From Nighthawk to Spitfire
Page 19
However, the Supermarine name also had a British pedigree. It had been applied in previous times to cannons emitting fire, to angry cats, and to anyone displaying irascibility or a hot temper, especially women – as evidenced in 1762 when Lord Amherst is quoted as saying to his mistress, ‘Not so fast, I beg of you, my dear little spitfire’; and Shakespeare echoed the general sentiment when King Lear defies the elements: ‘Rumble thy bellyful! Spit, fire! Spout, rain!’
In 1778, a Royal Navy vessel was named Spitfire – a euphemistic version of Cacafuego, a Spanish treasure galleon captured by Sir Francis Drake; thereafter, the navy used the name nine other times up to 1912. It was also used in the titles of several pre-war films and thus at that time was not just a relatively obscure part of the English vocabulary. By now, the word would probably have become obsolete – had it not been for the Battle of Britain and many more wartime actions involving Mitchell’s fighter.
AFTER MITCHELL
Spitfire Mark Is of No. 19 Squadron (first to be equipped with the aircraft) and the realised bomber project. (From paintings by the author)
MITCHELL’S BOMBER AND HIS DEATH
By the early part of 1937, Mitchell was to be seen less and less at Supermarine as it had now become clear that the cancer operation of 1933 had not been a successful procedure. Yet, in the last full year of his life and, even when he was still supervising the Spitfire design, another major innovative project for a bomber had been occupying his mind.
This was in response to Air Ministry specification B.12/36, which called for a high speed, four-engined bomber with a range of 3,000 miles, capable of carrying a 14,000lb bomb load or twenty-four soldiers. It also had to be able to be broken down into component parts for transport on the existing railway system and to lift off from a 500ft runway, clearing a height of 50ft at the end. For this last purpose there was the added requirement to provide a catapult take-off capability because of the small airfields currently in use and, particularly, in order to extend the bomber’s potential range and load capacity.
At the same time, the wingspan was to be limited to no more than 100ft (in view of the transport considerations, rather than because of the size of existing hangars, as is often claimed). It also had to have a retractable ventral turret as well as nose and tail guns and had to be capable of staying afloat for several hours in the event of being forced down in the North Sea or Channel, as might be expected if the international situation did not improve.
Author’s painting, based upon Supermarine drawing No. 31600, sheet 2, and Supermarine works model.
It is interesting that Shorts and Supermarine were each awarded contracts for two prototypes rather than, for example, the Handley Page or Vickers firms which had extensive experience of the larger sort of land-based machines. But, in view of some of the Ministry requirements, it might be noted that both Supermarine and Shorts had a great deal of experience of water-resistant hulls and Supermarine had just provided the RAF and navy with the very efficient Stranraer and the catapult-stressed Walrus.
In the same month that the very positive Martlesham Heath report on K5054, the Spitfire prototype, had been received, Mitchell’s tender for the bomber was sent to the Air Ministry and must have confirmed the officials’ regard for Mitchell’s standing in the aviation industry. Despite having a proposed wingspan of 97ft, the aircraft was to make use of a single spar wing supported by torsion-resistant leading-edge boxes on a similar principle to that developed for the much smaller Spitfire. Also, unusually for its time, fuel was to be carried in these leading edges, thereby saving weight, and with the tanks adding to the rigidity of the wing. Behind this spar component, the structure allowed sufficient room for the main stowage of bombs, thus avoiding the need for conventional tiered fuselage stowage which would have substantially increased the fuselage cross section, with the attendant penalty of extra drag.
Prior to this design, the Polish PZL P37 medium bomber had made extensive use of bomb bays in the wing between the engines and the fuselage, but Mitchell’s bomb stowage arrangements in the wings was more extensive and not adopted in any of the other front-line bombers of the Second World War. Indeed, it anticipated post-war designs and was further evidence of Supermarine’s Schneider Trophy concerns to increase airframe efficiency by paying, instinctively as it were, particular attention to the reduction of frontal area. As a result, when Bomber Command officers inspected the Supermarine mock-up in October 1937 after Mitchell’s death, they were concerned about the restricted headroom throughout the fuselage; but such were the exigencies of war, and besides, Mitchell had always made reduction of frontal area one of his first priorities.
From Supermarine drawing No. 31600, sheets 5/6, showing leading edge tanks and alternative stowage of bombs: 27 × 500lb (left) and 29 × 250lb (right).
A further refinement was the proposal to place the required armament well below the eye-line of the gunners, not only giving them an improved view but also enabling a reduction in the cross section of the turret and a more rapid traverse of the guns.
Three versions of the bomber were proposed:
1 Type 316 with Bristol Hercules engines, deltoid shaped wing and single fin (see drawing p.163 and below).
2 Type 318 with Rolls-Royce Merlin engines, but otherwise similar to 316.
3 Type 317 with Bristol Hercules engines, twin fins, and wing leading and trailing edges tapering almost equally (see model illustrated below).
Photographs of two prototype fuselages, which were almost completed before they were destroyed by enemy action, do not show what fin and wing type was to be fitted. Twin fins are illustrated opposite, with the Type 317 wing, whose equal taper design would have been less complex to design and build – an important consideration at a time when a new and more formidable bomber was urgently needed. It might also be noted that Mitchell’s aerodynamicist, Beverley Shenstone, who was familiar with advanced wing theory and who was, no doubt, a strong influence on the Type 316 and 318 deltoid wing shape, left the company in 1938, and so perhaps the more conventional and less complex wing shape would most likely have prevailed.
From Supermarine drawing No. 31600, sheet 1.
A Supermarine model of the Type 317 heavy bomber. (Courtesy of Solent Sky Museum)
In November 1938, Mitchell’s team was able to submit a lighter and smaller design than their rival for the same specification and produced a set of estimated performance figures which make an intriguing comparison with published figures for the earliest marks of the most well-known British four-engined bombers of comparable size:
Aircraft
Power Rating
Range
Bomb Load
Max. Speed
Supermarine (est.)
1330hp
43,680 miles
8,000lb
330mph
Stirling I
1590hp
41,930 miles
5,000lb
260mph
Halifax BI
1145hp
41,860 miles
5,800lb
265mph
Lancaster I
1390hp
42,530 miles
7,000lb
287mph
More often than not, Supermarine estimates were actually achieved when their designs flew (one remembers the Spitfire performance when the right propeller was found), and so it will always be a matter of conjecture as to whether the extraordinarily competitive figures for Supermarine’s proposed bomber would have been attained – and at what saving of life when war did begin. After all, it was conceived at the same time as the Stirling and Halifax, but with an estimated speed close to that of the new fighters and its projected range and bomb load were also impressive.
It might, however, be maintained that, with the need for volume production – using standard gun turrets and probably being forced to add a dorsal one too – the Supermarine estimates might have been proven to be rather optimistic in respect of a production machine.
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sp; Unfortunately, the matter remains one of rueful speculation as previous lack of urgency in aircraft development resulted in the project only reaching the stage of two prototype fuselages before they were destroyed by enemy bombing.
The chief designer never lived to learn of the fate of his last projects, just as he never actually saw his Spitfire go into squadron service before the Second World War started. Towards the end of February 1937, he went into a London hospital. The prognosis was not good and a stay at the Cancer Clinic in Vienna was arranged in the April of that year. Letters testify to his dismay at not being able to continue his input into the design of the bomber, but it had become clear that this was not possible. Mitchell returned to Southampton on 25 May 1937, the very day that his first Spitfire, Type 224, was finally retired to become a ground target at the gunnery range at Orfordness. He died on 11 June, aged 42.
As he invariably gave full credit to his design staff in his speeches, it was fitting that he requested they be given first place at his funeral, and it is perhaps significant that Harry Griffiths’ recollection of Mitchell’s death prompts a memory of his relationship with this team:
On the day he died Arthur [Black, chief metallurgist] and I were standing at the bench discussing a problem when Vera Cross, R.J.’s faithful secretary over many years, came in and just said, ‘It’s all over’. Arthur looked at me and shook his head then he turned away and was silent for a long time.
At the annual dinner that year we stood in silence in his memory and then drank a toast: ‘To a very gallant gentleman.’
The Christmas before his untimely death he arrived late for the annual design staff dinner, and in spite of a place having been kept for him at the head of the table he insisted on sitting at the other end with us lads and sharing a joke and some wine.
THE SPITFIRE AFTER MITCHELL
Before his death, Mitchell had had the satisfaction of attending the Vickers Press Day, where his Scapa, Walrus, Spitfire and Stranraer were all on display together. With the last three, he had produced respectively the slowest and the fastest aircraft in the RAF and the fastest biplane flying boat. Following the orders for the fifteen production Scapas and seventeen Stranraers, he then saw his company receive the orders for a total of 217 Walruses and 310 Spitfires. Here was a fitting epitaph for a designer, but he could not have imagined the extent of the future wartime requirements and varied duties of these last two aircraft, particularly the Spitfire.
Soon after the death of Mitchell, Joe Smith moved from the post of chief draughtsman to that of chief designer and the credit for fully realising the potential of Mitchell’s fighter design must go to him and his team.
Joe Smith. (Courtesy of Solent Sky Museum)
Nearly thirty main variants of the Spitfire, as well as numerous modifications, followed from Mitchell’s prototype, and it is a measure of the contribution of Smith and the design team to the war effort that an average of over four distinct marks of Spitfire per year were developed.
Whether Mitchell would have pursued a similar course with these modifications, or if he would have pressed the Air Ministry for a completely new design must always remain a matter of speculation. Certainly the pressures of war would not encourage the tooling-up necessary for a new type as long as modifications of existing aircraft could conceivably meet the changing wartime requirements. As Smith said, justifying his continuous modifications to the Spitfire Type, ‘the hard school of war leaves no room for sentimental attachments and the efficiency of the machine as a fighter weapon is the only criterion’.
Shortly after the Hurricane entered service, Hawker had had to begin work on a new design because their current fighter did not have the potential for further development – producing the Tornado, which eventually emerged as the Typhoon and the Tempest. Joe Smith, on the other hand, had faith in the development potential of Mitchell’s design, saying that it would ‘see us through the war’. His Schneider Trophy experience of developing the 900hp S5 into the similar, slightly larger, 1,900hp S6 and then into the strengthened 2,350hp S6B must surely have pointed the way.
Quill identifies one other particular event that might very well have been of considerable influence upon Smith’s faith in the long-term potential of Mitchell’s design – Supermarine’s planned attempt on the World Land Speed record then held by the Howard Hughes’ H-I racer. Compared with the current Mark I aircraft’s 367mph (with a Merlin II rated at 990hp), a specially prepared Spitfire airframe and a specially rated Merlin engine (developing 2,000hp) was estimated to achieve a top speed of 425mph at sea level.
However, the venture was abandoned after Germany increased the record to 463mph. Nevertheless, Quill is surely correct that the attempt must have had a definite influence on Smith’s thinking, and J.D. Scott wrote in his history of Vickers, ‘By 1940 Joe Smith … had reached the conclusion that the Spitfire design was capable of the most extensive, and indeed of almost infinite, development.’ The various marks of Spitfire demonstrated that this was the case, to the extent that Rolls-Royce, when designing the Griffon engine to succeed the Merlin, tailored the new engine to fit the existing fighter’s airframe.
Joe Smith’s persistence with Spitfire modifications was vital to the war effort, not only because of problems with the initial Hurricane replacement, the Typhoon, but also because deliveries of the formidable Tempest only began in October 1943. Even then, the latter’s top speed was not better than the Spitfire Mark XIV, which could achieve 447mph thanks to the newly employed Griffon engine.
Of course, there were economies of type development – a new mark of an existing aircraft, however radical, required much less time and effort to design than a brand new type. Woolston quotes Vickers’ figures, which revealed that no later mark required more man-hours spent on design than on the Spitfire Mark I. The highest number was 165,000 man-hours devoted to the Spitfire 21, compared with 330,000 man-hours on the far less complex Mark I – with the average time per mark being about 41,000 hours.
In terms of performance figures, the extent of the developments achieved by Joe Smith and his team can be summarised by the following comparison between the first and the last production versions:
Spitfire Mark I
Seafire 47
Maximum speed
362mph
452mph
Engine power
1050hp
2350hp
Fuel capacity
85gal
287gal (inc. 90gal drop tank)
Normal loaded weight
5820lb
10,300lb
Wing loading
24lb/sq. ft
42.2lb/sq. ft
Service ceiling
31,500ft
43,100ft
Maximum range
575 miles
1,475 miles
Climb to 20,000ft
9.4 min
4.8 min
Rate of roll at 400mph
14 degrees/sec.
68 degrees/sec.
Maximum diving speed
450mph
500mph
In the course of this development, the weight of ammunition carried had almost doubled, and that of the protective armour now amounted to more than the weight of an average pilot. Indeed, Jeffrey Quill has calculated that, at its maximum gross take-off weight, the Seafire 47 was equivalent to a Mark I Spitfire with the additional load of thirty-two ‘airline standard’ passengers each with 40lb of baggage.
While the extraordinary development of Mitchell’s ‘basic’ fighter is well illustrated by the above, it would not be realistic to give too triumphal an account of the Spitfire’s development. Many modifications were rather desperate attempts to avoid the production of a completely new type. Jeffrey Quill, who had by far the most extensive experience of testing the various Spitfire types, has written that almost every design change, with the urgency of wartime demands, produced problems with flight handling.
The first production Mark I, Eastleigh, May 1938. (Courtesy
of E.B. Morgan)
A well-laden Seafire 47, c. 1949. (Courtesy of E.B. Morgan)
Some of the factors which most affected controllability were the progressive increase in speed and weight, in propeller blade area (‘propeller solidity’), and in moments of inertia due to the redistribution of increasing weights, usually in terms of longitudinal or directional stability. Solutions were often inelegant even though usually effective.
There was also the major problem of converting the Spitfire into the Seafire for aircraft carrier operation, as the comparatively fragile land fighter had hardly been designed for the rigours of the ‘controlled accidents’ of landing on the pitching decks of aircraft carriers. And one particular photographic reconnaissance conversion also had its problems: the PRD/Mark IV version was found to be incapable of flying straight and level for the first half hour after take-off because of the necessary disposition of its very heavy fuel load.
But, to end on a more positive note, most photo-reconnaissance versions of the Spitfire were far less problematical, and many versions of the fighter were regarded as exceptional aircraft. In particular, perhaps the best fighter, from a handling point of view, was the Mark VIII; the most successful high-altitude fighter was the Mark XIV; the most outstanding PR (photo-reconnaissance) variant, the PR19; and the most complete naval version, the Seafire 47.