By the 1950s, the turbojet engine was firmly entrenched as the aviation powerplant of the future. In response, a myriad of companies, both in the East and West, undertook various aircraft projects to satisfy a plethora of requirements by their respective air services. In Britain, where the turbojet was brought to life by engineer Frank Whittle, the various World War 2 defense powerhouses jumped at the chance to fulfill Royal Air Force (RAF) requirements of the period - with the Soviet Union being the enemy of the day. One such requirement - a design that would eventually lead the country's aero-industry down the path to the "swing-wing" PANAVIA "Tornado" attacker of the 1970s - became the "B.90" project aircraft proposed by Blackburn Aircraft.
The P.90 was drawn up as single-seat, twin-engine fighter featuring an all-swept-wing arrangement (swept edges showcased at both mainplanes and tail surfaces). Like other fighters of the 1950s, it utilized a classic turbojet configuration in that the nose section was cut-off to act as the intake in aspirating the turbojet installations within. The aircraft was to be powered by two turbojet engines - these seated in an "over-under" configuration within the fuselage - to achieve the desired high-speed performance. The concept of stacking the engines meant that the fighter had to be given a deeper-than-usual fuselage though it remained quite slim from the top-down profile.
The other unique quality of this aircraft was in the proposed use of a variable-sweep wing mainplanes in which these members could be extended outwards or swept back against the fuselage sides to adapt the aircraft to various flight envelopes (low-and-slow, high-and-fast). The mainplanes were seated at midships while being mid-mounted.
The cockpit was positioned at front in the usual way with the intake ductwork to pass under the cockpit floor. The pilot would sit under a framed canopy offering adequate vision around the aircraft. Over the rear of the airframe was positioned the sole vertical tail unit running from near-midships at the fuselage dorsal spine and extended out over the engine exhaust ports at the rear. A retractable wheeled undercarriage is assumed for ground-running but not formally detailed in the available Blackburn plans.
As drawn up, the B.90 was given an overall length of 61 feet with an extended wingspan of 65 feet. With wings tucked in, the value became 35.2 feet. Weight was to reach 34,600lb when loaded with fuel and ammunition.
Armament was to become a pair of 30mm ADEN automatic cannons, these recessed in the walls of the forward fuselage ahead and installed below the cockpit floor line. The firepower inherent in this arrangement was enough to bring down any aircraft being flown by the enemy.
To power the fighter, Blackburn engineers focused on a pair of Armstrong Siddeley "Sapphire" Sa.4 turbojet types outputting 9,760lb of dry thrust each. This could be enhanced to 12,000lb of thrust each with reheat (afterburner) engaged. The Sapphire was a logical choice, the powerplant used to drive the Gloster "Javelin" and Hawker "Hunter" fighters as well as the Handley Page "Victor" nuclear-capable bomber. The axial-flow engine was produced, under-license, in the United States by Curtiss-Wright as the famous "J65".
Estimated performance specs included a maximum speed of 895 miles-per-hour, capable of reaching Mach 1.35 in straight-level flight, at around 45,000 feet of altitude. Due to the speeds and altitudes at play the fighter would have been completed with pressurization and an ejection seat.
All told, the proposed B.90 was a sleek offering for its time, despite its deep appearance, as it showcased a balanced collection of smooth and sharp lines.
In any event, the B.90 was not furthered beyond its proposed paper form and eventually fell to aviation history. Many other swing-wing design proposals eventually followed it, these provided by the various defense players of the period, and ultimately British industry, in conjunction with several European partners, could hang their hat on the work that would produce the excellent Tornado strike platform to come in 1979.