HMS H42

HMS H42 was a British H class submarine that sank with the loss of all 24 of its crew after an accidental collision in 1922. The sub was built by Armstrong Whitworth, Newcastle Upon Tyne. She was laid down in September 1917 and was commissioned on 1 May 1919.

On 23 March 1922, under the command of Royal Navy Lieutenant Douglas Staley, H42 was practising torpedo attacks against British destroyers steaming off Europa Point, Gibraltar, when she surfaced unexpectedly only 30 or 120 yards (27 or 110 metres) – sources differ – ahead of the destroyer HMS Versatile (D32). Versatile, making 20 knots, went to full speed astern on her engines and put her helm over hard to port, but had not yet begun to answer her helm when she rammed H42 abaft the conning tower, almost slicing the submarine in half. H42 sank with the loss of all hands. An investigation found H42 at fault for surfacing where she did against instructions.

Design
Like all post-H20 British H-class submarines, H42 had a displacement of 423 LT at the surface and 510 LT while submerged. It had a total length of 171 ft, a beam of 15 ft, and a draught of 12 m. It contained a diesel engines providing a total power of 480 hp and two electric motors each providing 320 hp power. The use of its electric motors made the submarine travel at 11 kn. It would normally carry 16.4 LT of fuel and had a maximum capacity of 18 LT.

The submarine had a maximum surface speed of 13 kn and a submerged speed of 10.5 kn. Post-H20 British H-class submarines had ranges of 2985 nmi at speeds of 7.5 kn when surfaced. H42 was fitted with an anti-aircraft gun and four 21 in torpedo tubes. Its torpedo tubes were fitted to the bows and the submarine was loaded with eight 21 in torpedoes. It is a Holland 602 type submarine but was designed to meet Royal Navy specifications. Its complement was twenty-two crew members.