Introduction. The definitions contained in this chapter are exact meanings of the terms commonly used in reference to the modern submarine and its operation. These terms and explanations represent accepted interpretations and provide an understanding of the functions of the equipment.

2Al. Surface condition. A submarine is in surface condition when she has sufficient positive buoyancy to permit running on her main engines.

2A2. Diving trim. The term diving trim designates that condition of a submarine when it is so compensated that completing the flooding of the main ballast, safety, and bow buoyancy tanks will cause the vessel to submerge with neutral buoyancy and zero fore-and-aft trim.

2A3. Rigged for dive. A submarine is rigged for dive by so compensating the vessel and preparing the hull openings and machinery that the vessel can be quickly and safely submerged and controlled by flooding the main ballast tanks, using the diving planes, and operating on battery-powered main motors

2A4. Running dive. A running dive consists of submerging a submarine while running on battery power. 

2A5. Stationary dive. A stationary dive consists of submerging a submarine without headway or sternway. 

2A6. Quick dive. A quick dive consists of rapidly submerging a submarine while running on main engines.

2A7. Submerged condition. This term designates a condition of a submarine in which all fixed portions of the vessel are completely submerged and the variable ballast is so adjusted that the submarine has approximately neutral buoyancy and zero fore-and-aft trim. 

2A8. Final trim. Final trim is the running trim obtained after submerging, in which

  the fore-and aft and over-all weights have been so adjusted that the boat maintains the desired depth, on an even keel, at slow speed, with minimum use of the diving planes.

2A9. Compensation. Compensation is the process of transferring ballast, in the form of water, between the variable tanks, and between the variable tanks and sea, to effect the desired trim. 

2A10. Main ballast tanks. Tanks that are provided primarily to furnish buoyancy when the vessel is in surface condition and that are habitually carried completely filled when the vessel is submerged, except tanks whose main volume is above the surface waterline, are known as main ballast tanks.

2A11. Variable ballast tanks. Ballast tanks that are not habitually carried completely filled when submerged and whose contents may be varied to provide weight compensation are known as variable ballast tanks. Variable ballast tanks are constructed to withstand full sea pressure.

2A12. Negative tank. The negative tank is a variable ballast tank providing negative buoyancy and initial down-angle. Submarines normally will operate submerged in neutral buoyancy and without trim when the negative tank is nearly empty. It is used to reduce the time required in submerging from surface condition, to reduce the time required to increase depth while operating submerged, and to prevent broaching when decreasing depth. It may be blown or pumped. 

2A14. Bow buoyancy tank. The bow buoyancy tank is a free-flooding, vent-controlled


tank with its main volume above the normal surface waterline. It is located in the extreme bow of the vessel and is formed of the plating of the superstructure. Its function is to provide reserve surface buoyancy, emergency positive buoyancy in the submerged condition, and to aid in surfacing.

2A15. Auxiliary tanks. The auxiliary tanks are variable ballast tanks located at or near the submerged center of buoyancy, and are used to vary the over-all trim of the boat.

2A16. Trim tanks. The trim tanks are the variable ballast tanks nearest the bow and stern of the boat and are used to provide fore-and-aft compensation.

2A17. Normal fuel oil tanks. Tanks designed solely for containing the engine fuel oil are known as normal fuel oil tanks.

2A18. Fuel ballast tanks. The fuel ballast tanks are designed to be utilized as fuel oil tanks for increased operating range. When empty, they may be converted to main ballast tanks, providing additional freeboard and thereby increasing surface speed. 

2A19. Expansion tank. The expansion tank, connected between the head box and the compensating water main, admits sea pressure to the fuel oil tanks. It receives any overflow from the fuel tanks resulting either from overfilling the fuel system or from temperature expansion. The bilges are pumped into this tank to prevent leaving an oil slick or polluting a harbor. 

2A20. Collecting tank. The collecting tank, connected to the fuel oil tanks through the fuel transfer line, serves as a water and sediment trap for the fuel oil being transferred to the fuel pump.

2A21. Clean fuel oil tanks. The clean fuel oil tanks are storage tanks located within the pressure hull. They receive clean fuel oil from the purifiers and are the supply tanks from which the engines receive their clean fuel. 

2A22. Poppet valve drain tank. The poppet valve drain tank is located under the platform deck of the torpedo room immediately 

below the breech of the torpedo tubes. The air and water from the poppet valves, incident to the firing of torpedoes, is discharged into this tank. 

2A23. Fresh water tanks. The fresh water tanks contain potable water for drinking, cooking, and certain sanitary facilities.

2A24. Battery fresh water tanks. The battery fresh water tanks are storage tanks for the distilled water used in watering the main storage batteries. 

2A25. Sanitary tanks. The sanitary tanks receive and store the ship's sanitary drainage until conditions permit overboard discharge. 

2A26. WRT tanks. The WRT, or water round torpedo, tanks are variable ballast tanks, located in the forward and after torpedo rooms, for flooding or draining the torpedo tubes. 

2A27. Main vents. The main vents are valves operated hydraulically, or by hand, for venting the main ballast tanks when flooding. They are located in the top of the risers of the main ballast tanks. 

2A28. Emergency vents. The emergency vents are stop valves in the vent risers near the tank tops and are used in case of damage to the, main vents. They permit sealing the tank to prevent accidental flooding and also permit blowing the tank if desired. 

2A30. Riding the vents. Riding the vents is a surface condition in which the main ballast tanks are prevented from completely flooding by the closed main vents which prevent the escape of air. 

2A31. Flood Valves. Flood valves are hinged covers at the bottom of certain ballast tanks which may be opened to admit or expel sea water. 

2A32. Flooding. Filling a tank through flood ports, open flood valves, or other sea connections, is known as flooding.


2A33. Blowing. Blowing a tank consists of expelling its contents by compressed air. 

2A34. Pumping. Pumping a tank consists of using a pump to transfer liquid from the tank to sea, from sea to tank, or from one tank to another. The tanks must be vented during this operation. 

2A35.Bow planes. The bow planes are horizontal rudders, or diving planes, extending from each side of the submarine near the bow.

2A36. Stern planes. The stern planes are horizontal rudders, or diving planes, extending from each side of the submarine near the stern. 



2B1. General. Standard phraseology is the product of years of experience and has been developed to combine precision, brevity, and audibility. The following procedures have been approved for submarine communications, both airborne and over interior communication systems. Strict adherence to these procedures increases the speed of communications and reduces the chances of error and misunderstanding. The standard phrases, developed for the various activities of a submarine, are included in the chapter in which their use occurs. bility and to minimize confusion. This is standard for the service, and should be followed invariably.

The numeral "0" is spoken as "Ze-ro" for all numerical data except ranges. In giving ranges, "0" is spoken as "Oh." When "00" occurs at the end of a number it is spoken as "Double-oh."

Examples: "Bearing too ze-ro ze-ro." "Range fi-yiv oh double-oh." 

a. Bearings and courses are spoken 

0 Ze-ro or Oh (stress on both syllables of Zero) 5 FI-yiv (stress on first syllable)   
1 Wun 6 Six
2 Too 7 Seven
3 Thuh-REE (stress on second syllable) 8 Ate
4 FO-wer (stress on first syllable) 9 Niner
2B2. Voice procedure. All messages should be spoken clearly and loudly enough to be heard above the noises and voices of the various compartments. Talk slowly and speak distinctly, do not run words together. Make the listener hear all you say the first time you say it.

2B3. Numerals. Exhaustive tests have demonstrated that numerals should be spoken in the following manner to provide intelligi-

as three separate digits. 
Examples: "Bearing ze-ro zero thuh-ree."
"Steer course wun niner six."

b. Speed and torpedo depths are spoken as two separate digits.

Examples: "Speed ze-ro six and wun half knots."
"Set depth wun too feet."


c. Angle on the bow is spoken as a single compound number preceded by "port." or "starboard."

Example: "Angle on the bow port thirty fi-yiv."

d. Depth to keep, and bubble, or angle of the boat and angle on the planes, are spoken as separate digits.

Example: "Six fi-yiv feet, too degree up bubble, too zero degrees rise on the bow planes." 
e. Time is spoken in standard Navy terminology .

Examples: "Ze-ro ze-ro thirty." "Ze-ro ate hundred." "Seventeen thirty fi-yiv." "Ze-ro niner ze-ro fi yiv."

2B4. Messages. a. Messages over a telephone or talk-back normally consist of two parts: 1) the call and 2) the text. There should be no pause between these parts for acknowledgment by the receiver.

Example: "After room, open outer doors aft."

b. When it is necessary to prevent misunderstanding, the station calling should identify itself immediately after the call. 

Example: "Control, forward room: we heard a bumping noise along the hull !"

2B5. Acknowledgment. a. Each message should be acknowledged by an exact repetition. "Aye, aye" should not be used because it gives the originator no clue as to whether or not the message has been understood correctly.

Example: Message. "After room, open outer doors aft." Acknowledgment. "After room, open outer doors aft."

b. When an order has been executed, that fact is communicated to the originating station. Example: Statement of execution. "Conning tower, the outer doors have been opened aft." 

Acknowledgment. "Conning tower, the outer doors have been opened aft." 

c. When a question cannot be answered immediately, it is acknowledged and the word "Wait" added. The question is answered as soon as the information is available. 
Example: Message. "After Engine Room, how are the bilges ?" 

Acknowledgment. "After Engine Room, how are the bilges? Wait." 

Reply, after the information is obtained. "Control, six inches of water in the after engine room bilges." Acknowledgment. "Control, six inches of water in the after engine room bilges." 

d. If the acknowledgment shows that the message has not been heard correctly, or if the originator himself decides to change the message, he says, "Belay that," and gives the correct form.

e. A repeat is requested whenever there is any doubt concerning the content of a message.

2B6. Emergency messages. In case of emergency, the station making announcement calls, "Silence on the line." All other stations cease talking until the emergency message has been completed.

2B7. Courtesy. The words "sir" and " please", and so forth, are not used on interior communication circuits. On a combat vessel, courtesy consists of making telephone messages as brief and efficient as possible.


2C1. Acceptable abbreviations. In the box below are given some of the most frequently used abbreviations. They are time savers and should be used whenever possible. In the interest of uniformity throughout the Service they should be used exactly as they appear here.
W. S.  water pressure test for strength 
W.T.  water pressure test for tightness 
W.S.&T.  water pressure test for strength and tightness 
A.S.  air pressure test for strength 
A.T.  air pressure test for tightness 
A.S.&T.  air pressure test for strength and tightness 
O.S.  oil pressure test for strength 
O.T.  oil pressure test for tightness 
F.O.T.  fuel oil test for tightness 
L.O.T.  lubricating oil test for tightness
O.S.&T. oil pressure test for strength and tightness 
MBT  main ballast tank 
FBT  fuel ballast tank 
NFOT  normal fuel oil tank 
CFOT  clean fuel oil tank 
NLOT  normal lubricating oil tank 
WRT  water round torpedo 
psi  pounds per square inch 
hp  horsepower 
rpm  revolutions per minute 
shp  shaft horsepower 

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