The design of the Canberra has been described as being of a simple nature, somewhat resembling a scaled-up Gloster Meteor fighter, except for its use of a mid-wing. The fuselage was circular in cross section, tapered at both ends and, cockpit aside, entirely without protrusions; the line of the large, low-aspect ratio wings was broken only by the tubular engine nacelles. The Canberra had a two-man crew under a fighter-style canopy, but delays in the development of the intended automatic radar bombsight resulted in the addition of a bomb aimer's position in the nose. Each crew member has a Martin-Baker ejection seat, except in the B(I)8 and its export versions where the navigator has an escape hatch and parachute provided.
The wing is of single-spar construction that passes through the aircraft's fuselage; the wingspan and total length of the Canberra were almost identical at just under 20 metres. Outboard of the engine nacelles, the wing has a leading-edge sweep of 4° and trailing-edge sweep of -14°. Controls are conventional with ailerons, four-section flaps, and airbrakes on top and bottom surfaces of the wings. The use of swept-wings was examined but decided against as the expected operational speeds did not warrant it, and it would have introduced unresolved aerodynamic problems to what was aimed at being a straightforward replacement for the RAF's Hawker Typhoon and Westland Whirlwind fighter-bombers.
The fuselage of the Canberra is of semi-monocoque construction with a pressurised nose compartment. Due to the use of a new alloy, DTD683, the undercarriages of the Canberra suffered from stress corrosion, which caused them to decay within a few years. The extreme hazard posed of undercarriages collapsing during landings, especially if the aircraft were carrying nuclear weapons, led the RAF to institute regular inspections, at first using radiography before moving to more effective and reliable ultrasound technology. The Canberra is made up mostly of metal, only the forward portion of the tail-fin is made from wood.
Thrust was provided by a pair of 30 kN axial flow Rolls-Royce Avon turbojets. The manufacturer specified that Coffman engine starters should be used to start the engine. An improvised method of starting the engine using compressed air was heavily discouraged by Rolls-Royce, but some operators successfully operated the Canberra's engines in such a manner, the benefit being significant cost savings over cartridges. The aircraft's maximum take-off weight was a little under 25 tonnes.
"The value of the Canberra experience cannot be over-estimated. It is the only modern tactical strike and reconnaissance aircraft in service with the RAF and many other Air Forces. More Canberra aircraft are in service with foreign countries than the Viscount, which holds the record for British civil aircraft. This is due to the flexibility of the Canberra in its operational roles and performance ..."
Manufacturer's brochure, 1957.
The Canberra could deploy many conventional weapons, typical weapons used were 250-pound, 500-pound, and 1000-pound bombs, the total bomb load could weigh up to 10,000 pounds (4.5 t). Two bomb-bays are housed within the fuselage, these are normally enclosed by conventional clam-shell doors; this was substituted for a rotating door on the Martin-built B-57 Canberras. Additional stores up to a total of 2,000 pounds (0.91 t) could be carried upon underwing pylons. Operators often developed and installed their own munitions, such as Rhodesia's anti-personnel bomblets, the Alpha bomb, a varied range of munitions were employed on Canberra fleets around the world. Anti-personnel flechette bombs were tested successfully from the Canberra by Rhodesia, but not used operationally due to international agreements.
In part due to its range limitation of just 2,000 miles (3,200 km), and its inability to carry the early, bulky nuclear bombs, the Canberra was typically employed in the role of a tactical bomber as opposed to that of a strategic one. In British service, many of the Canberras that were stationed at remote overseas locations did not undertake modifications to become nuclear-capable until as late as 1957.