Saturday, 30 June 2012

R.J.Mitchell's Walrus – 'he looped the bloody thing'

Supermarine Seagull III (from painting by author)
The Walrus  owed its origin to a 1933 Australian order for a replacement for the Supermarine Seagull IIIs which the Royal Australian Air Force had been operating since 1926.
In view of the deck landing limitations and porpoising characteristics of the obsolescent Seagull [see my Blopost:"Precursors of R.J. Mitchell's Walrus"], the new machine would have to be a complete re-design – and so the move to metal structures, slab-sided fuselages, and the experience of the intervening years, produced a quite distinct type within the older formula.
   One important example of the re-design was the employment of a fully retracting undercarriage, for the first time. A more obvious aspect of the redesign of the Seagull predecessor was the hull – it now shared the more aggressive, slab-sided, features of the Scapa and the later Stranraer but did not have their upward sweep to the tail unit. But, whilst the direct attachment of the lower wings to the hull was similar to these two aircraft, the upper centre section had a less than tidy trailing edge, as it had to be cut back for clearance of the pusher propeller and cut back again for the folding-wing arrangement. The engine nacelle also contributed to the somewhat ‘minimalist’ appearance of the new design by being quite noticeably off-set to counteract the corkscrew pressure of the propeller slipstream on the fin.
Supermarine Seagull V/Walrus from a painting by the author
   Thus the new machine was clearly no beauty and when, in June 1933, the prototype was seen by the Air Ministry Director of Technical Development, he said to Clifton: ‘Very interesting; but of course we have no requirement for anything like this’. Perhaps this reaction had some bearing on the test pilot’s performance at the second SBAC Show at Hendon. The Aeroplane described the event:
This boat made its maiden flight on 21 June, five days before its first public appearance, but Mr. Summers [Vickers chief test pilot]  proved its qualities by throwing it about in a most carefree manner. Of its performance little is known but there can be little doubt about its amiability and general handiness in the air and on the ground. One must be prepared to see all sorts of aeroplanes looping and rolling with abandon nowadays, but somehow one has, up to now, looked to the flying-boat to preserve that Victorian dignity which one associates with crinolines, side whiskers, bell-bottom trousers and metal hulls. The Seagull V destroyed all one’s illusions.
Henry Knowler, Chief Designer at Saunders Roe who watched the display in the company of Mitchell, reported the designer’s understandable surprise and anxiety at the low level antics of the five-day old prototype. ‘He looped the bloody thing,’ Mitchell kept repeating to everyone he met.
The Seagull V, as it was known to the Australian government, then underwent modifications and trials. Summers had criticised the rigidity of the undercarriage and its steering capacity and, after these deficiencies had been put right it went to the Marine Experimental Establishment at Felixstowe, five weeks after its maiden flight. Evaluation tests then lasted until the end of October, after which the Seagull went to the Royal Aircraft Establishment at Farnborough for the catapulting trials required by the Australian Government.
    Despite lengthy trials, including the successful catapult trials for the Australian order, no Air Ministry order was expected and so it would appear that the future of Mitchell’s design would rest solely with the Australian Government’s requirement. However, movements were afoot nearer to home, as reported in Caspar John’s Foreword to The Supermarine Walrus by G. W. R. Nicholl:
To the late Rear Admiral Maitland W. S. Boucher, D.S.O., 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  N.2 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. The aircraft was then taken back to home waters for the continuation of trials at Sheerness and in the Solent until May when it was returned to Supermarine for the fitting of re-designed wing-tip floats to give better buoyancy, the removal of the wheel brakes for lightness and for an improved layout of the observer’s compartment. Further fleet operation trials continued, including landings in 30-knot winds and six-foot waves off the Kyles of Bute and underway recovery onto a warship making up to 13 knots through rough water. As a result, on the 27th of August, the Australian government ordered 24 production Seagull Vs, A2-1 to A2-24.
    Thereafter, the prototype was renumbered K4797 and, on New Year’s Day, 1935, handed over to the Fleet Air Arm. As the prototype had first flown in June, 1933, it is clear that the Admiralty had needed time to be convinced that open sea and catapult operation from their capital ships would work smoothly. In all probability, the earlier Australian initiative and the developing international situation had helped to overcome any doubters in the Admiralty and so an initial order was placed on 18 May, 1935, for 12, serial numbers K5772 to K5783, shortly followed by a second for eight, K8338 to K8345, and then a much larger order for twenty-eight, K8537 to K8564.
   A name was now to be chosen for the British machine, unlike the Australian one – which retained the Seagull V appellation. In the past, Supermarine amphibians and flying boats had been favoured mainly with reasonably attractive seabird names: Sea Eagle, Sheldrake, Seamew, etc. whilst the name Sea Lion was a nod in the direction of the engine used. It is thus an interesting comment on what Caspar John had called its ‘somewhat improbable’ appearance that the far less glamorous name "Walrus" was now chosen. Nevertheless, it was not only the first of its type to be catapulted with a full military load but also the first British-designed military aircraft with a retracting undercarriage. The first British batches of 48 aircraft ordered was increased dramatically in 1936 with the requirement for another 168 machines, L2169 to L2336. Despite its initially very doubtful future and backward-looking appearance, the Walrus then became the last and the most successful of all Mitchell’s reconnaissance amphibians and the navy's standard fleet spotter.


For reference sources, see my Blogpost: “Source Material and References" – an extended bibliography is included in my R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire (details below) which also provides material for wider reading, grouped according to specific areas of interest. 

More information on the Seagull V/Walrus, photographs and a three-view drawing, as well as a full account of all Mitchell's completed designs and of the man behind them, will be available in a few weeks' time:
Advance Notice – 
R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire.
This is a much expanded, completely up-to-date, second edition of my earlier work with 50% more photos, and 25% more text – 380 pp. instead of 250. There are general arrangement drawings of Mitchell’s 21 main aircraft types which flew, as well as 40 other drawings. There are 24 photographs, featuring or including Mitchell, as befits the first fully detailed and, I hope,  definitive account of the man and his work at Supermarine.
To obtain a copy at pre-publication prices, please enquire via the contact form in the sidebar.



Monday, 25 June 2012

R. J. Mitchell's Spitfire – a Close Run Thing

When Mitchell’s first fighter design, Type 224, was failing to satisfy the Air Ministry specification F.7/30, there was another monoplane which might very well have attracted favourable Ministry support instead: the Bristol Type 133, the first British fighter design with both retractable wheels and stressed-skin construction. But, when the aircraft was almost ready to go for competitive tests at Martlesham Heath, it entered into a flat spin; the test pilot had to abandon the one-and-only prototype and so time was available for Supermarine to try to improve upon their proposal – although it should be noted that, in view of the British manufacturers’ disappointing responses to F.7/30 that there was even talk in the Ministry of purchasing Poland’s all-metal monoplane, the PZL P.24.
Meanwhile personnel were changing in the Air Ministry: the Chief of the Air Staff, Sir Hugh Trenchard, who had favoured the bomber as a deterrent, had retired and his successor, Sir John Salmond and his Deputy, Sir Charles Burnett, were more sceptical of this approach. They were very actively supported by Hugh Dowding who joined the Air Staff in 1930 as Air Member for Research and Supply; as he later became the Commanding Officer of RAF Fighter Command, it is not surprising that he held the view that ‘the best defence of the country is fear of the fighter’.
    It was thus fortunate for Mitchell that the Air Ministry and its departments were headed by RAF officers who had by now come to the conclusion that fighter development had to be significantly stepped up. Whilst F.7/30 can be seen as the milestone specification which brought our seaplane designer into the reckoning, the future support of certain Air Ministry officials in some difficult days ahead for the Spitfire-to-be had much to do with the close and mutually respectful relations between Supermarine and the RAF since the Southampton and S.5/6 Schneider Trophy days. It might also be noted that two particular Ministry men were active at this time: Group Captain Cave-Brown-Cave, the Director of Technical Development from 1931 to 1935, who had led the Far East Flight in one of Mitchell’s Southamptons which had never let his team down, and Major Buchanan, who had been the Air Ministry representative at the 1925 Schneider Competition and vocal afterwards in his support for British participation in these events.
   It should thus come as no surprise that, even before trials of the F.7/30 prototypes had been concluded, Specification F.5/34 was issued, which  stated that a retracting undercarriage was required and eight machine guns to provide ‘the maximum hitting power’. It also specified that ‘the maximum speed at an altitude of 15,000 feet shall not be less than 275 mph and at 5,000 feet not less than 250 mph’; and ‘the time taken to reach 20,000 feet is not to exceed 7½ minutes’. As Mitchell’s Type 224 modification had only promised a top speed of 265 mph and a climb to 15,000 feet in over eight minutes, it is not surprising that it had only received a lukewarm response from the Air Ministry.
    Fortunately, the Air Ministry, in October, 1934, agreed to Supermarine submitting a quotation for a different machine and Rolls-Royce had, by then, decided that their current engines were not capable of being developed into the sort of power plant needed for the next generation of fighters. Something between their 22 litre Kestrel and Goshawk engines and their 37 litre Schneider Trophy ‘R’ engine, was thought to be appropriate and so the company had begun design work on a further 12-cylinder Vee engine, initially expected to deliver a healthy 1,000 hp. As this new engine had passed its 100 hour test in the July of 1934, the board of Vickers (Aviation) Ltd decided on 6 November to finance the design of a fighter, powered by this new engine. Sir Robert McLean, the chairman of the board, some time later described how he had decided that Mitchell and his design team, in view of the adverse effect of Air Ministry requirements on the Type 224 [see my Blogpost: 'R.J. Mitchell's Stuka'],  should design a ‘real killer fighter’ in advance of any Air Ministry specification and that ‘in no circumstances would any technical member of the Air Ministry be consulted or allowed to interfere with the designer’.
   This intervention by Sir Robert was a result of his appreciation of Mitchell’s work which went right back to the take-over of Supermarine in 1928 – although McKinstry has recently pointed out that the chairman was, in fact, not unwavering before his support for the Supermarine designer finally won out. The alternative proposal which had attracted the attention of the chairman was the Venom, a development of the promising but ill-fated F.7/30 entry, the Vickers 151 Jockey, which had also succumbed to a flat spin. Like the Spitfire, the Venom had a stressed skin cantilever wing, retractable undercarriage and a metal monocoque fuselage (in fact, when it did fly, three months after the Spitfire prototype, it attained a top speed only 37 mph lower than the Supermarine prototype – with a less powerful radial engine). Clearly, this machine could have developed into a very serious challenge to the Supermarine project and, indeed, Beverley Shenstone, Mitchell’s aerodynamicist, later reported that ‘in my opinion the Spitfire would not have been born if Mitchell had not been willing to stand up to McLean, particularly in the era when McLean clearly preferred the Venom concept to the Spitfire concept because it was cheaper and lighter’.
   But once Mitchell’s proposal had been agreed upon, the combination of a Vickers/Supermarine/Rolls-Royce/Mitchell design must have stirred things up within the Air Ministry, for events moved very quickly thereafter. On December the 1st, £10,000 was allocated for the building of a prototype and a full design conference was called at the Air Ministry on the 5th of the same month. The whole contract situation was quickly regularized when a very brief Specification F.37/34 was formally signed on the third of January, 1935. It should be noted that this new specification was headed ‘Experimental High Speed Single Seat Fighter (Supermarine Aviation Works)’ and it stated that, basically, ‘the aircraft shall conform to all the requirements stated in Specification F.7/30 – that is, Mitchell was permitted to design a four-gun ‘experimental’ aircraft but without other firms being invited to tender in the usual way. It would seem that the three successive Schneider Trophy wins by the Rolls-Royce/Supermarine combination had not been forgotten by the new Air Ministry officials.
   Notwithstanding this initiative, three months later, the Air Ministry issued requirement F.10/35 in April 1935, which called for at least six, and preferably eight, guns to ‘produce the maximum hitting power possible in the short time available for one attack’. Thus the Supermarine fighter being designed had to offer something special, for F.10/35 called for a  maximum speed of ‘not less than 310 mph.’ – and so one suspects that Supermarine and Vickers were looking well beyond their four gun model and towards new armament requirements when their elliptical wing shape was decided upon – the thin wing approach that Mitchell had come to believe in could only accommodate increased weaponry with a broad chord wing well outboard of the fuselage and beyond the required retracting undercarriage housing.
   In this connection, the later comments of Mitchell’s stress man, Clifton concerning Mitchell’s doubts about information derived from model testing deserve recording:
I think that Mitchell decided to make the wing as thin as he did, and I wouldn’t like to be positive about this, but my recollection was that it was against some advice from the National Physical Laboratory in that case where wind tunnel tests, I believe, showed that there was no advantage in going below a thickness chord ratio of 15%, whereas, the [Spitfire] wing was 13% at the root and 6% at the tip. . . subsequently it was found that when you made proper allowance for that, there was an advantage, as the testing could be shown to prove, in going thinner.
At that time, Hawkers had been advised by the National Physical Laboratory that their recent wind tunnel results had shown no drag penalty with the thicker Hurricane wing; however, the Laboratory scientists later found this advice to be incorrect. Fortunately Mitchell’s instincts were proved correct.
   It was also fortunate that, about this time, F. W.  Meredith of the Royal Aircraft Establishment, Farnborough, came up with a ducted under-wing radiator that not only made little difference to the lines of the machine but actually used the heat exchange of the radiator to produce some thrust at high speed rather than to create drag, as in previous practice, thus encouraging confidence in Supermarine’s predicted 350 mph for their new fighter.
K 5054  the Spitfire Prototype (from a painting by the author)
    Nevertheless, when the new prototype first flew early in 1936, Mitchell confessed to being very disappointed that the top speed was ‘a lot slower than I had hoped for’ –– and, as its test pilot, Jeffrey Quill, said: ‘unless the Spitfire offered some very substantial speed advantage over the Hurricane, it was unlikely to be put into production. Thus the disappointing speed performance of our prototype at that early stage was something of a crisis and Mitchell was reported to be 'a very worried man’.
   And so the prototype was given a special new paint job and, by 9th May, 1936, re-emerged with a very smooth light blue-grey finish, thanks to fillers and to automobile paint supplied by Rolls-Royce. Yet the speed of K5054 was still less than hoped for, as the aircraft’s top speed of 335 mph was still too close to that of the Hurricane, rumoured to be achieving 330 mph. Just after the prototype Hurricane had flown, Mitchell saw it for the first time. ‘He did not see it close up but only at a distance. He came back to Itchen very worried, and walked into the erection shed and looked at the first incomplete Spitfire. He said, "Camm’s got a tiny little machine. Ours looks far too big"’.
    In fact, the Hurricane had three feet more span than the Spitfire but the supposed narrow margin between the top speeds of the two new aircraft might very well have resulted in a contract going exclusively to the Hawker. Luckily, the fitting of a new propeller (Quill recalled the previous flight testing of ‘some 15 to 20 different designs’) on 15th May produced a dramatic increase to 349 mph – a very impressive leap of more than 100 mph over that of the Gladiator which, as a stop-gap, had eventually been awarded the F.7/30 contract.
   When one remembers how two promising F.7/30 contenders were eliminated when the one-and-only models crashed, it is worth recalling that the equally unique Spitfire prototype nearly came to grief when handed over to Fl. Lieut. (later Air Marshall Sir) Humphrey Edwardes-Jones at the test centre, Martlesham Heath:

There was no air traffic control in those days and I had no radio. As I made my approach I could make out a Super Fury some way in front of me doing S turns to lose height before it landed. I thought it was going to get in my way but then I saw it swing out to one side and land, so I knew I was all right. But it had distracted my attention at a very important time. As I was coming in to land I had a funny feeling that something was wrong. Then it suddenly occurred to me: I had forgotten to lower the undercarriage! The klaxon horn, which had come on when I throttled back with the wheels still up, was barely audible with the hood open and the engine running. I lowered the undercarriage and it came down and locked with a reassuring ‘clunk’. Then I continued down and landed. Afterwards people said to me, ‘You've got a nerve, leaving it so late before you put the wheels down’. But I just grinned and shrugged my shoulders. In the months that followed I would go quite cold just thinking about it: supposing I had landed the first Spitfire wheels-up! I kept the story to myself for many years afterwards.
With hindsight, one wonders how a crash-landing of the one-and-only untried prototype would have affected its future, given the usual Air Ministry practice of only ordering one prototype from a firm [for the German contract exercise, equivalent to the British F.7/30 requirement, four firms had each been authorized to build three prototypes].

Events in Europe were certainly now creating an even greater urgency to find an adequate replacement for the standard RAF fighters of the day and so Edwardes-Jones had been instructed to telephone the Air Ministry as soon as he got down from this first flight:
Normally, a firm’s test pilot would bring in a prototype aircraft for service testing, and it would be first handed over to the boffins who would weigh it very carefully and check that the structure was as it should be. It was usually about 10 days before it came out for its first flight with us. With the Spitfire prototype, it was quite different. Mutt Summers brought her over, and orders came from the Air Ministry that I was to fly the aircraft that same day and report my impressions…
Once down I rang the number at the Air Ministry I had been given, as ordered. The officer at the other end [Wilfred Freeman, Air Member for Research and Development] said … ‘All I want to know is whether you think the young pilot officers and others we are getting in the Air Force will be able to cope with the aircraft’. I took a deep breath – I was supposed to be the expert, having jolly nearly landed with the undercarriage up! Then I realised that it was just a silly mistake on my part and I told him that if there were proper indications of the undercarriage position in the cockpit, there should be no difficulty. On the strength of that brief conversation the Air Ministry signed a contract for the first 310 Spitfires on 3 June [1936], eight days later.



For reference sources, see my Blogpost: “Source Material and References" – an extended bibliography is included in my R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire (details below) which also provides material for wider reading, grouped according to specific areas of interest. 

More information, photographs and a three-view drawing of the Spitfire prototype, as well as a full account of all Mitchell's completed designs and of the man behind them, will be available in a few weeks' time:
Advance Notice – 
R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire.
This is a much expanded, completely up-to-date, second edition of my earlier work with 50% more photos, and 25% more text – 380 pp. instead of 250. There are general arrangement drawings of Mitchell’s 21 main aircraft types which flew, as well as 40 other drawings. There are 24 photographs, featuring or including Mitchell, as befits the first fully detailed and, I hope,  definitive account of the man and his work at Supermarine.
To obtain a copy at pre-publication prices, please enquire via the contact form in the sidebar.


Sunday, 17 June 2012

R. J . Mitchell's Air Yachts


R. J. Mitchell was responsible for two luxury air yachts although both, in fact, began as military orders. The first looked backwards to the Southampton but the second might very well have led to a Supermarine equivalent of the Catalina.

The first came about as a request from Denmark for a torpedo-carrying version of the Southampton; it was to be called "Nanok", Inuit for polar bear, and first flew in 1927.  But all was not well as the necessary positioning of the torpedoes, one on each side of the aircraft, produced problems when  dropping only one torpedo and the three-engined layout that had been requested by Denmark was also found to produce trim problems. Mitchell's response was to fit an auxiliary elevator higher up between the three fins but this lowered the flying speed some mph below that contracted for.  And so, in the end, the Royal Danish Navy took delivery of a standard Southampton instead.

Luckily, in 1928, the Hon. A. E. Guinness was persuaded of the potential of a private flying-boat and thus the unwanted Nanok was converted into an ‘air yacht’ with comfortable cabins to carry up to twelve passengers. Now finally named ‘Solent’ and registered G-AAAB, it soon became a familiar sight, flying from the Hythe seaplane base on Southampton Water to Dún Laoghaire harbour, County Dublin, and thence to Lough Corrib, County Galway, close to Ashford Castle, its owner's home.

The second Air Yacht was to follow in 1930, again a cancelled military prototype, which began as Air Ministry specification 4/27, calling for an armed reconnaissance flying-boat. Instead of the expected wooden-hulled biplane, there appeared an uncompromising all-metal monoplane with a wing-span of 92 feet and powered by three engines which were faired into the wings. It had a plank-shaped parasol wing with sloping V struts supporting the wing about two thirds out
Air Yacht (from a painting by author)
from the centre-line and the hull, instead of the curvaceous design made famous with the Southampton, was a flat-sided type and strengthened with horizontal corrugations; it also had extremely angular fins in keeping with the rest of the general arrangement. 
     The new design still had fabric covered flying surfaces but it had one feature which made it stand out from all other Supermarine aircraft and its contemporaries and this was the employment of sponsons attached to the lower sides of the hull instead of the customary wing-tip floats. Not only in this respect but also in respect of the overall design, the aircraft bore an uncanny resemblance to the earlier Dornier Wal seaplanes: indeed a Supermarine employee, Harrry Griffith, later wrote the Mitchell "had allowed himself to be lured by some of his bright boys into following other people's ideas".
    Unfortunately, the aircraft did not give a dramatic argument for going over to monoplanes as its maximum speed was well below expectations. And so it was  re-engined with 525 hp Armstrong-Siddeley Panthers and was then found to be capable of 117 mph; however, it was still not possible to maintain height with any significant payload when one of the three engines was throttled back. Also, Penrose  recorded that ‘unfortunately the sponsons suffered battering by waves and even on calm water gave inferior take-off compared with the usual chined British hull' although he did go on to say that ‘assessed as an engineering structure of considerable aerodynamic cleanness, the Air Yacht was a big step forward compared with the established three-engined Iris biplane, of which four were in the course of delivering to the RAF, or the Calcutta-derived Short Rangoon prototype due to fly in the summer.’ Griffiths, also gave a negative report: ‘It had a very long take-off run and there was always doubt as to whether it would leave the water at all with a full load of passengers, stores and fuel. Refuelling in those days was done with hand pumps from barrels taken out on a barge. There is a story (unconfirmed but, knowing the man, possibly true) that Biard, the test pilot, refused to attempt a full load take-off and ‘went through the motions’ of filling with fuel by pumping from a number of barrels, some of which were empty'.

And so, by 1931, Supermarine began to try to salvage matters by seeking civil registration,  in the expectation of fulfilling an order from the Hon. A. E. Guinness for a replacement for his ‘Solent’ Air Yacht. The new machine’s boxy hull certainly provided very suitable dimensions for the passenger cabin: 35 feet in length, 6 feet 6 inches in height and 8 feet in width. It was luxuriously appointed with owner’s cabin complete with bed, bath and toilet, a galley with full cooking facilities beneath the wing, and additional wash basins, toilet and comfortable lounge with settees and sideboards in a separate cabin for five other passengers; and the temperature could even be regulated by a blown air system.

Unfortunately Guinness turned to a Saro product and the Air Yacht was put in storage. But eventually a Mrs. June Jewell James, a keen motor-boat and flying enthusiast. saw the aircraft and negotiated its purchase from Supermarine in 1932. She named her new acquisition ‘Windward III’ and became so impatient to have the use of her new purchase for a cruise to the Mediterranean and North Africa that she insisted on starting some days before the prearranged departure date.
Biard has supplied a description of the frantic preparations and of one-and-only cruise attempted in the aircraft. After Mrs. James and her companions were nearly drowned in a fierce storm, when anchored in Cherbourg Harbour, Biard flew the Air Yacht down to Naples whence Mrs. James proceeded to obtain audiences with both the Pope and Mussolini. Biard had then to hand over the Air Yacht to a relief pilot as his stomach muscles, which had been torn in the S.4 crash of 1925, needed surgery. Unfortunately, the Air Yacht suffered an engine failure and stalled into the sea on take-off in the vicinity of Capri on January 25. The owner suffered a broken leg but otherwise there were no serious injuries sustained; the aircraft was too badly damaged to be worth salvaging.


Had Mitchell lived long enough and had the Air Ministry generally shown a more single-minded faith in monoplane flying boats, one wonders if Mitchell’s last flying-boat, the Stranraer biplane, would instead have been a Supermarine Air Yacht type equivalent to the American Catalina which equipped twenty-one RAF and RCAF squadrons during World War II. Incidentally, the predecessor of the Catalina was the Consolidated Commodore, with a parasol fabric covered wing like the Air Yacht and with about the same span; it appeared in the same year as Mitchell’s machine but was far less clean, aerodynamically, with well over thirty supporting struts.



For reference sources, see my Blog: “Source Material and References. " An extended bibliography is included in my R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire (details below) which also provides material for wider reading, grouped according to specific areas of interest. 

More information, photographs and a three-view drawing of the Air Yacht, as well as a full account of all Mitchell's completed designs and of the man behind them, will be available in a few weeks' time:
Advance Notice:  
R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire.
This is a much expanded, completely up-to-date, second edition of my earlier work with 50% more photos, and 25% more text – 380 pp. instead of 250. There are general arrangement drawings of Mitchell’s 21 main aircraft types which flew, as well as 40 other drawings. There are 24 photographs, featuring or including Mitchell, as befits the first fully detailed and, I hope,  definitive account of the man and his work at Supermarine.
To obtain a copy at pre-publication prices, please enquire via the contact form in the sidebar. 



Thursday, 7 June 2012

Mitchell’s Amphibian Bomber and an Enigma; The Scarab and the Sheldrake.


Supermarine Sheldrake
Supermarine Scarabs
(from paintings by the author)


The Scarab, which first flew on 21 May, 1924, was a powerful fighting machine for its period and was the only Mitchell design sold exclusively outside the British Empire;  the other Supermarine amphibian at this time, the Sheldrake, was an enigma. 

The Sheldrake
The result of the criticisms of the Supermarine Seagull [see my Blogpost: 'Precursors of R.J. Mitchell's Walrus'] was that, in 1923, an Air Ministry order was placed for an improved version. The resultant aircraft was the Sheldrake whose flying surfaces were virtually identical to those of the Seagull but which had a more efficient boat-like hull very similar to that of the Sea Eagle . It is surprising that the noisy stabilising screens on either side of the engine were still retained, as was the separation of the pilot from the rest of the crew – which already had been addressed in the Seagull II [see my Blogpost: 'Pre cursors of R.J. Mitchell's Walrus'].
   Even more surprising was the apparent inactivity around the Sheldrake – perhaps the first flights of the Sea Eagle and of the Sea Lion III, the first production batch of the Seagull IIs, and consideration of the larger flying-boats, the Scylla and the Swan, were important factors here – but, for whatever reasons, its only known public appearance is recorded as late as 1927, at the Hamble Air Pageant, where it could be seen to be an obsolescent type.

The Scarab
Meanwhile, a year after the Sheldrake was ordered, the second of our aircraft made its maiden flight – the first of a Spanish order for twelve aircraft. There was no prototype for this aircraft – as it was in a great many respects similar to the Sheldrake, the Air Ministry order for the Sheldrake provided most of the design work.

King Alfonso of Spain was a regular visitor to the Hendon RAF Air Shows and must have had an early appreciation of the new British ‘control without occupation’ tactics whereby air power, not ground forces, was used to control insurgent tribes in areas of the British Empire or in areas mandated to Britain by the League of Nations. As a result, the Spanish Royal Naval Air Service asked Supermarine for an amphibian to be produced, capable of carrying a bomb load of 454 kilos, as it had been noticed the passenger carrying capacity of the Sea Eagle promised a suitable basis for a design.
   In the new, Scarab, version, the engine was returned to the more familiar pusher configuration as the crew were all now, more conveniently, grouped together in front of the wings – with the navigator/bomb-aimer also having a position in the hull immediately behind and below his cockpit position.  The fuel tanks were now removed from the hull and placed above the middle section of the top wing. The space not now required in the fuselage was used for twelve 50 lb. bombs which could be dropped via a sealable aperture in the bottom of the hull. Four 100 lb. bombs were also carried under the wings and the total weight of bombs carried amounted to the equivalent of six men. The Scarab also had a crew of three and had to carry a machine-gun, ammunition and a considerable amount of fuel – thus making it an attractive powerful fighting machine for its period, given its single engine.
   The first Scarab made its maiden flight on 21 May, 1924, but whether all the twelve that were ordered actually saw service is unclear. One was damaged on acceptance trials when its Spanish pilot hit the side of a Union Castle liner when taking off; and they had to survive a severe Bay of Biscay storm stowed under tarpaulins as deck cargo. Nevertheless, Scarabs were seen above Barcelona at the 1925 Royal Review of the Spanish forces by King Alfonso and they equipped a seaplane carrier, the Dédalo, a converted merchant vessel – being lowered into the water or raised from it by crane.
    They were based at Carageno from whence they took part in actions against Riff and Jibala insurgents in the Spanish Moroccan campaign, including bombing raids in support of an amphibian  landing at Al Hoceima.
    The Moroccan conflict ended soon afterwards in 1926 and so Supermarine publicity ran as follows: "A large number of these machines have been bought by the Spanish Government, and these have been in operation for the past year in Morocco with the most satisfactory results [my italics]."

No Scarabs were ordered by the British Government but the Spanish order for the twelve machines was, at that time, quite substantial, especially coming soon after the order for 25 Seagull II aircraft and the three Sea Eagles.





For reference sources, see my Blogpost: “Source Material and References" – an extended bibliography is included in my R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire (details below) which also provides material for wider reading, grouped according to specific areas of interest. 

More information on the Scarab and the Sheldrake, photographs and three-view drawings of them, as well as a full account of all Mitchell's completed designs and of the man behind them, will be available in a few weeks' time:
Advance Notice – 
R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire.
This is a much expanded, completely up-to-date, second edition of my earlier work with 50% more photos, and 25% more text – 380 pp. instead of 250. There are general arrangement drawings of Mitchell’s 21 main aircraft types which flew, as well as 40 other drawings. There are 24 photographs, featuring or including Mitchell, as befits the first fully detailed and, I hope,  definitive account of the man and his work at Supermarine.
To obtain a copy at pre-publication prices, please enquire via the contact form in the sidebar.