Lieutenant Commander Henry C. Dinger, Commanding Officer, Maumee, to Rear Admiral Henry B. Wilson, Commander, United States Naval Forces in France
AMERICAN NAVAL BASE.
November 28, 1917.
From : Lt.-Comdr. H.C. Dinger, USN.
To : Commander, Patrol Squadrons
Subject: Method of hunting for submarines.
1. The following method of hunting enemy submarines is suggested for possible development.
Searching for submarines in suspected locality with destroyers or fast gunboats and yachts in company with listening vessels and air craft.
2. Some of the larger vessels should be fitted with submarine detectors (Walser, Fessenden, or other type which permits the use of the detector while vessel is in motion). The listening vessel equipped with sea tubes should be a vessel capable of complete silence while sea tube is being used. This requirement is met by the 110 ft. chasers which are equipped with gasoline engines and can stop whenever listening is to be done.
3. A submarine hunting expedition would then consist of 4 fast yachts or destroyers, one of which is equipped with a submarine detector, 6 110 ft. chasers carrying sea tubes and one or more aircraft. The submarine being reported, this unit should proceed to the probably locality in a formation as indicated: a base course is assigned, zigzag, a speed of 12 knots to be maintained. The chasers to stop every 5 minutes or at other intervals found most efficient and listen. The destroyer with detector also listens, continuously. The other destroyers move ahead or drop astern ready to move at high speed on receipt of information that submarine has been located. When a submarine has been located, the destroyer fitted with detector keeps in close touch. The 110 ft. chasers approach and listen at intervals and depth bombs are dropped as soon as submarine is found to be near enough.
4. It is believed that by this method of search, there is a fairly good chance of catching a submarine after once being sighted. The air craft would keep a general lookout to locate submarine at any time and give warning. The exact manoeuvers of the chasing unit would be developed by practice and experience. The combination of listening devices together with high speed vessels fully capable of attacking submarines offers a possible means of reducing the submarines that operate.
5. The necessary vessels to put the above scheme in operation are already present. If some of the fast yachts and destroyers were equipped with submarine detectors, that are capable of being operated while underway, all the equipment for starting submarine chasing would be ready.
6. It is recommended that one or more U.S. vessels be designated to have the (Walser) submarine detector installed for trial and possible use as above indicated.
7. The Walser apparatus is being made at the Arsenal, Brest, and sufficient experience has been had with it to indicate that it has promising possibilities. (Report of observations made by Ensign E. R. Cassidy).