Vice Admiral William S. Sims, Commander, United States Forces Operating in European Waters, to All United States Naval Forces Operating in European Waters
U. S. NAVAL FORCES OPERATING IN EUROPEAN WATERS,
U. S. S. MELVILLE, FLAGSHIP,
30, Grosvenor Gardens,
London, S. W. 1.
7, January, 1918.
From: Force Commander.
To: All Forces.
Subject: Depth Charge Policy.
1. The Depth Charge being the most effective weapon against submarines, and its effectiveness being proportional to the number which are available for use in an attack, it is manifestly desirable for anti-submarine craft to have ready for use the maximum number which can be carried with safety.
2. In the past the number of depth charges available has been limited but this deficiency is now fast being rectified. Large shipments are soon expected from the United States.
3. British and U. S. Depth Charges are of the same external dimensions and shape but differ in firing mechanism. Both are considered safe under proper care and handling. The principal dangers are (a) explosion by shock from gun blast, (b) explosion at low speeds due to being knocked overboard by collision, torpedo or mine damage, or accident, (c) premature explosion of one charge by that of another dropped within 100 feet, and (d) explosion by direct gun hits.
4. Danger (a) can be avoided by restricting the arc of fire of nearby guns or, in view of the relative importance of the depth charge in present anti-submarine campaign, by actually not using guns in the immediate vicinity.
The other dangers can be minimized if not prevented by care in handling, proper use of the safety features and by maintaining a continuous watch of expert men on the depth charges while underway. From experience it would seem justified to habitually keep depth charges set safe depending upon the special watch to arm those in the chutes ready for dropping when given an alarm signal from the bridge. This question should properly be left to Commanding Officers. In case of an impending gun action all depth charges should be dropped overboard.
5. Steps are underway in the Queenstown Destroyers to build racks aft which will stow 12 to 24 charges near centre line and clear of deck to permit seas to pass under. Each depth charge to be individually secured by lashings. In order to continue using present bridge dropping gear and to save time and avoid complication these racks will be for stowage only.
When the alarm is sounded the depth charge watch immediately arms those in the chutes, and stands by to replace them from the racks as fast as they are dropped from the bridge.
6. Studies should be made of the best tactics of using a number of depth charges by vessels both singly and in pairs, whenever it is found possible to reach a definite mark of submergence of a submarine.
With destroyer speed it should be possible to lay a barrage of depth charges with excellent chances of preventing escape. By dropping a charge just beyond point of submergence, then putting helm hard over and dropping a series thru a turn of 180 degrees, then easing helm to cover wider arc in the turn thru the next 180, the chances should be excellent of preventing escape whether the submarine maintained course or turned full right or left submerging.
7. Immediate steps should be taken at all bases to provide racks and other equipment in order that an increased number of depth charges can be put into use as fast as they arrive.
Extra storage on shore should be provided.
8. As fast as any plans either of tactics or equipment are developed at any base they should be immediately communicated to other bases as a matter of information.
Wm. S. Sims.