Conversion units and operational conversion units (OCUs) were training units of the Royal Air Force (RAF).
With the introduction of new heavy bombers, the four-engined Short Stirling, Avro Lancaster, and Handley Page Halifax, the Royal Air Force introduced heavy conversion units (HCU). These HCUs began forming in late 1941, to qualify crews trained on medium bombers to operate the heavy bombers before final posting to the operational squadrons. Some of the HCUs were involved in bombing operations over Germany.
After the end of the Second World War, the role of the HCUs was taken over by the operational conversion units (OCUs). Although the units had nominal bases, different flights and individual aircraft usually were detached nearer the operational bases.
RAF OCUs are training units that prepare aircrew for operations on a particular type or types of aircraft or roles. Some OCUs have a shadow, or reserve, squadron designation, which is used if the unit has a war role.
F-35 Lightning – RAF Marham
Typhoon – RAF Coningsby
Hawk T.2 – RAF Valley
Support helicopter (Puma and Chinook) – RAF Benson
Air Mobility (Atlas and C-17) – RAF Brize Norton
ISR (Wedgetail, Poseidon) – RAF Lossiemouth
ISR (Reaper, Protector,Rivet Joint and Shadow) – RAF Waddington
Tutor – RAF Wittering
Some aircraft types operated by a single squadron, which includes most transport aircraft, and most ISTAR aircraft, are not big enough to need a dedicated OCU squadron for their training requirements; they may only have a few at any time. Therefore, smaller squadrons also incorporate training facilities to allow them to process aircrew onto their aircraft type. Some roles, such as ISTAR, require more rear crew for the aircraft, such as weapon systems officers (WSOs) and weapon systems operators (WSOps) – their training can be more generalised, and this is carried out by 54 Squadron at RAF Waddington. This reduces the training requirement on the individual ISTAR squadrons, by providing aircrew who require only aircraft conversion training when they reach their squadrons.
Pilots are trained directly onto their aircraft type by the frontline squadrons using training "flights". An example of this is the OCU flight of 24 Squadron, which trains new Atlas and C-17 aircrew onto the aircraft.
115 Squadron trains flying instructors for all three branches of the British Armed Forces. 207 Squadron trains both RAF and Royal Navy pilots on the F-35 Lightning.
OCUs are monitored by the RAF's Central Flying School to maintain training standards. Training is delivered by qualified flying instructors (QFIs) and qualified weapons instructors, and frontline squadrons also have qualified individuals to deliver continual and refresher training after the OCU. OCUs generally also provide training for those aircrew selected to become QFIs on an aircraft type – an example would be the now disbanded 208(R) Squadron, which previously trained aircrew for the now disbanded 100 Squadron, QFIs for 208(R), and provided refresher training for aircrew joining the RAF aerobatic team, the Red Arrows, on the Hawk T.1.
| Unit | Dates | Aircraft | Base | Notes |
|---|---|---|---|---|
| Aug 46–Aug 49 Sep 49–Jun 55 Jun 63–Sep 74 Oct 74–Sep 91 | Oxford I, Beaufighter X Hornet F.1 Mosquito III/TT.35 Tiger Moth II Vampire F.1/FB.5/T.11 Meteor F.3/F.4/T.7/F.8/FR.9 Tempest II Martinet I Spitfire XIV/XVI/XVIII/XIX/F.22 Javelin T.3 Lightning F.1/F.1A/F.3/T.4/T.5 Jaguar GR.1/T.2 | RAF Molesworth RAF Bentwaters RAF Driffield RAF Stradishall RAF Middleton St. George RAF Coltishall RAF Lossiemouth | Formed at Molesworth by re-designating 1335 (Meteor) CU. Disbanded at Driffield to become 203 AFS. Re-formed at Stradishall by renaming 203 AFS. Re-formed at Middleton St. George by merging the Lightning Conversion Squadron RAF and the Fighter Command Instrument Rating Squadron RAF. Disbanded at Coltishall. Immediately re-formed at Lossiemouth by re-designating the Jaguar Operational Conversion Unit RAF. Disbanded at Lossiemouth to become 16 (Reserve) Sqn | |
| 227 OCU 227 (AOP) CU | May 47–Dec 47 Dec 47–May 50 | RAF Andover RAF Middle Wallop | Formed by re-designation of No. 43 OTU Became the Air Observation Post School RAF. | |
| 228 OCU | May 47–Sep 61 May 65–Dec 66 Aug 68–Jul 92 | Formed by merging No. 13 OTU and No. 54 OTU Became 64 (R) Sqn | ||
| 229 OCU | Dec 50–Sep 74 Nov 84–Jul 92 | Formed from 'B' and 'D' Flights of 226 OCU. Reformed 1957 at Chivenor Disbanded 2 September 1974 at Chivenor when relocated to Brawdy to become the Tactical Weapons Unit RAF Reformed at Coningsby in 1984 and designated 65 (Shadow) Squadron from 31 December 1986 Became 56 (R) Sqn. | ||
| 230 OCU | Mar 47–Oct 52 Aug 53–Feb 55 May 56–Aug 81 | Lancaster I/III Lincoln B.2 Mosquito III/B.35/NF.36 Tiger Moth Anson XIX Vulcan B.1/B.2 Hastings T.5 Canberra T.4 | Formed by re-designting No. 1653 Heavy Conversion Unit RAF Disbanded 15 October 1952 to become the Reserve Training Squadron RAF Became the Lincoln Conversion Flight RAF at Upwood 1 February 1955. | |
| 231 OCU | Mar 47–Dec 49 Dec 51–Dec 90 May 1991–Apr 93 | Formed by re-designating No. 16 Operational Training Unit RAF re-formed at Bassingbourn by re-designation of 237 OCU Disbanded at Wyton, 15 December 1990, to become the Canberra Standardisation and Training Flight Re-formed at Wyton 13 May 1990 from the Canberra Standardisation and Training Flight | ||
| 232 OCU | Feb 55–Jun 65 Feb 70–Apr 86 | At Gaydon, 30 June 1965, the Victor element became the Tanker Training Flight RAF Re-formed at Marham 6 February 1970 by amalgamating the Victor (B.2) Training Flight RAF and the Victor Training Unit RAF. | ||
| 233 OCU | Sep 52–Sep 57 Oct 70–Sep 92 | Became 20 (R) Sqn | ||
| 235 OCU | Jul 47–Oct 53 | Became the Flying Boat Training Squadron RAF | ||
| 236 OCU | Jul 47–Sep 56 Jul 70–Sep 92 | Formed by re-designating No. 6 OTU | ||
| 237 OCU | Jul 47–Dec 51 Oct 56–Jan 58 Mar 71–Oct 91 | Formed by re-designating No. 8 OTU Became 231 OCU at Bassingbourn. Re-formed at Wyton, 1956, by re-designating 'C' Squadron of 231 OCU. Re-absorbed by 231 OCU January 1958. | ||
| 238 OCU | 1 Jun 52–Mar 58 | Formed by re-designating the Airborne Interception School RAF | ||
| 240 OCU | Jan 48–Apr 51 Dec 71–Oct 93 | Formed by merging 1333 (TS)CU with 1382 (T)CU | ||
| 241 OCU | Jan 48–Apr 51 Jul 70–Oct 93 | Formed by re-designating No. 1332 Heavy Transport Conversion Unit RAF Became No. 55 (Reserve) Squadron RAF | ||
| 242 OCU | Apr 51–Jul 92 | Became 57 (R) Sqn | ||
| 1330 CU | Jun 44–Mar 46 | No. 1 (Middle East) Check and Conversion Unit RAF re-designated. | ||
| 1331 CU 1331 HTCU | Sep 44–Jan 46 Dec 46–Jan 48 | Harvard IIB Vengeance IA/II/IV Beaufighter VI/X Spitfire VIII Mustang IV Mosquito III Oxford I Blenheim V Thunderbolt I/II Hurricane IIC Wellington XVI Liberator III/VI | RAF Mauripur RAF Risalpur RAF Syerston | Formed by re-designating Check and Conversion Flight RAF. |
| 1332 (T)HCU 1332 HTCU | Sep 44–May 47 May 47–Jan 48 | Became 241 OCU. | ||
| 1333 (TS)CU 1333 TSCU | Mar 45–Jul 46 Jul 46–Jan 48 | RAF Leicester East RAF North Luffenham | Formed by re-designating No. 107 OTU Merged with 1382 (T)CU to become 240 OCU. | |
| 1334 (TS)CU | Apr 45–Mar 45 | |||
| 1335 (M)CU | Mar 45–Aug 46 | Became 226 OCU | ||
| 1336 (TS)CU 1336 TCU | Jun 45–Mar 46 | |||
| 1380 (TS)CU 1380 TCU | Aug 45–Jan 46 | Formed by re-designating No. 81 OTU | ||
| 1381 (T)CU | Aug 45–Feb 48 | Formed by re-designating No. 105 (Transport) Operational Training Unit at Bramcote.[10] | ||
| 1382 (T)CU | Aug 45–Jan 48 | Formed by re-designating No. 108 OTU Merged with 1330 (TS)CU to form 240 OCU. | ||
| 1383 (T)CU | Aug 45–Aug 46 | Formed by re-designating No. 109 OTU | ||
| 1384 (HT)CU | Nov 45–Jun 46 | Formed by re-designating No. 6 Lancaster Finishing School RAF | ||
| 1385 (HTS)CU | Apr 46–Jun 46 | Absorbed by 1333 (TS)CU | ||
| 1584 (HB)CU | Nov 43–Feb 44 | Formed by re-designating No. 1584 (Heavy Bomber Conversion) Flight RAF. Became 1673 HCU. | ||
| 1651 CU 1651 HCU | Jan 42–July 44 May 44–Mar 45 Mar 45–Jul 45 | During 1942 it flew 49 operational sorties for RAF Bomber Command with a loss of five aircraft. Formed by merging No. 26 Conversion Flight RAF and No. 106 Conversion Flight RAF. Absorbed No. 15 Squadron Conversion Flight RAF and No. 24 Squadron Conversion Flight RAF. | ||
| 1652 CU 1652 HCU | Jan 42–Jun 45 | During 1942 it flew 42 operational sorties for RAF Bomber Command with a loss of three aircraft. Formed by merging No. 28 Conversion Flight RAF and No. 109 Conversion Flight RAF. Absorbed No. 35 Squadron Conversion Flight RAF | ||
| 1653 CU 1653 HCU | Jan 42–Oct 42 Nov 43–Nov 46 | Formed by re-designating No. 108 Conversion Flight RAF Became No. 230 Operational Conversion Unit RAF in March 1947. | ||
| 1654 CU 1654 HCU | May 42–Jul 42 Jul 42–Sep 45 | During 1942 it flew 12 operational sorties with a loss of two aircraft. | ||
| 1655 MCU | Aug 42–May 43 | RAF Horsham St. Faith RAF Upper Heyford RAF Marham | ||
| 1656 HCU | Oct 42–Nov 45 | RAF Lindholme | Formed by merging 103 and 460 Squadron Conversion Fights. | |
| 1657 HCU | Oct 42–Dec 44 | Formed by merging 7, 101 and 149 Squadron Conversion Fights. | ||
| 1658 HCU | Oct 42–Apr 45 | Formed by merging 10, 76 and 78 Squadron Conversion Fights. | ||
| 1659 HCU | Oct 42–Mar 43 Mar 43–Sep 45 | Formed by merging 405 and 408 Squadron Conversion Fights. Trained Canadian aircrew. | ||
| 1660 HCU | Oct 42–Nov 46 | Formed by merging 61, 97, 106 and 7 Squadron Conversion Fights. Absorbed by No. 1653 Heavy Conversion Unit. | ||
| 1661 HCU | Nov 42–Aug 45 | Formed by merging 9, 44 and 49 Squadron Conversion Fights. Short Stirlings replaced the planned re-equipment with Handley Page Halifaxs.[11] | ||
| 1662 HCU | Jan 43–Apr 45 | |||
| 1663 HCU | Mar 43–May 45 | |||
| 1664 HCU 1664 (RCAF)HCU | May 43–Apr 44 Apr 44–Apr 45 | The unit had the Canadian name Caribou. | ||
| 1665 HCU 1665 (HT)CU | Apr 43–Jun 43 Jun 43–Jan 44 Jan 44–Aug 45 Aug 45–Jul 46 | Re-designated as No. 1665 (HT)CU on 10 August 1945 | ||
| 1666 HCU 1666 (RCAF)HCU | Jun 43–Oct 43 Oct 43–Aug 45 | The unit had the Canadian name Mohawk. | ||
| 1667 HCU | Jun 43–Oct 43 Oct 43–Feb 44 Feb 44–Nov 45 | |||
| 1668 HCU | Aug 43–Nov 43 Jul 44–Mar 46 | Disbanded November 1943, re-formed July 1944. | ||
| 1669 HCU | Aug 44–Mar 45 | |||
| 1670 (T)CU | Jun 44–Jan 45 | Became No. 8 Refresher Flying Unit RAF | ||
| 1671 CU | Feb 44–Jun 44 | Formed from AI Mk VIII Conversion Flight RAF | ||
| 1672 (M)CU | Feb 44–Aug 45 | |||
| 1673 HCU | Feb 44–Apr 44 Apr 44–Nov 44 | Formed by re-designating No. 1584 (Heavy Bomber) Conversion Unit RAF. | ||
| 1674 HCU | Oct 43–Nov 45 | |||
| 1675 HCU | Oct 43–Aug 44 Aug 44–Oct 45 | Formed by re-designating No. 5 Heavy Bomber Conversion Unit RAF, Lydda | ||
| 1678 HCU | Sep 43–Jun 44 | RAF Foulsham RAF Waterbeach | ||
| 1679 HCF | May 43–Jan 44 | RAF East Moor RAF Wombleton | Merged into No. 1666 HCU | |
| 1699 (BS)CU 1699 HCU | Oct 44–Jun 45 | Became the Lancastrian Flight of No. 231 Squadron RAF | ||
| All-Weather OCU | ?–? | nomadic | ||
| Argosy CU | Nov 61–Apr 63 | Became the Argosy Flight of 242 OCU | ||
| Belvedere CU | Aug 64–Aug 68 | Absorbed by the Short Range Conversion Unit RAF | ||
| Short Range CU | Aug 64–Jul 67 | Became the Helicopter Operational Conversion Flight RAF | ||
| Jaguar OCU | Jun 74–Sep 74 | Formed from Jaguar Conversion Team RAF. Became 226 OCU | ||
| 5 Heavy Bomber Conversion Unit | ?–? | RAF Lydda, RCAF Boundary Bay and RCAF Abbotsford] | Became No. 1675 Heavy Conversion Unit RAF. In April 1944 RCAF Boundary Bay No. 5 Operational Training Unit (for Heavy Conversion) established when 17 B-24 Liberators were scheduled to arrive fresh from American factories that first month. However, only sixteen would actually be delivered. By Sept 30th 1944 RCAF 5 O.T.U. reported B-24 Liberators; Abbotsford 24, Boundary Bay 14, total 38. B-25 Mitchells; Boundary Bay only total 35. Bolingbrokes; Boundary Bay only total 5. P-40 Kittyhawks; Boundary Bay only 8. Norseman; Boundary Bay only 1. Total aircraft on Unit strength 87 | |
| Heavy Bomber Conversion Unit, Salbani | Sep 42–Jul 43 | Became No. 1584 (Heavy Bomber) Conversion Unit RAF – see above. | ||
| Heavy Glider Conversion Unit | Jul 42–Oct 44 | Became No. 21 Heavy Glider Conversion Unit RAF | ||
| 21 HGCU | Oct 44–Dec 47 | Whitley V Albemarle GT.VI Horsa I/II Oxford I Tiger Moth I Miles Magister Hotspur II/III Hadrian I Stirling IV Halifax III/VII Master II | Formed by re-designation of the Heavy Glider Conversion Unit RAF | |
| 22 HGCU | Oct 44–Dec 47 | Formed by re-designation of an element of the Heavy Glider Conversion Unit RAF | ||
| 23 HGCU | Oct 44–Dec 45 | Albemarle GT.I/ST.V/ST.VI Horsa I/II Oxford I Hadrian I Proctor III | RAF Peplow | Formed by elements of No. 83 Operation Training Unit the Heavy Glider Conversion Unit RAF |
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Army Air Corps