Bristol's twin-engined planes?

[tomo pauk]

Bristol's Blenheim, Beaufort and Beaufighter were significant part of not only RAF, but other airforces. Later combat-plane designs, Brigand Buckingham, were too late for the ww2.

Starting date being Blenheim's 1st flight, 12 April 1935, how would you further develop the 'line' of the planes? The engines should be the historical Bristol products, yet the planes should accept other ones available for the historical users. Armament electronics also being historical types. The designs should be tailored for more roles - no tightly-knit approach (but also not too big the resulting plane)
Timing of the designs should be 1940 (1st design), 42 (second), 44 (3rd), or, 1940 (1st design), 43 (2nd design).

 

[davebender]

Bristol Beaufighter

Fuel Capacity:
A total of 550 Imperial gallons (2500 litres) in four fuel tanks consisting of two 188 Imperial gallon (854.5 litre) fuel tanks in the centre-section and two 87 Imperial gallon (395.4 litre) fuel tanks in each outer wing section. Long-range fuel tanks when fitted include one 29 Imperial gallon (131.8 litre) fuel tank mounted outboard of each engine nacelle. A 24 Imperial gallon (109 litre) fuel tank can be installed in the port gun bay and a 50 Imperial gallon (227.2 litre) fuel tank can be installed in the starboard gun bay, with the guns removed.

Range:
1,470 miles (2366 km) on internal fuel with torpedo. 1,750 miles (2816 km) with torpedo and long range tanks.

The Beaufighter carries a lot of internal fuel which means a large combat radius. It can easily strike maritime targets 600 miles away. Once the torpedo is gone it's almost uncatchable by December 1941 Japanese fighter aircraft. A few squadrons of these could cause serious damage to Imperial Japanese Army transport fleets at the beginning of the Pacific war.

Of course they need to be in the Pacific to do any good. Not piddled away in Europe or Africa.

 

[Wildcat]

The RAAF did use the Beaufighter, built them too.

 

[Shortround6]

Bristol's Blenheim, Beaufort and Beaufighter were significant part of not only RAF, but other airforces. Later combat-plane designs, Brigand Buckingham, were too late for the ww2.

Starting date being Blenheim's 1st flight, 12 April 1935, how would you further develop the 'line' of the planes? The engines should be the historical Bristol products, yet the planes should accept other ones available for the historical users. Armament electronics also being historical types. The designs should be tailored for more roles - no tightly-knit approach (but also not too big the resulting plane)
Timing of the designs should be 1940 (1st design), 42 (second), 44 (3rd), or, 1940 (1st design), 43 (2nd design).

Unless you can really change the engine development time line things are going to go pretty much as they did historically. Engine wise, Bristol spent just about all their time and money on the sleeve valve engines. The Mercury was just too small for any but a major rework to show much improvement (more than 10% or so). The Sleeve valve Perseus was also too small to show much improvement over the Mercury (same bore and stroke=same displacement). The Taurus turned out to be a turkey and this set back the Beaufort program a great deal and caused the Blenheim to be retained in production and service longer than if the Taurus had worked as hoped. P&W twin wasps were the preferred alternate engines for the Beaufort, unfortunately for the British a ship carrying the first several hundred twin wasps was torpedoed, forcing the retention of the Taurus. Australian Beauforts dodged the Taurus bullet. Hercules comes on line in 1940, after quite a while of production headaches with the sleeves. SO it's debut is both later than planned and in fewer numbers. It is also in demand for the heavy bomber program. Between getting the Hercules into production, futzing about with the Taurus, and Bristol firing Roy Fedden, the Centaurus was basically put on the shelf for a period of time, much like the Griffon. This delayed it's service use, no matter what airframe used it.

In order to make major changes in the airframe you also have to get the air ministry to change a number of their requirements. The Blenheim was practically a STOL aircraft compared to later bombers. A landing speed (or stalling speed?) of 50mph and a claimed take-off run of 296yds. ALL British planes could not use more than 35lbs of air pressure in the tyres to reduce the chances of rutting the grass airfields until some time in 1938, I believe, so any design work done before that time has to deal with certain tyre sizes to handle a given weight, This sort of restriction went out the window in just a few more years but helps explain why some of the early planes suffered a lower performance than you might expect.
Other things are the rapid development of better flaps. Early flaps weren't much more than air brakes. They created much more drag than they did lift and were used to steepen the glide slope for a shorter approach and landing run rather than operating at higher weights. This meant that lift for take-off had to come from wing area and airfoil shape. This meant the first 3 Bristol twins were stuck with a larger, higher drag wing than some other planes of similar size and mission had. A Bristol Blenheim had 4sq ft more wing area than an A-20. It's wing was probably thicker too, I haven't tired to measure them.

And again for timing, if you want the the plane to actually see combat in WW II you have had to put pencil to paper in 1942 or so. The Bristol Buckingham bomber (first production version in March of 1944) was a slow, twisted development of a bomber version of the Beaufighter first proposed in 1939. After several revisions the design that was finally built was on the drawing boards in 1941.

 

[Edgar Brooks]

Bristol (just like every other British manufacturer) will respond to the procurement policy of the government of the time. The Air Ministry decide that they need a twin-engined something-or-other, and the various manufacturers are invited to tender. Their design team(s) come up with something to match the requirements, tenders go in, and the Air Ministry choose the one (or more) that they like best. For a company to arrive at a design, first, is a rarity, and even de Havilland needed the backing of Sir Wilfrid Freeman to get the Mosquito cleared.

 

[Shortround6]

Bristol (and other manufacturers) will use the existing aircraft, at times, as a starting point for a new design or as an argument to the Air Ministry ( or government Agency) that their design can be produced quicker or cheaper or both than a competitors all new design. This was part of the attraction of both the Beaufort and Beaufighter. They were low risk, hopefully quick to get into service aircraft compared to a rival design that might offer more performance but would not be available for squadron service as soon. The airframes may have been low risk but unfortunately the engines were not.

 

[tomo pauk]

Beaufort was designed produced in order to equip the RAF with a torpedo-bomber.
My take on that would be a plane with a bomb bay, mid- or high-wing, featuring maybe both slats fowler flaps, so the wings can be of somewhat thinner profile. Low-risk part of the engines would be covered by usage of the Pegasus engines (for prototypes 1st series), wing being stressed for Merlin and Hercules (such planes built from, say, Spring of 1940). The MGs would be 4 in the wing roots (replaced with belt-fed Hispano when available), space for 4-6 in outer wings, 2 in the back. An adaptation for the NF job would include 4-6 belly mounted MGs, ammo feed from bomb bay (all akin to the NF Blenheim); we should have the Merlin, or even Hercules versions by then. Radar as available. All in all, a British Ju-88?

 

[davebender]

Aircraft need to be in the right place at the right time to do any good.

How many torpedo armed Beaufighters were at Rabaul and Ambon during January 1942 to fight Japanese invasion forces?

 

[Shortround6]

Beaufort was designed produced in order to equip the RAF with a torpedo-bomber.
My take on that would be a plane with a bomb bay, mid- or high-wing, featuring maybe both slats fowler flaps, so the wings can be of somewhat thinner profile. Low-risk part of the engines would be covered by usage of the Pegasus engines (for prototypes 1st series), wing being stressed for Merlin and Hercules (such planes built from, say, Spring of 1940). The MGs would be 4 in the wing roots (replaced with belt-fed Hispano when available), space for 4-6 in outer wings, 2 in the back. An adaptation for the NF job would include 4-6 belly mounted MGs, ammo feed from bomb bay (all akin to the NF Blenheim); we should have the Merlin, or even Hercules versions by then. Radar as available. All in all, a British Ju-88?

From Wiki:

"The Beaufort came from Bristol's submission to meet Air Ministry Specifications M.I5/35 and G.24/35 for respectively a land-based twin-engined torpedo-bomber and a general reconnaissance aircraft. With a production order following under Specification 10/36"

"The first prototype rolled out of Filton in mid-1938. Problems immediately arose with the Taurus engines continually overheating during ground testing...."

"With Blenheim production taking priority and continued overheating of the Taurus engines there were delays in production, so while the bomber had first flown in October 1938 and should have been available almost immediately, it was not until November 1939 that production started in earnest"

Designing the plane to use Hercules or Merlin engines and house 20mm guns in the wing roots would call for almost an entire new wing (especially with Fowler flaps) and slats would do squat. Twin engine bombers should not have an angle of attack of 14-15degrees or higher.

See: http://i366.photobucket.com/albums/oo102/keithintheuk/035.jpg

you would be starting over again in 1938-39 and throwing out all the work done up to that point, delaying service entry by months if not a year or more.

 

[tomo pauk]

you would be starting over again in 1938-39 and throwing out all the work done up to that point, delaying service entry by months if not a year or more.

From April 1935 - End 1939, the British have plenty of time to design a far better airplane, than an warmed-up Blenheim. Throwing up the work is far better thing than throwing up the trained crews anyway. Biplane fighters SB-2 bombers in ww2, T-26 tanks in 1941/42, 2pdr ATGs in 1942, M3/M5 tanks, P-40s and Hurricanes in 1944, Pz-38(t)s Blenheims in 1942 - all capitalising upon the previously done work, yet hardly good examples of combat use.

Designing the plane to use Hercules or Merlin engines and house 20mm guns in the wing roots would call for almost an entire new wing (especially with Fowler flaps) and slats would do squat. Twin engine bombers should not have an angle of attack of 14-15degrees or higher.

Okay, then no slats
I've specified already that the new wing would be thinner - that implies it's a new design.

BTW, could we conclude that HP Hampden would be as good/bad without the slats, as it was with them?

 

[woljags]

they did try griffon engines in the beaufighter briefly

 

[tomo pauk]

Imagine them on something sleeker

 

[Juha]

Hello Tomo
with Pegasus one easily ended up with underpowered turkey like Botha.

Juha

 

[tomo pauk]

Botha's problem was indeed the lack of power, but also the lack of wing area - only 3/4s of the Hampdens, but for same empty weight. Or, for the 10% more wing area, the plane was weighting 20% more than Blenheim. On about the same engine power.

 

[Jabberwocky]

Aircraft need to be in the right place at the right time to do any good.

How many torpedo armed Beaufighters were at Rabaul and Ambon during January 1942 to fight Japanese invasion forces?

How many torpedo armed Beaufighters were in existence anywhere during January 1942? Zero.

You can't just conjure up something that doesn't exist yet and then blame the RAF/RAAF for not having the right aircraft at the right place at the right time.

The first Torbeaus weren't in service until late 1942. That leaves the Beaufort as the only reasonable alternative.

The first Australian Beaufort wasn't flying until August 1941 and the first RAAF Beauforts didn't enter squadron service until February 1942, and even then it was a while before the aircraft was considered ready for combat service. Australian crews, unused to such large, high-speed aircraft, had a rough time with their Beauforts in the early operational period.

 

[Shortround6]

The British had a major engine problem in the late 30s. Bristol had Three 9 cylinder radials and a 14 cylinder radial, all of about 1000hp or less (down to under 900hp), and one 14 cylinder of 1300-1400hp but not in real production. The Armstrong-Siddeley Tiger was also a 900hp engine and none too good at that, Napair had the 1000hp Dagger and it wasn't quite ready either. That leaves the Merlin and in 1939 a single speed Merlin on 87 octane gas doesn't have the needed oophf for a bomber.
Please note that the Beaufighter II was being worked on in 1939 in response to an anticipated shortage of Hercules engines.

The British did send many aircrews on missions with planes that were not good enough, the alternative of waiting for better aircraft is not undertaking the missions at all and in fact not having aircraft to undertake those missions or any other missions.

Please note that many of the missions under taken by Blenheims and Battles in 1939-40 were not what the planes were designed for. They were light strategic bombers not tactical bombers. No tactical bomber needed a range of over 1000 miles in 1939-1940. Misuse and lack of co-ordination and escort was as much to blame for high loses as the actual design of the planes.

Also please note that the Bristol aircraft used the space between the spars and the engine nacelle and fuselage for the main fuel tanks with long range tanks going between the spars outboard of the engine nacelles. Thinner wings mean less fuel, will the thinner wing offer enough lower drag at cruise to offset the fuel reduction?

Anything the British could have done would be tweaking. The Blenheim and other British planes of the time did not have the best build quality. More careful sealing of joints and gaps and more attention to fit and finish would have helped speed a bit. good look at the planes in a wind tunnel with drag reduction in mind may have helped. Fitting a 2 speed supercharger to the Mercury (not that hard to do as the Pegasus had one) would have helped a bit, a better defensive set up would have helped, like a flexible gun in the nose rather than a fixed gun way out in one wing. A turret with twin guns instead of the single gun would also have helped. The strange notion that the turret should be retractable so that the plane had a good cruise but extended the turret to create high drag when in the combat zone needed a rethink. maybe try to desing a low drag turret in the first place rather than retractable ones?

The problem is that all these tweaks are only going to change things by single digit percentages. A MK I with a short nose was modified for photo-recon work with about 250 hours being put into rubbing the aircraft down, sealing all joints and gaps with tape, repainting with a smoother finish fairing the lower nose with light alloy, removing the turret and installing shorter, squared off wing tips. They got the speed up to 278mph from 263mph. The plane was later fitted with Rotol constant speed propellers, a few more modifications and the engines run at 9lb of boost and 2750rpm for a true speed of 294mph at 13,000ft.
A 280-290mph Blenheim fighter might have been more effective against bombers than the historic versions but still come woefully short against Me 110s or Ju 88s.

Also please note that the aircraft that became the Armstrong-Whitworth Albemarle had it's start as the Bristol type 155, an improved Beaufort with tricycle landing gear and Taurus engines in 1938.

It is the failure of the new engines to be developed in time and the failure of some of the replacement aircraft that kept the Blenheim and Beaufort in production and service for several years after it was hoped to retire them.

 

[davebender]

I thought that was the point of this discussion.

Our starting date is 1935. Australia has 6 years to field effective maritime attack aircraft. If the torpedo armed Beaufighter cannot be ready then we need an interim aircraft. I would rather have stringbags during 1941 then Beaufighters during 1943.

 

[Juha]

Again very good analysis, Shortround6.
IMHO Fedden with his sleeve fanatism cost GB dearly during early war years. Fedden also seems to hve underestimated the importance of good supercharger, not even at first to be interested in the advice R-R gave on that to Bristol's engine team.

Juha

 

[Edgar Brooks]

From April 1935 - End 1939, the British have plenty of time to design a far better airplane, than an warmed-up Blenheim./QUOTE]
To do what? In the 1930s nobody believed that France would be defeated, so there was no (visualised) chance of the Germans using the Channel, meaning that they had to go round the top of Scotland, and risk the attentions of the Navy, and all destroyers carried torpedoes.
The Beaufighter was rushed into service as a nightfighter, to replace the Blenheim fighter, and was only considered for other roles when the Mosquito proved that it could take over the nightfighting role, especially with the two-man crew together, rather than several feet apart.

 

[merlin]

Well I'm going to try and be a bit more inventive/creative! This is 'off the top of my head' so please forgive the detail on dates!

When the production planes for the new 'heavy' bombers were presented the Chamberlain - in winced at the cost, and did his best to delay large scale
production - until the situation with German worsen - after all if 'peace' prevails we won't need all these big bombers.
So, I think for an ATL it could be plausible for the Air Ministry on hearing this to go get their heavy bombload another way.
Bristol put forward a design for the spec that became the Halifax Manchester - rather than the Vulture of the latter it was to have Hercules, and the span
was about twenty feet less.
Hence, the Air Ministry order this and dress it up as a Blenheim replacement! And just in case there's a problem with the Hercules, they give AW a chance
with their Deerhound engine. Then, a 'bright spark' mentions that the original spec includes torpedo carrying ability i.e. 2 x 18", so thinking of rationalising
production - once the design is proven the Beaufort ( Botha) are cancelled. But to give another option because this will be a big aircraft in comparison - if
it can be done - have the new Beaufighter aircraft the ability to carry torps.

So, with luck the bigger Bristol Twin (Buckfast) enters service in mid-late '40, in time to make a mess of the invasions barges with its bigger bomb load. The Beaufighter
also enters service slighter earlier than OTL. And in 1942 the Beaumont enters service - a bomber version of the Beaufighter - but with a bigger fuselage.