United Kingdom aircraft test serials are used to externally identify aircraft flown within the United Kingdom without a full Certificate of Airworthiness.[1] They can be used for testing experimental and prototype aircraft or modifications, pre-delivery flights for foreign customers and are sometimes referred to as "B" class markings.[1]
An initial set of markings was introduced in 1929, each company was allocated a letter to which would follow a number, sometimes with a hyphen or a gap between.[1] For example, A was allocated to the Armstrong Whitworth Aircraft and A 1 was used in March 1930 on an Armstrong Whitworth Starling.[1] Sometimes Hawker and Vickers would also add the letters PV to the markings to indicate a private venture (that is a type in development not paid for by the Air Ministry).[1]
The presentation was changed to look like a military serial for security reasons during the Second World War.[1] For example, the prototype de Havilland Mosquito was allocated test markings E-0234.
Following a change back to the original system in 1946 a new system was introduced on 1 January 1948.[1] Each company was allocated a number which followed the British nationality marking G and then followed by an individual identity number.[1] For example, Blackburn Aeroplane & Motor Company were allocated G-2 and the first allocation G-2-1 was used on a Miles Messenger used as an engine testbed for the Cirrus Bombardier.[1] Companies could allocate and re-use the identities as they liked, some ran in sequence from 1 and others used the aircraft manufacturers serial number as part of the marking, for example G-51-200 was a Britten Norman Islander with a manufacturers serial number of 200.[1] Allocations of codes from defunct companies have been reallocated.
| Allocation | Company | Notes |
|---|---|---|
| A | Armstrong Whitworth Aircraft | Replaced by G-1 in 1948 |
| B | Blackburn Aeroplane & Motor Company | Replaced by G-2 in 1948 |
| C | Boulton Paul | Replaced by G-3 in 1948 |
| D | Portsmouth Aviation | Replaced by G-4 in 1948 |
| E | de Havilland | Replaced by G-5 in 1948 |
| F | Fairey Aviation | Replaced by G-6 in 1948 |
| G | Gloster Aircraft | Replaced by G-7 in 1948 |
| H | Handley Page | Replaced by G-8 in 1948 |
| I | Hawker Aircraft | Replaced by G-9 in 1948 |
| J | Parnall Aircraft | Out of use by 1946 |
| J | Reid & Sigrist | From 1947, replaced by G-10 in 1948 |
| K | Avro | Replaced by G-11 in 1948 |
| L | Saunders-Roe | Replaced by G-12 in 1948 |
| M | Short Brothers | Replaced by G-14 in 1948 |
| N | Supermarine | Replaced by G-15 in 1948 |
| O | Vickers Armstrongs | Replaced by G-16 in 1948 |
| P | Westland Aircraft | Replaced by G-17 in 1948 |
| R | Bristol Aeroplane | Replaced by G-18 in 1948 |
| S | Spartan Aircraft | Out of use by 1936 |
| S | Heston Aircraft | Replaced by G-19 in 1948 |
| T | General Aircraft | Replaced by G-20 in 1948 |
| U | Phillips & Powis later Miles Aircraft | Replaced by G-21 in 1948 |
| V | Airspeed | Replaced by G-22 in 1948 |
| W | G & J Weir | 1933–1946 |
| X | Percival Aircraft | Replaced by G-23 in 1948 |
| Y | British Aircraft Manufacturing | Out of use by 1938 |
| Y | Cunliffe-Owen | 1940–1947, replaced by G-24 in 1948 |
| Z | Auster Aircraft | Replaced by G-25 in 1948 |
| AB | Slingsby Sailplanes | Replaced by G-26 in 1948 |
