Associated with the pump is a chain of gears which drive a traveling worm valve which determines the limit of travel.  A spring-loaded pilot valve and a spring-loaded, lever-operated control valve complete the assembly.  All valves are piston type.  
          Operation of the control valve opens ports to the travel limit valve and, if the ports of this valve are open, to the pilot valve, operating the piston and opening ports to admit hydraulic oil to the hydraulic motor.  This then rotates the windlass, raising or lowering the periscope as desired.  
          The raising and lowering device for both periscopes is similar, except that two control valves and a selector valve are provided for the fixed eye level periscope, which is in the after position, in order to permit the operation to be controlled from either of two locations.  
          For the fixed-eye level periscope a pedal-operated control valve is provided, which connects with a periscope  
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  turning motor.  This is smaller than the hoist motor and is mounted overhead on the periscope casing, where it operates to turn the periscope and the attached observer's seat under control of the pedals or, if desired, a hand wheel.  
          Associated with each of the periscope hoists is a gauge which shows the amount of the periscope exposed.  It operates on a dual water-column basis in which one column consists of a Papenberg gauge showing the external water pressure calibrated in meters submergence, and the adjacent column shows the position of the periscope head.  The height of the water level which shows the top of the periscope is determined by the position of a bellows which is geared to the periscope hoist and is compressed as the periscope is raised, thereby displacing water from the interior of the bellows chamber into the water column.  Several variations on this mechanism have been seen, but all operate on the same basic principle.  
          The gyro compass is of the Anschuetz bell type, which has been manufactured and installed commercially for many years.  For further remarks, see section S62.  
          The magnetic compass is a standard compass mounted in a pressure-proof case in the superstructure forward of the conning tower fairwater.  Lighting is provided, and an optical train leads through the pressure hull to the steering station in the control room, where the image of the rose and azimuth circle appears on a ground glass screen.  
          The log is the familiar pitometer type, but instead of being operated by way of tubing extending into the vessel along a sword arm, it is operated by dynamic pressure obtained at the stem, and static pressure obtained from the sea amidships.  Pressure differentials are obtained magnetically and are integrated in terms of the known characteristics of the ship to show speed and miles run.  
          Depth gauges are of two types:  (a)  the normal dial spring manometer type pressure gauge, and (b)  the water column.  
          One 25-meter (82 ft.) manometer gauge is provided in the control room, and five 200-meter (656-foot) gauges are provided, two in the control room and one each in the conning tower and each torpedo room.  
          One residual buoyancy and depth gauge reading up to 18 meters is provided in the control room.  It is a Papenberg water column type gauge 1175 mm (46.27") long.  
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  operating on a straight compression basis, i.e; the upper end is closed, and the lower end can be opened to sea pressure.  The level of water in the gauge is adjustable.  Two scales are provided:  the left hand scale showing the residual buoyancy in metric tons, and the right hand scale showing the depth in meters measured from the bottom of the keel.  
          A similar column type depth gauge is provided, which gives a visual presentation of the amount of snorkel above the surface of the water.  This is located next to the one above, at the diving station.  
          The clinometers are of the usual bubble type, with the exception of one, which is a plumb bob hung in the forward control room bulkhead door opening, with an indicator scale on the bottom of the door sill.  
          The trim angle indicators are of two types.  One is dial type on which is shown a small representation of the ship, and a line representing the water plane.  When the ship takes an angle, the representation takes the same angle with reference to the water plane.  This gauge works on the principle of a pendulum.  
          The second type of trim indicator is a very long closed loop of piping, with long axis fore and aft and the short axis vertical.  The vertical portion of the loop at its forward end is a water column, and is constructed of two conical tubes for the purpose of modifying the scale, thereby increasing the accuracy with which small angles can be read.  
          The navigational equipment provided is normal and generally of a standard commercial type.  The gyro-sextant is unusual, however, and one has been sent to the Naval Observatory for exploitation.  A report thereon is not available at the moment of writing.  
          The Anschuetz gyro compass is a commercial product, but has not been used in recent years by the U.S. Navy, although hearsay has it that certain vessels were so equipped in 1917-1919.  The unit is notably smaller and lighter than the current U.S. Navy standard type, and while its life is probably shorter, this is offset by the fact that spare balls can be carried on board and used to replace improperly working elements.  It is thought that troubles  
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  experienced by personnel on one vessel in the maintenance of the unit may be in part due to unfamiliarity, as verbal report from other vessels indicated that when the air cooling system had been slightly modified, no further trouble was experienced.  
          The periscope hoist mechanism is of interest as showing what can be done with hydraulic power, when applied to an accurately cut gear drive on a rope hoist, to reduce noise.  The control, however, is unnecessarily elaborate, and shows a lack of realization of the principles which should govern, i.e; simplicity and ruggedness, as brought out in Navtechmisseu report 305-45 on hydraulic systems.  As therein mentioned, the attempt to apply the same type of controls to a hydraulic system of increased scope on the XXI vessels was a failure, and resulted in a change.  The earlier vessels, however, all have the control valve, pilot valve and operating valve on the periscope hoist, although the control of the periscope turning motor is direct.  
          The depth gauges are not generally remarkable.  The combination gauge for showing the amount of periscope extended and amount of submergence does provide a direct reading for each, and a comparative reading at the same time, on a relatively large scale.  The corresponding water column depth gauge in the control room permits increased accuracy in gauging depth within submergences which allow of periscope observations.  
          The column type trim indicator permits accurate trimming and early observation of any tendency of the vessel to change angle under control of the planes.  Its character, however, is such as to introduce a large inertia factor which would make it unreliable except for operations not involving intentional change in angle.  
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