Naval History and Heritage Command

Lieutenant Commander Ronan C. Grady, Commander, Submarine Division Five, to Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters

U. S. S. Al-1, Flag,

<Queenstown>

28 August 1918.    

From:     Commander, Submarine Division Five.

To:       Commander, U.S.Naval Forces Operating in European Waters.

Via:      Commander, Submarine Detachment.1

SUBJECT:  Balancing and Silent Running – Report of.

Reference:     (a): Force Commander’s letter No.AC 29884 of 17 August 1918.2

     1.   In compliance with reference (a), report of balancing and silent running of submarines is submitted herewith:

 (a)  TO AVOID SURFACE CRAFT.

          On several occasions the AL-boats have avoided surface craft by running directly away submerged at 60-feet at high speed for five minutes and then continuing at slow speed. This was done where it was considered improbable that the surface craft had sighted the periscope. Also on several occasions the surface craft have been avoided while the submarine was on the surface, by the latter altering course as soon as the other craft was distinguishable as friendly.

 (b)  HOSTILE LISTENING CRAFT.

          No experience has been had with hostile surface craft. However the first exercises in Bantry Bay with Submarine Chasers indicate that it is very difficult for Submarine Chasers to follow a submarine running at slow speed. The Submarine Chasers hear a submarine at 200-yards but then don’t seem able to center very well, and beyond 200-yards lose the submarine entirely. Under conditions where listening boats make contact the general opinion is that constant changes of course at slow speed should be made until the listeners are thrown off. It is the opinion that, if on soundings in smooth water to go to the bottom is the best maneuver unless the indications are that the enemy suspect the move and are searching for you. Then the best thing is to run away at slowest speed. The foregoing is the procedure which in the opinion of the submarine officers should be followed when the periscope has not been sighted and listening contact has been made accidentally or after scouting. If the periscope has been sighted by ships close aboard the opinion is that a fast run should be made immediately to get out of the listening range or out of bombing area. Then as it is possible for listeners to a follow a submarine when the latter is making six to eight knots submerged, it is best to slow down and run as nearly silently as possible on various courses.

 (c)  ABILITY OF SUBMARINES TO BALANCE.

          Actual experience in the Bristol Channel shows that it is possible to balance between fifty and eighty feet while stopped for from half an hour to four hours. This has been done by the AL-boats on several occasions and from ten to fifteen minutes many times. The AL-4 stopped for four hours except for two minutes. This is entirely an accidental occurrence. In the open sea off the Irish Coast the usual procedure is to obtain a fine trim and run at slowest speed which is about 1.7 knots. Every ten minutes the boat is stopped to listen in. After stopping the boat will not change depth for ten minutes if the trim is good and then only very slowly so that by starting at slow speed again as soon as the boat starts to settle or rise the depth is maintained. On this form of patrol no machinery except the main motors and the gyro compass motors are used, and the boat is practically silent after the main motors are stopped. About every hour the pumps are used to pump out about one hundred pounds which usually leaks in. Balancing by running the periscope out and in is not attempted but it is considered feasible. However this would require running the periscope motors and sonner or later would require pumping so pumping is considered to be the most practical way of controlling the trim.

(Signed)  R.C.Grady

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117-524/M.     1st endorsement     U.S.S. BUSHNELL,

                                   28 August,1918.

From:     Commander, Submarine Detachment.

To:       Commander, U.S.Naval Forces Operating in European Waters.

     1.   Forwarded

W.L.Friedell3