1935-45: alternative British bombers

[nuuumannn]

RAF does not order the Whitley here, but a 4-engined bomber instead of it.

Oddly enough, the Whitley's basic structure was based on the AW.23 bomber transport. Model at the Midland Air Museum. It was designed to compete against the Bristol Bombay, which won the requirement.

MAM 17

Structurally, AW used the same formula for its metal construction, which was robust, but that big chunky thick wing profile doesn't favour high speeds and high altitudes.

Okay, 3 people didn't exactly liked my idea of foxing the Germans, so I'd forget it - A-W makes a proper 4-engined bomber instead.

Actually four - I pointed out it wasn't smart before anyone else here.

Bomb bays were all around the map for not only British bombers, curiously enough the bomber with most generous wing cells was the one with greatest payload - the Whitley. With advent of Whitley and Wellington, bomb bays/cells and payloads of British bombers were a big step ahead of any European or Japanese bombers. Going for a big bomber will just reinforce this.

British bomb bays weren't actually all over the map, since the Brits had a rather limited range of bomb sizes they could carry, and the object of the designers was to get their bombers to carry as large a load of those little bombs as possible, hence the diversity in size and distribution. The only British heavy bomber that really could carry the bigger bombs without modification, say 4,000lb and over, was the Manchester/Lancaster (and the Mosquito at a stretch). The Stirling's bomb bay was longitudinally sectioned, therefore able only to carry the biggest pre-war bombs and the Halifax's complex door arrangement meant it could only carry a 4,000lb bomb with its doors slightly open, which introduced drag issues, which the aircraft was plagued with already. The Wellington's was sectioned similarly to the Stirling and the Whitley had two bays, one each fore and aft of the wing box, as well as wing cells, which again restricted the size of what could be carried.

Building a new design of bomber needs quite a bit of hindsight and it is thanks to all those extra and un-needed requirements, like catapulting the Manchester and being able to carry two torpedoes that made the Lancaster with its massive bomb bay - dimensionally the biggest in the business - able to carry the big loads it could.

 

[Shortround6]

Weight of the bomber might or might not be a problem on anything that is not tarmac, but ground pressure needs to be kept in check - IOW, heavier bomber will need bigger wheels or more of them, when compared with a lighter bomber.

I believe the British standard was 38lb/sq in so even a Blenheim I needed 333 sq in of contact area for it's tires, (including tail wheel) This obviously affects wheel and landing gear size (and nacelle size for wheel storage. This was to avoid making ruts in the grass field, Helps explain why some of the british bombers had such large looking tires. Of course gross weights grew a considerable amount during design and development, not to mention later versions, so later versions either just pumped up the tires with a bit more air or fitted heavier duty tires with more air.

As for the take-off strips, Wellington I, Hampden*, Manchester and 1st Halifax used 1300-1400 yds, Wellington III under 1100 yds, Whitley with Merlin just 1000 - the big, thick and 'tilted' wing has it's advantages. No british bomber used much of a high-lift devices that help with take offs, like the Fowler flaps, or even something like the 'Junkers flaps', so there is opportunity for improvement.

That is what they used, not what they were designed for. Or they didn't meet the original specification in that regard.
Blenheim I...... 700 yrds take off at 12,500lbs to 50 ft. 685 yds landing from 50 ft at light weight, (9400lbs?)
Blenheim V.....950 yrds take off at 17,000lbs to 50 ft. 800 yds landing from 50 ft at light weight, (12,000lbs?)

extreme example?

If we are allowed to "design" a plane that was allowed an extra 35% of take off distance and an extra 16-17% of landing distance than the historical planes were designed to meet then I am sure we would wind up with something different.

High lift devices were being introduced at a rather fast pace. Early flaps, like Gladiator, Hurricane, Spitfire and some American planes were used to steepen the approach and shorten the ground run (reduce landing distance from 50 ft) not to get the plane off the ground. They were NOT lift devices. First production plane to use Fowler flaps flew in prototype form in July of 1937, But you can't add Fowler flaps to an existing wing. you have to design the wing from the start to use them. Any plane that was even 1/2 completed (even just in drawings) was probably far too late to throw out the wing and start over without delaying the whole project by months. And British planes were tending to run late (too long in design and development ) to begin with.

The crappy propellers would have been an easier fix, assuming the British could increase production, to improve take-off performance on the early machines.
1937 to 1942 covers the period of introduction of the Fowler Flap to the double slotted Fowler Flap. The B-17 used a simple split flap and it was rarely, if ever, used for take-off.
Not that the B-17 is a gold standard for advanced aeronautics in WW II but to put in context that many of the British large bombers used in the war were not really behind the times either.

 

[Shortround6]

Tomo, if you don't have this Book I would recommend it.

The Author has a number of other books but this is a nice one volume overview of the British AIrcraft and paper designs of the time.

For instance the British wasted a crap load of time and energy on specification B1/39 for an armed bomber. Nine companies made proposals. The main feature of this specification (Jan 1939) was the incorporation of TWO gun turrets each with four 20mm cannon. A fair amount of the bomb load was to be 500lb bombs carried in wing cells to leave a large part of the fuselage (and the CG) free to accommodate the turrets.
Avro type 680 design

None of this work lead to anything.
The vast majority of work on later specifications for 75 ton and 100 ton bombers also lead to nothing, the best result was work done by Bristol on an eight engine bomber did help with the design of the Brabazon airliner which flew in 1949.

Bomber used the same coupled Centaurus engines but for pusher props, not tractors.
Cover picture for the Book was a Vickers design.

How much existing designs were ignored or problems papered over while designers/engineers worked on these more "modern" designs I don't know.

 

[nuuumannn]

In fact, I have a copy of that book sitting next to me as I write this - well worth getting a hold of.

A fair amount of the bomb load was to be 500lb bombs carried in wing cells to leave a large part of the fuselage (and the CG) free to accommodate the turrets.

This again shows the British lack of foresight in designing big bombers, even while the first big modern designs to B.12/36 and P.13/36 are being cemented with the manufacturers - no one is thinking beyond the existing bomb dimensions. It's interesting to note that for B.1/39, commonly called 'The Ideal Bomber' performance specifications were still below those that the Lancaster achieved in its B.III variant, although the predictions of 44,000lb bomb loads with a maximum weight of 160,000lbs seems excessively like our Russian giant bombers, huge, lumbering multi-engined monstrosities that would have proven terribly vulnerable.

 

[tomo pauk]

That is what they used, not what they were designed for. Or they didn't meet the original specification in that regard.
Blenheim I...... 700 yrds take off at 12,500lbs to 50 ft. 685 yds landing from 50 ft at light weight, (9400lbs?)
Blenheim V.....950 yrds take off at 17,000lbs to 50 ft. 800 yds landing from 50 ft at light weight, (12,000lbs?)

extreme example?

Indeed, an extreme example. Blenheim was of very light structure - 'tare weight' of Beufort 13000 lbs vs. the Blenheim I of under 8100 lbs - and was carrying a light payload (bombs, fuel, guns, ammo) on the Mk.I, all of this making the Mk.I a very light A/C for take off and flight. The 'no free lunch' rule applies as ever.
(fun fact: Beaufort have had one of the highest G load factor of ww2 bombers; 9.4G vs. most of them being under 6G (only the as-designed dive bombers were rated for greater G load factor, for obvious reasons))

Numbers I've quoted above are from data sheets, ie. real world figures. Mostly mid-1941 dated data sheets.

If we are allowed to "design" a plane that was allowed an extra 35% of take off distance and an extra 16-17% of landing distance than the historical planes were designed to meet then I am sure we would wind up with something different.

Having much more power also helps. The Wellington III (Hercules engines) have had shorter take-off distance than Mk.I by some 20%; 50% of increase of take-off power easily cancelled out the 15% increase of max weight and then some.

High lift

devices were being introduced at a rather fast pace. Early flaps, like Gladiator, Hurricane, Spitfire and some American planes were used to steepen the approach and shorten the ground run (reduce landing distance from 50 ft) not to get the plane off the ground. They were NOT lift devices. First production plane to use Fowler flaps flew in prototype form in July of 1937, But you can't add Fowler flaps to an existing wing. you have to design the wing from the start to use them. Any plane that was even 1/2 completed (even just in drawings) was probably far too late to throw out the wing and start over without delaying the whole project by months. And British planes were tending to run late (too long in design and development ) to begin with.

British big bombers typically landed at half the distance vs. what they needed to clear the 50 ft obstacle. So I'd try to focus on actual high-lift devices (that can also be used to shorten the landing distcance; the big bombers of the day didn't flew much at high AoA). Eg. Ju-52 flew already in 1932, so the 1st generation of the bomber monoplanes for RAF can copy the Junkers flap, while second generation (roughly what historically were Stirling, Halifax and Machester) can do the Fowler flap.
I'm not familiar on British developments of high-lift devices in 1920s-30s, bar the Handley-Page slats (those do not seem to help Hampden to shorten the t-o strip) - hopefully someone can chime in and add to this discussion.

The crappy propellers would have been an easier fix, assuming the British could increase production, to improve take-off performance on the early machines.
1937 to 1942 covers the period of introduction of the Fowler Flap to the double slotted Fowler Flap. The B-17 used a simple split flap and it was rarely, if ever, used for take-off.
Not that the B-17 is a gold standard for advanced aeronautics in WW II but to put in context that many of the British large bombers used in the war were not really behind the times either.

British large bombers were generally very good, even if the 'air industry' of UK was capable for even better designs in the time of interest - they created a 4-engined bomber back in the Great War after all - and even if doctrine was very questionable.

 

[Shortround6]

Numbers I've quoted above are from data sheets, ie. real world figures. Mostly mid-1941 dated data sheets.

Figures for the Blenheim are from data sheets. By Mid 1941 the British were well into expanding the size of airfields from what they were in 1935-37. Stirling may have been required to lift off the runway in 500yds (not clear 50ft) which put a real kink in it's design
That requirement was also the source of the catapult launch idea. It goes away real quick eitehr when the shooting starts or when they figured the shooting was about to start.

British big bombers typically landed at half the distance vs. what they needed to clear the 50 ft obstacle. So I'd try to focus on actual high-lift devices (that can also be used to shorten the landing distcance; the big bombers of the day didn't flew much at high AoA). Eg. Ju-52 flew already in 1932, so the 1st generation of the bomber monoplanes for RAF can copy the Junkers flap, while second generation (roughly what historically were Stirling, Halifax and Machester) can do the Fowler flap.

The Junkers flap was high drag in cruising flight. Junkers didn't use on the Ju 88 though the Ju 86 and Ju 87 did.
The Halifax and Manchester were ordered off the drawing board just a few months after the prototypes were ordered (but far from flying) at just about the same time that the Lockheed 14 flew. Unless you want to delay the two British bombers by months the Fowler flap is a no-go. Stirling is even further along in the design process.

More later.

 

[wuzak]

British bomb bays weren't actually all over the map, since the Brits had a rather limited range of bomb sizes they could carry, and the object of the designers was to get their bombers to carry as large a load of those little bombs as possible, hence the diversity in size and distribution. The only British heavy bomber that really could carry the bigger bombs without modification, say 4,000lb and over, was the Manchester/Lancaster (and the Mosquito at a stretch). The Stirling's bomb bay was longitudinally sectioned, therefore able only to carry the biggest pre-war bombs and the Halifax's complex door arrangement meant it could only carry a 4,000lb bomb with its doors slightly open, which introduced drag issues, which the aircraft was plagued with already. The Wellington's was sectioned similarly to the Stirling and the Whitley had two bays, one each fore and aft of the wing box, as well as wing cells, which again restricted the size of what could be carried.

The Wellington's bomb bay was a single long one with three longitudinal sections divided by two bomb beams.

One of the beams could carry bombs on both sides, but I am not sure if the other could for smaller bombs.

Some were modified for carrying the 4,000lb HC bomb by removing the beams and installing a single point bomb rack. The bomb bay doors had to be modified as well.

The Wellington was the first to drop the cookie in combat.

I'm not sure if the modifications made into a later production aircraft.

As an aside, a bomb beam from a Wellington was being modified to be fitted to a Mosquito with a bulged bomb bay, allowing it to carry 8 250lb target indicators. 8 500lb MC bombs would also have fitted, but the CoG would have been too far rearwards.

 

[yulzari]

Don't under estimate the task involved in making longer concrete runways. Not just transitioning from grass to concrete but the expansion of the airfields themselves to take in land for longer runways. The southern half of England (the relevant bit for offensive airfields) is crowded and good farmland. This made land pricey and the budget could not afford concrete and large land purchases until re armament was well under way. Building the long concrete new airfields for the RAF (and in the second half of the war, USAAF) was the largest construction programme ever undertaken in Britain and ate up a lot of desperately valuable farm land and fit labourers to boot. Labour shortages forced the agricultural force to rise to be 1/5 PoWs, the Land Army of women recruited and conscripts were diverted from the forces into the mines to keep up coal production. This was one of the greatest undertakings of the British war effort yet is the least lauded. By 1945 the British Army in NW Europe was running out of infantry with WW1 levels of losses.

It is so easy to ask 'why they did not just build longer concrete runways'. It was an enormous task to do it, mostly in wartime with competing demands. In the USA land was cheap and the population could provide the labour, materials and machinery far more easily. The energy cost alone of producing the cement for the concrete makes the Atlantic Wall look like a garden hobby project. The nearest more modern equivalent is to the motorway construction programme which was a doddle by comparison. You are building a small town with each airfield to boot.

The Naziboys who slaver over assorted prototype large Luftwaffe projects should look at the logs where repeatedly the same few airfields are used and flights with problems had to fly long distances to find an airfield long enough to land on.

It is all much more complicated than just making a whizzo aeroplane.

 

[wuzak]

W wuzak - care to post a bit more on the HP high-speed bomber (dimensions, engines, bomb load/fuel load etc)?

The only dimensions I could find were the wing span (75ft) and wing area (800sq.ft.), which were not contained in the H-P document, but in a discussion of the paper "A Memorandum on Bombing Policy and its Influence on Design" by George Voklert, H-P's chief designer. For comparison, the Manchester (closest to the original P.13/36) had a span of 90ft 1in (compared with an estimate of 88ft in the document), and a wing area of 1,131sq.ft. (1073sq.ft.).

Volkert based his paper on the P.13/36 specification that the Halifax and Manchester were built to.

P.13/36 specified 3 load cases:
(a) 1,000lb bomb load with 1,000 mile range, take-off in 500 yards
(b) 2,500lb bomb load with 2,000 mile range
(c) 3,500lb bomb load, 3000 mile range and accelerated take-off (catapult)

The estimates he put up for the three load cases were (the numbers in parentheses are the crew required for each case):

                             P.13/36    New Bomber
Tare Weight (lb)               18350         16447
Crew and Parachutes (lb)     (4) 800       (2) 400
Guns (lb)                        144           NIL
Ammunition (lb)                  520           NIL
Bombs (lb)                      1000          3000
Bomb Gear (lb)                    56           168
Oxygen (lb)                      117            55
Total Military Load (lb)        2864          3831
Petrol (UKG)                     557           529
Petrol (lb)                     4289          4070
Oil (lb)                         270           260
Total Weight (lb)              25773         24608
Cruising Speed (mph)             278           300

                             P.13/36    New Bomber
Tare Weight (lb)               18350         16447
Crew and Parachutes (lb)    (6) 1200       (3) 600
Guns (lb)                        144           NIL
Ammunition (lb)                  520           NIL
Bombs (lb)                      2500          5000
Bomb Gear (lb)                   140           250
Oxygen (lb)                      262           120
Total Military Load (lb)        5069          6254
Petrol (UKG)                    1075          1018
Petrol (lb)                     8280          7850
Oil (lb)                         432          4151
Total Weight (lb)              32131         30966
Cruising Speed (mph)             275           297

                             P.13/36    New Bomber
Tare Weight (lb)               18350         16447
Crew and Parachutes (lb)    (6) 1200       (3) 600
Guns (lb)                        144           NIL
Ammunition (lb)                  520           NIL
Bombs (lb)                      3500          7000
Bomb Gear (lb)                   196           350
Oxygen (lb)                      262           120
Total Military Load (lb)        6125          8354
Petrol (UKG)                    1605          1515
Petrol (lb)                    12360         11670
Oil (lb)                         630           595
Total Weight (lb)              37465         37066
Cruising Speed (mph)             273           295

The aircraft was to be powered by two Rolls-Royce Vultures, as per the P.13/36 specification. This would, with our hind sight, led to development problems and performance deficiencies due to the troubled Vulture development.

Estimated top speed was 380mph, but the design was not a fully developed proposal.

 

[tomo pauk]

The Junkers flap was high drag in cruising flight. Junkers didn't use on the Ju 88 though the Ju 86 and Ju 87 did.

Ju 86G (BMW 132 engines) cruised, with extended belly 'turret', as fast as the much smaller Blenheim - 325-337 km/h. Wing area was almost double on the Ju 86, 883 sq ft vs. 465 on Blenheim.
Max speed of Ju 86 was same as on Hampden (20% bigger wing on Ju 86).

The Halifax and Manchester were ordered off the drawing board just a few months after the prototypes were ordered (but far from flying) at just about the same time that the Lockheed 14 flew. Unless you want to delay the two British bombers by months the Fowler flap is a no-go. Stirling is even further along in the design process.

More later.

With an early 4 engined bomber by A-W, plus the historical Weelington and Hampden, I can wait. Wait for Shorts to not to design the Stirling with the too big a fuselage, for HP to make Halifax with Hercules, and for Avro to make 4-engined bomber.

 

[fastmongrel]

Are you sure on the Ju86 speeds. I get 325kmh max speed and cruise at 250kmh clean.

Max speed of the Hampden was 400kmh cruise at 325kmh.

 

[buffnut453]

Rather surprised nobody has mentioned the Supermarine B.12/36 yet. I've often wondered if, had it been developed, it could have achieved the hoped-for performance. After all, the estimated performance specs were pretty impressive: maximum speed between 325 and 360 mph; cruising speed 260 mph; operating ceiling 30,000 ft; range 3,000 miles.

 

[tomo pauk]

Are you sure on the Ju86 speeds. I get 325kmh max speed and cruise at 250kmh clean.

Max speed of the Hampden was 400kmh cruise at 325kmh.

I've 'boxed' the most interesting values, like engine power (both maximum and maximum continouos settings; BMW 132N engine; BMW 132F power and related speed being in brackets), speed and weight. It might be likely that max cont was used for cruise here, like it was often time with data sheets with Jumo 211.



That is from the manual available on this site.

I have two data sheets for Hampden, one lists 234, another 245 mph, both on mean weight.

 

[Glider]

I admit that I find the concept of the RAF needing more bomber designs slightly amusing. They could have done with some other types like a decent land based maritime patrol aircraft, but bombers types, they had plenty of.

 

[tomo pauk]

I admit that I find the concept of the RAF needing more bomber designs slightly amusing. They could have done with some other types like a decent land based maritime patrol aircraft, but bombers types, they had plenty of.

Perhaps someone is indeed trying to make RAF buying more bomber designs.
I'd cut the number of the designs, even if not by much. Eg they will not buy Botha, while Hampden gets the torpedo (torpedos?) earlier so there is no need for Beaufort.

 

[wuzak]

Perhaps someone is indeed trying to make RAF buying more bomber designs.
I'd cut the number of the designs, even if not by much. Eg they will not buy Botha, while Hampden gets the torpedo (torpedos?) earlier so there is no need for Beaufort.

No Beaufort, no Beaufighter?

 

[tomo pauk]

No Beaufort, no Beaufighter?

Have Bristol make a big 2-engined fighter from ground-up from 1937, that is still smaller than historical Beaufighter?
Stick the Merlins on Blenheim? Or, since this is the alt bombers thread after all, make the Mosquito by the time it was 1st suggested.

 

[Shortround6]

Something in the Ju 86 speeds certainly seems a bit off.
Max continuous is often max rich cruise.

The Blenheim (or indeed most British data sheets) do not give max rich cruise. For the Blenheim IV max cruise was 2400rpm and 3 1/2lbs boost. Max lean cruise was 2400rpm and 1 1/2lbs boost. British bombers (or the early ones) had two pitch props and were in high pitch from very shortly after take-off. MK IV was supposed to cruise at 225mph at 15,000ft at 2400rpm and 1 1/2 lbs boost, the extra 2lbs boost should have been good for about 12% more power (roughly).

Most high lift devices cause greater or lesser amounts of drag, even when not in use. However it is hard to get a good understanding of how much because the high lift devices often allow other design choices to be made, like a smaller/ lower drag wing.

Consider 3 American airliners of the 1930s.

Boeing 247.

• Crew: 3
• Capacity: 10 pax, baggage and 400 lb (181 kg) of mail
• Length: 51 ft 7 in (15.72 m)
• Wingspan: 74 ft 1 in (22.58 m)
• Height: 12 ft 1.75 in (3.7021 m)
• Wing area: 836.13 sq ft (77.679 m2)
• Empty weight: 8,921 lb (4,046 kg)
• Max takeoff weight: 13,650 lb (6,192 kg)
• Fuel capacity: 273 US gal (227 imp gal; 1,030 l)

Performance

• Maximum speed: 200 mph (320 km/h, 170 kn)
• Cruise speed: 189 mph (304 km/h, 164 kn) at 12,000 ft (3,658 m)
• Range: 745 mi (1,199 km, 647 nmi)

Douglas DC-2

• Crew: two-three
• Capacity: 14 passengers
• Length: 61 ft 11.75 in (18.8913 m)
• Wingspan: 85 ft 0 in (25.91 m)
• Height: 16 ft 3.75 in (4.9721 m)
• Wing area: 939 sq ft (87.2 m2)
• Empty weight: 12,408 lb (5,628 kg)
• Gross weight: 18,560 lb (8,419 kg)

• Maximum speed: 210 mph (340 km/h, 180 kn) at 8,000 ft (2,400 m)
• Cruise speed: 190 mph (310 km/h, 170 kn) at 8,000 ft (2,400 m)
• Range: 1,000 mi (1,600 km, 870 nmi)

Lockheed 14 (P & W Hornet engines)

• Crew: two
• Capacity: 12-14 passengers
• Length: 44 ft 4 in (13.51 m)
• Wingspan: 65 ft 6 in (19.96 m)
• Height: 11 ft 5 in (3.48 m)
• Wing area: 551.0 sq ft (51.19 m2)
• Empty weight: 10,750 lb (4,876 kg)
• Gross weight: 15,650 lb (7,099 kg)
• Max takeoff weight: 17,500 lb (7,938 kg)
• Fuel capacity: 644 US gallons (2,440 l; 536 imp gal)

Performance

• Maximum speed: 250 mph (400 km/h, 220 kn) at 5,800 ft (1,800 m)
• Cruise speed: 215 mph (346 km/h, 187 kn)
• Range: 850 mi (1,370 km, 740 nmi) at max weight 17,500 lb (7,900 kg)

The high lift devices of the Lockheed 14 allowed for the about same payload (crew, passengers, luggage and mail) to be carried at higher speeds in a physically smaller and lower drag airplane. While still operating out just about the same size airfields. From a different source the landing speed of the Boeing 247 was 58mph, DC-2 was 62mph and the Lockheed 14 was 65mph.
I would note that the Lockheed used leading edge slots in the wing. Many planes in the 30s used slot or slats not for improved lift (you need the slot or slat to cover most of the leading edge to do that) but to improve or maintain aileron control near the stall. This is what the Hampden had them for and the first 50 or so Halifax's.

Certain aircraft had quite a bit of built in drag which often does not get mentioned. Part of the scheme for a super Halifax not only called for a longer span, higher aspect ratio wing of lower drag but the the regular Halifax wing 2 spar wing had a number of span wise riveted seams which caused a lot of drag. The construction of the new wing was laid out to use chordwise riveted seams whenever possible, When comparing aircraft and their features we have to be careful of attributing performance (or lack of performance) to just a few features or details when other features/details might have just as much impact/effect.

 

[Shortround6]

Have Bristol make a big 2-engined fighter from ground-up from 1937, that is still smaller than historical Beaufighter?

The whole idea of the Beaufighter was that it could be made quickly and easily using Beaufort parts and tooling without having to go back to square one and starting over. It did cut some time off the design/development but perhaps not as much as they hoped.

The British design and experimental shops were stretched thin, very thin during the 30s and the war years which is why development often took so long, Having just about every company submit a proposal for just about every requirement didn't help (an exaggeration but really, 9 different aircraft proposed for the Jan 1939 heavy bomber specification?) as each proposal was accompanied by a set of drawings, sometimes a model, and estimated weights, CG, performance estimates and so on. The were not just quick sketches on an envelope with a few hasty calculations. And some of those proposals had several different engine options. each of which required preliminary estimates/calculations.

Perhaps starting in 1937 would have given Bristol the time and by ditching the Beaufort given them the manpower. But then they would have been using their experience from the Blenheim and not the experience gained in designing the Beaufort or at least not as much. Bristol had worked on at least two proposals for torpedo plane based off the Blenheim before starting work on the type 152, First shown in a Brochure on Feb 21nd 1936. It was much modified by the time it was ordered and the permission to switch from the Perseus engine to the Taurus was granted in July of 1937.

There is a terrifying thought. Cancel the Beaufort and design a large twin fighter using the Taurus engine like the Gloster twin. The Taurus does it's historic high dive into a damp sponge and Bristol is scrambling franticly to change the design to take Hercules engines in late 1939/early 1940 and the Beaufighter misses it's introduction as a radar equipped night fighter.
Not needed as the British have plenty of radarless Defiant night fighters in 1940/41

 

[nuuumannn]

he Wellington's bomb bay was a single long one with three longitudinal sections divided by two bomb beams.

That's right, it was sectioned. As originally constructed it was laid out in three distinct sections to contain the bombs, as evident in the door layout, which, as you correctly stated had to be modified for carrying bigger bombs. In this view you can clearly see the door layout as originally intended, which is five lengths of door divided into four separate parts each.

Wellington bomb bay