In diving, the diving plane angles vary according to the amount of trim and the diving rate. In submerging, the command “Report on depth” may be given, and as soon as the planesman receive this command he reports the change in depth every five meters, or every one-fourth meter at periscope depth. As the ordered depth is approached, the trim is reduced and the planesman reports the diving depth reading on the depth gauge.

In crash diving, the submarine must be rigged for emergency blowing of the fore and aft main ballast tanks if the trim rapidly increases and exceeds the permissible. The midship tanks may have to be blown if there is a loss of buoyancy due to incorrect calculation of the weight of the submarine or spontaneous blowing of the negative tank.

5. Diving of a Submarine and Control of the

Diving Planes in Stormy Weather

Diving in heavy seas, like ordinary diving, commences with the command “Proceed to your stations, rig for diving.”

In a large wave, the submarine must dive with the negative tank full and at high speeds, creating a considerable hydrodynamic force on the diving planes.

In the initial stage of diving, the bow planes must be set for diving and the stern planes for surfacing, thus permitting the submarine to remain on an even keel and also creating a downward force. After the submarine deck submerges, the stern planes must be reset for diving. Then the stern and bow planes will create a trim by the head, thus assuring rapid submergence of the submarine. The negative tank should be blown at a depth not less than periscope depth.

6. Handling a Submarine Snorkeling

A submarine begins snorkeling submerged when the “general quarters" alarm is sounded. In rigging for snorkeling, the submarine crew takes the following measures:

1) rigs for snorkel propulsion (charging) the diesel and line shaft indicated by the Commanding Officer of the submarine (the electric motor operating in this case is on the same side as the diesel which will not be snorkeling);

2) rigs the intake and exhaust vent for snorkeling;

3) raises the snorkel mast and drains it into one of the tanks or into the bilge;

4) checks for water in the snorkel gas and air lines;
5) opens the snorkel air valve and starts the blower;

6) starts the engine at low speed by order of the Commanding Officer of the submarine.

The command “Trim the submarine at a depth of so many meters" is given before the snorkeling submarine begins diesel operation. The transition to snorkel operation is made upon completion of trimming, after which Condition No. 2 is sounded.

At the time the submarine begins snorkeling, additional hydrodynamic forces and moments arise, considerably altering the equilibrium of forces and moments while operating submerged, necessitating a corresponding adjustment of the diving planes in order to compensate for them.

The buoyancy of the submarine does not change in hoisting the masts, since the water they contain will constitute part of the underwater displacement of the submarine.

After the diesel engine is turned on, pressure is created throughout the entire engine gas exhaust system. As the indicated exhaust pressure is attained, the upper double-action snorkel valve is opened. After the submarine begins snorkeling, it acquires positive buoyancy due to removal of water from the exhaust lines. In this case, buoyancy is reduced to zero by taking an appropriate amount of ballast into the auxiliary tank.

The transition from small to large engine loads is accomplished gradually in order to prevent vapor formation on the surface of the sea near the exhaust nozzles.

Maintaining a submarine at the ordered depth while snorkeling is a primary task. Care must be taken to assure that the float valve is not submerged. In heavy seas and whenever the planesman is unable to maintain the submergence depth precisely, the snorkel air induction may take water. In this case the float valve is closed, producing a sharp pressure drop inside the submarine.

When a high vacuum develops, the diesel must be stopped and the submarine begins operating submerged on electric motors, rising to periscope depth.

After the submarine stops snorkeling and the exhaust lines are filled with water, the submarine acquires negative buoyancy.

In the transition from snorkeling to operating submerged, residual buoyancy is reduced to zero by pumping an appropriate quantity of ballast from the auxiliary tank.

The shift from snorkeling occurs as follows. With the command "Crash Dive,” personnel stop the operating diesels and disengage their clutches, shut off the ship ventilation system, close the exhaust lines, open the snorkel kingston and lower the snorkel mast, start the electric motors, dog down the bulkhead sluices, and rig the engine compa ment for diving. Then, by means of the way and rudders, the submarine dives to the ordered depth. The negative tank is filled if the need arises.

7. Handling a Submerged Submarine

The diving depth of a submarine is varied by creating a trim, and through speed and buoyancy. A well trimmed submarine must be controlled entirely by the stern planes. The bow planes are used:

1) in crash diving;

2) in turning the submarine;
3) in the presence of negative buoyancy;
4) to develop trim in varying the diving depth;

5) in propelling with electric motors at cruising speed. In order to achieve a rapid change in diving depth, the bow planes must be set to full down (or up) and the stern planes used to maintain the necessary trim.

In proceeding to the ordered depth, the submarine must be controlled by the stern planes. The bow planes are set at zero or, if the need arises, are set to surface (or dive).

The negative tank should be filled to accelerate diving under extreme circumstances, for example, to avoid ramming or in event the submarine broaches due to a wave and is unable to submerge by headway.

A submarine in neutral trim making a turn assumes a trim by the stern. The greater the speed of the submarine in turning and the greater the angle of the diving plane, the less often this phenomenon occurs. The planesman must be informed whenever the vertical rudder is adjusted and eased.

Control of a submarine at periscope depth in heavy seas is complicated by the fact that the submarine tends to broach due to the wave. A submarine operating at periscope depth in fresh weather must:

1) have slight negative buoyancy;
2) proceed at least at moderate speed;

3) have a slight trim by the head.
It is recommended steering a course beam on to the sea.

Whenever due to a high sea it is impossible to maintain periscope depth, it is necessary to operate at a safe depth and to proceed at a speed at which the submarine can be maintained at periscope depth.

If a submarine broaches in a rough sea, it is submerged by filling the auxiliary tank and then blowing it.

When a submarine dives to considerable depth it acquires negative buoyancy due to compression of the hull. The creation of negative buoyancy is indicated by an increase in the trim by the stern and a corresponding need to increase the angle of adjustment of the diving planes for surfacing.

In diving under circumstances permitting the submarine to surface, with the creation of a large trim (immediately after filling the midship tank or tanks), and with a subsequent increase in this trim, the submarine should stop diving and surface.

For this purpose, the main ballast tank vents must be closed, the midship tanks blown and a bubble admitted to the end tanks according to the trim.

8. Counteracting the Loss of Buoyancy and Trim The primary causes of buoyancy loss with a simultaneous increase in trim are as follows: a) When the submarine is diving:

1) penetration of water in the pressure hull;
2) inaccurate calculation and method of trimming;

3) failure of personnel to observe filling of auxiliary and special ballast tanks, torpedo tubes, missile tubes, etc.;

4) blowing of the negative tank at the wrong time. b) Submerged:

1) penetration of water in the pressure hull;

2) failure to periodically adjust the trim and drain the bilges and special tanks;

3) spontaneous filling of the annular spaces of the torpedo tubes, tanks, missile tubes.

A loss of buoyancy, not accompanied by the appearance of trims, can result from compression of the pressure hull at great depths or during passage of the submarine into an area with a lower water density.

In event of uncontrolled and increasing trims during diving (immediately after the midship ballast tanks are filled) or in event of accident while submerged, due to penetration of water in the pressure hull, the submarine should immediately surface if the tactical situation permits.

In operating submerged, if there is an increase in trim by the head caused by jamming of the planes in diving position, the following steps must be taken immediately:

1) blow the forward ballast tanks under high pressure until the trim is reduced;

2) go astern, if need be increasing the speed to the maximum possible in order to overcome diving inertia and to prevent the submarine from plunging. From the beginning of reduction in trim, periodically (every hour) remove a bubble from the forward ballast tanks, not permitting the decrease in trim to accelerate or to pass abruptly through zero;

3) with a reduction in trim to zero, to go ahead, if need be increasing to full speed so that the submarine can be controlled using the remaining pair of properly operating diving planes.

In order to counteract spontaneous surfacing of the submarine with trims by the stern, caused by jamming of the planes in surface position, in the majority of cases all that is needed is to decrease speed or to stop.

In operating submerged, if a trim by the head develops, caused by penetration of water in one of the forward compartments, the following steps must be taken immediately:

1) blow the forward ballast tanks under high pressure until there is a decrease in trim;

2) increase to maximum speed, adjusting the planes for diving at full throw in order to produce a trim by the stern and to maintain it within required limits.

In reducing trim it is necessary to periodically (every hour) remove excess air from the forward ballast tanks, without permitting acceleration of increasing trim and an abrupt shift to trim by the stern. In every case an air cushion should remain in the blown tanks, approximately equal to the volume of the flooded portion of the compartment.

As the trim approaches zero, the following measures must be taken if the submarine continues to dive:

1) blow the midship ballast tanks until the submarine begins to rise;

2) maintain the trim and surfacing speed within required limits by changing speed, the diving plane angles and the volume of the air bubbles in the ballast tanks.

If a trim by the stern develops under way, as a result of penetration of water into one of the after compartments, the following steps must be taken immediately:

1) begin partial blowing of the after ballast tanks, continuing until there is a decrease in trim;

2) increase the speed as required and set the planes for diving in order to overcome the increasing trim and to reduce it to the required level as determined by the weight of water taken on and the lever arm of the flooded compartment.

In reducing the trim, the excess air must be removed periodically (every hour) from the after ballast tanks, while preventing the decrease in trim from getting out of control and preventing the development of a trim by the head. In each case an air bubble should remain in the blown tanks, approximately equal to the volume of the flooded portion of the compartment.

If in the process of decreasing the trim the submarine continues to dive, blowing of the midship ballast tanks must be started, continuing until the submarine begins to rise. If this measure produces a significant reduction in the rate of decrease in trim, the after ballast tanks must be blown again.

As the trim approaches the required amount for the given case, the following steps must be taken:

1) resting assured that the stern is “light” and that the decreasing trim can achieve the required value, remove once again the excess volume of bubble from the after ballast tanks;

2) maintain the required surfacing rate with the best possible trim by varying the speed, diving plane angles and the volume of the air cushions in the ballast tanks.

If under the circumstances of the situation a damaged submarine cannot surface, then after compensating for acquired negative buoyancy and the trimming moment resulting therefrom, the submarine is kept within a given depth range by varying the speed, diving plane angles and the volume of the air in the main ballast tanks.

9. Handling a Submarine in Fresh Weather

Maintaining a submarine at periscope depth with a state of the sea of 4-5 and higher is quite difficult, since in this case an additional buoyancy force is acting on the submarine, created by the heavy sea. This force is created by the warping of equal-depth surfaces in the mass of water affected by wave action, producing a change in pressure gradients with depth, whereby the pressure

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