HMS Pioneer ( R76 ) HMS " Pioneer " was a " Colossus " - class aircraft carrier built for the Royal Navy during World War II . She was modified whilst under construction into an aircraft maintenance carrier . The ship arrived in Australia in mid - 1945 to support operations by the British Pacific Fleet against Japanese forces . She supported the British attacks on the Japanese Home Islands from mid - June until the end of the war in August from a base in the Admiralty Islands . The ship and her facilities were used to help repair Hong Kong ' s infrastructure in late 1945 and she returned to the UK in early 1946 . " Pioneer " was immediately placed in reserve upon her arrival and she was sold in 1954 for scrap . Design , description and construction . The " Colossus " - class carriers were intended to meet a shortage of naval flight decks . Their design was based on that of the " Illustrious " - class aircraft carrier s , but modified to permit rapid construction in commercial yards . " Pioneer " was not completed to her original design ; the success of the maintenance aircraft carrier prompted modification of the ship , whilst under construction , to an aircraft maintenance ship without aircraft catapult s . " Pioneer " had an overall length of , a beam of , and a draught of at deep load . She displaced at standard load . Each of the ship ' s two sets of Parsons geared steam turbines drove one propeller shaft . Steam was supplied by four Admiralty three - drum water - tube boilers operating at a pressure of . The turbines were designed for a total of and gave " Pioneer " a speed of . The ship carried of fuel oil which gave her a range of at . In order to maximize space for workshops and stores , the ship ' s arresting gear and catapult were not fitted ; two large deckhouses were added to port of the island and on the rear of the flight deck . The ship had a single hangar , high . Aircraft were transported between the hangars and the flight deck by two aircraft lifts ( elevators ) ; each measured . Two large cranes were mounted on the flight deck to move aircraft and stores to and from the flight deck . The ship carried two small self - propelled lighters to allow unflyable aircraft to be transferred between ships or to shore facilities . Bulk petrol storage consisted of . The ship ' s crew totaled 854 , plus 222 in her aircraft repair department . The ship was equipped with six quadruple mounts for the QF 2 - pounder Mk VIII gun ( " pom - pom " ) . These gun mounts could depress to −10° and elevate to a maximum of + 80° . The Mk VIII 2 - pounder gun fired a shell at a muzzle velocity of to a distance of . The gun ' s rate of fire was approximately 96 – 98 rounds per minute . She was also fitted with 19 Bofors 40 mm autocannon in single mounts . The Bofors fired a shell at a muzzle velocity of . It had a rate of fire of about 120 rounds per minute and a maximum range of . All of the guns were mounted on the flight deck , not in sponsons on the side of the hull like her half - sisters that were completed as aircraft carriers . Each " pom - pom " mount was provided with a separate fire - control director fitted with a Type 262 gunnery radar . " Pioneer " was ordered on 7 August 1942 under the name " Ethalion " , but was renamed " Mars " later in 1942 . She was laid down at Vickers - Armstrong in Barrow - in - Furness on 2 December and was launched on 20 May 1944 The ship was renamed " Pioneer " in July 1944 after the decision had been made to convert her to an aircraft maintenance ship . and was completed on 8 February 1945 . Service . After working up , " Pioneer " sailed for Australia on 30 March 1945 . She arrived in Sydney on 13 May and was transferred to Manus Island , in the Admiralty Islands , on 21 June to prepare for operations off Japan . She was still there when Japan surrendered on 15 August and had repaired 24 aircraft since her arrival . " Pioneer " arrived in Hong Kong in late September to help with the rebuilding of the colony ' s infrastructure . Her sailors restored power , telephone service and repaired trains and buses . She made one trip back to Manus , but was back in Hong Kong in late November . The ship sailed for Sydney the following month and departed for the UK on 17 February 1946 . Upon her arrival , she was placed in reserve . " Pioneer " was sold for scrap in September 1954 and broken up in Inverkeithing .