Early developments of the turbojet engine, with then very limited power output, restricted somewhat the size and type of aircraft able to take advantage of this new power plant. Thus, it was not until Air Ministry Specification B.3/45 was issued that the English Electric Company was able to design and build Britain's first turbojet-powered bomber -the first such aircraft to serve with the RAF. A prototype flew for the first time on 13 May 1949.
The original intention had been to produce a two-crew aircraft which would rely upon radar for the accurate delivery of its bomb load. But although the four prototypes were built to this configuration, the first production Canberra B.2 carried a crew of three and were configured for visual bombing. Of mid-wing monoplane configuration, these aircraft were powered by two 28.91kN Rolls-Royce Avon 101 engines and could carry internally 2,722kg of conventional or nuclear weapons. Canberras entered RAF service with No 101 Squadron at RAF Binbrook in May 1951. These aircraft were unarmed, relying (as had the war-time de Havilland Mosquito) on being able to show their opponents a 'clean pair of heels'.
Subsequent variants included: the B.6 bomber with 32.92kN Avon 109; the B(I).6 intruder variant; B(I).8 two-seat long-range night interdictor or high-altitude bomber, built also as the B(I).58 for India and B(I).12 for New Zealand and South Africa; a conversion of the B.6 with additional underwing hardpoints for weapons, designated B.15; and a generally similar B.16 with more radar equipment. Performance was such that it was logical to develop photo-reconnaissance versions. The PR.3 (based on the B.2) first flew on 19 March 1950 and was followed by the PR.7 (similar to the B.6) and the high-altitude PR.9. Other RAF Canberras included T.4/11/17 and 19 trainers; and the target-towing TT.18.
The Canberra has been supplied to many air forces, has been licence-built in Australia, and has the distinction of being the only modern aircraft of British design to be licence-built in the USA. Under the USAF designation B-57 the Martin Company built 403. At a later date a number of these were converted by General Dynamics to serve as ultra high-altitude strategic reconnaissance aircraft. These were provided with a wing span of 37.19m, two 80kN Pratt & Whitney TF33-P-11 turbofan engines (replacing the conventional power plant), plus two 14.68kN Pratt & Whitney J60-P-9 turbojets in underwing pods, and many equipment and avionics changes to fit them for their specialised role.
