Fast bombers for 1938-42

[tomo pauk]

'Fast' meaning that their speed is at least 90% and preferably 95+ % of speed of the current fighters. Defensive guns' armament is kept at minimum. Service use is at least by the time of Munich crisis (Autumn 1938), although a new type can enter service by late 1940/early 1941 in order to use the latest aerodynamics, engines (if they make real improvement to justify a switch to a whole new aircraft), strauctures, materials etc. Obvoiusly the development will need to start a few years before service use.
Number of engines does not matter, a country can have several types and sizes of fast bombers suggested. The engines themselves are strictly historical as they are available for a country that is to make the bombers - be it from own production, or, for smaller countries, the engines one can reasonably hope to buy abroad or did so historically. A proper bomb bay is needed, so the fast bomber does not become a slow bomber. Thread includes carrier-capable bombers.
People are encouraged to look beyond Mosquito

 

[GrauGeist]

The often overlooked French Leo451 comes to mind in this scenario.

 

[tomo pauk]

Germans might've based their fast bomber on the Bf 110+Do-17 combo perhaps? Looking at the Bf 110 itself, it offered a good turn of speed despite the thick wing profile - 18.5% t-t-c at root, 11% at tip. I'm also not sure that 2R series of profiles was the best what was available back in late 1930s either. What Bf 110 lacks is a bomb bay, capacity for at least 1000 kg bomb (one only), or maybe two 500 kg bombs. Mating the Do-17 fuselage (with streamlined nose, not the later ones with blocky nose) with Bf 110 wing might produce such an aircraft - fast enough, even when bombed-up. Wing area on the Do-17 was 55 sq m, vs. 38.4 on the Bf-110. Granted, a wing with thinner t-t-c ratio might increase a speed a somewhat.

 

[Greyman]

Boston is about as good as it gets here I think.

 

[tomo pauk]

For the British: something sized as Blenheim, but with Merlins.
Another suggestion - Henley's fuselage, but with wings' design taken from Spitfire, appropriately increased to perhaps at 280-300 sq ft, vs. Henley's 342 sq ft.

 

[wuzak]

I'd suggest Volkert's high-speed unarmed bomber idea from his paper.

So two Vultures (not yet found wanting), estimated top speed of 380mph and bomb loads of up to 7,000lb.

Speed may have (probably would) fall short of estimates, depending on how well the design is carried out and the Vultures not being detuned too much.

Service entry would probably be similar to Manchester - so around 1941.

 

[Shortround6]

'Fast' meaning that their speed is at least 90% and preferably 95+ % of speed of the current fighters. Defensive guns' armament is kept at minimum. Service use is at least by the time of Munich crisis (Autumn 1938),

Hmmm, 7 squadrons equipped (or equipping) with Blenheim Is as of Jan 1st 1938 9 months before the Munich crisis. Top speed for the Blenheim I was "claimed" to be 280mph (not born out in practice).
British figure they have the "fast bomber" thing in the bag and sign on the dotted line, Shadow factories for both airframe and engine are contracted for, a massive undertaking for the time. However it may have been premature and left the British with too little ability to switch to a more modern aircraft in 1940-41?

Only place to get Merlins from would have been Battle and Defiant production.

Trouble is that the Battle production, at least until some point in 1940, is needed to help replace over 30 squadrons worth of Hawker Hart and Hind light bombers in service in Jan of 1938.
Battle squadrons went from 5-6 to about 10 by Jan 1940 although some squadrons may have changed type of aircraft more than once in two years.

The Defiants don't go into production until 1940, at least in any real numbers.
By Jan 1st 1940 Blenheim's equip 11 bomber squadrons at home, 6 in France and 11 overseas.

Please remember that the Mosquito was originally schemed as using Merlin X engines and carrying 1000lb of bombs. Fast yes, effective?

Germans are pretty much down to the DO 215 for an historic airplane for a fast bomber. The JU 88s really weren't that fast and the Bf 110 is going to slow down with a fatter fuselage.
With the available engines in most countries the plane is either going to be too slow or not carry a big enough bomb load.
Early A-20 with R-2600 engines was fast but both bomb load and range were lacking.

 

[GrauGeist]

and the Bf 110 is going to slow down with a fatter fuselage.

The Bf162 was based in the Bf110 and did have decent performance.
However, it and the Hs127 (which also had good performance) lost out to the Ju88 because it could carry a larger warload.

 

[nuuumannn]

The JU 88s really weren't that fast and the Bf 110 is going to slow down with a fatter fuselage.

Compared to what? The Ju 88 had a maximum speed of over 290 mph, there weren't many other bombers capable of that speed in 1939/1940. 'Fast bomber' is a relative term and therefore in the time period Tomo stipulates, 250 to 280 mph is considered fast, especially when the fastest already in service in the mid-30s could just exceed 200 mph. Before the He 111, Do 17 and Ju 88, the Ju 86 couldn't even exceed 200 mph and the Ju 52 bomber transport, couldn't exceed 120 in level flight. Before the Whitley, Hampden and Wellington the RAF had the Overstrand, at a paltry 140+ mph maximum speed, still faster than the Ju 52/3m mind you.

The Bf 162 anyone? It was certainly fast, but could only carry 750 kg of bombs.

 

[Shortround6]

The Bf 162 anyone? It was certainly fast, but could only carry 750 kg of bombs.

Ten 50kg bombs inside, more weight or larger bombs carried outside.

BF 162 used the DB 600 engines so a production version could have gone faster with DB 601s. But it had a 3ft more wing span than a Bf 110 and a couple feet more length so not quite Bf 110 speeds even with the same engines.

 

[nuuumannn]

The other thing about this thread is we are dealing in maximums. Cruise speed and payload over a given distance is far more important in a bomber. you don't fly your mission at maximum speed. A higher cruise speed over the target area means less time over the target area, but it does mean less time to aim at the target. The Ju 88 had a cruise speed of around 230 mph carrying up to 2000 kgs of load internally and externally.

 

[tomo pauk]

Hmmm, 7 squadrons equipped (or equipping) with Blenheim Is as of Jan 1st 1938 9 months before the Munich crisis. Top speed for the Blenheim I was "claimed" to be 280mph (not born out in practice).
British figure they have the "fast bomber" thing in the bag and sign on the dotted line, Shadow factories for both airframe and engine are contracted for, a massive undertaking for the time. However it may have been premature and left the British with too little ability to switch to a more modern aircraft in 1940-41?

So Blenheim will not cut it as-is, RAF needs something more promising. One of reasons for this thread.

Only place to get Merlins from would have been Battle and Defiant production.
Trouble is that the Battle production, at least until some point in 1940, is needed to help replace over 30 squadrons worth of Hawker Hart and Hind light bombers in service in Jan of 1938.
Battle squadrons went from 5-6 to about 10 by Jan 1940 although some squadrons may have changed type of aircraft more than once in two years.

There was 200 worth of Henleys manufactured, so let's cancel them. Gets enough of Merlins for the 1st 100 of 2-engined bombers. Tone down Battle production past the 1st 700-800 vs 2200, that's for another 700-750 of 2-engined bombers. Need, be, make a few hundred of Battles with Pegasus or Perseus engines for bombers' training.
Axe the Botha, plenty of metal and manhours to save there.

Please remember that the Mosquito was originally schemed as using Merlin X engines and carrying 1000lb of bombs. Fast yes, effective?

Effective, especially once it is figured out that German fighters have a problem to shoot it down.
It is far faster easier to attach bigger bombs on an existing performer, rather than to have bombs around while not having a performer to attach them to. As found out both by British and French, where the fastest bombers of 1940 have had the best survival rates.

Germans are pretty much down to the DO 215 for an historic airplane for a fast bomber. The JU 88s really weren't that fast and the Bf 110 is going to slow down with a fatter fuselage.
With the available engines in most countries the plane is either going to be too slow or not carry a big enough bomb load.
Early A-20 with R-2600 engines was fast but both bomb load and range were lacking.

Ju-88 will not cut it. Fuselage of Do-17 was slim.
A-20 needs more fuel in the wings and a bomb bay not cut in two halves, nothing earth-shaking there.

 

[tomo pauk]

The other thing about this thread is we are dealing in maximums. Cruise speed and payload over a given distance is far more important in a bomber. you don't fly your mission at maximum speed. A higher cruise speed over the target area means less time over the target area, but it does mean less time to aim at the target. The Ju 88 had a cruise speed of around 230 mph carrying up to 2000 kgs of load internally and externally.

That is the Ju-88's problem - anyhting bigger than 50 kg bomb needs to be hanged out in the breeze. Despite the Ju-88 being a fairly sized aircraft. So it will be slow; bombs are outside, fuselage was wide, wing was big, engines were okay but nothing special, cockpit is blocky.
I'm not sure whether the 'bomb cells' from the He-111 might fit on the historical Ju-88, an 8x250 kg bomb load is useful from the 1938-42 perspective. No dive-bombing with the cells, though.
'Our' Ju-88 should look more as the A-20 or Do-215 (mid- or high-wing, so the spars don't interfere with bomb bay size) if it is to be really fast, with wings closer to 450 sq ft area, rather than to 500 sq ft?

On the other hand - Germans (Dornier actually) was using engines in push-pull fashion in 1930s - so have Dornier make a bomber with push-pull engines early on? The Do-335 was 1st designed as a bomber.

 

[GrauGeist]

The Do335 as produced, retained the bomb bay, too.

 

[nuuumannn]

That is the Ju-88's problem - anyhting bigger than 50 kg bomb needs to be hanged out in the breeze. Despite the Ju-88 being a fairly sized aircraft. So it will be slow; bombs are outside, fuselage was wide, wing was big, engines were okay but nothing special, cockpit is blocky.
I'm not sure whether the 'bomb cells' from the He-111 might fit on the historical Ju-88, an 8x250 kg bomb load is useful from the 1938-42 perspective. No dive-bombing with the cells, though.
'Our' Ju-88 should look more as the A-20 or Do-215 (mid- or high-wing, so the spars don't interfere with bomb bay size) if it is to be really fast, with wings closer to 450 sq ft area, rather than to 500 sq ft?

I think it was a problem of German bombers, or indeed a lot of bombers of the period. Apart from British bombers, the standard internal warload of most pre-war bombers was pretty small compared to later. The bomb cells idea was not a good one; in the He 111 it was a compromise based on the fact the airframe was designed to be relatively streamlined and the cabin designed to carry passengers as well, so the answer was to make cassettes installed in the cabin and make holes in the belly where the bombs drop from their cassettes and to increase the number of bombs carried had to be mounted vertically. British bombers favoured individual bays, the Whitley, Battle, Halifax wing bays etc, even the Wellington's bay was sectioned longitudinally. It restricts the size and number of bombs that can be carried and adds built-in obsolescence, but to be fair, designers in the 30s weren't always the greatest at predicting the future.

I reckon you and the other guy who mentioned the A-20 are onto something. Great aeroplane, although crew positions weren't the best for communication. Nonetheless, became ubiquitous and had a good performance because of its slender profile.

 

[Shortround6]

A-20 needs more fuel in the wings and a bomb bay not cut in two halves, nothing earth-shaking there.

A-20 didn't have a bomb bay cut in half. It was narrow, result of the fuselage width. It was tall, from the bottom of the plane pretty much to top. Originally designed for many small bombs in vertical tubes. once they went for larger bombs horizontally they hit a limit. They could fit two 500lbs side by side but not hung from side racks like B-17s, B-25s and B-26s used which meant only one layer of bombs. Plenty of room over the bombs for more fuel though. Later versions got 325 gallons in upper bomb bay tanks while still holding four 500lb bombs.
I don't know the differences between the early and late versions that allowed for several thousand pounds more gross weight. But they were fairly minor.

It does seem to be the best shot the Americans have at a fast bomber. The B-26 was pretty fast in the early versions (about 20mph slower than the A-20) but to hit such speeds it's gross weight was so low that it really wasn't carrying any more bombs than the A-20 any further (465 gal of fuel?)

 

[wuzak]

It does seem to be the best shot the Americans have at a fast bomber. The B-26 was pretty fast in the early versions (about 20mph slower than the A-20) but to hit such speeds it's gross weight was so low that it really wasn't carrying any more bombs than the A-20 any further (465 gal of fuel?)

What if the B-26 had V-3420s?

2 x 2,600hp instead of 2 x 1,850hp.

 

[tomo pauk]

A-20 didn't have a bomb bay cut in half. It was narrow, result of the fuselage width. It was tall, from the bottom of the plane pretty much to top. Originally designed for many small bombs in vertical tubes. once they went for larger bombs horizontally they hit a limit. They could fit two 500lbs side by side but not hung from side racks like B-17s, B-25s and B-26s used which meant only one layer of bombs. Plenty of room over the bombs for more fuel though. Later versions got 325 gallons in upper bomb bay tanks while still holding four 500lb bombs.
I don't know the differences between the early and late versions that allowed for several thousand pounds more gross weight. But they were fairly minor.

Bomb bay was cut in two halves by a fuselage element to which the bomb bay doors actuation mechanism was attached. picture
Tall bomb bay indeed allowed for extra fuel tanks to be carried while 4x500 lb bombs were carried.

It does seem to be the best shot the Americans have at a fast bomber. The B-26 was pretty fast in the early versions (about 20mph slower than the A-20) but to hit such speeds it's gross weight was so low that it really wasn't carrying any more bombs than the A-20 any further (465 gal of fuel?)

Yes, A-20 seems to be the best bet. Already the DB-7 was fast, despite similar size and not great engines.
B-26 will need a shorter, narrower and lighter fuselage if we want it to be faster, so it can retain the smaller wing without going to such a prominent wing incidence. The 2-stage R-2800s will also help, ditto for the turboed R-2800s.

What if the B-26 had V-3420s?

2 x 2,600hp instead of 2 x 1,850hp.

Should be faster. The V-3420 was not a thing in this timeframe, though.

OTOH - how about a DB-7 with V12 engines?

Re. bomb bay of A-20 vs. DB-7 - perhaps the racks for small bo,bs were too clumsy? Just my guess.
Width of the bomb bay of the A-20G was 32 in at the bottom, 28 in at the top, max height 62.5 in, max length ~160 in (~13.3 ft; two halves' lengths combined).

 

[wuzak]

Bomb bay was cut in two halves by a fuselage element to which the bomb bay doors actuation mechanism was attached. picture

Picture is of a cutaway Hurricane Tomo.

 

[tomo pauk]

Picture is of a cutaway Hurricane Tomo.

Whoops, I'll edit the post