(source: Public Record Office ADM 186/55: CB1548 German Navy Tactical Orders)
Gg. 3855 A. 3.
Alterations and Additions No. 71.
1. The 9th and 10th Half-Flotillas, I, V, VII and IX Destroyer Flotillas are trained for mine searching by daylight.
2. The Half-Flotillas to take station ahead and pass sweeps. Signal: O. L. - Take up stations ahead with gear. The half-flotilla proceeds ahead of the squadron; speed of destroyers will passing sweeps seven knots, time required about 20 minutes; breadth covered by two boats about 100 yards, a line abreast of five boats about 400 yards.
3. Proceeding with sweeps passed: After the sweep has been passed report NSX - "Mine searching sweep passed." Speed while searching 11 - 15 knots; with a speed less than 11 knots the bights of the sweep may sink and touch bottom and slip themselves. The squadrons decide what distance they are to be astern of the half-flotilla and maintain the same during the cruise. It is not possible to buoy the searched channel, as destroyers have only sufficient buoys on board for marking positions where sweeps slipped.
4. Altering Course: Mine searching half-flotillas can only turn in succession by altering course two points at a time and be describing a large circle. The diameter of the turning circle is about 2-3 miles. With well-trained half-flotillas course signals can be made about every two minutes. In order to improve the station of the sweepers relative to the squadron by taking ground to the right or left, the Senior Office of the Squadron may use the following signals:-
NST - Mine searchers move your position obliquely to the right of the squadron.
NSR - Ditto - to the left.
OS - Proceed along the old or ordered course.
These movements are carried out by turning in succession two points. Should the half-flotilla be suddenly obliged to get out to the way at night, the Senior Officer's boat will sound on her whistle or siren one or two blasts for each turn of two points.
5. Depth Keeping: The very lowest depth of water at which it is just possible to use the gear is 39.3 ft. The kite will then keep at a dept of 32.1 ft and the sweep at a depth of 27.2 ft. Mines are still caught if their upper edge is 22.3 ft below the surface. In order to avoid giving false alarms when the gear touches bottom owing to irregular speed, etc, it is advisable in practice not to use the gear at a dept of water of less than 50 feet.
If any change in depth keeping is to be made, speed must temporarily be decreased to 11 knots.
6. Lights: When proceeding with ships darkened ahead of a squadron:- (a) Wing-boats must show dimmed stern lights; (b) the guide must show a toplight, screened from ahead.
7. Alarm signals when sweeps slip:-
|(a)||Signal by Day||Signal by Night|
|Senior Officer's Boat||Flag M, white double star, 10-second blast on siren, M by searchlight until repeated, MMM by W/T.||10-second blast on siren, MMM by W/T|
|Other Boats||Flag M and white double star, 10-second blast on siren.||10-second blast on siren.|
(b) Conduct of the Half-Flotilla. The boat in question will drop a mine buoy att once, fitted by day with two yellow balls, by night with a green light. The sweep is hove in. the further procedure depends on whether the squadron wishes to hold on, or to avoid the minefield, or to turn 16 points.
In order to establish whether the slipping of the sweep was the result of its catching a mine, the sweeping half-flotilla, or another half-flotilla which has been kept in readiness, is to resweep that particular part of the channel again with a newly passed sweep.
(c) Conduct of the Squadron. If the sweeping half-flotilla, or another half-flotilla which has been kept in readiness, is to resweep the route, or another route clear of the minefield, the squadron will at first make a 16-point turn together. As soon as the half-flotilla has passed its sweeps, the squadron will resume the old or follow the new course astern of the half-flotilla.
8. Relief (Change of Watch - Translator) of Half-Flotillas. A half-flotilla proceeding with minesweeping gear passed, must be relieved at least every four hours (this relief may not correspond with that of the war watches). The speed of the squadron will be seven knots until the new half-flotilla has passed its sweeps between the half-flotilla to be relieved and the squadron. the relieved half-flotilla hauls out and heaves in sweeps.
9. Heaving in Sweeps. For this purpose the half-flotilla will proceed at four knots; duration of the operation 20 minutes.
10. Sailing Orders must contain:
(a) The speed at which the search is to be made.
(b) The depth at which the search is to be made (dependent on depth of water to avoid the gear's touching bottom and draught of ship).
(c) Conduct on mines being reported (Minenalarm).
(d) Intended course.
For C-in-C, High Sea Fleet
The Chief of Staff
(signed) VON TROTHA
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