Operating Procedures124
Test Procedures132


All U. S. Navy torpedoes have the starting lever, the side setting gyro setting sockets, the-depth setting sockets, and the speed setting sockets (when fitted) in the same locations relative to the center line of the torpedo and to its tail. Torpedoes are divided into three groups according to the location of the guide stud, the distances from the tail to the front of the guide stud being 109.0 inches, 141.44 inches, or 150.44 inches, depending upon the length of the torpedo.

The torpedo tubes described in this pamphlet were designed primarily for the Mark 14 torpedo, which has the front of the guide stud 141.44 inches from the end of the tail, hence they will accommodate such torpedoes without any adjustment or alteration of either the tube or the torpedo. The

  length of this torpedo has been increased to 246.0 inches, but this increase in length does not in any way affect the operation of the torpedo tube.

These tubes were designed also to accommodate the Mark 10 Modification 3 torpedoes, which have the front of the guide stud 109.0 inches from the tail, by changing the stop bolt to the rear housing, described in Chapter S, page 109 of this pamphlet. With this torpedo, however, as with all others except the Mark 14 and Modifications, it is necessary to use the gyro setting socket adapter described in Chapter 7, in the section on the Gyro setting mechanism, and specifically on page 90. This adapter is required if gyro angles are to be set while this torpedo is loaded in the tube. Mark 10 Modification 3 torpedoes are originally issued with a guide stud which is Tee shaped in

Figure 222
Figure 222 Loading the torpedo first step. A tail piece having one end shaped to fit into the propeller shaft, and with a pulley at the other end, is inserted in the propeller shaft, and the cable is led around the end of the pulley. Illustrations on the following pages show the succeeding steps.

cross section, and which is too high to suit the guide slot in torpedo tubes such as those described in this pamphlet. The flat, low guide stud used on the Mark 14 torpedoes is to be used. This guide stud has holes for four bolts, whereas the Mark 10 Modification 3 torpedo air flask is tapped for only three bolts. Therefore, when attaching the guide stud on the torpedo, the vacant hole in the guide stud should be placed toward the tail of the torpedo.

The foregoing also applies to torpedoes Mark 9 and Modifications. In addition, on older Modifications of Mark 9 torpedoes, the depth index runs to only 25 feet instead of to 50 feet as on modern torpedoes, and the scale index is 51 degrees of dial to five feet of depth instead of 20 degrees to five feet, so that the scale on the depth setting mechanism on the tube may not be read directly when these torpedoes are

  being used (although, from the foregoing information, an equivalent scale may be readily prepared).

In Chapter 2, describing the barrel, reference is made, briefly, to the overall lengths and the effective lengths of bow and stern tubes, the effective length referring to the length of torpedoes that can be accommodated in the tubes. Experience on any submarine will soon make it possible to determine at a glance whether any given torpedo of a known length can be fitted into either the bow or the stern tubes of the particular vessel. There are certain torpedoes, principally the Marks 11, 12, and 15 torpedoes, of the original length of 271.0 inches, which can be fired from the stern tubes of some submarines. These torpedoes, however, have the front of the standard guide stud 150.44 inches from

Figure 223
Figure 223 Loading the torpedo, second step. The block and tackle is attached to the two eyes on the breech door locking ring.

the tail, therefore a special guide stud (see O.P. 586) must be used for these- torpedoes, and the lower end of the stop bolt must be shaped to fit the special guide stud. The stop bolts now issued are so shaped, these being shown in all applicable illustrations in this pamphlet.


Certain British torpedoes are of suitable length for firing from the tubes described in this pamphlet by using the special guide stud, although none of the operating or setting mechanisms on the tube will line up properly with the torpedo. The "air lever," which corresponds with the starting lever on USN torpedoes, is farther forward, and is to port of the torpedo center line instead of to starboard. Furthermore, as the air lever swings to the rear to start the torpedo, its tip rises above the 21.125 inches inside diameter of the tube. Hence, should it be found necessary to attempt to use these British torpedoes, it will be necessary to improvise means, such as a lanyard, for starting the torpedo, also to cut off the tip of the air lever so that it will not dig into the wall of the tube when the lanyard is pulled.


The following are the steps necessary in firing a torpedo, though it is not necessary that they be executed in the exact sequence given here:

(a) Ready the torpedo: Set the speed setting socket in the torpedo to "Intermediate" on three speed torpedoes, or to "Low" on two-speed torpedoes; that is, with the flat side of the socket parallel to the center line of the torpedo. The mechanism on the tube must also be set to "Low." Set the depth setting socket on the torpedo, also on the tube mechanism, to "10 feet." Set the torpedo gyro to "0," the corresponding setting for the tube mechanism being "0" for a bow tube and "180" for a stern tube.

(b) Prime the firing valve in accordance with the following steps, there being no charge in the impulse tank, or the impulse stop valve, if fitted, being closed:

  (1) Open the filling valve on the firing valve head, also the drain valve on the firing valve body.

(2) Fill with clean, fresh water through the filling funnel until the water flows, not merely drips, from the drain valve.

(3) After the water stops flowing from the drain valve, close both valves.

(4) Exercise the firing valve by hand, or by firing air charges inboard, as described later in this chapter.

(5) Repeat steps 1, 2, and 3.

Note-Opening either the filling valve or the drain valve on the firing valve after the impulse pressure is on the firing valve may fire the tube. The hand wheels originally fitted on these valves are now being replaced by small square knobs so that a wrench or a pair of pliers will be required for opening or closing the valves. Also, there is no positive way of knowing exactly how many shots one "priming" is good for. Very little, if any, of the priming water should be lost, either by firing or by evaporation. However, the possible excessive tube pressures due to firing with too little water in the throttling chamber are considered sufficient to warrant the extra trouble of filling the throttling chamber frequently, especially so when firing is anticipated.

The firing valve may be exercised by hand by removing the filling valve and inserting the firing valve lifter in the tapped hole in the head of the bolt which secures the orifice disc to the firing valve cup, as described in Chapter 5, see page 56.

(c) Inspect the bore, with the breech door open, and using a flashlight or a portable lamp, to make certain there is no foreign object in the tube, also that the stop bolt is down, the tripping latch is up, and that the spindles of the depth setting, the speed setting, and the gyro setting mechanisms are in the out or retracted position.

(d) Open the vents inboard.

(e) Load the torpedo, easing it forward, gently, against the torpedo stop bolt in order to avoid dam age which might prevent the stop bolt from with drawing properly when the tube is fired, or which might cause it to lift prematurely.

As the torpedo is being loaded into the tube, make


Figure 224
Figure 224 Loading the torpedo, third step. With the block and tackle attached, the torpedo is eased along the runways until it enters the tube, making certain that the guide stud on top of the torpedo enters the guide slot in the top of the barrel. 
certain that its stop valve is open, that the starting gear is set to run, and that the starting lever safety stick, lock or wedge has been removed.

When loading Mark 11, 12, or 15 torpedoes or Modifications, which require the special guide stud previously referred to in this chapter, it is necessary to engage the stop bolt in the slot near the end of the guide stud instead of against its front face. To do this, load normally until the front face of the guide stud is against the stop bolt. Then raise the stop bolt by "firing" as when firing an air charge inboard, but without pressure in the impulse tank, or with the impulse stop valve closed. Hold the firing key closed, or the firing lever down, and load the torpedo in a few inches further, but not more than 8 1/2 inches. Release the firing key or lever and ease the torpedo home.

With the Mark 11, 12, or 15 torpedoes or Modifications, it is even more important to engage the stop gently, and without a jar, than with other torpedoes, since the special guide stud is necessarily weaker than the standard guide stud. Make certain that the interlocking mechanism is properly re-engaged, the same as after firing an air charge inboard.

  (f) Remove the propeller lock.

(g) Charge Impulse Tank-The impulse stop valves at the firing valves may be either open or closed while charging the impulse tank. In either case, the tightness of the firing valve should be observed during the charging operation if practicable. This may be done quite readily if the breech doors are open. A small leak of air through the firing valve will reduce the impulse tank pressure, possibly to a dangerous degree. Also, if the muzzle doors are open, it will cause a bubble trail, or, if the muzzle doors are closed, it may build up a sufficient pressure in the tube to crack open the muzzle door, in which case whatever tube pressure exists in the after portion of the tube will act to force the torpedo against the stop bolt, which is not designed to effectively resist such pressure.

The firing valve is supposed to be held closed by the impulse tank pressure in the chamber above the valve until the instant of firing. The air which enters this chamber to build up and maintain the pressure does so by "leaking" past the outer cylindrical wall of the valve through small grooves in the piston rings on the valve. These openings must be very


small in order that sufficient air will not pass through them to impede the opening of the valve by preventing the sudden drop of pressure in the chamber above the valve which should be caused by venting it when firing. On the other hand, if these openings are clogged, as by heavy grease, corrosion products, or other foreign matter, the valve will fly open if pressure is put on it too rapidly, as by suddenly opening the stop valve to admit full impulse pressure, or, conceivably in extreme cases, by too sudden a rise of impulse tank pressure while charging with the impulse stop valve open. After charging the impulse tank, close the charging valve. Do not let the tank "ride" upon the line.

(h) With tail stop retracted, close the breech door, and take up tightly on the tail stop, to make certain that the forward face of the torpedo guide stud is against the stop bolt. Then, if the tail stop plate is not fitted with a rubber disc to bear against the torpedo propeller nut, back off the tail stop about one-tenth of a turn to prevent binding the stop bolt.

(i) Enter setting spindles, the gyro, depth, and speed, first ascertaining that all readings on the setting dials correspond with the known settings on the torpedo. It is considered that the most practical way of insuring that the settings correspond is to make a practice of maintaining both the tube units and the sockets in the torpedoes set as follows, except when torpedoes are loaded and initial settings have been made:

Gyro-Set at 0 degrees. If spread setting mechanisms are fitted, set these at 0 degrees also.

Depth-Set at 10 feet.

Speed-Set tube units to "low." The sockets in the torpedoes have previously been set to "low" in two-speed torpedoes, and to "Intermediate" in three speed torpedoes, in accordance with the instructions given in step (a) of this section.

(j) Poppet Valves-Check the, poppet valves to make certain that the gag nuts are backed off, and that manually operated stop valves in the poppet valve drain lines are open.

(k) Flood Tube, when ordered.

(l) Set gyro, depth, and speed, when ordered, and withdraw the depth and speed setting spindles.

  (m) Open the muzzle door, when ordered, making certain that the operating shaft is turned through its full movement, until stopped.

(n) Throw interlocking lever to "Tube Ready to Fire" position, and report tube ready to fire.

(o) When firing, be sure to hold the electrical firing key closed, or the firing lever in the "firing" position if firing manually, for at least two seconds, preferably four. Otherwise, the firing valve may close before the torpedo receives a full impulse.

(p) Close the muzzle door.

(q) Close poppet valve (as described in Chapter 6, on page 71) after the tube has vented the impulse air through the poppet valve, but before an excessively large quantity of water has entered. If the poppet valve discharges into a bilge or an open tank which already contains water, some of this water will be blown up into the torpedo room, giving the impression that water is entering through the poppet valve before such is actually the case. According to the best information available, an interval of at least five seconds is to be expected between firing and any large rush of water through the poppet valve.

(r) Close muzzle door.

(s) "Blow down" the tube, when ordered. Immediately after a war shot in the vicinity of enemy surface vessels, this may not be desirable. When all water is out of the tube, close the drains and vent the blowing air from the tube.

(t) Do not attempt to open the breech door until all water is out of the tube, and the pressure in the tube has equalized with that in the ship.


Reference to the Ordnance Pamphlet covering the specific mine issued for use is necessary in order to secure the correct instructions regarding the operation of torpedo tubes when they are being used to launch mines.


It is intended that dummy torpedoes be fired, generally speaking, for one of two purposes: (a)


For training personnel; (b) to test the operation of a tube, or the shutter clearances, or other features connected with the operation of the tube. In either case, the dummy torpedo is used for the purpose of simulating as nearly as practicable the firing of an actual torpedo without hazarding the loss of a valuable mechanism. It is suggested, therefore, that the routine of firing be carried out, or simulated, so far as circumstances permit, when firing dummy torpedoes as well as when firing live torpedoes. An exception would be the firing of dummy torpedoes with the poppet valves inoperative for the purpose of progressively acquainting new personnel with the operation of torpedo tubes.

From a digest of the Bureau's records, it appears that, with a given impulse pressure, and at a given depth, the maximum tube pressure may be expected to be from four to six pounds per square inch lower, and the ejection velocity possibly three feet per second higher, with a dummy torpedo than with a live torpedo. Such effects might be expected from the fact that a dummy torpedo, being proportioned to float, is several hundred pounds lighter than the live torpedo which it simulates.


Generally speaking, water slugs are fired for the purpose of (a) training personnel; (b) exercising tube mechanisms; (c) establishing or checking firing valve clearances. If the last, the results are not to be regarded as conclusive, but only as indicative of what may be expected from actual firings. In this connection, it is understood to be the practice of one builder of submarine torpedo tubes to establish firing valve clearances such that, when on the surface, a maximum tube pressure of 59 to 65 pounds per square inch will be attained when firing water slugs with an impulse tank pressure of 400 pounds per square inch. It appears to be the result of this builder's experience that, when such pressures are attained, the desired pressures and velocities are apt to follow at all depths when firing torpedoes with the prescribed impulse tank pressures. See, however, Section 9 of this same chapter.

Do not have the poppet valve "on" when firing water slugs. This is important, since without a torpedo, mine, or dummy in the tube it will open

Figure 225
Figure 225 Loading the torpedo, fourth step. When the torpedo is part way in the barrel, the safety guard is removed from the starting lever, and the index dials on the depth, gyro, and speed mechanisms in the torpedo are checked to make certain they are properly set, also that the torpedo stop valve is open, and that the starting gear is set to run.

immediately when the service line pressure is applied to the operating cylinder. The safest procedure is to gag the poppet valves when firing water slugs. Arrangements have been devised from time to time to permit the poppet valve to function in connection with the firing of a water slug, but since the operation does not exactly duplicate, in timing, the results obtained when firing a dummy or a live torpedo, and since the use of such arrangements is attended by the hazard of lodging some foreign material in the way of the muzzle door, or in the poppet valve, the use of such arrangements is not recommended.


Air charges, in general, are fired inboard for the purpose of (a) instructing personnel, or (b) exercising certain operating mechanisms of the tube, such as the firing mechanism, stop mechanism, and the gyro setting spindle retracting mechanism. The procedure for firing an air charge inboard is as follows:

(a) Open the breech door. The breech door is to remain open until the interlocking mechanism has been reconnected and locked.

(b) Withdraw depth and speed setting spindles.

(c) If a torpedo is in the tube, and it is desired to make certain that it does not slide forward past the stop bolt while that bolt is raised at the firing of the air charge, withdraw the gyro setting spindle, pull the torpedo back a few inches and lash it there. This will also prevent the breech door from being closed during the exercise.

Note-This precaution of pulling the torpedo back and lashing it in place is important. On at least one occasion a torpedo has slid forward past the stop bolt while a tube was being exercised, and the muzzle door was damaged to such an extent that it could not be remedied without dry docking.

(d) Unlock and remove the padlock from the firing interlock signal arm (the interlock warning "flag"), and raise that arm to the vertical position. This disengages the firing interlock bolt from the clutch shaft (as shown in Figure 85 on page 46),

  and permits the stop and firing mechanisms to function regardless of the position of the breech door or the drain valve interlock lever, as explained in Chapter 4 (see page 46).

(e) Open the firing impulse stop valve, if one is installed on the tube.

(f) Charge the impulse tank to not over 100 pounds.

(g) Throw the firing interlock lever to "Tube Ready to Fire," and report tube ready to fire air charge inboard.

(h) When ordered, "fire" the tube.

(i) Throw the firing interlock lever to "Muzzle Door Unlocked" position, lower the firing interlock signal arm, engaging the interlock bolt with the clutch shaft, then engage and lock the padlock.

(j) Place the tube in original condition, or in other condition, as ordered.


The following notes concern the handling of Mark 15 or Modifications torpedoes in the after torpedo rooms of vessels in which the after tubes are long enough to take these torpedoes. They also apply to other torpedoes of comparable length (22 feet 7 inches), such as Marks 11 and 12. These notes are taken from service experience, hence they should be carefully observed.

To load these torpedoes into the torpedo room, first remove the wooden loading chock, or skid, just inside the loading hatch, to give room for lowering the tail. The cradle, instead of being secured and pivoted at its lower end on the deck, is entirely suspended by chain falls. The same chain hoists may be used as when handling the cradle normally; that is, two forward, at the sides, and one in the center, aft.

Lower the torpedo in the normal manner until its nose joint about touches the deck. Then lower the tail, raising the nose end of the cradle slightly if necessary, to allow the torpedo to be slid down a little more in order that the tail will clear. As the nose of the torpedo slides between the sling lines to


the after, or lower, chain hoists, those lines may be chafed severely. This can be remedied by the use of a strong-back or yoke having the chain hoist hook applied at the center, and short lifting lines running from the ends to the sides of the cradle.


It was originally intended that a single impulse tank pressure of 400 p.s.i. should be used with this type of tube at all depths from surface down to 120 feet to keel, with any type of torpedo, and in both bow and stern tubes. The firing valve was adjusted so that, at 120 feet to keel, a torpedo launching velocity of 30 to 40 feet per second was attained with a maximum tube pressure of 60 to 70 p.s.i. more than the "static head" (depth, in feet, from surface to the centerline of the tube, multiplied by 0.44, giving p.s.i.). This setting was obtained by calibration firings of water slugs while on the surface, the valve clearance being established to give a maximum tube pressure of about 60 p.s.i. The higher launching velocities attained at lesser depths

  were accepted in order to obtain the advantage of a uniform impulse tank pressure.

Subsequent to the adoption of poppet valves, and principally to favor their successful operation, the variation of impulse tank pressures with depth was authorized. From surface down to periscope depth, the authorized impulse tank pressure became 300 p.s.i., from periscope depth to 120 feet to keel 400, and from 120 to 180 feet to keel 525 p.s.i. The valve clearance was established as before. No variation of impulse tank pressure was authorized for different torpedoes, for different ship speeds, or between bow and stern tubes.

Extensive experimental firings have recently been completed. These firings were conducted with the idea of determining impulse tank pressures which would:

(1) Eliminate the launching bubble to the greatest practicable degree.

(2) Favor the run of the torpedo to the greatest possible extent, that is, launch it in such a way that it would have the minimum tendency either to broach or to take an initial dive. The following data and conclusions proceed from these firings:

Figure 226
Figure 226 Loading the torpedo, fifth step. The torpedo is eased further into the tube, riding on the tube rollers, the block and tackle is detached, then the torpedo is eased gently info place against the stop bolt, care being taken to avoid damaging the stop bolt by forcing the Torpedo against it.


Tubes Best
Impulse Tank


Tubes Best
Impulse Tank

*Above 12 knots Mark 18 torpedoes may be expected to broach and run erratic when fired from bow tubes.

Since the originally intended maximum impulse tank pressure was 400 p.s.i., higher pressures than

  this should not be used unless the impulse tanks, piping and firing valve bodies are known to have been successfully subjected to hydrostatic test in accordance with the requirements of the Bureau of Ships (150 per cent of working pressure).

For best performance with the pressures set forth above, the firing valve clearance should be established to give a maximum tube pressure of about 60 p.s.i. when a water slug is fired on the surface, with an impulse tank pressure of 300 p.s.i.

No torpedoes other than Marks 18 and 23 were fired during these tests. If other torpedoes must be fired before more complete information is published, proceed in accordance with relative speeds. For example, a torpedo Mark 14 or Modification should, if set for high speed, be fired with the impulse tank pressure established for the torpedo Mark 23. If set for low speed, the impulse tank pressure for a mark 18 should be used.

Poppet valves should be used at all depths.

Poppet valves should be timed, with a stop watch, as follows, in order to eliminate the bubble effectively:

Keel depthValve open
30-90 ft.5 sec.
90-120 ft.3 1/2 to 4 sec.
120-209 ft.2 to 2 1/2 sec.

It is the purpose, in this section, to outline the basic information necessary in order that the testing of torpedo tubes may be approached intelligently. The successful launching of torpedoes is dependent upon obtaining a sufficient impulse to get the torpedo entirely clear of the tube, and of the ship's structure, without mechanical interference. At the same time, if an excessive charge is used, the launching bubble will be large.

Also, if the hydraulic brake in the firing valve does not function as intended to slow the opening of the valve, the tube pressure will build up too

  rapidly, and therefore will reach an excessive maximum. In this connection, the short-time after body test pressures of certain torpedoes, in pounds per square inch, are as follows:

Mark 8 Mod. 3 C or D75 p.s.i.
Mark 8 Mod. 4, 5, 8150 p.s.i.
Mark 9 Mod. and Mods. except 1A75 p.s.i.
Mark 9 Mod. 1A85 p.s.i.
Mark 10 Mod. 385 p.s.i.
Marks 11, 12, 15 or Mods150 p.s.i.
Mark 14 or Mods150 p.s.i.
All later150 p.s.i.

The foregoing are the pressures which the after bodies are supposed to withstand for short periods without leakage. The actual collapsing pressures of the various after bodies are considerably higher, so that the firing of torpedoes in war, when it is known that the afterbody test pressures will be exceeded by the maximum tube pressures, is justified since, even if slight leaks are opened in soldered joints, the chances are in favor of the completion of the run.

When the recovery of a torpedo is an object, the afterbody test pressures should not be exceeded.

In general, torpedoes should be launched with at least 30 feet per second velocity. This should insure clearing the tube and hull.


Taking actual test data as to tube pressures and torpedo velocities is considered necessary at the original commissioning of a vessel, and after all firing valve overhauls involving the replacement or repair of the firing valve body, the firing valve head, or its throttling insert if fitted, the firing valve

  cup, or the firing valve orifice disc, in order to make certain that the operation of the tube is correct. It is also considered highly desirable that such test data be taken at other times in order to get an occasional operating check and to acquaint personnel with the circumstances attendant upon torpedo launchings known to be in accordance with the requirements as to pressures and velocities, or otherwise.

These tests are made by using the Torpedo Tube Test Set, which should be found available on tenders and at yards and bases customarily working with submarines and destroyers. The complete description of the test set, with instructions for its use, is given in NAVORD. O.D. No. 717.


During each period in drydock a bore gage should be run through every tube. The standard bore gage is 21.08 inches in diameter, as against 21.0 inches without air charge for a torpedo, and 21.06 inches for a dummy, and it is longer than the cylindrical

Figure 227
Figure 227 Loading the torpedo, sixth step. When the torpedo is in place against the stop bolt in the tube, the propeller lock is removed, and the breech door is closed and locked, the tube being further readied for firing as explained in the preceding pages of this pamphlet.

portion of a torpedo. Therefore, if tubes are bore gaged occasionally, the sticking of torpedoes in tubes should be minimized. Since the bore gage is larger in diameter than a torpedo, the roller height which best suits a bore gage may not be the best for a torpedo. Hence, if roller settings are changed to permit the passage of a bore gage, they should be checked carefully afterwards with a torpedo while the vessel is water borne.


This gage should be used at intervals, and when ever there is reason to suspect any projection within the tube, whether it be the tripping latch, the stop bolt, or one of the setting mechanism spindles, which is a departure from the standard due to wear or deformation. These barrel center line gages should be found on tenders and at yards and bases customarily working with submarines.

At the time of gaging, the registry of all spindles with dial readings should be checked, and each spindle should be forced sideways in several directions to make

  certain that, first, each spindle has the degree of flexibility necessary so that it will engage its mating socket in a torpedo even though not directly in line with it, which may be the case due to necessary manufacturing tolerances or to slightly incorrect roller adjustments; and, second, that each spindle centering spring has sufficient force to return the spindle to its centered position when released after being pushed out of line. Do not close the breech door when a barrel center line gage is in position to check the tripping latch, since the tripping latch linkage will thereby be broken or at least bent so that the tripping latch will no longer engage the starting lever of a torpedo properly.


This constitutes the process of establishing the mean point of impact of the tubes so as to properly align periscopes. It is described fully in Chapter V, Section B, paragraph 35, of Ordnance Pamphlet No. 762, entitled "Alignment of Ordnance Installations on Board Ship."

Figure 228
Figure 228 Removing the Torpedo from the tube. Should it be necessary, for any reason, to remove a torpedo from the tube once if has been loaded, the block and tackle is attached to the propeller shaft, making certain that the spindles of the setting mechanisms are disengaged or refracted from the sockets in the torpedo. The torpedo is then pulled gently out of the tube and onto the runways.

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