23 - class airship The " 23 " class were rigid airship s produced in the United Kingdom during the First World War . They were designed by Vickers , who also built the first and last of the four ships , with the other two being built by William Beardmore and Company and Armstrong - Whitworth . While the " 23 " class was never used in combat , the four ships provided many hours of valuable training and experimental data for British airship crews and designers . Although a total of 17 of these ships were contemplated at one time , only four were ever built . The " 23 " class was found to be significantly overweight , leading to its cancellation in favour of the more - refined R23X class . Design and development . The " 23 " class had a structure similar to that of the earlier " 9r " . An extra bay was inserted amidships , and the nose and tail widened allowing more gas capacity and increased lift . The exterior keel had a widened section amidships incorporating a bomb bay , sleeping quarters , radio room and toilet . Three gondolas were suspended from the keel . The fore and aft cars each contained a single Rolls - Royce Eagle driving twin swivelling propellors , while the middle car contained two " Eagles " with one fixed propeller each . The forward car contained the control room , but there were also emergency controls in the aft car . Ballast and fuel were carried in tanks along the keel . Rudders and elevators were of the cruciform Schütte - Lanz type . The design drawings were approved in October 1915 and a further 16 airships of the same class budgeted for . In April 1916 , ten ships were approved , to be built by a further three contractors besides Vickers . However , in light of improving technology and information about German designs , only three more of this class , and two of the improved R23X class were built . The rest would be " R31 " class ships . Operational history . " 23r " . Construction was commenced by Vickers on 1 January 1916 at Barrow - in - Furness , Cumbria . Construction was delayed by materials shortages ( including the shortage of linen caused by the Easter rising in Ireland ) and strikes . The trial flight took place at Barrow on 19 September 1917 . The ship was found to have less than the rated lift so the dynamos , bomb gear , and furniture were removed to save weight . A Maybach engine from the crashed Zeppelin " L 33 " replaced the Rolls - Royce in a new rear car , this one without emergency controls . " 23r " flew to RNAS Howden , Yorkshire , on 15 October 1917 , and then to RNAS Pulham , Norfolk , on 29 October . She flew over central London on 6 December , bringing the city to a standstill and generating a wave of patriotic fervour . Despite the identification markings being clearly visible to millions of Londoners , the censors banned publication of the name of the ship . A record flight of 40 hours 8 minutes was made in May 1918 , as well as experiments with defensive armament of a 2 - pounder ( QF gun and three machine gun s . The shells from the large gun caused the ground crew at Pullham some alarm when they ricochetted off the ground instead of exploding harmlessly . In July , experiments were made with parasite fighter s , in the hope they could defend the airship . First an unmanned , then a manned , Sopwith Camel were launched successfully . In November , the experiment was successfully completed with two other manned Camels . " No . 23r " overflew the surrender of the German submarine fleet at Harwich in November 1918 , before being modified for experiments with the three - wire mooring system in March 1919 . She was deleted in September 1919 after a total of about 320 hours . " 24r " . " 24r " was built by William Beardmore and Company at Inchinnan , in Renfrewshire , Scotland . When the decision was taken to lighten the overweight " 23r " and " 25r " in October 1917 , " 24r " was tested as well . The problem was found to be even worse , with " 24r " weighing around 1 , 500 lb ( 680 kg ) more than her sisters – a difference that was eventually traced to the use of slightly larger and heavier fasteners throughout her structure . A solution was required with some urgency , since Beardmore ' s construction shed needed to be cleared so that work could begin on " R34 " , but the problem was exacerbated by " 24r " needing all the lift possible in order to safely navigate the hilly Scottish countryside . Eventually , the decision was taken to completely strip her aft power car – removing the engine and all associated machinery . While this gave " 24r " more than enough lift , it limited her top speed to only 35 mph ( 56 km / h ) . It was intended that the rear power car would be eventually replaced with one of lighter design , but this was never carried out , and " 24r " operated throughout the war with only three engines . On one occasion , this led to a situation over Bass Rock where the airship was held immobilized by a headwind , prevented from making any headway at all . She was eventually retired in December 1919 with a total flight time of 164 hours and 40 minutes over a distance of 4 , 200 mi ( 6 , 720 km ) . " 25r " . " 25r " was built by Armstrong - Whitworth and completed five weeks after " 23r " , in October 1917 . When found to have the same weight problems during trim trials carried out in a hangar at Armstrong - Whitworth ' s airship works at Barlow , North Yorkshire , she was similarly lightened , carrying out her first test flight on 14 October 1917 . In later flights , another problem emerged in the form of surging within her gas bags . This had the effect of suddenly and unpredictably moving the ship ' s centre of lift , thereby causing instability . Despite this problem , the airship ( by now known as R 25 ) was officially accepted into service on 23 December 1917 , and continued in service until September 1919 , by which time she had flown 221 hours and 5 minutes and covered 5 , 909 mi ( 9 , 454 km ) . " R26 " . R26 ( the first airship designated under the new system of adding an " R " prefix rather than an " r " suffix for rigids ) had the benefit of only being in the early stages of construction when the weight problems with her sisters were discovered , allowing weight - saving measures to be implemented from the outset . On 4 – 5 June 1918 , she set a new endurance record for the " 23 " class by carrying out a patrol of 40 hours 40 minutes . With " 23r " , she oversaw the surrender of the German U - boat s at Harwich , before being assigned to experiments in early 1919 to investigate the practicalities of mooring airships in the open . While promising at first , her envelope was eventually soaked with rain , and the airship was subsequently beaten into the ground by a snowstorm . Although refloated by removing her power cars , the structural damage was found to be too great to warrant repairs , and she was struck off for scrap on 10 March .