Aircraft Code Markings

It has been the practice throughout the history of the Fleet Air Arm for the majority of its aircraft to carry code markings as a means of identification. These have been known variously as side numbers, Fleet numbers or call signs. The latter is a reference to their use for radio identification purposes. For the historian they have the great advantage that they very often enable the parent squadron or unit of an aircraft depicted in a photograph or referred to in a document to be readily identified.

When the first few 400-series flights were formed in April 1923 as part of the RAF, the latter had no standard system of identification markings. Consequently, although a few of the new units adopted codes, such as single letters or single numbers, the majority did not. However, this state of affairs was not to last long, and at a meeting towards the end of 1923 aboard the battleship HMS Queen Elizabeth, it was decided that aircraft these flights would adopt standardised markings.

The new markings would consist of single or double digit numbers painted in a coloured band along the fuselage sides. The colour of each band would indicate the parent carrier of the flight concerned. Thus, of the carriers then in service or shortly to commission, HMS Argus aircraft would carry green fuselage bands, those in HMS Furious red, HMS Hermes white and HMS Eagle black. When HMS Courageous came into service it adopted blue, and this was followed by yellow for HMS Glorious. Finally, just before the outbreak of war, HMS Ark Royal adopted a three-coloured band consisting of two blue strips separated by a red one, all of equal size. The only exceptions to the colour band system were the later catapult flights, which carried their code numbers painted directly on to the fuselage sides.

The system of numbering which was adopted was based on the numbers of the flights to which they were allocated. Thus the fleet fighter flights, being numbered in the 401-419 range (though not all taken up), used codes 1-19. Simiiarly 20-39 were allocated to fleet spotters (420-439 range), 40-59 to fleet reconnaissance aircraft (440-459 range) and finally 60-89 to fleet torpedo aircraft (460 onwards). To avoid the possibility of signalling error, no digit was duplicated within a code, so that numbers 11, 22, 33 and so on were never taken up. These numbers were painted on to the appropriately coloured fuselage band, which was generally a diagonal one, though many variations were employed, especially in the early days.

The first change in the numbering system occurred in April 1929 when the 420-series of flights was abolished. The fleet reconnaissance flights were being phased out, except in the case of some catapult flights, and conse-quently an extended 450-series of flights absorbed the four existing flights in the 420-series. The direct conn-ection with flight number allocations was now relaxed, and the fleet fighter range of codes was extended to become 1-29. The newly-titled fleet spotter reconnaissance flights then adopted 30-59, the fleet torpedo bomber flights (as they were to become) used 60-89, and fleet reconnaissance flights 90-98.

By this time, however, the system was getting cumbersome, the number of new flights steadily increasing as newer and bigger carriers came into service. In January 1932, therefore, a completely new system came in to use.

Codes could now comprise up to three digits, and no two codes would be identical at any one time, irrespective of the fuselage band colour. They continued as before to avoid duplication of digits, but this was extended so that no digit was ever used twice within a particular combination. Thus such numbers as 221, 212 and 122 were not to be taken up within a sequence. As a further refinement, separate sub-series of codes in each of these sequences were reserved for the different areas of the world in which the Fleet then operated. Thus torpedo bomber flights now adopted codes in the range 1-99, and also 01-09. Reconnaissance aircraft used 201 onwards, fighters 501 onwards and spotter reconnaissance aircraft 701 onwards (Home) and 801 onwards (Mediterranean).

The next change occurred in April 1933, when most of the flights were regrouped into squadrons. For the most part these simply adopted the code sequences inherited from their predecessors, extended where necessary to cope with increases in complement. A further re-organisation of the system took place, however, during 1935-1936, probably for security reasons, this being the time of the Abyssinian Crisis and the emergence of Nazi Germany. Catapult aircraft now generally carried codes in the 001-099 series, the 102-series was reserved for fighters, the 501-series for fleet reconnaissance, and 601 onwards for fleet spotter reconnaissance. There were a few minor exceptions to these sequences. When the catapult flights were re-grouped in July 1936 to become 700-series flights, they retained the cede allocations for the most part, extended as required.

A short-lived identification scheme which came into use in some squadrons early in 1937 was the use of two-letter combinations in place of the number codes. In this, each squadron was allocated a block of such codes, such as AA to AL and AM to AX, but only a few actually adopted them before the system was abandoned.

Tension in Europe continued to mount, and both the RAF and the FAA gave further consideration to new systems of aircraft code markings. By the Spring of 1938 these had both been formulated, the RAF settling for two-letter squadron combination plus an individual letter, whilst the FAA was to have a basically similar system in which the unit cede was to be a letter/number combination. However, whereas in the RAF system the unit code was placed one side of the fuselage roundel and the individual letter to the other, the FAA code was to be painted left to right (letter/number/letter) irrespective of its relation to the position of the roundel. In most instances it was painted entirely on one side of the roundel, though in some early cases it appeared on the vertical tail surfaces in various layouts.

The new FAA code markings were first painted on the aircraft in May 1939, when the Admiralty finally regained control of its Air Arm from the RAF. Unlike the RAF, though, the new codes were adopted not only by the first line squadrons, but by the catapult squadrons (as they had now become) and also the training units and second line units which adopted squadron numbers from 750 onwards. In the case of first line squadrons the new cedes were init-ially painted as before on the coloured fuselage carrier bands, but these were quickly painted out on the outbreak of war.

Although this wartime FAA code system appears baffling, the basic principles were quite simple. The problem is that its pattern changed as the war progressed, and also that it was quite possible for two units to use identical codes, though not generally in the same theatre of war.

The central number was a class number indicating its function. In the case of operational carrier aircraft there were by 1939 only two main categories, being spotter reconnaissance for which numbers 1 to 5 were allocated, and fighter for which numbers 6 and 7 were used. The prefix letter to these indicated the parent carrier, the initial letter of whose name was usually adopted for this purpose. Thus TSR squadrons in HMS Ark Royal were initial-ly coded A2 (810 Sqdn), A3 (814 Sqdn), A4 (820 Sqdn) and A5 (821 Sqdn), whilst her fighters used A6 (800 Sqdn) and A7 (803 Sqdn).

In the original allocation, numbers 8 and 9 were used by catapult aircraft. Number 8 was reserved for wheeled aircraft fitted with floats for this purpose (i.e. Swordfish seaplanes), whilst 9 was for catapult amphibians and fixed float seaplanes (i.e. Walruses and Seafoxes). Number 0 was to be for autogyros, experimental aircraft and the like.

The original prefix allocations, not all of which were taken up, were A - HMS Ark Royal, C - HMS Courageous, E - HMS Eagle, F - HMS Formidable, G - HMS Glorious, H - HMS Hermes, I - HMS Illustrious, M - a new carrier under construction, N - HMS Indomitable, 0 - Observer training aircraft, P & Q- converted liner carrier, R - HMS Argus (TSRs), T - Flying training aircraft. U - HMS Furious, V - HMS Victorious, W - Shore station aircraft, X - Experimental, Y & Z Shore station aircraft.

Catapult squadrons had their own series of prefix letters. Some of these duplicated the main sequence, but since they were restricted to suffix numbers 8 and 9 there was no danger of duplicating codes. The allocations made were A - HMS Albatross (floatplane), B - Battle Cruiser Squadron, C - 1st Battle Squadron, D - Battleships in reserve, E- 2nd Battle Squadron, F- 1st Cruiser Squadron, G - 2rid Cruiser Squadron, H - 3rd Crui-ser Squadron, J- 4th Cruiser Squadron, K- 5th Cruiser Squadron, L - 6th Cruiser Squadron, M - Cruisers in reser-ve, N - 8th Cruiser Squadron, P & Q - Armed Merchant Cruisers, U & V - spare. Some minor alterations were made to these allocations in practice, but essentially they were used as originally intended, until being largely superseded in January 1940, when all the catapult squadrons were amalgamated as No.700 Squadron which was then allocated code G9, though it probably never took this up.

The code system was basically geared to the first line squadrons, and had to be adapted to meet the needs of the training and other second line squadrons. Initially this was not too difficult a problem, though a little licence had to be taken with the basic rules. To allow for the fact that many would have mixed equipment, it was laid down that they would use the class figure relating to their main equipment. Thus at Ford and Lee-on-Solent most of the observer training squadrons used codes in the W1 to W5 range, being equipped mainly with TSR aircraft, but No.751 Squadron used W9 being a Walrus-equipped unit. In effect W-prefixes were reserved for observer training squadrons.

Similarly, X-prefixes were used in practice by TAG training squadrons, except that X8 was reserved for use by No.778 Squadron, the Service Trials Unit. Deck landing training squadrons used T-prefixes, and Fleet requirements units used R-prefixes. O-prefixes were earmarked for oper-ational pools, though it is not certain that these were taken up. Y-prefixes were used by fighter schools (Y6 and YT), torpedo schools (Y2, Y3, Y4 and YS), and seaplane schools (Y8 and Y9), and in all of these the suffix numbers were correctly employed for their main equipment. It was recognised that some training squadrons might become unusually large, and these were authorised to use the class number 0 for the overflow. Thus at Ford both Nos.750 and 752 Squadrons had to use codes in the WO series, and No.750 continued to do so after moving to Trinidad.

The first important change occurred in April 1940, when some changes were announced to the original prefix allocations, though some of these simply recognised what had actually been happening in practice. In the carrier series, B became HMS Indefatigable, while C became vacant with the loss of HMS Courageous. In the shore-based series, 0 became Armament training, P - pools, Q - Communications and Miscellaneous, R - FRUs, S - Shore-based operational squadrons and Y - Torpedo and fighter schools. At the same time it was announced that in future only shore-based aircraft would carry the full code, and those which were carrier based would abandon the prefix letter. In actual fact, some carrier squadrons, such as No.810, continued to carry prefix letters until well into 1941. Another anomaly was that during the North African landings (Operation Torch) squadrons embarked in HMS Formidable adopted the identification marking Ø as a prefix to their codes.

In May 1941 permission was given for stations with more than one non-operational squadron to modify the class numbering system to meet local needs. It was suggested that numbers 1 and 2 would be appropriate where these used multi-seater aircraft.

By May 1942 there were so many second line squadrons, and some were becoming so large, that a revised coding system was introduced in which the prefix letter indicated the parent station. The initial allocation of these was A -Arbroath (and Dundee satellite), B -Easthaven, C-Creel, D-Donibristle, E - Eastleigh, F - Lawrenny Ferry, H -Hatston, K - Machrihanish, L - Lee-on-Solent, M - St. Merryn, N - Henstridge, P - Campbeltown, R - Stretton, S - Sandbanks, T - Twatt, V - Evanton, W - Worthy Down and Y - Yeovilton. A further modification at that time was that instead of using O-codes for additional aircraft, they would retain these original code with a horizontal bar over the individual letter.

Further changes took place in January 194S in the allo-cation of shore base letters, and eventually it became necessary to use two-letter combinations, when there be-came more UK stations than available single letters. These later allocations included B - Donibristle, D - Dunino (later Drem), E - Easthaven, F - Fearn, G - Henstridge, I - Eastleigh (later Crimond), J - Eglinton, K - Inskip, M - Machrihanish, N- Maydown, 0- Burscough, P- Dale, Q-Belfast (Sydenham), R- Ronaldsway, S - St. Merryn, U-Hinstock, V- Woodvale, X- Abbotsinch, Z - Grimsetter (later Zeals), AA - Dundee, AH - Burscough, AN - Campbel-town, AN - Anthorn, AR - Ronaldsway (later Ayr), AT - Crimond (renamed Rattray), AY - Haldon, BH - Ballyhalbert, BY - Charlton Horethorne, CM - Culham, ED - Dunino, EL - Eastleigh (previously I), EV - Evanton, FD- Ford, GM Grimsetter, HA - Halesworth, GP - Gosport, IT - Milltown and ST - Stretton.

Another change in January 1943 was the abolition of barred letters in the repeated alphabets used by large units. Instead these gave way to black individual letters where these were used a second time. Seemingly a rather confusing means of identification, and one which not all units adopted. Hinstock, for instance, used duplicated individual letters (e.g. U2AA) on the Oxfords of No.758 Squadron. Another variant was No.785 Squadron at Sand-banks, which used a B-prefix for its L3 code on some aircraft (e.g. BLBS). No.738 Squadron, the School of Air Combat at St. Merryn, chose to ignore the standard system entirely and ceded its aircraft AC-A, AC-B, AC-C etc.

By 1944 quite a number of shore bases had been established overseas, and prefix letter allocations were also made for these, as follows. A - Addu Attoll (Gan) (later Brisbane), B - Bankstown, C - China Bay (Trincomlee), D - Dekheila, G - Gibraltar, H - Hastings (later Cochin), J - Jervis Bay, K - Katukurunda, L- Colombo, M - Ta Kali, N - Kantall (later Nowra), P - Puttalam (later Ponam), Q - Coimbatore, R - Port Reitz (later Sulur), T - Tambaram and W - Wingfield.

Under this new system, squadron identification numbers for second line squadrons were allocated on a station basis, rather than centrally as hitherto, Numbers 1 to 7 were earmarked for training squadtrons, and 8, 9 and 0 for FRUs, communications units, trials traits and other miscellaneous formations. It was again suggested that in the training squadrons numbers 1 and 2 be used for multi-seaters.

Many British naval squadron working up in the United States used carrier-type number/letter combinations for identification purposes. These were in fact an abbreviated form of the full call-sign, which also included the central letter B (for British). Some squadrons, however, carried the full combination until embarking for the United Kingdom, in the form, for example, 2BA, 2BB, 2BC etc. Another variation amongst American-trained squadrons, particularly on Corsairs, was the allocation of V-codes to each squadron, to be used in combination with individual numbers. An example of this was No.1852 Squadron, which numbered its aircraft 1V1O, 2V1O, 3VlO etc until embarking, when it adopted individual letters as the only identification.

Developments were, in the meantime taking place amongst the markings borne by aircraft of carrier-based first line squadrons. From October 1943 these had largely been grouped as Wings. Some of these continued to use number/ letter codes as identification, but many of those in escort carriers used a combination of a letter denoting the carrier concerned plus an individual letter. In August 1944 the fighter wings standardised on a letter/number/ letter combination, the first letter in each case denoting the wing concerned, the number the particular squadron within the wing, and the last letter the individual air-craft.

Not every wing to which a code was allocated actually formed, and of those that did form, not all troubled to use the new system. Allocations under this system were A - 15 Wing, B- 26, C- 9.9, D- 4, E - 16, F- 35, G - 28, H - 24, I - 11, J - 44, K - 3, L - 6, M - 18 (aircraft of Macships), N- 40, 0-10, P- 30, Q- 43, R- 5, S - 49, T - 47, U - 22, V - 42, W - 7, X - 33, Y - 37 and Z - 13. These could be changed periodically by local Commanders-in-Chief if extra security was required. In fact, although intended basically for fighter wings, their use was not entirely confined to these, the Swordfish of No.836 Squadron, for instance, using their own variation for a time, being a combination consisting of the Wing letter M, an individual number and the flight letter. Thus, the Sword-fish of ‘B’ Flight of No.836 Squadron carried codes M1B, M2B, and M3B at that time, later reverting to their more normal B1, B2 and B3.

Aircraft in anti-submarine escort carriers began to carry two letter markings, of which the first denoted the carrier and the second the individual aircraft. The class numbers for other first line squadrons were now changed, so the TBR squadrons were to use 1 to 3, two-seater figh-ter and dive bomber squadrons 4 and fighter squadrons 5 to 9 and also O.

A further development, in April 1945, was the allocation of deck identification letters for all forms of carrier, which in many cases were to be identical with the carrier letter prefixes borne by its aircraft. Where the carriers were operational, these letters could be changed period-ically for security reasons. The letters initially allo-cated to home-based fleet and escort carriers were B- HMS Barrier, F - HMS Ranee, G - HMS Smiter, I - HMS Trouncer, J - HMS Trumpeter, L - HMS Glory, N - HMS Puncher, 0 - HMS Pretoria Castle, P - HMS Premier, O - HMS Queen, R - HMS Reaper, S - HMS Searcher, T - HMS Patroller, U - HMS Pursuer, V - HM Ravager, X - HMS Vindex, Y - HMS Nairana and Z - HMS Campania.

Macships were similarly marked, though such markings were never carried on the aircraft. The allocations were MA- Acavus, MB- Empire MacCoil, MD- Amastra, MF-Ancylus, MH- Empire MacAlpine, MJ- Empire MacMahon, MK - Empire MacAndrew, ML- Empire MacCabe, MM - Empire MacKay, MN- Empire MacCallum, MO- Empire MacKendrick, MP - Alexia, MQ- Adula, MR- Gadila, MS - Empire-MacDermott, MU- Empire MacRae, MV- Rapana, MW- Miraida and MX-Macoma.

In June 1945 the carrier aircraft identification system was again changed. General purpose escort carriers would continue to use the letter/letter code system, but those in assault carriers, and all those in fleet and light fleet carriers would revert to a letter/figure/letter system. In this system the initial letter would denote the tactical unit to which the squadron belonged, the other two symbols continuing as before to denote the particular squadron and the individual aircraft. In order to avoid overlapping in neighbouring theatres of war, initial letters A to J were to be used only by the Home Fleet and East Indies Fleet, whilst N to Z could only be used by the Mediterranean Fleet and the British Pacific Fleet.

The British Pacific Fleet had, however, by this time adopted yet another system of identification on its air-craft, somewhat akin to that of the US Navy alongside which it was operating. From April 1945 the parent carrier letters were used as fin marking, and the fuselages car-ried a three-digit number for individual identification. Each carrier used the same basic combination of codes, those in the 111 to 169 range being reserved for single seat aircraft, 270 to 298 for two-seaters and 370 to 398 for three-seaters.

In 1946 this system was used as a basis for a universal coding system which in essence has survived to the present day, though in modified form. All FAA aircraft, whether at home or abroad, would carry a three digit fuselage number of which the first digit would denote its layout or fun-ction. Thus single-nearer aircraft would use codes 100 - 199, two-seaters 200- 299, three-seaters 300- 399 and multi-engined aircraft 400-499. The remaining numbers were to be used by units with a specialised function, and thus FRU aircraft used 500-599, multi-engined light trainers 600~, a spare series was 700-799, communications were 800-899, station flights used 900-999 and experimental, tactical trials and development aircraft used 000-099. These numbers were to be used as call signs, but the call sign 99 was specifically reserved for Air Group Commanders, therefore British Pacific Fleet squadrons were told to avoid using 299 or 399. At least one Corsair carried code 99, and examples are known of Training Air Group Commanders using codes 199 or 299 on their aircraft.

As in the British Pacific Fleet system, each ship or station used the same sequence of numbers, allocations to individual aircraft being made locally. Also as in that system, fin letters were used to denote the parent ship, but in the case of shore bases a two-letter combination was used, this being the call sign of the station concerned. Commonwealth carriers were encompassed by this system, to aid identification when operating together. The Royal Australian Navy also used the three-digit system, and used the two-letter fin code NW for its shore base at Nowra, but the Royal Canadian Navy preferred to adopt its own aircraft identification system, which it used in con-junction with that of the Royal Canadian Air Force. The Australians have continued to use a fairly similar system to that of the FAA, changing to 900-series codes for second line units in 1955, and then to 800-series codes for both first and second line units in 1958, fin codes being dropped in recent years.

The FAA changed the system of code allocations in January 1956, though not their appearance. Codes were no longer to be allocated by stations, but would be issued centrally to each squadron, though again on a function basis. Thus FRUs and Communications squadrons would be given codes in the range 000-099, first line squadrons 100-499, training and auxiliary squadrons 500-799, reserve squadrons 800-899 and station and ships flights 900-999. The use of the 800 series by reserve squadrons was short-lived as they disbanded in March 1957.

In the initial allocations under the new system, blocks of numbers were allocated to squadrons in their numerical sequence. Thus No.800 Squadron had 100-114, No.801 had 115-129, No.802 had 130-144 and so on. Second line squad-ton were similarly allocated codes in numerical sequence, whilst those of station and ships flights were in alphabetical sequence. With the constant formation of new units and the disbandment of those which had served their purpose, it was inevitable that this neat series of allocations could not last very long. Attempts were made at first to real locate blocks of codes to new squadrons in something like their correct sequence, but this gradually became more difficult, and in some instances codes blocks had to be allocated outside those for which they were intended.

By July 1965 the situation had become very confused, and as a consequence a fresh start was made. Codes were once again to be allocated to squadrons on a station basis, but this time within broad blocks without any regard for their function. This would give greater flexibility provided no big organisational changes took place.

Under the initial allocations the broad range 001-399 was reserved for first line carrier squadrons, 400-499 to helicopters attached to small ships and 500-999 to air-. craft of shore-based units. Each of these ranges was sub-divided,’ so that in the 001-399 range HMS Ark Royal took 001-057, HMS Eagle 060-147, HMS Victorious 230-277 and HMS Hermes 301-347. Carrier aircraft did not have codes con-taining 8 or 9, to avoid signalling confusion. Ashore, Portland used 500-539, Culdrose 540-599, Lossiemouth 600-699, Yeovilton 700-759 and Brawdy 760-817, with other miscellaneous units taking 818-999. It is not uncommon under this system for second line aircraft to omit the first digit of their code.

Essentially this system remains in use to the present day, though with some modifications. It no longer in-cludes Commando squadrons, which in 1971 adopted their own system comprising a unit letter and an individual letter. Some re-organisation within the blocks had taken place by 1975. HMS Ark Royal retained its 001-057 range, but HMS Eagle had gone out of service and its codes largely real-located. 060-063 were now for use by a Sea King pool, 064-065 by RSRE Malvern, 100-127 by a Sea Harrier pool, 140-145 by HMS Tiger and 200-227 by HMS Bulwark. The former HMS Victorious air group had transferred to HMS Hermes in 1968, rating with it the code range 250-277. This had left vacant the 301-347 range, which was partially used to provide codes 300-317 to the new FAA base at Prestwick, and partly to make further codes available for small ships flights, these by now using 320-347 in addition to the 400-477 range. HMS Invincible, then under construction, was allocated 350-357, but in the event never took it up.

Ashore, Portland was now using four ranges, 500-517, 610-617, 630-637 and 650-677. Culdrose had increased its single range to 540-599, whilst Yeovilton still used 700-759. By now Lossiemouth was at a much reduced strength and consequently had given up its 600-699 range in favour of 760-777. Apart from the Portland allocations already mentioned, this was reallotted as 600-607 to Honington, 620-627 to Leuchars and 640-647 to Yeovilton. As to the miscellaneous units, 810-829 was given to Lee-on-Solent, 830-880 to FRADU Yoevilton, 895-897 to BRNC Dartmouth and 901-912 to the BRNC AEF at Roborough.

Not all of these allocations were taken up, but they remain substantially the same at the time of writing. Honington and Leuchars no longer have a FAA presence, and their code allocations have been taken over by Culdrose and Portland respectively. HMS Invincible used 360-362 for a time on its helicopters, before taking over part of the old HMS Ark Royal range. Recent usage has been in the ranges 000-021 HMS Invincible, 123-127 HMS Illustrious, 132-135 HMS Hermes, 140-146 HMS Tiger, 264-274 814 Squad-ron, 300-307 Portland, 314-315 HMS Illustrious, 320-347 small ships flights, 350-357 Culdrose, 361-362 HMS Illus-trious, 400-479 small ships flights, 501-599 Culdrose, 620-627 Portland, 630-637 Portland, 640-647 Portland, 700-708 Prestwick, 710-737 Yeovilton, 830-879 FRADU Yeovilton, 895-897 BRNC Dartmouth and 901-912 BRNC AEF Roborough.

SOURCE: The Squadrons of the Fleet Air Arm, Ray Sturtivant, 1984, Air-Britain

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