Top 10: Cancelled British fighter planes

As well as the designs that actually felt the air beneath their wings, there is a tantalising treasury of designs that never made it. Some were ahead of their time, some rather behind and some, perhaps all, the victim of bad timing. Each offers a tantalising glimpse of what could have been and some truly brilliant engineering solutions. Here are ten of them.

Before any TSR-2 enthusiasts ask, we plan to feature the TSR-2 in a future article on cancelled bombers

The long history of British expertise in stealth technology has not been discussed a great deal. Britain pioneered radar-absorbent material for aircraft, worked on reduced radar observability for nuclear warheads in the early 1960s and was able to create a world-class stealth test-bed in the Replica model. Prior to Replica, in the 1980s Britain was working on an aircraft concept so advanced it was classified until 2006: the BAe P.125.

The P.125 study was for a stealthy supersonic attack aircraft to replace the Tornado. The BAe P.125 was to be available in both a short take-off and vertical landing (STOVL) version and a conventional landing variant. The conventional variant would feature a central vectoring nozzle, the STOVL version would have three vectoring nozzles.

In some ways, the P.125 was more ambitious than the Lockheed Martin F-35B Lightning II; the aircraft was to have no pilot transparencies, with the reclined pilot instead immersed in synthetic displays of the outside world. It is likely that this formidable interdictor would have been even less visible to radar than the F-35.

Despite its 1980s vintage many of its low-observable features are reminiscent of today’s latest fighters, while other features, such as its unorthodox wing design, are unique. The project was quietly dropped when Britain joined the Joint Strike Fighter (F-35) programme in the 1990s.

The P.1214 studies tried to solve the inherent limitations of the Harrier concept. The Harrier’s Pegasus engine, with its steerable thrust, blesses the Harrier with the ability to take off and land vertically – and even fly backwards. Unfortunately, you can’t put conventional afterburners on a Pegasus engine.

There are several reasons for this: the hot and cold air is separated, the inlets do not slow the airflow sufficiently for serious supersonic flight, and the jet-pipes would be too short. Conventional afterburners on a Harrier would also set fire to everything (it was tried from the 1960s and proved problematic).

This is a shame as a Harrier desperately needs thrust on take-off and could do with the ability to perform a decent high-speed dash. Though conventional afterburners are out of the question, you could, however, use plenum chamber burning (PCB). This technology was developed for the Mach 2 Hawker Siddeley P.1154, which never entered service.

PCB chucks additional fuel only into a turbofan’s cold bypass air and ignites it (a conventional afterburner puts the burning fuel into the combined cold and hot gas flows). Worried that this already eccentric idea might seem too conventional, BAe decided to add an ‘X-wing’ configuration with swept-forward wings to produce the coolest fighter concept of the 1980s

The aircraft was first proposed in mid-1943, the combination of jet engine speed and the flexible basing options of a flying boat being regarded as advantageous in the Pacific theatre. Development lagged, however, and the aircraft didn’t fly until 16 July 1947.

Three aircraft were built, two of which crashed. The simultaneous development of the Princess by Saunders-Roe contributed to the slow work on the SR.A/1, and this was compounded by the decision by Metropolitan-Vickers to cease turbojet engine production.

Although exhibiting quite sprightly performance, by the time the SR.A/1 had flown, the Pacific War was over, and there was no more need for such an aircraft. In addition, the Fleet Air Arm was operating numerous aircraft carriers, and the development of capable jet-powered, carrier-based aircraft allowed power projection without the need for airfield construction.

Additionally, of course, the large number of airfields constructed during the war also provided many basing opportunities for conventional land aircraft. The idea of water-based jet fighters did not die after this however, and the US would later create the extremely good-looking, but also equally unfortunate Convair F2Y Sea Dart.

Fast, but outpaced by changes in the threat – and in government policy – the Saunders-Roe SR.53 was proposed to meet a requirement for a point-defence interceptor capable of climbing to 60,000 feet (18,288 m) in 2 minutes and 30 seconds. The driver for this need was concern about the threat posed by Soviet bombers armed with nuclear weapons.

The SR.53 was a compact, delta-winged, mixed-power aircraft with a 1640 lb thrust Rolls-Royce Viper jet engine and a 8000 lb (3636 kg) de Havilland Spectre rocket. The armament was intended to be the Firestreak infrared air-to-air missile. The operational concept was to climb to altitude using the rocket motor, accelerate up to a maximum speed of Mach 2.2, complete a ground-guided interception and then return to base using the jet engine.

The aircraft was reported as being pleasant and easy to fly. The second prototype was lost in a fatal, aborted-take-off accident in June 1958, and the programme was eventually cancelled in July 1960, after 56 test flights. The highest speed reached in the flight-test programme was Mach 1.33 (some sources put this at Mach 1.45).

During the seven-year development, a great deal of change had occurred in aerospace capabilities: jet-engine development had produced far more powerful and reliable engines; radar had improved its ability to detect targets at long range; the Soviets had moved towards the development of standoff weapons; and surface-based guided missiles had improved in capability. These technical advances effectively invalidated the operational concept for the SR.53. 

The MB3 appeared in 1942, the result of a prudent Air Ministry decision in 1939 to obtain a powerfully armed fighter as an alternative to the Hawker Typhoon if the Typhoon programme ran into insurmountable technical difficulties or serious delays. The aircraft that emerged looked sensational, especially when the unprecedented armament of six 20-mm cannon was fitted.

Despite looking insane, it was unusually sensible: a multitude of access panels made it far easier to maintain than its contemporaries, and its tough structure (a more advanced version of the load-bearing tubular-box type favoured by Hawker) would have given it greater survivability.

It was apparently easy to handle and extremely fast. Unfortunately, we don’t know exactly how fast, because less than two weeks after the first flight the Napier Sabre engine that powered it did what Napier Sabres were doing in droves in 1942, and ceased working.

The MB3 was destroyed in the subsequent forced landing, which also killed test pilot Valentine Baker (the ‘Baker’ of Martin-Baker).  This was a serious blow to the company and affected designer James Martin (the ‘Martin’ of Martin-Baker) so much that he devoted the rest of his career to making aircraft safer by developing ejection seats, which Martin-Baker continues to produce to this day.

The Fairey Delta 2 experimental aircraft was the first aeroplane to exceed 1000mph (1,600 km/h) and in 1956 it took the World Airspeed Record to 1132mph (1,822 km/h). It was a beautifully simple design with the delta wing’s inherent advantages of low supersonic drag and great structural strength.

A year earlier, Britain’s Air Ministry had issued Operation Requirement F155T, specifying a supersonic interceptor able to intercept Mach 1.3 bombers at 60,000 feet (18,300 m). After initially proposing a modestly updated weaponised Delta 2, Fairey came forward with the mighty Delta 3 −, super-high performance interceptor with state-of-the-art technology − and won the contest.

Mixed propulsion, of jet engine and rocket, was necessary to meet the extremely demanding specification, which called for the fighter to reach 60,000 feet at a range of 70 nautical miles (130 km) from base in 6 minutes, at a speed of at least Mach 2. The maximum climb-rate would have been phenomenal, leaving even the English Electric Lightning for dust and rivalling today’s fastest climber, the Eurofighter Typhoon.

The aircraft was to be armed with two of the giant Red Dean missiles, a unit which, coming thirty years before the AMRAAM and even ten years before the AIM-54 missile, was ambitiously planned as an active-radar-guided missile. Heavy, ultra-high-performance interceptors did not prove popular in the West, however. The Fairey 3 was cancelled in 1957.

Hawker tried to turn their highly successful transonic fighter, the Hunter, into a supersonic aircraft as their offering in response to the Air Ministry’s Operational Requirement F.155. The limitations of the Hunter – the lack of air-to-air missile capability, decent enough radar and the ability to reach supersonic speeds – would be addressed by a radical redesign.

The new fighter-interceptor, the P.1103, would include a completely new fuselage and wing, a seat for the radar operator, a far more powerful engine and missile armament. To make room for the new radar, a chin intake was adopted.

Following official rejection, Hawker had faith in the design and continued with it as the self-financed P.1121. Power was to come from a single de Havilland Gyron jet engine (Hawker fighters were always single-engined) and the aircraft was to be armed with Red Top missiles, rockets and ADEN 30-mm cannon.

Maximum speed was estimated at an astonishing Mach 1.35 at sea level – and a rather more believable Mach 2.35 at higher altitudes. But the Air Staff only reluctantly reconsidered the design before again turning their noses up at it. Hawker persisted with the idea until 1958.

Despite the aforementioned crash of the MB3 in 1942 due to the failure of its Napier Sabre engine, it was apparent that the plane was worthy of further development. Martin-Baker proposed a Rolls-Royce Griffon-powered version, the MB4, but a more thorough redesign was favoured by the Air Ministry and the MB5 was the result.

A fair contender for the best British piston-engined fighter ever flown, the MB5 was well-armed (though with the less-impressive total of four, rather than six, cannon), very fast, and as easy to maintain as its predecessor. Flight trials proved it exceptional, with a top speed of 460 mph (740 km/h), brisk acceleration and docile handling.

Its cockpit layout set a gold standard for piston-engined fighters. The only thing the MB5 lacked was good timing. It first flew two weeks before the Allied landings in Normandy. Appearing at the birth of the jet age, with readily available Spitfires and Tempests, both of which were themselves excellent fighters, there was never a particularly compelling case for producing the slightly better MB5.

There is also a suggestion that the MB5 never received a production order because on the occasion it was being demonstrated to assorted dignitaries, including Winston Churchill, the engine failed. If this is true, it must rank as the worst reason for the non-procurement of an outstanding aircraft in aviation history.

The M.20 was a thoroughly sensible design, cleverly engineered to be capable of excellent performance yet being easy to produce with minimal delay at its nation’s time of greatest need. As it turned out, its nation’s need was never quite great enough for the M.20 to go into production.

Flying for the first time a mere 65 days after being commissioned by the Air Ministry, the M.20’s structure used wood throughout to minimise the aircraft’s use of potentially scarce aluminium, and the whole nose, airscrew and Merlin engine were conveniently supplied as a single, all-in-one ‘power egg’ unit, as it was already in production for the Bristol Beaufighter II.

To maintain simplicity, the M.20 dispensed with a hydraulic system, and while this meant that the landing gear wasn’t retractable, the weight saved allowed for a large internal fuel capacity and the unusually heavy armament of 12 machine guns with twice as much ammunition as either the Hurricane or the Spitfire.

The M.20 was slower than the Spitfire but faster than the Hurricane, and its operating range was roughly double that of either. Due to the M.20 being viewed as a ‘panic’ fighter – an emergency back-up if Hurricanes or Spitfires couldn’t be produced in sufficient numbers – production of the M.20 was deemed unnecessary since no serious shortage occurred of either of the existing fighters.

By the mid-1950s, it was obvious that, in the event of war, Warsaw Pact forces would quickly obliterate NATO airbases. For NATO aircraft to mount counter-attacks (some with tactical nuclear weapons), they would need to operate from rough, unprepared airstrips. This capability could turn air arms into survivable ‘guerrilla’ forces able to fight on after the apocalypse.

Vertical take-off and landing (VTOL) was also tempting to many navies, as it could eliminate the traditional hazards of carrier landing. If an aircraft could stop moving forward before it landed, the task of settling on a tiny, pitching deck would be far easier. Likewise, it could liberate ships from the need to carry enormously heavy catapult-launch systems and could even allow small ships to carry their own high-performance escort aircraft.

Hawker’s P.1154 was declared the winner of NATO’s Basic Military Requirement for a supersonic ‘jump jet’, but history repeated itself. Though nobody was tied to buying the winners of NBMR contests, it seems unfair that no country outside Britain was forthcoming in wanting to invest in the aircraft. At least Hawker still had a generous British Ministry of Defence budget to work with and the type was selected to replace RAF Hunters and the Royal Navy’s de Havilland Sea Vixens − what else could go wrong?

Two things. The first was the differing needs of the Royal Navy and the RAF. The RAF wanted a single-engined single-seater. The Navy wanted a two-seat, twin-engined aircraft. To some degree, both of the Navy’s wants may have been driven by safety regulations regarding nuclear-armed aircraft. On 2 February 1965,  P.1154 was cancelled on cost grounds.

This an abridged version of a chapter from The Hush-Kit Book of Warplanes Vol 1. Follow Joe Coles on Substack, Twitter X  or Blue Sky.

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