-H.M.S. Hood Reference Materials-
1941 CAFO 501 – Nomenclature of Armaments
(Capital Ships and Aircraft Carriers)

Updated 12-Aug-2007

This document is a modern transcription of a portion of Confidential Admiralty Fleet Order 501 from the year 1941. It concerns the proper names of armament carried aboard large Royal Navy warships. The original file is held at the Royal Navy Library at the Royal Navy Base, Portsmouth. This Crown Copyrighted material is reproduced here by kind permission of the Royal Navy Library.

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C.A.F.O. 501. –Nomenclature of Armaments
(Capital Ships and Aircraft Carriers.)

(G. 01076/41.–6.3.1941.)

    With the introduction of H.A./L.A. and close range armament of various calibers in new and re-constructed ships, some confusion has arisen as to the nomenclature to be used for the different mounting, directors and calculating positions.

    2. In order to obtain as much standardization as possible, the following general policy has been decided upon: –

        Main armament mountings (this applies to groups of mountings in aircraft carriers): –
            A, B, X, Y, etc.

        Secondary armament mountings: –
            S.1, S.2, S.3, S.4, etc.
            P.1, P.2, P.3, P.4, etc.

        Tertiary armament mountings (other than machine-guns): –
            1, 2, 3, 4, 5, 6, etc.

            Odd numbers starboard, even numbers port (centre line mountings take their number in the fore and aft sequence).

        Machine-guns: –
            M.1, M.2, M.3, M.4, etc.

            Odd numbers starboard ; even numbers port (centre line mountings take their number in the fire and aft sequence).

            Directors, transmitting stations, calculating positions, etc, should be named after the mountings or group of mountings which they control.

    3. For H.M. Ships “ Nelson,” “ Rodney,” “ Hood,” and H.M. Ships “ King George V ” and “ Illustrious ” classes, the general policy is to be interpreted as follows: –

H.M. Ships “ Nelson “ and “ Rodney “

    Main armament
        A, B and X turrets, aloft, armoured and lower ; 16-in., T.S.

    Secondary armament
        S.1, S.2, S.3, P.1, P.2 and P.3 turrets; S.F., S.A., P.F. and P.A. directors, starboard, 6-in., T.S., port, 6-in., T.S.

    Tertiary armament
        No.1 H.A., No. 2 H.A., No. 3 H.A., No. 4 H.A., No. 5 H.A. and No. 6 H.A.; No. 1 H.A. director and H.A.C.P., No. 2 H.A. director and H.A.C.P.

H.M.S.  “ Hood  “

    Main armament
        A, B, X and Y turrets, aloft and armoured directors, 15-in., T.S.

    Secondary armament
        S.1, S.2, S.3, P.1, P.2 and P.3, and No. 4 H.A. ; S.F. director and H.A.C.P., P.F. director and H.A.C.P., aft director.

    Tertiary armament
        Pom-poms 1, 2 and 3, directors 1, 2 and 3.
        Machine-guns. M.1, M.2, M.3 and M.4.


“ King George V Class  “

    Main armament
        A, B  and Y turrets, ; forward and after D.C.T.s ; 14-in., T.S.

    Secondary armament
        Starboard fore group–S.1 and S.2 turrets ; S.F. director and H.A.C.P.
        Port fore group–P.1 and P.2 turrets ; P.F. director and H.A.C.P.
        Starboard after group–S.3 and S.4 turrets ; S.A. director and H.A.C.P.
        Port after group–P.3 and P.4 turrets ; P.A. director and H.A.C.P.


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