Deadman Switch - WI Supermarine Type 317 not cancelled

[soundnfury]

A tale of R. J. Mitchell's other legacy...

Ch. 1: Departure

26th September, 1940. Villacoublay, base of III./KG.55.

"Meine Freunden, ihre Ziel: Southampton." [My friends, your target: Southampton.]
Oberstleutnant Hans Korte gestured to the map on the easel behind him. As usual, the briefing for the day's raid took place outdoors, in the shadow at the forest's edge. The Heinkels of Kampfgeschwader 55 were to attack Supermarine's Woolston Works in Southampton. If they did their work well, Korte emphasised, the RAF's main supply of Spitfires would be interrupted, potentially swinging the advantage back to the Luftwaffe in a battle which had lately turned sour. Ever since those blasted British bombers had raided Berlin, and the Luftwaffe had been turned to blitzing London in reprisal, the fights had repeatedly gone in the RAF's favour. "Aber ohne Spitfeuer," he said, "was machen sie noch?" [But without Spitfires, what can they still do?]
Perhaps Korte, and his superiors who had planned the raid, would have been given pause had they realised the extent of the dispersal programme; destroying the works at Woolston, while it would certainly cause trouble for the RAF, would hardly be a knock-out blow. However, unknown to the Germans, something else was taking shape on the bank of the Itchen: the two prototypes of R.J. Mitchell's big bomber, at that time known only as the "Supermarine B.12/36 aircraft" or the "Type 317". Powered by four Bristol Hercules radial engines, it was projected to lift as much as 21,000lb of bombs - nearly ten tons.
"Der Start wird in 20 Minuten. Das ist alles," [Take-off is in 20 minutes. That's all.] Korte finished the briefing, and walked over to his aircraft. Standing by the fuselage, near the black identification letters G1 + AC, he exchanged a few remarks with his crew, before they climbed aboard the Heinkel 111 and began pre-takeoff checks. The raid was carefully timed: they would arrive over the target about fifteen minutes after a Jabo Geschwader, who would shake up the defences and hopefully exhaust the fuel of the RAF fighters.

~~~

The Gruppe had taken off and joined formation with its two fellow Gruppen of KG.55, based at other nearby airfields. Keeping position to Korte's port was Hauptmann Schlemell, who, the Oberstleutnant knew, would be annoyed not to be leading his Gruppe. As commander of KG.55, Korte was supposed to limit his flying time, lest he suffer the same fate as the previous commander, Stoeckl, who had been shot down six weeks earlier; but for a raid on a key target like this, he was determined to lead from the front. Now the bombers had reached altitude and were approaching the English Channel.
"Wo sind unsere kleinen Freunde?" [Where are our little friends?] asked Korte. The fighter escort was late - as usual, he thought - and the RAF were bound to have a squadron or two up to meet them over the target.
"Dort nach links," said the radio operator, "sie kommen jetzt nach unten." [There, to the left, they're coming down now.]
As the first Jagdstaffel moved into position above the bomber formation, a loud crackling and popping noise erupted from the starboard engine of Korte's Heinkel.
"Verdammt," he swore, "Motorschaden." [Damn, engine failure.]
Both Korte and his navigator tried every trick to recover a surging engine, but to no avail. The propellor was feathered, and the aircraft, losing speed, dropped out of formation.
"Der Stellvertreter wird in Kommando gestellt," [The deputy leader is placed in command.] Korte broadcast to the Geschwader. At least now Schlemell will get his chance, he thought, as he turned his stricken bomber homeward.

~~~

The navigator in Hauptmann Schlemell's crew was worried. "Wir sollten Swanage schon gesehen." [We should have seen Swanage by now.] The formation was approaching the south coast of England, and landforms were coming into view.
"Könnte es sein?" [Could that be it?] replied Schlemell, pointing at a headland.
"Ja, selbstverständlich," said the navigator, "dreimal Rolf machen." [Yes, evidently; steer 30 degrees to starboard.]
But in fact this was Selsey Bill, and instead of taking them over the New Forest, the turn led the bombers across the South Downs. As they flew on, and Southampton failed to appear, Schlemell became more and more agitated, while his navigator frantically re-read his maps.
"Ach!" the nav. exclaimed. "Horsham steht da unten, der Ziel liegt im Westen." [That's Horsham down there, the target is to the west.]
But it was too late, for cloud was rolling in over the target. Rather than lead the Geschwader into a fruitless attack on a defended target, Schlemell ordered the formation to attack Horsham town centre. After all, he thought, there's no point in wasting the bombs.

~~~

Report of Day Air Raids, 26/9.

An attempted raid on the London Docks by approximately 20-plus Dorniers was intercepted by 11 Group and dispersed.
A formation of 20-plus Messerschmitt 110s attacked the Supermarine works at Woolston, but bombing was inaccurate and the factory buildings are undamaged.
30-plus aircraft of unidentified type attacked Horsham, causing 139 casualties, no damage of military significance.
Several individual fighter-bombers made hit-and-run attacks London and Colchester over the course of the day.
Refer to Fighter Command report for details of air combats.​

~~~

Internal MAP Memorandum dated 26th Sept.

Re. B.12/36, raids of Tuesday and today not significantly impacted schedule.
Vickers-S.marine says still expect 1st flt prototype December.​

 

[soundnfury]

Ch. 2: Taking Shape

31st October, 1940. Supermarine works, Woolston, Hampshire.

"It's a bloody silly rule." Joseph Smith, Chief Designer of Supermarine, was on the 'phone to some jobsworth at the Air Ministry, trying to get them to agree on the service name for the bomber. The rule in question was that RAF bombers were named after British towns, preferably those with historical significance. Smith didn't want the Type 317 to be given some stodgy name like Somerton or Stourbridge. In his opinion, the only sensible choice was to name it the Mitchell, after his predecessor. 'R.J.' had drawn up the original designs for the B.12/36 bomber, before his death from cancer three years ago; he had been annoyed at the Air Ministry's choice of name for his fighter, and Smith saw this as a chance to right that wrong. The bureaucrat on the other end of the line felt otherwise, though, and was still wittering at him. "Look, I don't care if the Yanks are already using the name," Smith snapped back. "It's not like we're going to buy B-25s for the RAF, no-one's going to get confused."

~~~

"Well?" one of the draughtsmen, Crawford, quirked an eyebrow at him. Everyone in the drawing-office had heard Smith raise his voice, then hang up with excessive force.
"They'll come round to it," said the frustrated aircraft designer, "'soon as they can think of a way to back down without looking beaten. Maybe that would happen quicker if I hadn't gone off on one just now, but hey ho."
"Anyway," Smith continued, "the name's the least of our worries. Are we still having trouble with those oil coolers?"
"'Fraid so," Rogers, another engineer, chimed in, "these Bristol fittings are a pain in the neck." The firm's last experience, on the Spitfire, had been with the Rolls-Royce Merlin engine, neatly packaged into a 'power egg' that you could practically just bolt to the airframe and be ready to go. The Hercules, however, had proved much harder to 'plumb in', and new problems kept cropping up. The latest snag had resulted from some overheating problems another aircraft had experienced with the Hercules. Bristol had concluded that the oil coolers were too small for an engine of this power, and had designed an enlarged version, of which samples had just arrived at Woolston. But they couldn't be fitted to the inboard engines on the Type 317, because part of the wing structure was in the way.
"Well, we can't redesign the spar, there's no way we'd get the stressing worked out in time," said Smith. "Two things we can do. Stick with the smaller coolers, maybe just on the inners, and try to improve overall engine cooling. Maybe adjust the cowling, something like that. Or, we stick the new cooler on the end of a bent bit of pipe, and fit it in that way."
"It'd stick out, then," Crawford pointed out, "wing's not thick enough to bury it. You'd need a fairing over it, and we'd have to re-do the airflow past the engine."
"That idea's a bust, then," said Smith, "can't get time in Farnborough's wind tunnel for love nor money right now. And Vickers are busy using theirs for some new gewgaw for the Wimpy."
"But doesn't that scupper the cowling idea too?" asked Crawford.
"Sure, but the cowling's easier to change later," Rogers noted. "So if we use the smaller cooler inboard, and just limit the engine revs for now, then when the wind tunnel frees up we can sort it out."
"Sounds like a plan," Smith agreed, and marked out the changes on the master drawings. "Now, about the rudder cables..."
Sometimes it felt like aircraft design was an endless task.

~~~

The works chief, a lanky chap by the name of Hopkins, cast an appraising glance at the big bomber. The prototypes were both coming together nicely, he thought, and apart from a few rough edges around the engines, they almost looked ready to fly. They weren't, of course - plenty of equipment still had to be installed, and there was a list of change orders from the designers as long as your arm - but the airframe was all in one piece now, even sitting on its own wheels rather than jacked up on oversized trestles.
Still, the boss had promised the Air Ministry a first flight before Christmas, and that didn't look on the cards right now. Everyone was already working as much overtime as the company could afford, and there just weren't the resources to get everything done. Besides the Type 317, and the quantity production of the Spitfire I, there was the quick-release canopy mod, Hispano cannon conversions, parts for Spitfire IIs - the shadow factory wanted new jigs for the wings - and there was the Spitfire V development to worry about. Someone in the RAF had gotten panicked about the high-altitude Junkers, and now Supermarine were sticking an Merlin 45 on the front of a Spitfire to make a fighter that could catch it.
Breathing a weary sigh, Hopkins ambled over to the Spitfire V area, where a fitter was wrestling with some sheet metal. "Peter, you can put that down. I want you, John and Gerald to work on the Type 317."
The new Spit would just have to be delayed a little bit more, and maybe the bomber would be ready on time after all. Hopkins went looking for someone else to transfer; the 317 shop needed another riveter as well.

~~~

Diary of Station Commander, A&AEE, RAF Boscombe Down, entry for 31 Oct.

Contractors arrived today to extend the main runway, ready for testing the
new four-engined bombers. Making a lot of noise. Hopefully they'll be
done by the time Supermarine and Handley Page send us their prototypes.​

~~~

Bomber Command organisational note dated 31/10/1940.

No 207 Sqn to form at WADDINGTON, effective tomorrow, for introduction of
AVRO MANCHESTER into service. First batch of aircraft to be delivered on
05/11 with full spares and equipment.​

 

[Just Leo]

The Merlin on the Spit didn't install in the form of a Power Egg. The oil coolers on the 317 seem to have been envisaged as being hung below the engine nacelle and easily enlarged, although the oil pump of larger capacity was the real fix. There is precious little evidence that the prototypes even had wings fitted when destroyed OTL, but, of course, there's no evidence otherwise either.

 

[soundnfury]

The Merlin on the Spit didn't install in the form of a Power Egg.

Yeah, I realised after I'd written it that the Power Egg Merlin came later. But I couldn't think of a way to phrase "easily installed / plumbed, but not a Power Egg as such", so I just left it as is for now.

The oil coolers on the 317 seem to have been envisaged as being hung below the engine nacelle and easily enlarged,

Hmm, good point. How about having some sort of undercarriage support structure being in the way? Is that plausible?

although the oil pump of larger capacity was the real fix.

Wait, you say that as though there really were oil cooling problems on the Hercules. I just made that up; was I accidentally accurate?

There is precious little evidence that the prototypes even had wings fitted when destroyed OTL, but, of course, there's no evidence otherwise either.

Yeah, information about the prototypes OTL is scanty enough I can probably get away with bending things a bit for this TL. I'll need to, because the most plausible guess is that development was far enough behind the Stirling it would've been cancelled even without the raid - but that's no fun to write

Thanks for the criticism

 

[Just Leo]

Wait, you say that as though there really were oil cooling problems on the Hercules. I just made that up; was I accidentally accurate?

The cool oil problem is contextual in the long ascent to developmental maturity, not in the installation of the nascent engines likely to power the Supermarine 317, rated at 1330 hp. So, you're not accurate, but perhaps prescient.

 

[soundnfury]

So, you're not accurate, but perhaps prescient.

I'll take what I can get
Here's the next chapter...

Ch. 3: First Flight

29th December 1940. Eastleigh Aerodrome, Hampshire.

Four days late, but at least it was before the end of the year, mused Jeffrey Quill, at least the bomber would fly in 1940. Just.
He had been the second person to fly the Spitfire, after Mutt Summers, but now Quill was chief test pilot, and would at last get to make the maiden flight of a new aircraft type. The B.12/36 (they still hadn't been able to get agreement on the name, it was getting to be something of a joke at Supermarines) stood outside in the clear morning light, as Quill went through the paperwork. So many forms he had to check and countersign before the first flight; fuel load, C.G. limits, engine handling restrictions... the list went on and on. With a flourish he signed the last form in the stack (to acknowledge that the aircraft was not to be banked beyond 45 degrees pending further stressing calculations on the tailfin. As if he would fly a bomber that aggressively, let alone on its maiden flight!), handed the whole lot over to the fretsome fellow behind the desk, and stepped out of the control hut to look over the aircraft.
The bomber had a purposeful look about it, with those swept leading edges giving the wing an almost triangular appearance, and the bulky radial engines hung on the front - less widely spaced than on the Stirling, the aircraft from Shorts that competed to fill the B.12/36 requirement. Quill had, of course, heard the story of the ignominious end to the Stirling's first flight, when its undercarriage collapsed after landing. He hoped no such accidents would mar today's flight; Shorts were already ahead, having started series production in August, and the mandarins in Whitehall had been leery of the Supermarine design ever since R.J. passed away - as if somehow Smith weren't totally up to finishing the job. Ridiculous. In any case, the Stirling could only carry 14,000 pounds of bombs, barely two thirds of what could be squeezed into this mighty machine.
The design office had decided that flying the B.12/36 was too much for one man, a second pair of hands being essential to handle the engines, fuel pumps and various other systems. Quill wasn't about to complain; the big bomber was bound to be much more of a handful than the Spitfires he'd been test-flying for the past couple of years. Rogers, for his sins, would be his flight engineer for the first few flights, until Bristol got round to sending someone down like they'd promised.

~~~

"Booster pumps on. Gills open. Magnetos on." Rogers ran through the litany of checks. "Brake pressures OK. Accumulator fully charged. Pitch fully fine."
Quill adjusted the altimeter QFE, made sure the trim was neutral, and turned to face the engineer. "Ready to start up."
As Rogers held down the starter switch, the No.2 engine began to turn over. The cold engine coughed for a few seconds, before roaring into life. "1400 revs, holding steady. Starting No.1," said Rogers, as the port outer started to move. Soon all four engines were running, sending a rhythmic vibration through the body of the aircraft. After running up each engine in turn to check the magnetos, Quill taxied the big bomber out to the main runway. A fully laden bomber would need a much longer take-off run than was available here, but for the test flights, not only was the bomb bay empty, but the fuel tanks were only half full; Eastleigh's runway would be more than long enough for the job.
"Cleared for take-off." The outboard engines spun up to 2800rpm as Rogers throttled up to a boost pressure of +6; the inboard engines were held at 2600 by a detent, to avoid overtaxing the oil coolers. Quill released the brakes, and the Type 317 prototype began to pick up speed. Twenty knots, forty, sixty; the controls began to 'bite' as the tail came up (for the Type 317, like most aircraft of its day, was a tailwheel type). The bomber tried to swing to port, but Quill was ready for it and kept the nose straight. At 120 knots he eased back on the control column, and felt the aircraft respond eagerly. They were airborne.

~~~

It wasn't perfect. No aircraft ever is, the first time it flies, despite the story they liked to tell about the Spitfire. The Type 317's rudder was too heavy, the ailerons rather light; with the flaps down the trim changed too much and the aircraft seemed to lean eagerly forwards; the airspeed was at least five knots slower than the aerodynamicists had predicted - either that or they'd got the ASI calibration wrong. But these were minor things, could probably be fixed; could be lived with if not. Overall, Quill thought, this was a first class aircraft, and he was almost reluctant to bring the flight to an end. But the basic handling of the aircraft had been explored, and now it was time for the first landing. A fairly wide circuit was necessary, the Type 317 not being as nimble as the fighters that were normally test-flown out of Eastleigh, and the trim was becoming a nuisance again as he put down full flap for the final approach. Sweating with the exertion of flying the big bomber (there being no such thing as powered controls in those days), he lined up with the runway, kicked the rudder bar to allow for the slight crosswind, and set the prototype down - fairly gently - on the runway.

~~~

Reichswehr procurement order dated 29. Dezember (translated).

KRUPP ESSEN, a further 240 88mm Flak guns, to be delivered by end of
February. Standard wheeled carriages to be included.
SIEMENS MÜNCHEN, eight electrical alternators for searchlight power, to be
delivered by April 12th.​

~~~

No. 7 Squadron War Diary for week 23rd-29th December 1940.

Crew training continued in a desultory fashion due to further problems with
the squadron's Stirling aircraft. B-Beer is still being repaired after its
undercart mishap, while L-Leather and N-Nuts are awaiting replacement spark
plugs. All ground crews are working very hard however, and O-Orange was
able to fly every day this week, a 'first' for the squadron's Stirlings.
In fighter affiliation training on the 27th it was discovered that the
existing standard evasive maneuver is inadequate; pilots are experimenting
to find an alternative.​

 

[Just Leo]

Just to clarify, you're going for the model with "deltoid" wing planform and single fin, not my favorite model.

 

[merlin]

According to BSP - the '317' had the same bomb-load as the Stirling, well it would do - it was to the same specification.
Name - I would suggest Sheffield - it begins with 'S' and is an inland city!

 

[merlin]

Just to clarify, you're going for the model with "deltoid" wing planform and single fin, not my favorite model.

Out of curiosity, what was your 'favourite', and are you referring to the wing shape, or the design for the Spec??

 

[Just Leo]

Out of curiosity, what was your 'favourite', and are you referring to the wing shape, or the design for the Spec??

These are your choices, and I prefer the prettier one. As for final, chosen one, there's no proof one way or the other. In fact, there's no proof anything ever existed, photographically, beyond a fuselage mock-up.

 

[soundnfury]

Just to clarify, you're going for the model with "deltoid" wing planform and single fin, not my favorite model.

Yes. Personally I prefer it to the other, which looks too 'American' for my liking. Whereas from the side, the original 316 design just looks like a big Wimpy

 

[Just Leo]

Yes. Personally I prefer it to the other, which looks too 'American' for my liking. Whereas from the side, the original 316 design just looks like a big Wimpy

Curious indeed. The Wimpy featured a single fin, and a very American aircraft, very revolutionary, and quite Gooney-looking, had deltoid wing planform from the wing centre section outboard. In fact, they called it the Gooney Bird.

 

[soundnfury]

This TL isn't dead, it's just resting...
I'd like to remind readers that characters' opinions may not be my own.

Ch. 4: Trials and Tribulations

4th March 1941. RAF Boscombe Down, Wiltshire.

Heavy bombers, in the opinion of S/Ldr Salter, appeared to be cursed. Sometimes the A&AEE tested them and found them wanting. Sometimes they only revealed their faults after entering service. But for whatever reason, every one of the heavy bombers that British industry had produced had failed to live up to the manufacturers' exuberant promises. While the fighters astounded everyone with their performance, while the medium bombers at least did what they were built to do, the heavies just - didn't.
First there was the old Whitley. Slow, lumbering and inaccurate, probably the most useful thing it ever did (in Salter's opinion) was keep the Germans supplied with toilet paper back when we thought dropping leaflets was a good idea.
Then the Manchester, with its Vulture engines - which kept throwing their bearings and seizing up. Air Ministry was considering grounding them until something could be done about it; last he'd heard, half of 207 Squadron were flying Hampdens instead.
The Stirling, now, that one had looked promising for a while. Handily manoeuvrable even with six tons of bombs on board, but the performance at altitude was poor, the radius of action wasn't too good, and the less said about that damned undercarriage the better. Between the landing gear and the throttle controls, the Stirlings seemed to spend more time in the hangars than out of them. Still (he had to admit), the crews seemed to like it, at least when it was working. Maybe the sheer size of the aircraft gave them a feeling of power.
And now the Supermarine Mitchell and the Handley Page Halifax were lined up for testing; the former for development flying and the latter for its service trials. He hadn't found any flaws in the Halifax - yet; he was sure something would show up sooner or later - but the Mitchell's limitations were (to him) glaring. The engines weren't developing their design power - they'd been de-rated to deal with various issues, and the inboard pair had then been de-rated further because of some problem with cooling - and the airframe was overweight. The much-vaunted 21,000lb payload had been cut back and it looked like they'd be lucky to match the Stirling on that front. And it still had a fairing on the nose where the turret was supposed to be - Fraser-Nash had been having difficulties working around the quirks of the Mitchell's hydraulic system, and still didn't have an installation ready. When it came, it was bound to add yet more weight to the bomber, and cut into payload even further.
It wasn't all doom and gloom, though; Supermarine's changes to the flap profile had made the trim behaviour much better, and the servo rudder - while it looked a little old-fashioned - was working well enough. Whatever its failings as a weapon of war, the Mitchell was at least a 'pilot's aircraft', pleasant to fly. He called to his flight engineer, sitting across the Mess. "Hey Bairstow, shall we make a move on those engine handling tests? I thought we'd do the Mitchell first, if that's OK?"
"Sure thing, skipper."

~~~

7th March 1941. Stornoway House, Westminster.

"The Bristol Hercules," ran a Ministry of Aircraft Production technical report, "while adequate for initial working-up of the Supermarine Mitchell, lacks the growth potential the aircraft's development will require. Achieving a satisfactory performance will require engines in the 2,000hp class, which lies beyond that realistically achievable by the Hercules."
The report went on to recommend that Napier's 'H' engines be used, first the Dagger VIII in a resuscitation of the earlier Supermarine Type 316 concept, this paving the way for the development of a Sabre-engined version, the Type 316B. "Such an aircraft," the report continued, "would meet or exceed the original performance projections of the Type 317 on all axes. It must however be noted that the supply of Sabres would, initially, prove a limiting factor; volume production of the 316B would necessitate the opening of a Sabre production line at a shadow factory."
Lord Beaverbrook finished reading the report, and reached for the 'phone. "Fraser?" he spoke into the instrument. "I'm not happy with this Mitchell proposal. Hawkers never stop telling me about the trouble the Napier engines are giving with the Typhoon. Give me options."
"I suppose there's always the Vulture," replied the Director-General, Eric Fraser, "but if you think the Sabre has problems-"
"-the Manchesters are even worse, I know," the Minister interrupted. "It's a scandal. Are you sure we can't get more out of the Hercules?"
"Well, Bristol are offering the Centaurus, but that won't be ready for at least a year, probably more. Supermarines did say they needed wind-tunnel time to improve the 317's cowling, they hope to get at least another 75hp out of each engine that way, so that's an interim option."
Beaverbrook was a decisive man, and it didn't take long for him to formulate a plan. The Hercules cowling work would be given priority on the Farnborough wind-tunnel, while Supermarines would be given Instruction To Proceed with a prototype of the Dagger-engined variant. The Sabre would also have its priority increased, getting resources that otherwise would largely have gone to the Rolls-Royce Griffon. Meanwhile, the order book for the Manchester would be cut back until the Vulture showed some sign of improving reliability. Avro's proposal for a four-Merlin version had already been rejected - with all three of the current four-engined 'heavies' proving troublesome and consuming more than their fair share of industrial capacity, the last thing MAP wanted was another one.

~~~

11th March 1941. The skies above Kent.

F/Lt Evans sharply banked the Beaufighter to follow the bomber. If it were a Halifax, he thought, he'd have snapped it in his cross-hairs every time, but this Mitchell was more nimble than it looked. As the bomber pulled out of its diving turn, though, its wings were level for just a fraction of a second too long, and Evans' camera clicked. "Gotcha!" he called over the R/T.
"Aw, not again," drawled the Aussie pilot flying the Mitchell. With good humour he added, "There's no shaking you, is there."
Evans grinned. "Ready to call it a day? We'll compare notes on the ground."
"Sure," came the answer.
Some twenty minutes later, having landed at Manston, Evans watched the big bomber coming in to land. By his reckoning, the title of best heavy bomber was a toss-up between the Mitchell and the Stirling, with the Halifax a poor third. The Stirling was at least as manoeuvrable as the Mitchell, but its operational ceiling was lower, and that would put it at greater risk from flak.
Supermarine's bomber was passing its fighter affiliation tests with flying colours; for all the gun camera pictures he'd obtained today, Evans was well aware it wouldn't have been such an easy 'kill' by night.
On discussing the 'combats' with the bomber crew, all agreed that the continued lack of a front turret on the Mitchell was not a serious handicap; a frontal attack was proving difficult even by daylight, while in darkness (Evans reckoned) it would be practically suicidal for the fighter, who would have the choice of colliding with the bomber or missing entirely and getting a packet from the rear-gunner for his pains. Their subsequent report on the day's tests reflected this, recommending that the faired-over nose be standardised for the production version, leaving the four-gun tail turret as the Mitchell's only defensive armament. This was to prove too radical for the Air Ministry, though, who insisted on the addition of a pair of waist guns.

~~~

Report from Supermarines to Vickers management, mid-March 1941.

Type 316 & 317 project status
Work on the first pre-production example of the Mitchell B. Mk I is now
well underway, though delayed slightly by the stream of modification
requests stemming from the Service evaluation.
The jigs for the Dagger-engined B. Mk II (Interim) prototype have been laid
out in Shop No. 4, and construction progress is meeting the schedules
projected in last week's report. The Dagger plumbing is giving much less
trouble than the Hercules.​

~~~

Performance figures of Supermarine Type 317 - Preliminary estimates.

Based on measurements by A&AEE Boscombe Down, extrapolated to full equipment.
Powerplant: 4x Bristol Hercules II of 1,272hp (outer) or 1,164hp (inner)
Maximum speed: 279mph at 14,500ft
Cruise speed (fully laden): 224mph
Radius of action: 1,750mi
Operational ceiling: 25,000ft
Rate of climb: 700ft/min
Payload: 16,000lb of bombs (21,000lb in overload condition)​

 

[soundnfury]

It's taken quite a while, but the next chapter is ready at last.

Ch. 5: Conversion Flight

22nd June 1941. RAF Coningsby, Lincolnshire.

"As you know, the first thing is to get the cockpit-drill spot on," explained F/Lt Hopgood. "You'll find it's rather different to the Manchester." 'Hoppy', as he was known, had done a few hours on the Mitchell in the eval unit, and, since the Group's HCU hadn't got going yet, was giving the other 106 Sqn pilots their introduction to the type. The fact that the Squadron effectively had a single instructor to train them didn't much matter, as the bombers weren't arriving particularly quickly either; and with the inevitable maintenance troubles of a new aircraft, it would take some time before the Squadron's equipped strength was enough to begin operations. In the meantime, un-'converted' crews would continue to fly their Manchesters on raids, albeit with some reluctance due to that type's continued difficulties.
Today, however, Hopgood was 'converting' his CO. W/Cdr Gibson had started the war on Hampdens, then done a tour on night-fighters which was truncated when Bomber Command needed experienced crews; the delays to the Spitfire V had meant that the Germans still held hopes of successful day attacks, and had not been pressing very hard by night. Meanwhile, the bomber force was undergoing rapid expansion - admittedly, mainly with Wellingtons, but it was hoped that soon the heavy bomber production lines would swing into action, and Bomber Command would have a corpus of hardened crews ready to spearhead the new bombing offensive.
"There are four sets of engine controls," Hopgood continued, "which are all grouped together here as you see. The flight-engineer has most of the corresponding instruments, but there are RPM repeaters to the right of the Sperry panel. Of course you've handled radials before, but it's only too easy to get confused if you switch back and forth between Manchester and Mitch."
"Guess I'll trust my flight-engineer to keep that straight," joked Gibson. "Where are the trim controls?"
"Right here, sir, behind the throttles. Except for some reason," added Hopgood, "the rudder trim isn't with them; it's on the bottom of the panel here. Rather awkward actually as the yoke gets in the way."
The two pilots went on to discuss such technicalities as flap settings, cruising speeds and fuel system layout. After the theoretical portion of the lesson was completed, it was time to turn to the practical, and Hopgood began the start-up checks.
A few minutes later, the big bomber was taxying out to the runway. The flight-engineer called over the R/T, "Hullo Control, F-Freddie requesting take-off clearance - over." "Go ahead F-Freddie" came the reply. The Mitchell turned onto the runway, ran up its engines, and released the brakes.
"She'll try to swing to port as the tail comes up," said Hopgood, his hands gripping the control column tightly, "but that's easily checked. Call out when we hit 110 knots, please." On reaching the specified figure, he brought the nose up - the flap improvements had lowered the take-off speed - and the aircraft left the ground. With the engines brought back to climbing revs., the undercarriage and flaps raised, the Mitch was now moving smoothly through the air with little vibration - not exactly comfortable, but as near as can be expected from a combat aircraft.
Hopgood demonstrated several tasks such as feathering an engine, 'ditching' the aircraft (in a flat stretch of cloud at 4,000ft), and the Mitch's particular variant of the '5 Group corkscrew' evasive manœuvre, before heading back to join the circuit at Coningsby.
"F-Freddie cleared to land," came the call from Control. With thirty degrees of flap, the airspeed dropped to 150 at a moderate sink rate. The undercarriage was lowered as the bomber turned onto the runway heading; two green lights proclaimed both wheels to be locked down. The flight-engineer called out the airspeeds as the aircraft approached the runway, in a flattish glide and with the nose quite high. Hopgood's face beaded with sweat as he struggled to keep the heavy bomber in balance, until at last they cut the throttles and bumped down just beyond the threshold, coming to a stop after about a thousand-yard runout.
"There," Hopgood grinned, "now you have a try."

~~~

1st August 1941. The same.

A Miles Mentor communications aircraft touched down and taxied round to the control tower. The passenger, AVM John Slessor, being somewhat lame was helped down from the aircraft by a nearby serviceman; meanwhile the wingco's car drove up to meet him. After the customary exchange of salutes, Slessor and Gibson got straight down to business.
"How are you finding your new aircraft?" asked the AOC.
"Rather decent for the most part," answered Gibson, "but, of course, we have had our snags. The main one is this business of the bomb-release gear. Apparently there's some electrical issue, because if you have the engines running, the moment you switch the ground-flight switch to 'flight' all the contacts open. F/Sgt Loftus was rather surprised when his load of practice bombs fell onto the tarmac!"
"Sounds most eventful. I trust a solution is being worked on?" said Slessor.
"Yes; the trouble's been traced to noise from the alternator, and a couple of erks have bodged up a choke fitting. We're testing it this afternoon."
The AOC asked if there were any other issues, and Gibson mentioned a problem that had shown up when practising escape drill. "If the bomb-aimer isn't careful, he bangs his head on something on his way out of the nose - it's just a bit too cluttered down there."
The conversation turned to the overall qualities of the Mitchell, Gibson opining that it was "a real pilot's dream to fly," though adding that they hadn't yet done any night-flying in the type. "We've got a cross-country pencilled in for tomorrow night, though," he continued.
"Good, because I want at least one flight operational within a fortnight," Slessor replied. "Pierse wants to get all the heavies in action, says really serious tonnage of bombs will silence Bomber Command's critics. You should hear what he says about 3 Group when they can't put up more than a dozen Stirlings."

~~~

9th August 1941. The same.

Though the bomb-release had been fixed (the choke proving successful), the stream of issues had, of course, continued. The night cross-country exercises had exposed an unexpected problem: the long parallel windows along the sides of the cockpit produced an endless series of reflections from the navigator's working light, impairing the pilot's vision. The curtain intended to cordon off the navigator's station failed to prevent this, as it only blocked the light from shining directly at the pilot, leaving the nav's window open for observations. To fully resolve the problem, it would be necessary to practically split the cockpit into two sections, rather than being glazed all the way along; this had been communicated back to Supermarine's for consideration in the B Mk. II development. In the meantime, extra (non-openable) curtains were added around the nav's station, producing an 'office' with no view outside; if he wanted to check up on the bomb-aimer's map-reading, the navigator would have to 'pop outside' to reach a window.
However, despite the difficulties, the 106 Sqn crews were optimistic about their new aircraft. After all, despite being brand new and untried, they were already causing fewer hassles than the Avro Manchesters they were due to replace. The ground crews, too, were finding that the rugged air-cooled Hercules was a welcome change from the temperamental Vulture, and maintenance of the airframe was just as straightforward as it had been with the Avro type. Some other parts of the equipment, though, were causing nuisances, particularly the defensive armament: the rear-turret had a tendency to jam after any particularly hard landing, due to a ball-race jumping its groove, while the waist guns tended to freeze up at altitude unless carefully wiped free of oil before take-off. It was hoped that an electrical heating system might be devised to deal with the latter problem, but the turret would need a re-design — until an improved unit could be fitted, the erks would be kept busy with a 'turret job' for every few sorties dispatched.
All things considered, the Service introduction of the Mitchell B Mk. I was proving to be neither especially smooth nor excessively troublesome; just another new type for the RAF to learn to operate.
But no battle plan, as the saying goes, survives contact with the enemy. The ultimate test of the new bomber was about to begin.

~~~

Aircraft Readiness Report 5 Group (extract), 10/8/41
No. 106 Sqn.
Manchester: of 12 IE + 6 IR, 10 offered for tonight
Mitchell: of 6 IE, 4 offered for tonight

~~~

106 Squadron Order of Battle, night of 10-11 August 1941
To attack oil targets in Hannover, target area G:
A-Apple, F/O Stoffer
C-Charlie *, P/O Ambleton
H-Howe, F/Sgt Cooper
L-Leather, F/Sgt Shaw
N-Nuts, P/O Smith
O-Orange, F/Lt Wooldridge
Q-Queenie, F/Sgt Ullason
Z-Zebra, F/O Worswick
To attack marshalling yards in Hamm, target area B:
B-Beer, F/Sgt Walker
D-Dog *, W/Cdr Gibson
F-Freddie *, F/O Kershaw
P-Peter, F/Sgt Jameson
Y-Yankee *, F/Sgt Loftus
Withdrawn J-Johnnie u/s engine failure.
An asterisk * indicates Mitchell; other a/c are Manchester

 

[soundnfury]

I also did some artwork, because every aerospace TL needs pictures of its vehicles...

AH611 "ZN-F", a Mitchell B.I of No 106 Sqn RAF.
Missing from this image are the waist guns, because I haven't figured out what the fixture would look like.

 

[zert]

I just read up on your story and you have my interest. This is a bomber I do not remember reading about, and I am enjoying it get through its teething problems. Update as you are able, but I shall follow.

 

[Just Leo]

W/Cdr Gibson's career seems to have had a boost for some reason.

Installation of a Napier Dagger would be of no benefit to the installation of a Sabre, and it was well known as a useless engine by this time, and unrelated in nature to its monstrous stablemate.

Original aircraft was to have a retractable dorsal turret, to maintain speed. The fact that such examples didn't exist was typical of the time. Waist guns didn't seem popular at the time either, since power-operated turrets were the fashion. Defense against beam attacks have relevance on a day bomber but seem unusual and useless at night.

 

[zert]

With Just Leo's comment, I do not recall off the top of my memory that very many British Bombers had waist guns. Mostly front, rear, and a top turret. Maybe a bottom one as well.

 

[soundnfury]

W/Cdr Gibson's career seems to have had a boost for some reason.

If I'm not mistaken, at this point OTL he was a S/Ldr commanding a fighter Flight in 29 Sqn. But 106 needs a CO, and to lead a Bomber squadron you need acting W/Cdr rank (hey, I don't make the crazy rules) so a W/Cdr he had to be. It's not that far off OTL, where intervention from Harris produces the same result by April '42. Chalk it up to butterflies and/or dramatic license.

Installation of a Napier Dagger would be of no benefit to the installation of a Sabre, and it was well known as a useless engine by this time, and unrelated in nature to its monstrous stablemate.

That's a valid point. On the other hand, never underestimate the stupidity of the MAP and Air Ministry
And yes, the B.II (Interim) will prove pretty useless, probably unsuitable for ops.

Original aircraft was to have a retractable dorsal turret, to maintain speed. The fact that such examples didn't exist was typical of the time. Waist guns didn't seem popular at the time either, since power-operated turrets were the fashion. Defense against beam attacks have relevance on a day bomber but seem unusual and useless at night.

Again, AM stupidity. Waist/beam guns, IIRC, featured on the Wellington, and at this point in time the Wellington is still BC's most successful aircraft.
The retractable turret may have been dropped from the spec after the Stirling's troubles with its retractable ventral turret (which was quickly deleted from that design also).

 

[Glyndwr01]

If I'm not mistaken, at this point OTL he was a S/Ldr commanding a fighter Flight in 29 Sqn. But 106 needs a CO, and to lead a Bomber squadron you need acting W/Cdr rank (hey, I don't make the crazy rules) so a W/Cdr he had to be. It's not that far off OTL, where intervention from Harris produces the same result by April '42. Chalk it up to butterflies and/or dramatic license.


That's a valid point. On the other hand, never underestimate the stupidity of the MAP and Air Ministry
And yes, the B.II (Interim) will prove pretty useless, probably unsuitable for ops.


Again, AM stupidity. Waist/beam guns, IIRC, featured on the Wellington, and at this point in time the Wellington is still BC's most successful aircraft.
The retractable turret may have been dropped from the spec after the Stirling's troubles with its retractable ventral turret (which was quickly deleted from that design also).

The Handley Page Hayford featured a rotating and retractable ventral "dustbin" turret.