To the late Rear Admiral Maitland W.S. Boucher DSO, Royal Navy [at that time serving in the Naval Air Division], goes the initiative for the introduction to the Fleet Air Arm of this somewhat improbable looking, yet highly successful flying machine.
He said to me one day in late 1933, ‘I’ve just been to Supermarines. I’ve seen a small amphibian. It looks handy, tough and versatile … something the navy needs. I want you to put it through its service trials. Off you go.’ With a Supermarine Southampton flying boat course at Calshot and some tests at Felixstowe intervening, off I went to Woolston to collect Seagull V N2 early in 1934.
Caspar John, son of the artist Augustus John and later Admiral of the Fleet, took the Seagull to Gibraltar for rough weather take-offs and landings and for fleet co-operation exercises, after which it was described as ‘the complete answer to our prayers’.
Thereafter, N2 was purchased by the Air Ministry, renumbered K4797, and on New Year’s Day 1935 it was handed over to the Fleet Air Arm for a short series of official acceptance trials. As the prototype had first flown in June 1933, it is clear that the Admiralty had needed some time to be convinced that open sea and catapult operation from their capital ships would work smoothly. No doubt the Australian initiative helped to overcome any doubters, and an initial British order was placed on 18 May for twelve aircraft.
The first machine of the 1934 Australian order flew on 25 June 1935, and after a further eleven had been completed, the Air Ministry took delivery of their first batch. The rest of the Australian order was then completed, along with a second batch of eight for the Air Ministry, and the developing international situation then contributed to a much larger order for twenty-eight.
A name was now to be chosen for the British machine, unlike those for Australia which retained the Seagull V appellation. In the past, Supermarine amphibians had been favoured mainly with ‘nice’ seabird names: Sea Eagle, Seagull, Sheldrake, Seamew, and so on, while the name Sea Lion was a nod in the direction of the engine used. It is an interesting comment on this latest amphibian’s ‘somewhat improbable’ appearance that the far less glamorous name ‘Walrus’ was now chosen.
Nevertheless, it was not only the first British aircraft to be catapulted with a full military load but it was also the first British designed military aircraft with a retracting undercarriage. Only a few months earlier, Admiral Sir Roger Backhouse had received a ducking when the prototype Walrus, being used as his ‘barge’, was landed in the sea with the undercarriage still down and turned turtle. After that, the Walrus was fitted with a horn to warn pilots of what was then a novel feature.
The original batches of forty-eight aircraft ordered for the navy was increased dramatically in 1936 with the requirement for another 168 machines. Despite its initially very doubtful future and its backwards-looking appearance, the Walrus became the last and the most successful of all Mitchell’s reconnaissance amphibians and the navy’s standard wartime fleet spotter.
PERSPECTIVES ON
THE SPITFIRE
The Spitfire prototype and Type 224. (From paintings by the author)
BRITISH FIGHTERS BEFORE
THE SPITFIRE
In order to appreciate the significant advance in design represented by Mitchell’s Spitfire, it is necessary to look back at the RAF fighters that came before it. The aircraft of the two decades after the end of the First World War were, almost without exception, biplanes with fixed undercarriages and powered by radial, air-cooled engines. However, the drag penalty of this type of machine, with its attendant struts and wires, began to have an increasingly inhibiting effect on performance. The drag of a particular airframe increases exponentially in relation to an increase in its speed – to double an aircraft’s speed would, theoretically, require four times its engine power (see the table on p.147, which includes details of the gradually increasing discrepancy between increases in engine power and speed in aircraft of this period).
One notable exception to the general pattern of fighter development was the Hawker Fury which, in 1931, showed a 16 per cent speed increase over the Bristol Bulldog for only 7 per cent more power – the result, in particular, of using a closely cowled, in-line, water-cooled engine. The Hawker Hornet, its predecessor, had already shown the advantage of such a power unit, but the new Air Ministry specification, F.7/30, gave no specific steer towards any particular engine configuration – contrary to the impression given by the employment of the in-line Rolls-Royce Goshawk engine in five of the competing designs, including Mitchell’s.
The Gloster Gamecock, which entered squadron service in 1926, had a top speed of 155mph and the Bristol Bulldog of 1929 was only about 20mph faster – an average increase of about 7mph per year. Thus, in 1931, when the Air Ministry released its new fighter requirement, no more than, say, 185mph might be expected if manufacturers responded to the new specification with the usual biplane configuration, air-cooled radial engine, and fixed undercarriage. It can therefore be seen that F.7/30, which was issued for the replacement of the Bulldog and which eventually led to the Spitfire, represented a significant challenge (although tempered by realism) to an unadventurous aircraft industry. The new type was required to have a top speed of ‘not less than 195mph’ while carrying double the number of guns.
The RAF had begun large-scale air exercises in 1927 and, as a result, it was appreciated how the biplane formula limited the fighter pilot’s view of ‘invading’ bombers. In this respect, the F.7/30 requirement was quite specific: ‘the pilot must have a clear view forward and upward’ and ‘particular care is needed to prevent his view of hostile aircraft being blanked out by top planes and centre sections’. One suspects a strong hint that monoplane prototypes might be welcome, but it is a reflection of the 1930 design scene that only three of the eventual eight entries were not biplanes. Mitchell’s machine was, unsurprisingly, a monoplane, but the only aircraft that was submitted with a retracting undercarriage was not his. Again, there had been no specific Ministry requirement in this respect.
It might be that certain omissions or limitations of F.7/30 are more obvious in hindsight, but it is still evident that it was something of a milestone in Ministry thinking, that it was feeling its way towards a new approach to fighter design. In summary, the specification called for a four-gun, single-seat day and night fighter with manoeuvrability and a ‘fighting view’, a speed of not less than 195mph at 15,000ft, a landing speed not more than 60mph, and a climb to 15,000ft in eight and a half minutes. Satisfying this 1930 requirement was unlikely to be easily achieved, especially as a low landing speed consideration for a night fighter might very well inhibit the design of a high speed machine otherwise dedicated to daytime flying.
Additionally, the choice of the new water-cooled, in-line, Goshawk engine did not help despite being predicted to produce 660hp (compared with the 450hp of the Bristol Jupiter VII radial engine of the Bulldog). This engine was designed to work with a new water cooling system, the so-called evaporative method, which was expected to bring with it significant reductions in drag – by not requiring conventional radiators to keep the engine coolant below boiling point. The water in the engine was kept under pressure by pumps, allowing it to heat to temperatures above 100°C and then the superheated water was released to turn to steam in a suitable container, with sides exposed to the airflow, where it would condense on cooling and be returned to the engine. The greater efficiency of this cooling method would therefore require an aircraft to carry less water and could operate via, and under, the skin of the aircraft, resulting in a zero-drag cooling system.
In practice, it was found that the steam condensers of the F.7/30 Westland entry could not cope with varying flight and atmospheric conditions, and the Blackburn prototype exceeded maximum temperatures within a few minutes. Additionally, the latter had ground handling problems, caused by its high centre of gravity, and never flew, thus justifying the opinion of its test pilot, ‘Dasher’ Blake, that ‘the little beast has no future’.
Two
other prototypes powered by the Goshawk engine, the Hawker PV 3 and the Bristol Type 123, fared little better. Type 123 encountered initial cooling problems and was also laterally unstable and was withdrawn. The Hawker entry (essentially, a re-engined Fury) paid only a brief visit to Martlesham owing to its unsatisfactory cooling system. (The similar cooling problems which dogged Mitchell’s Type 224 entry will be discussed in the next chapter.)
There were other disappointments. The top speed of the Westland entry was only 146mph and it took nearly nineteen minutes to reach 20,000ft (in appearance, it had some similarities with the company’s army co-operation Lysander, especially in the cockpit area, but this was hardly a recommendation for a fighter proposal). It would appear to have been unduly influenced by the F.7/30 concern for a good pilot position, as did the Blackburn entry, and like the Hawker and Bristol machines, both were basically conventional biplanes with fixed undercarriages.
Of the two monoplane rivals to Mitchell’s Type 224 entry, the Vickers Type 151 Jockey was 10mph slower and proposals to re-engine it came to nothing when the sole prototype was lost to a flat spin in June 1932. But at least the other monoplane might very well have attracted favourable Ministry support, instead of the Spitfire. Bristol decided to improve upon its Type 123 entry by substituting the Goshawk for a Bristol Mercury engine. This new Type 133 was a considerable improvement on its predecessor in other ways: despite now having an air-cooled engine, it was the first proposed RAF fighter with retractable wheels, and its stressed-skin construction, employing the recently invented Alclad sheeting, allowed for the design of a forward-looking cantilever monoplane. Its test pilot, Cyril Uwins, was very impressed by its performance and the top speed of 260mph but, when the aircraft was almost ready to go for competitive tests at Martlesham Heath, it also entered into a flat spin which was irrecoverable and the test pilot had to abandon another one-and-only prototype.
The surviving monoplane entry, Mitchell’s Type 224, ought to have had a competitive performance, thanks to Mitchell’s obsessive concern to keep frontal area to a minimum and its being a cantilever monoplane, but, apart from the problematic evaporative cooling system, it had the greatest wingspan and therein lay its main problem – as will be seen next.
MITCHELL’S STUKA – THE
FIRST SPITFIRE
Mitchell’s engagement with the land-based fighter concept began almost at the same time as the last of his Schneider Trophy racers was built. Thus, Mitchell’s qualifications for creating high speed aircraft were outstanding but, as we shall see, much of the under-performance of his first attempt at a fighter was not of Mitchell’s making. Equally, its genesis contradicts any assumption that the Spitfire developed directly from his Schneider Trophy machines or rose by some single conceptual leap after the designer returned to work at the end of 1933, following his operation for cancer.
As it was, in 1931 when the Ministry specification appeared, Mitchell had had to turn his mind to a military aspect of aviation that he had only briefly been engaged upon with the Sea King II of 1921 – and that aircraft was a flying boat, albeit a fast and manoeuvrable one at the time. Additionally, armament on his slower reconnaissance flying boats was provided via gunners in cockpits not via guns which would now probably need to be buried in the wings.
Alan Clifton recalled that Mitchell was uneasy about ‘his first venture into military aircraft’, recognising that he was ‘no expert in the field’. Thus, with typical pragmatism, he asked ‘Mutt’ Summers, Vickers’ chief test pilot, to arrange a visit to the Martlesham test centre to find out what RAF pilots considered to be most important in a fighting machine.
Type 224
Mitchell’s resultant design, Type 224, was an all-metal structure with a thick cantilever, inverted, gull wing and a short fixed undercarriage with large fairings (hence the comparison with the Junkers Stuka – see below).
Supermarine’s submission to the Air Ministry pointed out how this cranked wing configuration would produce a short, low drag undercarriage with a wide track for easy taxiing, and give ‘exceptional’ visibility for the pilot. An inverted gull wing and fixed undercarriage configuration meant that the latter would be reasonably short and light and would also help to satisfy the F.7/30 armament requirement – two of the four guns could be housed in the undercarriage fairings (the leading edges of the wings were to incorporate radiators for the evaporative engine cooling system). In addition, tanks to collect the condensed water coolant could be fitted low down in these fairings.
A large air brake was employed which could be lowered from the underside of the fuselage but nevertheless the Air Ministry, concerned about night operation and small, grass field landing strips, felt that the estimated wing loading of only 15lb per sq. ft was too high (Mitchell’s S6B loading had been 42lbs per sq. ft). Therefore, the wing was eventually drawn up with a generous 45ft 10in span which, in combination with a fuselage about the same length as that of the 28ft 10in span Schneider floatplane, looked somewhat out of proportion.
Type 224, at the 1934 RAF display, Hendon. (Courtesy of E.B. Morgan)
Type 224 first flew on 19 February 1933 and, unfortunately, it was found that the low pressure side of the pumps for the cooling system would often allow the coolant to turn into steam again, particularly during rapid climbs. (Mitchell’s early apprenticeship to a locomotive manufacturer did not include high-altitude problems!) Jeffrey Quill has recorded how he did not exactly please the chief designer when he commented on the situation:
I said that with the red [warning] lights flashing on all over the place, one had to be a plumber to understand what was going on. He didn’t say anything, he just looked very sour. He was rather sensitive about the aeroplane and obviously I had trodden on his toes.
Mitchell, understandably, was less than pleased when the pilot had to level off until all was working normally again, thus defeating the F.7/30 requirement of the fastest possible climb to intercept enemy bombers.
Apart from the cooling problems, the top speed of Type 224 also proved to be a disappointment and so, when Mitchell returned to work after his operation, modifications were proposed, including a retractable undercarriage, and elimination of the cranked wing. These proposals were submitted in July 1934 and were expected to improve the maximum speed of Type 224 by 30mph, but none were implemented and no further prototype was ordered. Test flying continued, and Vickers even named the aircraft ‘Spitfire’, but the way forward was unlikely to be with an unsatisfactory cooling system and with the conflicting Ministry requirements of slow speed landing performance and fighter agility.
The Junkers Ju 87B Stuka with early ‘trousered’ undercarriage.
Meanwhile, Junkers were producing the similarly configured Stuka. Because it was designed as a two-seater, the German machine had a much larger cockpit canopy but it notably featured an inverted cranked wing and fixed undercarriage; in the case of the early models, the wheels were similarly encased (see photograph opposite). It first flew on 17 September 1935 and, a year later, Blohm und Voss produced their Ha137, a fighter type which also had a cranked wing and a ‘trousered’ undercarriage.
This similarity can also be seen in the Kawasaki Ki-5 – not surprisingly, as it came from the same designer. Like the Type 224, it first flew in February 1934, thus showing that there was nothing derivative or eccentric about Mitchell’s basic approach, even if other factors had militated against it. The Japanese fighter had a span about 11ft shorter and, with over 200hp more, could reach 240mph – about 10mph faster than the Supermarine prototype. The Blohm and Voss Ha137 first flew thirteen months later and the in-line-engined versions reached a maximum speed of 205mph with a 610hp engine. Again, the span was about 9ft less than that of the Type 224.
Despite Mitchell’s disappointment with his fighter, it can be seen that its top speed of 228mph was actually quite creditable for its 600hp engine power, and the imposed penalty of the much larger wingspan – the other aircraft mentioned above averaged about 2ft longer than Type
224, while being about 7ft less in wingspan.
The Kawasaki Ki-5.
Thus, while Mitchell’s chosen configuration of a cranked wing and a short fixed undercarriage was not an eccentric choice, nor derived from other aircraft, the landing speed restriction must have been one of the main reasons why the Vickers chairman instructed Mitchell to design a private venture aircraft, the future Spitfire, without any ‘interference’ from the Air Ministry (see next).
THE REAL SPITFIRE – A CLOSE
RUN THING
Despite Mitchell’s success in the final three Schneider Trophy contests, it had begun to appear that Supermarine might not do equally well in producing a winning land plane fighter.
For example, when Mitchell’s first fighter design, the Type 224 ‘Spitfire’, was failing to satisfy the Air Ministry F.7/30 specification, there was the other machine of forward-looking design which might very well have attracted favourable Ministry support instead. The Bristol Type 133 was another monoplane and was also the first British fighter design with both retractable wheels and stressed-skin construction. It had a more streamlined sliding cockpit canopy and the wing roots were aerodynamically faired into the fuselage with fillets (which Mitchell had only experimented with during the later days of Type 224).
However, as mentioned previously, the one-and-only prototype crashed and so time was available for Supermarine to try to improve upon their proposal – although, in view of the British manufacturers’ disappointing responses to F.7/30, there was even talk in the Ministry of purchasing Poland’s all-metal monoplane, the PZL P24. This monoplane was faster than any of the British prototypes and many were equipped with the more impressive firepower of two cannons, as well as two machine guns.
From Nighthawk to Spitfire Page 16
