page_title: RAF Bomber Command aircrew of World War II
section_title: Operational training and conversion
hierarchical_section_title: RAF Bomber Command aircrew of World War II / Training / Operational training and conversion
caption_attribution_description: English: Wellington Mk IIIs of No. 30 Operational Training Unit at Hixon, Staffordshire, 6 September 1943. Wellington Mark IIIs (BK347 &amp;#145;BT-Z&amp;#146; and DF640 &amp;#145;BT-T&amp;#146; in the foreground) of No. 30 Operational Training Unit, lined up at Hixon, Staffordshire, for a leaflet dropping ("Nickelling") sortie over France.
context_page_description: The aircrews of RAF Bomber Command during World War II operated a fleet of bomber aircraft carried strategic bombing operations from September 1939 to May 1945, on behalf of the Allied powers. The crews were men from the United Kingdom, other Commonwealth countries, and occupied Europe, especially Poland, France, Czechoslovakia and Norway, as well as other foreign volunteers. While the majority of Bomber Command personnel were members of the RAF, many belonged to other air forces – especially the Royal Canadian Air Force, Royal Australian Air Force and Royal New Zealand Air Force. Under Article XV of the 1939 Air Training Agreement, squadrons belonging officially to the RCAF, RAAF, and RNZAF were formed, equipped and financed by the RAF, for service in Europe. While it was intended that RCAF, RAAF, and RNZAF personnel would serve only with their respective "Article XV squadrons", in practice many were posted to units of the RAF or other air forces. Likewise many RAF personnel served in Article XV squadrons.
  A total of 126 squadrons served with Bomber Command.
context_section_description: The next phase of training was usually in Britain at one of the Operational Training Units (OTU).  Aircrew memoirs repeatedly mention arriving at an OTU in large groups of mixed aircrew trades all assigned to the next course and being left to mingle in a large hall to form crews. The process of forming a crew generally followed the pattern of one or two men who knew each other from training schools deciding to fly together then looking for other members from different trades to team up with. Most crews were formed in this manner. Instructors were usually experienced aircrew being "rested" after completing an operational tour and were tasked to lead the airmen for 5 or 6 weeks on night flying, navigation, bombing, cross country, all-weather and air gunnery/fighter affiliation practice operations in the types of aircraft they were likely to fly operationally. The process was hazardous and crashes due to inexperience cost over 8,000 casualties, including instructors who had joined a crew needing particular support or guidance.
  In the first half of the war completion of training at an OTU would mean each crew transferring to an operational squadron and beginning their operational tour.  Assignment to a squadron was simply a process of making good recent losses and a squadron which had lost three or four crews in the previous week would expect the "feeder" OTUs to have replacement crews (known as freshmen or sprog crews) ready in the system to cover the losses. This effectively meant that any crew could go to any squadron within Bomber Command. During 1942 particularly, any maximum effort attacks such as the 1,000 bomber attacks on Cologne on the night 30–31 May 1942 and Essen on 1–2 June 1942 required more aircraft and crews than Bomber Command had available in its operational squadrons so crews at OTUs who were near the end of their courses and were rated as efficient, participated in the operation.
  During mid-wartime many crews trained using "tired" Vickers Wellington bombers, at OTUs and then had to convert, learning to fly the four-engined Stirling, Halifax or Lancasters which they would fly after joining their squadrons. This process occurred at Heavy Conversion Units.  During this time each crew would be joined by a flight engineer, and an additional air gunner to man the mid-upper gun turret although sometimes the gunners would agree to exchange turrets.
caption: 30 Operational Training Unit Wellingtons in September 1943
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