Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters, to Destroyer Flotillas Operating in European Waters
UNITED STATES NAVAL FORCES
Refer to OPERATING IN EUROPEAN WATERS. (F-12)
No. 1593-3. U.S.S. MELVILLE, FLAGSHIP.
BASE SIX [Queenstown, Ireland],
29 June 1918.
From: Force Commander.
To: Destroyer Flotillas.
Subject: Depth Charge Policy.
References: (a) Force Commander’s Letter 5321-1, 29 March 1918.
(b) Force Commander’s Letter 1359-25, 8 March 1918.
(c) C.B. 1334 – 1918.
(d) C.B. 1194 – 1916.
(e) C.B. 1348 – 1917.
(f) Instruction Book, Depth Charge Projector Mark I, Mod. II.
(g) Bureau of Ordnance Pamphlet 336-A, U.S. Depth Charge Mark II.
(h) Bureau of Ordnance Pamphlet 380, Flat Nose Shell.
(i) Action Reports, numbers 1 to 33 inclusive.
Inclosures: (1) Table “A”
(2) Table “B”
(3) Table “C”
1. Reports of recent attacks upon submarines by United States Destroyers and other vessels have made it possible to more thoroughly study the submarine question and to modify and improve our methods of attack.
2. After careful consideration of the methods used on different destroyers in attacking submarines, the Force Commander is of the opinion that there are a few requirements necessary in the organization of the depth charge control party, and the means employed in attacking and hunting the submarine, to insure success.
3. A brief discussion of these points follows:
(1) DEPTH CHARGE POLICY.
First of all, in order to co-ordinate the efforts of those connected with the handling of depth charges, the signal control, the gun, and torpedo control parties, it is necessary that each ship prepare a depth charge policy which will show clearly:
(a) The organization of the depth charge control party.
(b) Plan or plans it is desired to follow in making an attack.
(c) How the depth charges, torpedoes, and guns should be used by day or night.
(d) What to do with charges when in gun action with an enemy ship.
(e) Procedure in case of collision or fire.
(f) Safety precautions to be observed in handling charges.
(g) Inspections and tests.
In preparation of such a policy, the attention of Commanding Officers is invited to the above references and the comments contained in this letter.
(2) BATTLE STATION OF DEPTH CHARGE OFFICER._
In view of the
fact, (1) that the depth charge is the most effective weapon we have at present for use against the submarine, (2) that they are carried in large numbers, and (3) that they are used frequently, it is believed that there should be on each vessel a duly and regularly appointed “Depth Charge Officer” whose battle station at the time of an attack on an enemy submarine is aft, either on top of the deck house or on the fantail deck where he can best watch and supervise the handling and dropping of depth charges, to see that the settings are quickly and properly made, that the charges are dropped in accordance with signals, and in the case of a failure of a signal, to promptly use his own judgment and initiative in bombing the submarine.
shall be other than the Gunnery Officer, unless the complement of a destroyer has been so reduced as to make the detailing of this officer necessary.
(3) DEPTH CHARGE CREW._
In connection with the same subject, it is imperative that there be on each boat a regularly organized depth charge crew, trained and drilled in setting, dropping, and handling charges during an attack. This crew could be that normally stationed at the after gun as this gun is not used when attacking a submarine. The after magazine ammunition crew, which ordinarily supplies the after gun with ammunition, could be utilized in reloading the depth charge throwers. These ideas, of course, have been carried out on some of the destroyers and have, it is understood, worked very successfully.
(4) DEPTH CHARGE SIGNALS.
There should be more than one method of signalling from the bridge to the after deck house when it is desired to let go depth charges, and both means should be used simultaneously. Various means of signalling have been attempted and some have been found successful, they are:
(a) Siren whistle signal
(b) Electric bell
(c) Electric gong
(d) Klaxon horn
(e) Ship’s whistle
(f) Air whistle on after deck house
(g) Repeater back light on bridge in series with depth charge light aft
(h) Repeater back bell on bridge in series with bell aft
(i) Mechanical bell-pull
(j) Voice tube.
One requirement of a successful signal seems to be, that the officer on the bridge should know in some way whether or not the signal has reached the depth charge force aft, in other words it should be one that would be heard on the bridge or repeated back in some way. Frequent tests of these signals are necessary to assure oneself that they are always in operating order.
The Force Commander feels that neither the ship’s whistle nor the sirewhistle should be used in giving signals to the depth charge party as they are liable to be mistaken, by other vessels in the vicinity, for the signals ordinarily given to indicate changes of course.
(5) UNDER-ESTIMATION OF DISTANCE.
The information found in various action reports seems to indicate that Destroyer Commanders are very apt to under-estimate the following when making an approach:
(a) The distance that it is possible for the submarine to travel from the time of his submergence to the time the destroyer arrives at the point of submergence.
(b) The distance that the submarine can be ahead of the air bubbles or oil slick that form his wake.
(c) The distance the submarine can travel during the interval of time it takes depth charge to sink to get depth.
In this connection your attention is invited to reference (a), (b) and (c). The tables to be found in reference (b) have been modified and expanded to include all [p]robable speeds of the submarine when running submerged. See inclosures, tables “A” “B” and “C”.
Table “A” shows the distance that a submarine submerged can be from the oil or air wake made by it.
Table “B” can be used in making the approach in assisting Commanding Officers to determine how long they will have to run in order to overtake a submarine which has recently dived, or is showing an oil or air wake.
Table “C” shows the distance covered by the submarine at various speeds. Destroyer Commanders will keep tables “A” and “B” on the bridge together with a stop watch. In making the approach no opportunity should be neglected in using them to determine the location of a submarine submerged. As a general rule a barrage should not be commenced until the destroyer has arrived near the probable position of the submarine. In using any of these tables, it is, of course necessary to make an estimation of the submarine’s course and speed.
The Force Commander does not wish to limit or hamper Commanding Officers in making their attacks, but urges the use of all means at hand to insure success.
Referring to action report #30 it can be seen that when the Commanding Officer of the STERRET carefully calculated the position of the submarine by use of these tables his depth charges were much more effective and caused the enemy to broach.
(6) USE OF MARKER BUOY._
The great value of the marker buoy when commencing the barrage is indicated in the STERRET’S action report #30, as in almost every case the STERRET was able to pick up the submarine’s wake later through the use of this buoy. All destroyers will equip themselves with a number of suitable buoys and use them systematically when carrying out an attack.
(7) STUDY OF INTELLIGENCE REPORT._
It is believed the intelligence report published by the Queenstown Intelligence Officer should be carefully studied by Commanding Officers as they may be able to predict the possible movements of a submarine for which they are hunting or which they are attacking.
They should bear in mind that a submarine damaged will probably start for home, and in subsequently hunting for the submarine the most probable courses would be in a general home direction.
(8) METHODS USED BY SUBMARINE IN ESCAPING DEPTH CHARGE ATTACK.
Action No. 30 indicates to us for the first time what the submarine’s plans are for escaping the depth charge attack; that he commences zigzagging as soon as he hears the attacking destroyer in a position close to him and about ready to release depth charges. To meet this it seems to be absolutely necessary to mount additional Y guns and Thornycroft throwers and to vary impulse charges in the different throwers in order to make a cone shaped pattern. Attention is invited to the fact that in the Y gun by using 1 round of powder in the impulse charge, the depth charge can be thrown 50 yards; by using 1 1/4 pounds of powder, the depth charge can be thrown 66 yards; and by using 1 1/2 pounds of powder the depth charge can be thrown 80 yards. Any one of these impulse charges can be used with perfect safety in the Y gun as now mounted on our destroyers.
(9) USE OF TWO OR MORE DESTROYERS IN CARRYING OUT AN ATTACK.
The fact that a submarine commences zigzagging as soon as the destroyer is in an attacking position, illustrates how important it is to have more than one destroyer take part in an attack in order to cover as much area and as many probable positions of the submarine as possible.
(10) MANEUVERING ABILITY OF SUBMARINE.
Report of action #30 shows that a submarine is apparently able to turn very quickly and therefore, to ram a submarine the destroyer must watch for a favorable opportunity and be prepared to quickly follow if the submarine suddenly changes its course. Depth charges and guns must be used during the maneuver.
(11) REPORTS OF ACTION.
In order that reports of action may be of real value in developing our methods it is directed that Commanding Officers make such provisions as may be necessary to carefully accumulate and record data that may have a bearing on the attack.
Each report should show clearly:
(a) Latitude and longtitude, depth of water.
(b) State of sea, direction and force of wind.
(c) General bearing of the sun and moon, and the effect of sun or moon streak, if any.
(d) Estimated relative position of the submarine (or wake) when sighted. Give estimated bearing and distance.
(e) Estimated course and speed of the submarine.
(f) Appearance of submarine (or wake).
(g) Time, G.M.T. of sighting submarine.
(h) Time required to reach point of submergence after sighting submarine.
(i) Speed used in making the approach.
(j) Time of commencing barrage (by this it is meant the lapse of time before or after passing point of submergence or the end of the visible wake).
(k) Various speeds used during the attack.
(l) State whether or not you are equipped with listening devices, giving types and brief description of how used.
(m) Use of marker buoy.
(n) If more than one destroyer was employed the report of the Senior Officer should describe the methods used giving the signals sent and received.
(o) Were guns used, give number or rounds fired.
(p) Were torpedoes used, if so, how controlled and used.
(q) Methods used by submarine to escape the attack.
(r) What depth setting of charges was used.
(s) Estimated depth at which the submarine was running.
(t) Unusual features, remarks.
It is directed that Commanding Officers carry out the provisions of this letter , submitting to the Force Commander a copy of their Depth Charge Policy prior to 10 July 1918.