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Captain Joel R. Poinsett Pringle, Chief of Staff, Destroyer Flotillas, to Destroyer Flotillas Operating in European Waters




BASE SIX,          

27 April,1918.     


From:     Force Commander.

To  :     U.S. Destroyer Flotillas Operating in European Waters.

Subject: Sterett- Depth charging of U.S.S. AL-10 – 25 March.

     1.   The reports of the Commander Officer, Sterett, and Commanding O-fficer, AL-101are published, with comments, for the information of the Flotillas.

          Commanding Officer, AL-10 reports:-

     “At 1700, while on course North, sighted a destroyer through periscope bearing 240 degrees true. C tube reported a noise simultaneously on same bearing. Flooded adjusting and dove to 100 feet. Destroyer approached rapidly and course was changed to the Eastward and then to the Southward, keeping her astern. We had no idea that we had been sighted, as the gauge never showed less than 19 feet, and we went down very quickly, as soon as I distinguished her as a destroyer. She was heading right for us and her gray camouflage made a perfect disguise against the horizon, At first I thought it might be a submarine, and she was probably much closer than a figured. Sh[e] passed nearly overhead and dropped a depth bomb about 2000 yards beyond us. Fortunately she overran her distance. We could hear her stop and listen and then go ahead full speed. We were so heavy that we had to blow some water out and the bilge pump was run for a few seconds. The bilge pump gave our position away, as she let go her first bomb shortly after. We were now running slow speed parallel and holding our depth, but she was drawing ahead and we could not turn fast enough. Destroyer was also apparently drawing nearer. When a second depth bomb was let go I blew tanks and came to the surface for two reasons, one was that I did not want her to waste depth bombs. We opened the hatch and let go a recognition signal simultaneously. The destroyer was across our bow, dead in the water about 3000 yards away. We let go two more smoke bombs and exchanged blinker signals. She did not approach closer, but sent a signal that the U.S.S.Trippe was astern. She then proceeded on her course to the Eastward. I decided to remain on the surface until the Trippe passed. The Trippe hove in sight a few minutes later and we exchange smoke bombs and blinker signals. She then came close aboard and asked it we needed any assistance. We replied in the negative and requested permission to submerge, Permission was granted and the Trippe proceeded to the Eastward. She was only about 3000 yards away when we lost her through the periscope, although we could see her on deck for twice that distance. Submerged at 1830 and came to the surface at 2038. Took two star sights and found that we were about 20 miles to the Westward of our billet.  Our gyro compass had become grounded in the morning and we practically drifted all day. The current set us to the Westward.Ran East until midnight.

     The experienve with the destroyer leads me to believe that it is a waste of time to stand a periscope watch with our present periscopes. We delayed the destroyer about an hour and she wasted two depth bombs. We submerged as soon as we made her out, which however was not quick enough. The day was clear but the horizon was gray, and so was the destroyer. Our periscopes were clear at the time. One had [i.e., bad] feature about the periscope on this vessel not mentioned in previous reports, is the fact that the top consists of a round glass dome. Several officers have previously remarked that this dome was visible for a very long distance when the sun was shining brightly. This characteristic probably gave us away. The periscopes are not sealed and were admittedly experimental. Unfortunately, we were ordered to active service almost immediately after their installation. The dry air pump has to be run from one to two hours every day and makes more noise than the main motors and pumps combined. The listeners can hear nothing while the dry air pump is running. I have decided that the safest thing to do is to come to the surface for all surface craft, as we cannot make out theor [i.e., their] characteristics in time. The difficulty of this is that we cannot distinguish between a submarine and a destroyer when the latter is bow on. It is believed that a Grubb low power instrument2 would be far superior to our present installation. The forward periscope is not as good as the after one, and this one should be replaced first. It is habitually kept housed, except when the after periscope is out of commission.

     The behavior of the crew was without exception excellent, but after everything quieted down, there were signs of nervousness and the men were a little unstrung. I decided to run completely submerged for the greater part of the next day in order to give all hands a good sleep, and let them forget about it. Twenty-four hours after the incident, they were again in good spirits and as keen as ever.

     The noise and concussion were about the same as is experienced in the force top of a battleship when a turret is fired double barreled, just below.”

     Commanding Officer, Sterett, reports:-

     “Referring to paragraph 6, reference (b), the Sterett was the destroyer which on 25 March,1700, launched two depth charges on an oil slick evidently made by the U.S.S.AL-10.

     At 6:30 p.m. on 25 March, while en route to Irish Sea, 10 miles astern of the U.S.S. Duncan in Lat.51-34 N., Long.7-44 W., a distant oil slick was seen bearing 20 degrees on starboard bow, distant about 4000 yards. Sea exceptionally smooth, weather clear, Ship was headed for spot, speed 20 knots, search being made for perisvope. On close approach, a well defined oil patch about 50 yards long 15 yards wide was discerned but no indication of a moving wake was visible. Owing to the short, ribbon-like, form of the patch ot [i.e., it] was concluded that it had been made by a submerging submarine. One charge was dropped about 200 yards beyond the farther end. Both charges British Type D MK 11 pistol, setting 80 feet. The ship was then swung with left rudder and a large sweep was made vicinity. On second passage over oil slick only residue from charges was visible. A careful sweep of sea was made for further indications. Ship headed on course to regain position in scouting column at 1845.

     Shortly after this a odor less smoke bomb was seen bearing 10 degrees on port bow, distant about 4000 yards. Ship was swung towards it, and a conning tower of submarine was made out distant about 4000 yards. A second bomb of correct color was then fired by submarine. On further approach the submarine marked AL-10 was made out with men on deck. To indicate friendly intent the ship was swung about forty-five degrees to left, leaving the AL-10 on starbpard hand, signalling to her that the U.S.S. Trippe was about 10 miles astern.

     Being 25 miles from nearest patrol area QA on which the U.S.S. AL-10 was operating, the presence of a friendly submarine was not considered when attack on slick was made. From the time spent in approach on the slickm turning and passing the U.S.S. AL-10, and distance steamed, it is believed that the AL-10 was fully 5000 yards distant from the explosion of the charges, no allowance being made for her speed during operation. In fact, the AL-10 appeared to be so far from the slick that she was in no way connected with it at the time. No attempt was made to close her, in fact a turn from her was made to indicate friendly intent and this vessel then proceeded on mission.

     In this operation the following points were noted:

     (a)  The submarine left a distinct oil trace when she submerged which owing to calm sea and no wind, was not broken up until wash of propellers and depth charges disturbed it. Its appearance conformed closely to the submarine’s shape, heavier traces of oil laid to the North and West, possibly oil from exhaust.

     (b) At least ten lookouts were sweeping a circle of 6 miles diameter, some lookouts with, and some without binoculars. The AL-10 was not sighted unyil her first smoke bomb was fired and then very indistinct. It was about one-half hour before subset and submarine lay to the Eastward.

     (c) From report of the AL-10 it appears that her hydrophones gave false impressions of the Sterett’s movements.

     (d) A systematic launching of 20 charges would have placed some uncomfortably close to her.”

     4.   The following comments on the above reports are made:-

Report of AL-10.

     Navigation of AL-10 was poor. Submarines must be carefully navigated in order that they may be able to give out accurate information by radio or be enabled to carry out radio orders in the shortest time. They must also remember that there is no reason to believe a submarine sighted off a patrol area for British or U.S. submarines is friendly, and destroyers will treat all submarines so sighted as hostile.

     It is not believed that the AL-10 should have dived when the approaching vessel was seen to be a destroyer. The burden of proof is on the part of the submarine. Thee AL-10 states that she believed she was not seen. She also states that the top of here periscope consists of a round glass dome, and that this dome was probably visible in the sublight for a very long distance. As a matter of fact, the periscope was not sighted by the Sterett, but the very marked oil slick left by AL-10 was correctly played for a submarine. Our submarines must realize that a destroyer does not necessarily have to actually sight a periscope in order to warrant dropping a large number of depth charges. A well defined slick left no doubt in the mind of the Commanding Officer of the Sterett that a submarine was in the immediate vicinity.

     AL-10 for some reason gained the impression that Sterett was using listening device, with which that vessel is not equipped. Every care should be exercised by submarines to prevent oil slicks.

     The moral effect on the crew of the AL-10 was bad, and it was apparently a period of almost 24 hours before the boat would have been fit for efficient operation.

     This moral effect was probably much greater than it would have been in the case of a German submarine, as the enemy submarines have had much more experience in hearing depth charges explode when their submarine was submerged.

     Nevertheless there is bound to be a certain moral effect on some members of the enemy crew, and no opportunity should be lost to drop a number of charges,

Report of Sterett.

     Though no periscope was seen, the Sterett diagnosed the oil slick as a submarine, which assumption was correct. The actual position of the submarine was not located, as she was some distance from her oil slick. The Sterett expended only two depth charges, and then gave up the search. The expenditure of a larger number of charges was fully warranted, in view of the wake being that of a submarine.

     The Sterett should have approached closer to the submarine in order to establish her identity without question. The mere fact that proper smoke bomb was fired, that AL-10 was seen, and that men on deck were visible was not sufficient proof of her friendly character, especially as she was twenty miles off her assigned patrol, and as all of these same things could easily be duplicated by an enemy submarine. The mere fact that no friendly submarine was supposed to be in the area being traversed by the Sterett was sufficient cause for Sterett to approach close to and speak the submarine.

J.R. POINSETT PRINGLE,            

By direction.      

Source Note: Cy, DNA, RG 45, Entry 520, Box 413. Document identifiers at top of first page: “1547-12.: and “(G.3).”

Footnote 1: Cmdr. George W. Simpson, Commander, Sterett, and Lt. Cmdr. James C. Van de Carr, Commander, AL-10.

Footnote 2: Sir Howard Grubb is credited with perfecting the periscope. His factory in Dublin produced most of the periscopes used by the Royal Navy in World War I.

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