No. 5 Airfield Construction Squadron (5ACS) was a Royal Australian Air Force (RAAF) construction squadron. The unit was first formed in July 1942 and served in the New Guinea Campaign and Borneo Campaign during World War II. The squadron was one of only a few RAAF airfield construction units to be retained at the end of the war, and formed part of Australia's contribution to the occupation of Japan from 1945 until it was disbanded in June 1949. 5ACS was re-raised in August 1951 and worked on several RAAF airfields in Australia. It also provided small detachments of engineers to support RAAF deployments to South Vietnam and Thailand during the Vietnam War. The squadron was the RAAF's only airfield construction unit from 1961 onward, and was disbanded in December 1974.
History
World War II
On 7 July 1942, 250 men of No. 1 Mobile Works Squadron were detached from the unit while it was stationed at Ascot Vale, Victoria and organised into a new squadron intended to serve in New Guinea. This unit was designated No. 1 Mobile Works Squadron (Special Works Force), and arrived at Port Moresby on 7 August after a difficult voyage during which the ship carrying it from Australia it ran aground twice. The squadron began work constructing Wards Airfield on 14 August, and the first of the airfield's runways was ready for use three weeks later. The airfield's completion was delayed until January 1943 due to shortages of personnel and equipment, however. No. 1 Mobile Works Squadron (Special Works Force) was redesignated No. 5 Mobile Works Squadron (5MWS) on 16 November. In order to support Allied offensives in New Guinea 5MWS moved to Goodenough Island between late February and March 1943 where it constructed Vivigani Airfield. This facility initially comprised a fighter runway and bomber runway as well as headquarters, maintenance and logistics facilities. During March and April a detachment from the squadron also assisted No. 6 Mobile Works Squadron at Milne Bay. 5MWS departed Goodenough Island on 21 November for a period of rest and reconstitution in Australia.
In early 1944 5MWS became part of a force of RAAF and United States Army aviation engineer units which were selected to build airfields at Aitape in New Guinea from which air support would be provided to Allied operations around Hollandia after US Army forces landed there on 22 April. 5MWS departed Melbourne on 15 February, and eventually joined up with the main body of the airfield engineer force at Lae on 1 April where it received training in infantry tactics. The Landing at Aitape took place on 22 April, and 5MWS came ashore the next day. The airfield at Aitape was ready to be used from 25 April and was later expanded by the aviation engineers. On 6 July 5MWS landed on Noemfoor Island where it again formed part of an aviation engineer force tasked with repairing and expanding the island's airfields. Allied forces had first landed on the island on 2 July, and it was still not secure when construction work began. As a result, 5MWS personnel were required to man perimeter defences, during which they captured 12 Japanese personnel. While at Noemfoor 5MWS was redesignated No. 5 Airfield Construction Squadron (5ACS) on 18 July. As at 25 November, No. 4 Airfield Construction Squadron and 5ACS were the main units of No. 62 Wing. This wing formed part of the Australian First Tactical Air Force, which was the RAAF's main mobile force.
In January 1945 4ACS and 5ACS moved to Biak island where they worked on improving facilities used by the US Army and United States Army Air Forces (USAAF). In mid-May 1945 4ACS and 5ACS traveled together to Morotai. They remained on this island until June when they departed as part of the Australian-led Battle of North Borneo. The two squadrons landed at Labuan on 11 June and worked on repairing and maintaining the island's airfield until the end of the war on 15 August.
Occupation of Japan
While most of the RAAF's airfield construction squadrons were disbanded at the end of the war, on 17 November 1945 5ACS was informed that it would form part of Australia's contribution to the British Commonwealth Occupation Force (BCOF) in Japan. For this deployment it was assigned to No. 81 Wing. 5ACS' advance party arrived in Japan in late 1945 and the rest of the squadron arrived at Iwakuni to the east of Hiroshima on 22 February 1946. At this time the unit was under strength as only 14 officers and 189 airmen had volunteered for occupation duties, though a further 173 personnel arrived in March and April.