Supermarine Type B12/36, 317

I would agree with pretty much all of that but to be fair Supermarine had been building in metal since the end of 1926, albeit in small numbers and therefore ‘handbuilt’ rather than full-blown production.

27/9/40. You and I are sitting in Conference to select resources to deal with the respite achieved by luck and winter. They’ll be back in Spring,1941. We’ve spent all the $ we have, and more. Radlett, Rochester, Weybridge and Itchen/Woolston are all in the wrong place, so we’ve started the Agency/Shadow Factory scheme, to put production out of Luftwaffe range.
Q: What to build in auto and green field sites, off female and other untutored labour?

A: tangible products which can be Supervised by a handful of Quality Inspectors. Not origami schemes which may, may not work. A lot has not worked, inc. designs from long-proven metal-workers. Which Supermarine, in a muddy shed, was not. Even if T.316/317 might have shown enhanced prospects, like Super-schemes at Short, HP, V-A, what was needed NOW! was more Stirlings, some Halifaxes, anything better than Warwick (begun 1935. Where is it?), Manchester (begun 1936: why did we bother?), the Bristol twins (slow, in every way).

Headaches enough already. Don’t need more called T.316/317.

There is photograph of a model and two photographs of the fuselage taken in 1939 in ‘Company Profile 1913 – 1963 Supermarine’ published by the Aeroplane.

I’m sure there’s a photo of the mock up or the prototype in Putnam’s Supermarine Aircraft since 1914.

If it had entered service with the bomb cell arrangement as discussed the Type 316/317 would most likely ended up undertaking the role that the Stirling excelled at, that of Airborne Forces.
The over fixation on the size of a 500 GP bomb that drove the design of most of Britains bombers resulted in a series of aircraft that had bomb bays which were difficult to redesign to take larger bombs. In turn it also fixed in stone the size of supply containers that the Airborne Forces could use.
The CLE Mk 1 container was the maximum size to fit the bomb cells of the Bomber Transport designs made available to the Airborne Forces, Whitley , Wellington, Halifax and Stirling. As the CLE containers were limited to 350 lb the Stirling could carry a full bomb bay load of containers and still have capacity for an internal load.
Whilst early paratrooping trials of the Stirling used the circular floor exit left by the removal of the ventral turret, later development gave the Stirling a large rectangular opening and the long fuselage permitted the dropping of as many paratroops as a Dakota but with more equipment. It also allowed stores panniers to be dropped from inside the fuselage by means of a roller conveyor floor.
The Stirling’s roller floor was the first used operationally by the UK (Also a World first?), a method of supply drop which is today common place. The first UK aircraft to drop stores using a roller floor was the Horsa, but only in trials.

To slightly update my Post 31 last year…..It is certain that a wingless and tail less(!) mock of Type 316 / 317 was made, hung from the roof structure (with the Spitfire mock up) and destroyed in the bombing that devastated “K Shop” at Woolston on September 26th 1940. However TWO basic 316 / 317 fuselage structures were set aside also in K Shop and these were lifted in the bomb blasts and ‘bent’ around the vertical RSJ’s that formed part of the superstructure of that errecting bay.

Two more books (maybe more) have appeared since Post 31, with very small refernces to the bomber. [I]Secrets Of The Spitfire[I] by Lance Cole ISBN184884896 -X a biography of Beverley Shenstone the Supermarine copany aerodynamics wizard. Next is Spitfires’s Forgotten Designer about the life of Joe Smith – Mitchell’s succesor at Supermarine. ISBN 978 0752 48759 5 by Mike Rousell. This book surprised me with the number of exceptionaly clear photographs the author has found in the archives of Solent Sky Museum in Southampton. There is only a small amount of text to accompany the one photograph of the 316 / 317, but maybe one should consider asking if Solent Sky have more on this topic waiting to see the light of day!

Lastly I was reminded of yet another book (from 1985) now long out of print. Spitfire Odyssey by C R Russell, ISBN 0-946184-18-6. Young Russell started work at Supermarines in 1936 and he became a sheet metal worker. He says he produced some of the fittings for the bomber fuselage but his big contribution is the view of the company from within, the detailed recollections he gives of the staff , the jobs that he was issued with and of course the little snippets of information that are just mentioned and then passed by. We learn that he worked on the two fuselages of the Speed Spitfire project and it had a strengthened fuselage. Only one fuselage was used and that was for N17 of course. Russell also produced a second book Spitfire Postscript ten years later ISBN 0 952 4858 0X. If you can find a copy of either or both it is well worth while.

Sticking the bomb load in the wings is going to give a considerable inertia to manoeuvres in the rolling plane. Can you imagine trying to avoid searchlights by doing a corkscrew in that?

Incidentally, recent photos on a modelling forum (Britmodeller?) has shown that the Blenheim too had bomb cells in the wing centre section at the root.

Supermarine had been playing with the idea since 1931 and Gloster did too a few years later. It was fairly common really

As did the Anson .

The shallow bomb bay was a feature of all RAF bomber designs of the period except the Manchester/ Lancaster. This is because all the bombs available and specified were the narrow streamlined form. In all the confusion over the Stirling’s wingspan, it is perhaps sometimes forgotten that one key design feature was the requirement for 7x2000lb SAP bombs. This is why the Stirling has its long bomb bay, and hence disproportionately long fuselage that led to so many problems – and that ridiculous (if ingenious!) undercarriage. Colin Sinnet suggests that Short’s comparative inexperience with the give-and-take common to military specifications may have led to them pursuing an excessively difficult goal rather than arguing for a better compromise. The Stirling would certainly make better sense with a shorter bomb bay and thus more conventional undercarriage.

The design for the Manchester and HP56 (later Halifax) called for fewer 2000lb bombs but the additional carriage of torpedoes. Presumably it was the requirement to carry not just torpedoes, but their Monoplane Air Tails permitting drops at faster speeds, that led to the deeper bomb bays. HP requested and were given permission to drop this requirement to simplify (and hence quicken) the design of the HP57. This may have been a mistake, not knowing the penalty that retaining the feature may have had on the design. Either way, it seems that the Lancaster’s deep bomb bay was fortuitous rather than intended for the uses it was put to.

Incidentally, recent photos on a modelling forum (Britmodeller?) has shown that the Blenheim too had bomb cells in the wing centre section at the root.

Mitchell’s death was certainly a tragic loss but it is unlikely that the company’s fate in the pre-war years would have mapped out significantly different had he still been on seat. The Woolston site was in the process of redevelopment in the late ‘30s but was still restricted to much the same ‘footprint’ as it had back in the Pemberton Billing days, production of 250+ Walrus, a dozen or so Stranraer and 300+ Spitfires put a tremendous strain of the company, delays were all but inevitable and construction of the Type 317 had to wait until the Itchen Works were completed. There was nothing Mitchell could have done about that. Similarly the internal friction on the Vicker’s board that resulted in McLean’s departure and the absorption of Vickers Aviation and Supermarine into Vickers Armstrong would have been outside of his control. Bottom line….The Type 317 was doomed to long delay.
The aerofoil of the Type 317 was NACA 2218 (18% thickness-to-chord) from the root to the outer nacelles, the part that enclosed the bomb bays. So neither particularly thick nor thin. Supermarine estimated superior performance for Hercules power over Merlin mainly because the proposed Merlin F gave 250hp less. The Type 318, which would have been Merlin powered, was put aside quite early on Air Min instructions. There are some features of the original Type 317 design that were dropped during development, especially the low-profile Supermarine gun turrets; the tail turret was to be replaced by a FN design that fit less well to the contours of the aircraft and the ventral turret was also to be replaced by a FN type although as these did not perform well no doubt they, too, would have been deleted and replaced, presumably, by a dorsal type. Both these changes would have added drag and reduced performance. Supermarine’s proposed nose turret looks to me to have been dropped in favour of the Vickers low-drag type as used on the early Wellingtons. Of course this did not perform as well as expected and was replaced by a FN type, so I guess the Type 317 would have suffered the same fate. Whether as a result it would have proven superior, equal or inferior to the Lancaster and Halifax has to remain open to debate.
Note also that the designation Type 317 was adopted quite late on. The majority of drawings for what we know as the Type 317 actually carry 316 drawing numbers.

Supermarine 317, potential.

It’s hard to imagine what would have happened at Supermarine if Mitchell had remained fit and healthy, The 317 probably had more potential than it’s given credit for. Although the wing looks quite thick, it actually isn’t. With the low aspect ratio the thickness/chord ratio is a lot less than the Stirling, also the wing section is NACA 2200 series, same as the Spitfire. A major reason for putting a substantial part of the bomb load in the wing was that this partially counteracts the bending loads on the wings and reduces structure weight. There’s little doubt that this was a more advanced structure design than the other heavies, including the Lanc.
Clearly it wasn’t set up for blockbusters , grand slams and tallboys, but neither were B17s! It can only be conjecture now, but if Mitchell had still been around, if the prototypes hadn’t been destroyed, if the resources committed to the mediocre and expensive to build Stirling had been committed to the 317 instead, we might have been a lot better off. The use of radial engines wouldn’t necessarily have prevented it from being fast, the fastest Halifaxes were the late Hercules engined versions. There’s no doubt anyway that it could have used Merlins and if seen to be successful it may well have taken the place of the Halifax, so the engines would have been available. The later introduction of larger cased bombs would have been anyway handled by the Lanc, a faster more aerodynamically capable 317 alongside it could have given an excellent combination of strategic weapons, whereas the Halifax was more of a second rate alternative to the Lanc than a design of similar excellence but different capabilities. Mitchell’s early death was undoubtedly a national catastrophe, thank heaven for what he did achieve, but it could have been so much more.

Good Stuff.

What an interesting thread. It’s very rare that I can be bothered to read one from beginning to end these days, but this was well worth it. I can claim no specialist knowledge on the content of this thread but would make a few comments.
Mitchells bomber project has always intrigued me. I have yet to see more than a few thumbnails and sketches. It’s hard to draw many conclusions from such poor material. It seems clear that Mitchells death, the bombing of the works and the outdated capacity for only small bombs (Not to mention so many competing platforms.) put paid to what was otherwise an interesting design.
The reason that I’m so skeptical of these thumbnails is that, given the core reason for the Spitfires success and longevity (i.e; The thin wing.) then it follows that Mitchell would have sought to carry this over to the bomber. This can’t really be seen in thumbnails and sketches. This, along with the smaller cross-section of the fuselage and the drag-reducing turrets would probably been at the core of Mitchells thinking. He did, after all, have previous form for making fast machines. For these reasons I doubt that the radial-engines would have been included in his original design. He didn’t make rash claims for the Spitfire’s performance, so there isn’t any reason to think that Mitchell hadn’t got sound facts upon which to base his claims.

The Stirling has been mentioned a few times. There has been a propensity over recent time to ‘rehabilitate’ this machine. One might argue that the lack of a surviving example is a preservational faux-pas, but that does not make it a good a/c, even by the standards of the time. It was, to many, a carbuncle, with a blatantly oversized fuselage on a far too small a wing. The great length of the fuselage necessitated carrying around a vast, heavy, cumbersome undercarriage. Little wonder it was too heavy and underpowered. It looked like it had been designed by a committee. It’s bomb-bay was shallow, and bombed-up it had a poor ceiling and was relegated to use as a target-tug (What year..?). I used to fly with an old lag who had been a pilot on Stirlings in his youth. He wasn’t very complimentary about the Stirling at all…..! I’m sure that the aircraft was good for moral at the time, but as a machine to go to war in…… The Lanc’ wasn’t just a bit better, it was in another league.

It’s interesting to contemplate what might have happened to Mitchells design had the effort that was put into the Stirling been lavished upon it…. It may well have in fact proven to be fast, but it’d never been have been able to carry the outsized ordnance that the Lanc’ did. There was always work for the Lanc’.

In the event, the Mosquito came relatively close to what Mitchell was aiming for. As I have argued many times before, had the powers that be not been wed to outdated dogma, they’d have used most of the effort that went into the four-engined heavies on more Mosquitos – and probably saved material, wastage and the lives of thousands of aircrew…… Mosquito losses were, percentage wise, a mere fraction of the losses on the lumbering heavies, so Mitchell was clearly thinking along the right lines.

A very interesting series of postings on quite a fairly obscure subject. If I may add another little known source that is deserving of a much wider audience try to get hold of book entitled Never A Dull Moment written by Dennis Le P Webb, published in 2001, ISBN 1-900511-73-8 from J&KH Publishing.

The author joined Supermarines in 1926 as an indentured Management Apprentice. He retired from BAC after the TSR2 fiasco in 1971. The book has some errors as Denis aged 93 in 2001 ‘forgot’ to proof read the book and just authorised the go ahead to publish. The errors are usually easy to spot and to re-interpret, however.

That book tells more about Supermarines from behind the scenes than I have ever come across in any similar type of publication of any company I have ever read. There are plenty of substantiating facts – why was the first Spitfire order so late in delivery, how they coped after the bombing and so on. But about the Type 317 – almost nothing but he does explain the company situation at Woolston at that time and it can hardly be a surprise that the bomber design had to be neglected.

I also have a copy of Dennis’s unpublished chapter on the TSR2 saga from the management perspective at Weybridge which was his last management tasking before retirement. He thought I would like a copy of it after helping him get his life story published. As he said, Never A Dull Moment.

Most surviving drawings are now held in the RAF Hendon archive, but there are few and many in a poor state.
A further reason why the 317 may have been allowed to slip is that the bomb rack system could only hold bombs up to 500lb weight, the newer designs were more flexible.

There are many reasons why the 317 was much delayed. Firstly Woolston underwent a huge expansion in the late 1930s and the Works were rather chaotic as they produced Stranraers and walrus while tooling up for the Spitfire. Remember, the production order for 310 aircraft was more than double the total number of aircraft they had built in the previous 20 years. The 317 was to be built at new works upstream, known as the Itchen Works, while required new buildings.
Mitchell’s death was seriously disruptive, he had led the Design Office since 1919 and although he headed a talented team under Joe Smith in the Drawing Office and Alan Clifton in the Technical Office they were indeed rudderless for a time. Mitchell’s deputy, placed there by McClean when Vickers took over in 1928, was harold Payn, but he had little design experience. There was a delay before Joe Smith was named as Mitchell’s replacement.
Preparing drawings and jigs for subcontractors on the Spitfire dominated the company’s business after 1936 and new projects, even potentially good ones like the 317, got pushed into the background

Great write up thanks, it seems possibly that the Supemarine design was allowed to drift (partly with to do with some unfortunate events) along, at a time when full steam ahead was being afforded to the Short design?
Even if the Woolston factory hadn’t been bombed, wouldn’t it all have been a bit too late for the 317 at that stage?

Looking at the bomb cell arrangement in the diagram Chris kindly provides, it seems more exagerated than other bombers of the time with bombs being housed well outboard of the wings, I take it the dropping order of the bombs would have to be crucial to minimize effects on trim?

Retractable turrets would have been advanced at the time, but one would think that the advantages of reduced aerodynamic drag would be negated by extra weight and complexity.

Shortly after the Spitfire first flew on March 5th 1936 R J Mitchell who was quite unwell with the cancer that would kill him had already handed over the Spitfire design to the production team at Woolston Southampton. His mind was working on the design problems for the Supermarine 4 engined bomber.

It may be a good idea to look at the book by his son Dr. Gordon Mitchell Schooldays To Spitfire for some concise and additional clarity on this subject – there are several editions of this excellent and revealing book. I suggest it is a good basic resource.

I also have a recollection of talking a few years ago with one of Mitchell’s team about this bomber. Harry Griffiths was assistant to Arthur Black the company metallurgist and their laboratory and office were directly below Mitchell’s office at the works. Harry was there on both occasions when the bombing took place in September 1940 and he was of the opinion that the mock up of the bomber fuselage AND the Spitfire mock up were hanging from the rafters in one of the production areas and said both were destroyed. He also said that a completed bomber fuselage was also stored there and also destroyed. But wings had not been manufactured because of the great pressures on the company to manufacture Spitfires.

The point about the Vickers Armstrongs (ie the parent company at Weybridge) being quite capable of designing big bombers is well made. The Wellington was in production, the Warwick was following and so was the Windsor.

The Windsor was a four engined bomber but it arrived too late on the scene and the so successful Lancaster ( not overlooking other types either) especially ensured that there really was no point in continuing to develop it further. Vickers did however do some testing with the three prototypes that were made at their experimental aircraft Foxwarren hangars, taken to Wisley – not Brooklands – and at least the first of the three was flown.

It is an interesting geodetic body design from a collaboration between Rex Pierson and Barnes Wallace but probably owes little to Mitchell’s design from five or six years earlier.

As to the missing drawings of the Mitchell bomber. I believe most of the company drawings were saved in the bombing only to be burnt in the early 1960’s at Hursley Park near Winchester when Supermarine’s left there. Only a few early drawings of the Spitfire still exist inthe archives at Solent SKY Museum in Southampton. Other than that it is off to Cambridge University Library that houses the extant Vickers archives, I suggest.

It may be reasonable to presume that with the bombing of the Woolston factory, that it was not just the prototype that was destroyed, but the drawings as well; certainly none seem to exist, and that would have put paid to the development.

Supermarine didn’t have the capacity to build the bomber in anycase,and probably never realised the longevity of the Spitfire, and that design work would still be going on to the wars end; it’s well known that Vickers (chief) designer Wallis didn’t get on too well with Mitchell (or vice versa) and that wouldn’t have helped with the adoption of the project by Vickers.

A trawl round the net seems to suggest that the Type 316 was the single tail design and and the twin configuration Type 317 shown in post 1 the revised design and two prototypes of the 317 with Hercules engines were ordered. The Type 318 being a Merlin variant of the 317.

Also found an image showing the proposed bomb load layout of the Type 316 (Merlin or Dagger engines?). Seems there were three options for the power plant – either four 1,100hp Rolls-Royce Merlin, or 1,330hp Bristol Hercules, or 1,100 Napier Dagger although I also read that the Pegasus and Kestrel were in the mix early on. Also clearly shows the difference in design that Schneiderman mentioned in the 316 and 317 wing.

Other types in the frame for ‘Specification B.12/36’ were Armstrong Whitworth A.W.42, Boulton Paul P.90, Bristol design, Fairey design, Short S.29 Stirling, Supermarine Types 316 to 318 and Vickers Type 293

The link below gives further details on the proposed Type 317 specs and also shows the A.W.42 design along with various other types in the design phase

http://warbirdsforum.com/showthread.php?t=385

Chris