The specifications N.8/39 and N.9/39 must quite possibly rate as the most convoluted in the history of naval aviation. These two ‘sister’ requirements for naval fighters were first discussed in March 1939 and released to the industry in June of that year – but of the two designs that eventually resulted, one took nearly five years to get into service and the other missed the war altogether in terms of frontline service. Neither became operational in the originally intended role as fleet fighter, and both had switched to an emphasis on strike activities.

The two specifications were offered as direct replacements for the Blackburn Skua reconnaissance fighter (and its own stop-gap replacement, the Fairey Fulmar) and Blackburn Roc turret fighter. At the time the specifications were issued, the Skua and Roc had not seen combat, and the Fulmar was still a year and a half away from entering service. Crucially, none of the combat experience that was to have such a dramatic effect on naval fighter doctrine had yet been gained.

As a result, the Admiralty was still firmly wedded to the idea of a two-seat fighter. Both aircraft were expected to have a top speed of not less than 317mph (275 knots). The conventional two-seater was to be armed with eight 0.303in machine guns or four 20mm cannon, while the turret fighter must have a four-gun powered-turret as its main weaponry.

Westland, Hawker, Gloster, Blackburn, Supermarine and Fairey responded to the specifications. All offered designs to both requirements except Supermarine, which only tendered for the conventional two-seater – although Westland dropped out when its request for more time was refused. The deadline for submissions was the 15 September 1940, and the proposals were passed to the Royal Aircraft Establishment (RAE) for assessment.

All the submissions were low-wing monoplanes, but there were considerable differences within this layout.

First prototype Blackburn Firebrand DD804. The Firebrand emerged after a large scale redesign of Blackburn’s original, unconventional proposal

Fairey’s design for both specifications owed a great deal to the Fulmar, both types resembling a smaller, cleaned-up version of the earlier aircraft with simplified wing-fold and a variety of different engine installations.

This was unsurprising, as Marcelle Lobelle (designer of the Battle, P.4/34 light bomber and Fulmar) was also the lead designer on the N.8/39 and N.9/39 projects. The variety in engines proposed for a single design is surprising – these ranged from the small 1,302lb,1,050hp Bristol Taurus radial to the huge 2,360lb, 2,000+hp Napier Sabre.

The Supermarine design, the Type 333 showed Spitfire ancestry with its sophisticated streamlining, but with the wing planform considerably simplified from the iconic elliptical shape. Some of the characteristics of the elliptical wing were retained, but with a straight trailing edge and a cranked leading edge. Supermarine actually offered two differing types to the same specification, although essentially these were the same design but one was slightly bigger. The smaller was to be powered by a Rolls Royce Merlin with a similar installation to the Spitfire MkI, and the larger design was to be powered by a Rolls Royce Griffon.

The design team at Blackburn no doubt felt that there was more development potential to come from its previous designs. Therefore when the two requirements were issued, Blackburn submitted a design which owed much to the Skua/Roc. The two designs were structurally identical to the existing aircraft but incorporated some surprising innovations, and lessons learned from the Skua. Blackburn specified a 1,500 horsepower Bristol Hercules for the N.8/39 and N.9/39, countering the Skua’s greatest weakness – lack of power.

Of most surprise to the RAE was the ‘low-drag fixed undercarriage,’ which they felt was of ‘special interest’. The Dowty-lever type legs (themselves quite unproven at the time) were shrouded by aerodynamic covers and could be jettisoned in their entirety. Blackburn evidently wished to dispense with the reliability problems associated with retractable undercarriage and felt that the much simpler fixed units would help to keep serviceability high on long cruises in hostile conditions.

Most of the design submissions had unconventional tails. This was partly to get around the maximum folded width of 13’6” which caused difficulties for all the manufacturers, being 2’ narrower than the Skua which was already very compact when folded. Hawker, Gloster and Fairey tried various ways of folding the tail planes, while Supermarine tried to get away with a very small conventional tail within the width specified. Blackburn sought to get around the problem with a short-span, low aspect ratio tail plane with twin fins and rudders on the ends which increased the efficiency of the short tail plane and elevators through ‘end-plate’ effect.

The Blackburn N.8/39 gave particular attention to visibility for the observer (which the RAE noted was at the expense of performance) by pinching in the fuselage around the rear cockpit. A further area of emphasis was landing speed. The RAE noted that Blackburn had employed their own slotted flap ‘on which a considerable amount of wind tunnel work has already been done’. This was a development of the Skua flap which incorporated a much larger area of the lower surface of the wing and extended to the trailing edge, forming a slot as it deployed. Unfortunately, no drawings survive of the Blackburn design – it is fascinating to consider what it might have looked like.

Westland, Hawker and Gloster also submitted designs, but little is known of their tenders.

Ultimately the RAE preferred the aerodynamically uncompromising Supermarine despite concerns about its handling and safety – its small tail, designed to get around the specification’s tight width restriction, did not promise to offer the excellent low-speed control necessary for naval aircraft. Other designs had over-emphasised practicality over performance. The Supermarine, on the other hand, while potentially offering high performance, might not have sufficiently good control and the company had not offered enough detail in some areas to be sure that it was able to solve some of the significant practical problems associated with naval aviation.

Early production Firefly F.1 Z2030 at Ringway. The Firefly went into service after the idea of a two-seat fighter had been largely dismissed. Image RuthAS Wikicommons

The necessary folding wing raised some difficulties. Blackburn was one of the few British companies that had designed an aircraft with a folding wing, and their proposal for the N.8/39 and N.9/39 requirements were practical and sound. The submissions from some other companies, however, suggested they had not fully understood the problems associated with this design feature. Supermarine gave cause for concern and Hawker and Fairey providing insufficient detail. Several of the designs, such as the Gloster and Fairey, proposed to follow Blackburn practice.

The Admiralty and Air Ministry were unhappy with all the responses, and were beginning to turn their mind to higher performance single seat fighters. The first few months of war had shown that the performance of two-seat fighters might not be up to scratch, and some single-seaters would be required. The Roc had already proved itself largely useless. The full range of naval aviation problems still existed though. The Admiralty revised the specification and asked for higher performance single and two seat versions of N.8/39 while the turret fighter N.9/39 was shelved. A revised specification was issued in January 1940.

Somewhat optimistically, the Admiralty felt that asking for both two-seat and single-seat versions of the same basic design would speed development and ease production. In reality, it would compromise all the designs as to create the single-seater, it was necessary to design an aircraft that was large and bulky enough to be a two-seater, but with second cockpit simply deleted.

The specification was undoubtedly ambitious. It required an aircraft with greater top speed than any single-seater yet in British service, yet still requiring good deck landing capabilities and all the equipment and design features of naval aircraft, such as folding wings, catapult spools and arrester gear. The Admiralty wanted the single-seat version to be capable of 385mph (330 knots) and the two-seater to reach 350mph (300 knots) at 15,000ft.

The designers went back to the drawing board and came up with some markedly different solutions. Some threw out their previous designs and started from scratch. Supermarine, for example, simply offered a Griffon-powered naval development of the Spitfire.

The Fairey designs were also largely new, as Marcelle Lobelle had left the company and been replaced by Herbert ‘Charlie’ Chaplin. Chaplin had elected not to continue working with the design proposals developed so far, but to start again with the best design he could produce within the constraints of the requirement. The new design had elliptical wings, replacing the earlier straight-tapered planes, and was cleaner aerodynamically. Instead of a long glass-house canopy, the observer’s cockpit was recessed into the fuselage on the two-seater. The design was offered with either Sabre or Griffon, but Fairey pointed out that the take-off characteristics would be marginal with the Sabre.

Unlike most of the designs, Chaplin started with the single-seater and adapted it to incorporate a second cockpit, although in reality the aircraft was larger than a purely single-seat design would have needed to be.

Westland took advantage of the resubmission to join the tender process again, though as with the earlier design, little is known about Westland’s revised tender. The same is true of Gloster’s design, though it is known to be straightforward, with slotted flaps and ‘flaperons’ helping to maintain control during deck-landing.

Hawker’s new design used a Griffon, and was structurally similar to the Hurricane. (All the other designs were all-metal, stressed-skin structures). It used wing slots and slotted flaps to ensure good slow-flying characteristics.

Blackburn took the earlier criticism to heart and produced a much cleaner design with retractable undercarriage and a conventional tail. However, the wing flap arrangement was now even more radical, with full span slotted flaps and spoiler type ailerons which slid out of the wing’s upper surface. It was still powered by a Hercules.

The RAE was again very interested in this layout suggesting that it could potentially result in smaller, more efficient wings for high speed in flight but which could still give low landing speed and high controllability necessary for carrier landings. The Air Ministry was sufficiently impressed to order a small number of the Blackburn design to assess the wing layout, albeit in a less extreme form – partial span flaps and conventional ailerons. At this stage the design still had the Hercules engine. Although a single-seater, the design had evolved from a two-seater and as a consequence was larger than the ideal.

The RAE and Admiralty felt that the Fairey Griffon-powered offering was the best, and that 200 of the two-seat version would be ordered. The Norwegian Campaign had not yet taken place, and the Admiralty was beginning to feel that two-seat fighters might be sufficient for its needs after all, expecially with the Fairey’s projected top speed of 328mph.

However, the Admiralty was concerned that Fairey was taking on too great a proportion of the Fleet Air Arm’s aircraft design and production. It was felt that this could lead to a narrowing of the design talent focussing on naval aviation problems, and could also lead to other manufacturers losing interest in naval aircraft. In addition, the Blackburn design for full-span flaps and ‘spoilerons’ was attractive as a possible solution for combining good low-speed characteristics without a large, lightly-loaded but drag-inducing wing. Therefore 25 examples of the single-seat Blackburn design were ordered as an experiment.

Blackburn ‘Firecrest’ VF172 – another ill-fated Firebrand development

The Admiralty had already completely scrapped one set of designs and required another series of proposals, which were already compromised by the short turnaround time and the fact that the requirements were based on the earlier, flawed specifications. Their Lordships had changed their minds several times during the proposals, dropping the turret fighter and asking for a single seater. Now, they had dropped the idea of developing a single-seater from the same design.

Nevertheless, if matters had been left here, the outcome might not have been as disastrous as it was. Still, the meddling continued. The Admiralty had been disappointed not to have a really good Sabre-powered proposal, so the experimental Blackburn design was switched from the radial Hercules to the troublesome, liquid-cooled Sabre.

The idea of a small production run of experimental aircraft was then slowly evolved into a requirement for a combat aircraft. The most interesting aspects of the Blackburn design – its full-span flaps and spoiler ailerons – were shelved in favour of conventional ailerons and partial span slotted flaps.

The Fairey type was resubmitted to a new specification, N.5/40, which had been written around it. Its development was not especially tortuous. However, the build up into production was slow, partly because Fairey had understimated the number of machine tools it would need for its various production contracts, and rectifying this in wartime took time. The new aircraft, named Firefly, first flew in December 1941 and after 12 months only 20 aircraft had been produced. Its performance was slightly disappointing too in MkI form, with a top speed only just over 300mph. A considerably improved version with wing-root radiators and a more powerful Griffon missed the war.

The Blackburn type, now named Firebrand, flew in February 1942. It was reasonably fast, at 358mph, but was big, heavy and lacked agility – though it was able to out-dive a Spitfire during mock combat. It was modified to become a torpedo bomber and strike fighter, and was actually fully aerobatic even with a torpedo attached. Further design changes involved modified flaps and dive brakes on the wings. A second line squadron of Firebrands was established to explore tactical uses for the aircraft, and its various handling difficulties were slowly ironed out. There were more problems ahead though.

Problems with the Sabre and the ringfencing of the engine for Typhoons meant that the aircraft had to be redesigned to accept a Bristol Centaurus (ironically, an 18-cylinder development of the Hercules that the aircraft was originally designed for). This knocked back the testing and called for a major redesign of both the nose and the tail.

Eventually, by the fourth design mark, the Firebrand was felt to be fit for service. Even then, it was a difficult aircraft to fly and the two frontline squadrons were largely manned by qualified instructors. The Firebrand took part in several NATO exercises, though it missed out on combat action – the Royal Navy preferred to take Sea Furies to Korea in the strike-fighter role.

The Firefly did some useful work, as a strike fighter in the last two years of WW2 and later in Korea and the Malayan Emergency. It was able to carry out ground strikes, anti-shipping attacks and later anti-submarine work. Its long range and load-carrying was a boon compared with converted landplane designs (it could carry a full load of rocket projectiles and drop tanks). It even won some air-to-air plaudits, being able to out-turn Japanese Oscars and Zeroes and tear most enemy aircraft to shreds with its four 20mm cannon.

The Fleet Air Arm ended up with a large single-seater which had been developed from a two-seater design, and a smaller, lighter two-seater which had been developed from a single-seat design. Neither were suitable as a fleet defence and air-superiority fighter, and both took far too long to get into service in their definitive forms.

Fortunately, it seemed that the Admiralty was able to learn from its mistakes and by the end of the war was able to develop fighter specifications that led to capable aircraft such as the Hawker Sea Fury and later Sea Hawk. It was not all plain sailing – the programme that led to the Firebrand’s replacement, the Westland Wyvern, made that of the earlier aircaft look smooth. Blackburn had its own problems with the ‘Firecrest’, a strike fighter developed from the Firebrand which had as many difficulties as the Firebrand and died a natural death as a result of the end of hostilities and the jet age.

Still, the Firefly was an excellent fighter-bomber, and the Firebrand does not look like such a bizarre development when compared to several contemporary programmes in America. Numerous large, powerful naval strike aircraft were under development by the war’s end, including the Martin Mauler, Boeing XFB8 and Curtiss XBTC – all conceptually similar to the Firebrand. None of these had glittering service careers except the similar Douglas AD (later A-1) Skyraider. This became a popular, capable and long-lived attack aircraft that demonstrated what a well-sorted Firebrand might have been capable of.