Captain Joel R. Poinsett Pringle, Chief of Staff, Destroyer Flotilla, to Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters
UNITED STATES NAVAL FORCES
OPERATING IN EUROPEAN WATERS
U.S.S. MELVILLE FLAGSHIP.
BASE SIX [Queenstown, Ireland]
10 June 1918.
From: Chief of Staff, Destroyer Flotillas.
To: Force Commander.
Subject: Comment and Recommendations in regard to Flotilla Depth
1. The report of the action between the U.S.S. STERRET [i.e., Sterett] and an enemy submarine on the 31st of May and the 1st of June 1918,1 is going to make it possible for us to carefully go into our method of attack, and assist us in discovering the reasons why our former bombing experiences have been unsuccessful, also to ascertain what is wrong with our present method of depth charge control.
2. The report as submitted seems to be an excellent one and shows that a great deal of thought and care were exercised in carrying out the attack. It seems to me however, that there are a few things which could be improved right away on all boats of the Flotilla.
3. A brief discussion of these points is given below:
BATTLE STATION OF DEPTH CHARGE OFFICER.
In view of the fact, (1) that the depth charge is the only really effective weapon we have at present for use against the submarines, (2) that they are carried in large numbers, and (3) that they are used frequently, it seems only right 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 should be 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. Attention is invited to paragraph “18” of the above mentioned report in which it is said, “Attempted to release remaining two depth charges but failed on account of mistaken signals.” It is felt that if there had been an officer on the after deck house he would have let go the depth charge nearest the submarine without signal.
[It has] also developed that there was some misunderstanding about the safety pin in the depth charge chute releasing gear. This was either put in without orders or left in after instructions had been given to take it out, and it was this which prevented the dropping of the charge by the hydraulic gear from the bridge.
DEPTH CHARGE CREW.
In connection with the same subject, it is felt that there should 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 depth charge throwers. These ideas, of course, have been carried out on some boats and have worked very successfully.
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.
One requirement of these signals seems to be, that the officer on the bridge should know in some way whether or not the signals have reached the depth charge force aft, in other words it should be one that could 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.
UNDER-ESTIMATION OF DISTANCE.
Referring to paragraph “8” of the above mentioned report and conversations with the Commanding Officer of the U.S.S.STERRET and other destroyer commanders, I am firmly of the opinion that destroyer commanders invariably underestimate the following:
(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 which form his wake.
(c) The distance the submarine can travel during the interval of time it takes depth charge to sink to set depth.
Some of this information is laid down in Force Commander’s letter 1359-25 of 8 March 1918,2 and in the pamphlet on the British type D depth charge. These tables, however, do not contain all the information necessary, nor is it in a convenient form. Modified tables have been worked out by Lieutenant Alexander of the U.S .S. STERRET and will be supplied Commanding Officers for use in submarine attack. They are much simplified in form and contain all necessary information. Destroyer Commanders will be required to keep these tables on the bridge, together with a stop watch with which they will be used. During the approach the time the destroyer requires to get to the point of submergence must be carefully watched, and as a general rule the barrage should not be commenced until the destroyer has arrived at the actual probable position of the submarine.
It can be seen that when the Commanding Officer of the STERRET carefully calculated the different times, his depth charges were much more effective and caused the enemy to broach. In the above mentioned table the speed of the submarine is only calculated up to 5 knots, whereas they should be changed to cover speeds up to 10 knots. It is the opinion of the Commanding Officer of the STERRET that the enemy submarine could probably make about 9 knots submerged.
USE OF MARKER BUOY.
The great value of dropping the marker buoy when commencing the barrage is indicated in the STERRET’S action, as in every case the STERRET was able to get the submarine’s wake later through the use of this buoy. All destroyers will be instructed to equip themselves with a number of these buoys and use them systematically when carrying out an attack.
STUDY OF INTELLIGENCE REPORT.
It is believed that the intelligence report published by the Queenstown Base Intelligence Officer3 should be carefully studied by Commanding Officers as they may be able to predict 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. This idea seems to have been realized by the Commanding Officer of the STERRET as his report indicates.
METHODS USED BY SUBMARINE IN ESCAPING DEPTH CHARGE ATTACK.
Most important of all, this action 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 pound 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 guns as now mounted on our destroyers.
DEPTH CHARGE HOWITZER.
Attention is invited to the tremendous value of the depth charge howitzer would have had in this attack. I believe the Bureau of Ordnance should be urged to at once develop such a howitzer mounted in a recoil carriage and suitable for installation on destroyers.
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. The work of the CUSHING and FANNING in laying their barrages shows the necessity for the preparation of attack plans which could be used by two or more destroyers when attacking in company. The first barrages of the CUSHING and FANNING were apparently wasted. It is my intention to appoint a board of three or more experienced officers to take up the question of developing plans and signals for same, which could be used when carrying out such attacks.
MANEUVERING ABILITY OF SUBMARINE.
The report of the STERRET shows that a submarine is apparently able to turn very quickly, and therefore it is most difficult for a destroyer to ram a submarine unless conditions are particularly favorable, or unless the submarine is badly damaged. This however, should not discourage Commanding Officers in making the attempt, but depth charges and guns must be used during the maneuver.
SETTING OF DEPTH CHARGES.
Referring to paragraph “8” of the above mentioned report it will be seen that when the Commanding Officer of the U.S.S. STERRET estimated the depth of the submarine to be 300 feet he apparently obtained the best results from his depth charges, which in this case were only set for 200 feet. This only goes to show the urgent necessity for a pistol which can be set for 300 feet.
J. R. POINTSETT PRINGLE
Source Note: D, DNA, RG 45, Entry 520, Box 414. The signature is a stamp.
Footnote 1: The official report on the Sterett’s encounter with U-97, dated 5 June, appears above. On this engagement, see also: Sims to Pringle, 4 June 1918; and Pringle to Sims, 11 June 1918. See also the Sterett’s DANFS entry for a detailed account of the episode.
Footnote 2: This letter has not been found.
Footnote 3: The editors were unable to determine who held this assignment.