.jpg) SM U-21 loads a torpedo duringWorld War I. | |
| Class overview | |
|---|---|
| Builders | |
| Operators |  Austro-Hungarian Navy |
| Preceded by | SM U-14 |
| Succeeded by | U-27 class |
| Built | 1915–1917 |
| In commission | 1916–1918 |
| Completed | 4 |
| Lost | 2 |
| Preserved | 0 |
| General characteristics | |
| Type | submarine |
| Displacement |
|
| Length | 127 ft 2 in (38.76 m)[1] |
| Beam | 13 ft (4.0 m)[1] |
| Draft | 9 ft (2.7 m)[1] |
| Propulsion |
|
| Speed |
|
| Range |
|
| Complement | 18[1] |
| Armament |
|
TheU-20 class was aclass of foursubmarines orU-boats built for and operated by theAustro-Hungarian Navy (German:Kaiserliche und Königliche Kriegsmarine orK.u.K. Kriegsmarine) duringWorld War I. The class is sometimes referred to as theHavmanden class because it was based upon the design of theRoyal Danish Navy's 1911Havmanden-class submarines, three of which were built inFiume.
With a small fleet of six U-boats at the beginning of World War I, two of which were not operational, the Austro-Hungarian Navy acted to bolster its fleet. They reluctantly ordered fourU-20 boats in 1915 because construction could start immediately, even though theHavmanden-class design was largely obsolete by the beginning of the war. Political considerations caused the order to be split between Austrian and Hungarian firms, which contributed to construction problems and delays, keeping any of the boats from being operational until the middle of 1917.
The class boats were just over 127 feet (39 m) long and were armed with two front torpedo tubes, adeck gun, and amachine gun. The engines for the boats were unreliable, which compounded handling problems with the design. TheU-20 class did not claim any wartime successes, yet lost two of the boats—U-20 andU-23—to enemy action during the war. The remaining two were delivered aswar reparations and broken up. Theconning tower fromU-20, which was raised and salvaged in 1962, is on display in a military museum inVienna.
TheAustro-Hungarian Navy's U-boat fleet at the beginning ofWorld War I consisted of six largely experimental submarines, two of which were not operational.[3][Note 1] When it became apparent that the war would not be a short one,[4] Austria-Hungary moved to bolster their U-boat fleet by seizing the plans for the DanishHavmanden-class submarines,[5] three of which had been built atWhitehead's inFiume.[2] Although the Austro-Hungarian Navy was not happy with the design, which was largely obsolete,[3][6] it was the only design for which plans were available and which could be begun immediately in domestic shipyards.[3] The Austro-Hungarian Navy unenthusiastically placed orders for four boats on 27 March 1915.[4]
Before construction could begin, the Navy found itself in the midst of political situation because the Hungarian government demanded that a substantial portion of the submarine contracts be allocated to Hungarian firms.[4] After intricate negotiations,[4] the order was split into two orders of two submarines each, withU-20 andU-21 built at the Pola Navy Yard, andU-22 andU-23 built at the HungarianUBAG yard at Fiume.[5] The subcontracts were also divided between Hungarian and Austrian firms,[1] with about two-thirds going to Hungarian companies and one-third to Austrian companies.[6] This allocation of contracts, while politically expedient, exacerbated technical problems that resulted in numerous modifications and delays.[5]
TheU-20-class boats were ocean-going submarines that displaced 173 tonnes (191 short tons) surfaced and 210 tonnes (231 short tons) submerged. The boats were 127 feet 2 inches (38.76 m) long with abeam of 13 feet (4.0 m) and adraft of 9 feet (2.7 m). For propulsion, they featured a single shaft, a single 450 bhp (340 kW)diesel engine for surface running, and a single 160 shp (120 kW) electric motor for submerged travel.[1] The boats were capable of 12 knots (22 km/h) while surfaced and 9 knots (17 km/h) while submerged. Although there is no specific notation of a range for theU-20 class, theHavmanden class, upon which it was based, had a range of 1,400 nautical miles (2,600 km) at 10 knots (19 km/h), surfaced, and 23 nautical miles (43 km) at 8 knots (15 km/h) submerged.[2] TheU-20-class boats were designed for a crew of 18.[1]
TheU-20-class boats were armed with two 45 cm (17.7 in) torpedo tubes located in the front and carried a complement of two torpedoes. They were also equipped with a 66 mm/26 (2.6 in)deck gun and an 8 mm (0.31 in)machine gun.[1] The first of the class to be launched wasU-21, when it slid down the ways on 15 August 1916; the final boat launched wasU-22 on 27 January 1917.[1] The boats entered service between August and November 1917.[6]
During their active service, the boats of theU-20 class suffered from unreliable engines which compounded the already poor handling characteristics of the boats.[6] None of the class had any successes and two of their number were sunk during the war.[5]U-23 was the first sunk when she went down on 21 February 1918 from an explosiveparavane in theStraits of Otranto.U-20, thelead boat of the class, sank in July 1918 when she was torpedoed by the Italian submarineF12 in theTagliamento estuary. The remaining two boats were surrendered at war's end, withU-21 being ceded to Italy in 1920, andU-22 to France; both were broken up.[5]
SMU-20, thelead boat of the class, waslaid down on 29 September 1915 at the Pola Navy Yard.[7] She was launched on 18 September 1916.[1] During diving trials in March 1917,U-20 was accidentally rammed by the Austro-Hungarian Navy light cruiserAdmiral Spaun, which required seven months of repairs for the U-boat.U-20 wascommissioned on 20 October, and operated out of Pola andTrieste.[7] She was in the estuary of theTagliamento river in early July 1918 when she was spotted by the surfaced Italian submarineF12.U-20 was hit by one torpedo at a range of 650 yards (590 m) and sank with all hands west ofTrieste near position45°29′N13°02′E / 45.483°N 13.033°E /45.483; 13.033.[8][Note 2] The wreck ofU-20 was raised andsalvaged in 1962.[9] Remains of her crewmen were interred on the grounds of theTheresian Military Academy atWiener Neustadt.[10] Theconning tower and a midship section were donated to theHeeresgeschichtliches Museum inVienna, where they are on display.U-20 did not sink any ships during her service.[5]
SMU-21 was built at the Pola Navy Yard and was launched on 15 August 1916, and was the first of the class to be launched.[1]U-21 was damaged in a diving trial in January 1917, requiring seven months for repairs. The U-boat wascommissioned on 15 August 1917.[7] In early October,U-21 conducted patrols off theAlbanian coast, but a mid-OctoberMediterranean patrol was cut short by a leaky seal on her mainhatch. After an additional eight months of repairs,U-21 again conducted patrols off Albania. A broken piston in her diesel engine cut short her war career. At Pola at the war's end,[11]U-21 was ceded to Italy in 1920 as awar reparation and broken up.U-21 did not have any successes during the war.[5]
SMU-22 was built at the HungarianUBAG yard and was launched on 27 January 1917, the last of the class to be launched.[1] The still-incomplete boat sank in the harbor atFiume in June 1917, but was raised, repaired, and relaunched in October. From her November commissioning,U-22 conducted patrols off thePo River estuary and, later, northernAdriatic patrols fromTrieste. After three months of repairs for her failed electric motor in mid 1918,U-22 resumed service, patrolling theMontenegrin coast out ofCattaro.[7] In port at Cattaro at war's end,[11] she was ceded to France as awar reparation and broken up.[5]U-22 sank no ships during the war.[5]
SMU-23 waslaid down on 8 December 1915 at the HungarianUBAG yard and was launched on 5 January 1917.[1][7] She wascommissioned on 1 September and initially patrolled off the Italian towns ofRimini andAncona. After being transferred toCattaro in late December,U-23 departed on her final patrol on 20 February 1918.[7] The following day,[9]Linienschiffsleutnant Klemens Ritter von Bézard,U-23's only commanding officer,[12] guided the boat in an attack on the Italian transportMemfi in theStraits of Otranto.U-23 then came under attack from the ItaliandestroyerAirone; after first trying to ram the U-boat, the destroyer deployed an explosiveparavane. When the paravane came into contact with the submergedU-23, it blew debris into the air, sinking the submarine with all hands.[9] Like all of her sister boats,[5]U-23 had no wartime successes.[12]