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      HMS X-class / X-craft (series) Midget Submarine  

    HMS X-class / X-craft (series) Midget Submarine

    British X-craft were a critical player in operations leading up to D-Day.

     Updated: 2/11/2016; Authored By JR Potts, AUS 173d AB; Content ¬©www.MilitaryFactory.com

    The British naval fleet had to keep their battleships and carriers near or in home waters to protect the vital shipping lanes in the North Atlantic from the powerful German battleships stationed in Norway. The previous missions by the British to destroy the German capital ships in the North Atlantic had failed so a new weapon was needed. The "X class" craft were specifically designed and built to attack the key Nazi battleships KMS Tirpitz and KMS Scharnhorst as well as the pocket battleship KMS Lutzow.

    In 1942, an ultra-secret submarine training base was established at Lock Erisort on the Isle of Lewis in Scotland. By 1943, the Royal Navy had developed a 52-foot "midget" submarine named the "X-craft". The X-craft could remain at sea for days while carrying its own supplies for the required 4-man crew and could reach distances of 1,200 miles at underwater speeds of 6 knots. Dive capabilities were 300 feet depths (91.5 meters). The X craft had only one access hatch which would eventually prove a relatively lethal design feature in the event of an emergency. Her periscope was small, restricted by her overall design, and ultimately proved unreliable. Navigation was through a Browns A Gyro Compass and Auto Helmsman. The direction indicator utilized an AFV 6A/602 and shipbuilder Vickers Barrow UK was contracted to construct the boat. As midget submarines went, she was rather roomy though still required the use of short-statured crew members.

    The desired method of operation concerning the X-craft was to position the submarine as close to the target using one of two delivery systems developed: the boat could be either towed by a conventional submarine to be suspended underneath the target enemy ship or launched from the deck of a submarine to make its way to the target ship under its own power. The Admiralty chose two 3,570 lb conjoined mines of a high explosive nature to be attached to the sides of the boat via a bolt. These mines were then released by way of a hand crank when the vessel was positioned below the hull of an enemy ship. The explosive was equipped with a delayed fuse timer that allowed the boat to retire out of the blast area within time. The explosive used was Amatex, a standard and stable military explosive comprised of 51% ammonium nitrate, 40% TNT, and 9% RDX.

    Depending on the mission, a three- or four-man crew was selected consisting of one commanding officer, a first lieutenant, and engineer and a diver. The diver was in some ways a novelty position and useful on in the case that the craft ran afoul in anti-torpedo "netting" used to protect harbors. If called upon, the diver utilized an attached airlock to exit the vessel, letting sea water in to pressurize the compartment. Upon return to the craft, air pressure was used to force the water out of the small area, allowing the diver to reenter the submarine as needed.

    On September 11th, 1943 "Operation Source" began when six X-craft were towed by conventional Royal Navy submarines from Scotland into the North Sea, this voyage taking ten days. The submarines were manned by crossing crews during the trip while the attack crews stayed on the towing submarine until mission time. The KMS Lutzow was to be attacked by X-8, she being towed by HMS Sea Nymph. However, the side-connected cargo mines began to take on water and were forced to be jettisoned due to the extra weight. During the jettison the side cargo mines prematurely exploded, causing enough damage to the X-8 that her crossing crew was removed and the craft scuttled. The KMS Lutzow was free to fight another day.

    X-9 and X-10's mission was to attack the battleship KMS Scharnhorst at her mooring. During the crossing, the X-9 tragically sank with the crossing hands crew aboard when her towing cable snapped. X-10 continued on the attack plan alone. Her tow submarine, HMS Sceptre, released X-10 close to the target area. However, the crew found that the KMS Scharnhorst had moved into the North Atlantic. The X-10 rejoined HMS Scepter and was towed back to the Scotland base without ever having attacked the Scharnhorst.

    X-5, X-6 and X-7's target became the 58,000-ton battleship KMS Tirpitz moored in Kafjord. All three X-craft were released close to the target on September 20th, 1943 and began the attack independently. X-7 surfaced 4 miles from Tirpitz to charge batteries and open the hatch for fresh air before they attacked. In the meantime, X-6 was released by her tow, HMS Truculent, retreating the passage crew. At 2 am, X-6 came upon a torpedo net and a small German ship passing through. The X-6 commander decided to follow the ship through the open net and was successful. However, while on the other side of the net while still submerged, she hit a rock close to where the Tirpitz berthed. Not being able to move forward or reverse, the X-6 had to surface close to Tirpitz. She was ultimately detected by German look outs and was fired upon by small arms. The decision was made to set the timed fused before abandoning the craft and surrendering to the Germans.

    Unknown to the crew of the X-7 was that the crew of X-6 was on Tirpitz so the attack mission proceeded as planned. As the craft descended under the Tirpitz, she also came into contact with the hull which alerting the German crew. Now under the Tirpitz, one charge was released under the hull around the area of A and B turrets. The X-7 then moved 300 feet further astern and released the second mine under the aft turrets, these set with a 1-hour delay. The X-7 turned back towards the open sea and, at 8:12am, the charges exploded and lifted the Tirpitz eight feet out of the water. During the explosion and escape, X-7 was forced to surface after becoming entangled in the torpedo netting. The craft was half submerged and taking on water when the decision was made to abandon her through the single escape hatch. Lt. Place and crewman Aitken got out while crewmates Whittam and Whitley sadly went down with the sinking X-7. X-5 was never able to attack the Tirpitz as far as Admiralty records indicate. She never returned from her sortie and was presumed lost with all hands onboard. It is speculated that X-5 was sunk by Tirpitz as she approached while on the surface.

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    HMS X-class / X-craft (series) Technical Specifications

    Service Year: 1943
    Type: Midget Submarine
    National Origin: United Kingdom
    Ship Class: X-craft

    Structural (Crew Space, Dimensions and Weights)

    Complement (Crew): 4
    Length: 51.6 feet (15.73 meters)
    Beam (Width): 5.8 feet (1.77 meters)
    Draught (Height): 5.2 feet (1.58 meters)

    Surface Displacement: 27 tons
    Submerged Displacement: 29 tons

    Installed Power and Base Performance

    Engine(s): 1 x Gardner 4-cycle diesel engine developing 42 horsepower; 1 x Keith Blackman electric motor developing 30 horsepower; 1 x shaft.

    Surface Speed: 6.25 knots (7 mph)
    Submerged Speed: 5.5 knots (6 mph)
    Operational Range: 1,043 nautical miles (1,200 miles, 1,931 km)

    Armament / Air Wing

    2 x 3,570lbs of Amatex explosive charges on hull sides.

    Aircraft: None.

    Global Operators

    United Kingdom

    Ships-in-Class (20)

    X-craft (Prototype); X-3; X-4; X-5 TYPE: X-5; X-6; X-7; X-8; X-9; X-10; X-20 TYPE: X-20; X-21; X-22; X-23; X-24; X-25; XT-1; XT-2; XT-3; XT-4; XT-5; XT-6