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by Lt Cdr Geoffrey B Mason RN (Rtd) (c) 2001

U-class Submarines - Class Information

HM S/M United (Cyber Heritage, click to enlarge) return to Contents List 

Note on Pennant Numbers


These were used for visual signalling purposes. Prior to 1940 these identities consisted of two Numeric Flags followed by an Alphabetic Flag. In the Case of earlier Classes these identities were painted on  the  Conning Tower (eg H and L-Classes). Later Classes such as Rivers had no numbers painted externally but had  their name shown on the Conning Tower. Minelaying submarines also had no external identity on their conning tower but used Flag M inferior to the allocated Numeric.


After 1940 the system was changed and sequence of  the Numeric and Alphabetic Flags was reversed. Identities used for pre-war build were Flag N followed by two Numerics. The submarines built during the war had Pennant Numbers with Flag P followed by two or three Numerics. This identity was used alone in place of a Name for all purposes until early in 1943 when all existing wartime built submarines were given names and future builds were named before entering operational service. Details of the Pennant Numbers are shown in the List of builds with earlier identities in parenthesis.


U -  C l a s s   S u b m a r i n e s


G e n e r a l   I n f o r m a t i o n


Originally intended for use as training submarines this design was modified to provide gun armament to enable their use in war for short duration patrol duties. Diesel-electric propulsion was used to simplify the arrangements. One short-coming was the absence of a separate gun hatch which was provided in other Classes to enable minimum time possible when fast dive was required. All personnel outside the hull had therefore to use the conning tower hatch. Extensive build of this pre-war design took place during WW2.


General Particulars


              Displacement             540 Tons surfaced            730 Tons submerged.

                                                   (Note: Wartime builds were slightly larger)

              Armament                   6 x 21 Torpedo Tubes Forward with four reload weapons.

                                                   1 x 3 Gun.

                                                   (Note: Later Builds had only four torpedo tubes.)

              Dimensions                197 feet overall length, 16 feet beam and 12 feet 9 inches draught.

              Propulsion                  Two 618 BHP Diesel and two 825 HP Electric Motors.

              Speed                           11-12 knots surfaced             9-10 knots submerged

              Endurance                   3,800 miles at 10 knots.

              Complement                27. 31 in later builds.

              Diving Depth              200 Feet.



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