1936 to mid-42: fast 1-engined bombers instead of slow types?

[Shortround6]

They should have tried to improve its looks while they were at it.

compared to the original, they did, not that it was a high bar

 

[tomo pauk]

At 15,000ft the R-1830-17(single speed supercharger) wouldn't make any more power. The engine was not rated to use take-off power as military power.

Note that at 285mph the P-36A was using 30 more HP than the P-40 was using to go 310mph.
Note that at 285mph the P-36A was using 25% more power than the P-40 was.
Note that at 264mph the P-36A was using 25% more power than the P-40 was to go 258mph.

See the other thread about "what's in a name" to see the cowls and extension shafts that Curtiss, Sikorsky and Vultee were trying to use to reduce the drag of the R-1830, which was was smaller than the French, Italian and Soviet radials were to begin with.

Thanks for the effort to make the table, it is really handy.
American's also have the option to help themselves with turboes. They have had the P-30 such outfitted in service by mid-30s, while the 1st B-17A was delivered in early 1939.

Japanese didn't have much for options. Until they can build the DB 601 the Kawasaki (old BMW V-12) wasn't going to do the job. Radials or nothing.
Italians are in a similar place.

Francillion notes 950 HP at 12470 ft, and 850 HP for take off for the Ha-9-IIb - nothing eart-shattering, but much better than the old BMV V12s (or what French and Italains had before 1940). Power figures note that superchrager was used, unlike with grandpa BMWs. Yes, by 1940 the preferred engine should be a radial for the Japanese.
Italians can use the Isotta Fraschini Asso IX, and hopefully introduce the L.121 or L.122 from the same company. The switch to the radials is also likely here, unless Gremans allow the Italians to clean sweep the H-S engine factory in 1940.

French need a new version of the H-S V-12.
For the French this was as good as it got.

Designing a bomber around the 12Y instead of around the 12X is a good start for the French.

 

[don4331]

He.119:
Single engine - DB606A
Bomb load - 1,000 kg
Range - >3,000 km ferry; 1,000 km w/1 ton bomb load @ 500km/h.
Fast - max 590 km/h; cruise 505 km/h
Defensive armament of 1 - RCMG in dorsal position, but if you're going that fast do you need extensive defensive armament.
Crew includes navigator/bombardier to ensure accurate level bombing from altitude.

Engine up-gradable from 606 to 610 to 613.

Best you're going to get in '37.

Redesign of Curtiss Shrike without length limitation (36' to allow 2' fore & aft on 40' carrier elevator) and no wing fold for USAAF's entry.

RAF could build more/less similar plane around the Vulture or Sabre. (Hawker Henley with Vulture comes to mind).

Not aware of any engine for Italy/Japan in '37 of 1,750+ hp that was later produced in quantity.

 

[Wild_Bill_Kelso]

OK, the DB-7 weighed about 11,700lbs empty, the A-20G weighed almost 17,000lbs empty.
The A-20B went about 14,830 pounds empty, had no armor, no protection for the fuel tanks.
It was fast
It was also rated at 800 mile range with 1000lbs of bombs
You could swap fuel for bombs and carry a heavier load a shorter distance or less bombs a longer distance.

Please note the 3000lb empty weight increase for a pair of engines that "only" weighed about 1000lbs more for the pair.

So how does this "half" DB-7 -> A-20 recipe work?
400 mile range with 500lbs of bombs with the R-1830 engine?
Or 400 miles with 1000lb/800 miles with 500lbs?
The original DB-7 held 325 US gallons of fuel. 165 US gallons equals 137 Imp gallons.

Lets see how this works out..

Take a P-36 (wing about 1/2 the size of the DB-7 wing) Keep the R-1830 in the nose, take out the behind the pilot fuel tank and stretch the fuselage a bit to get in the 2nd crew man.
pad out the fuselage a bit to hold a pair of 250lb bombs and maybe you can put a small tank out in each wing to restore the fuel you took out from the fuselage.

Depending on the fuselage bomb bay you might get the plane to 300mph.

There were very fast DB-7/ A-20 variants with armor and SS tanks prior to 1942, and a decent (by early war / fast bomber standards) bomb load. It took a while to scale up defensive guns and more fuel for better range but all that improved too.

 

[K5083]

A twin out-performs a single with the same engine for all important bomber measures. Saving cost, a single just can't do it. Where there is an advantage to a single is for tactical types, attack aircraft intended to operate over the front lines of a land or sea battle, or for carrier types where only singles operated from carriers in WW2. Where is the chance of making a competitive single with one of the engines used by a Blenheim, A-20, Pe-2 or any decent bomber of the early war, never mind Mosquito?

 

[tomo pauk]

Where is the chance of making a competitive single with one of the engines used by a Blenheim, A-20, Pe-2 or any decent bomber of the early war, never mind Mosquito?

There is a lot of chance to make a competitive single-engined bomber for the early war if designers keep a watchful eye over the key factor: keep the drag reasonably low. Engine from the Blenheim will not do, however, but the engine from Battle or from Henley will, so will the one from A-20.
Keeping the drag can be attained via using the modern airfoil for the wing, and not too thick. Here the Battle or Henley will not cut in - airfoil is obsolete, with 18 to 20% t-t-c (root) being used. Use 13-15% instead. Wing size also matters, again Battle with it's huge wing is hopeless here, Henley is a bit better, but still too big (wing area of 342 sq ft - 15% greater than on the P-47; Hurricane's wing is a bad thing to increase in size in all 3 dimensions). British will want to call Supermarine's people here, their 13% t-t-c (root)wing Spitfire is a great start, area increased to perhaps 270-270 sq ft. Bombs go in the bomb bay.
De Havilland also comes to the mind as a company to design this.

We can take a look on the D4Y. On the equivalent of the Merlin III, DB 601A, V-1710 or M 105, it was good for 330 mph. Great fuel load (230 imp gals) was possible because there was no thought on the self-sealing tanks, something that non-Japanese will take care by 1940-41.
On a better V12 engine (when it worked, it was comparable with Merlin XX, DB 601E or the de-rated DB 605A, it was good for 363 mph.
D4Y was dive-bombing capable, as well as navalized (no folding wings, though).

 

[Wild_Bill_Kelso]

Not sure what sense one might expect.

You would probably want to look into a more thoroughly militarized or tailored He-70F. The airplane was underpowered but streamlined and very fast for its time. With 635 hp BMW-VI it was good for 377 Km/h. One specimen exported to Britain was refitted with Kestrel and an early 885hp Peregrine I and 418 Km/h (260 mph) and 481Km/h / 299 mph, respectively. The fuselage, however, may have been spacy enough to also consider the larger 1,200 hp JUMO-211.

That goes to something like the He-270V1 (1938), but with 1,250 hp JUMO-211 instead of 1,100 hp Db-601. Still struggling to reach 300 mph, though. Not really useful, in my opinion.

He 70 was pretty fast but being made out of magnesium, rather tragically vulnerable

 

[Shortround6]

Where is the chance of making a competitive single with one of the engines used by a Blenheim, A-20, Pe-2 or any decent bomber of the early war, never mind Mosquito?

The A-20 is simply in class by itself. But that is because of the engines. The A-20 has almost twice the power of a Blenheim. (A-20s never had the R-1830 engines)
So yes, R-2600 engines were used in a number of single engine attack bombers. But that automatically means a bigger, heavier aircraft than a Mercury, M-105/Hispano powered plane (or even a Merlin powered plane) Once you stick the big 1900lb radial in the nose and the needed fuel you have a plane that is going to wind up several thousand pounds heavier than the others.

 

[SaparotRob]

But it'll look really cool.

 

[Shortround6]

British will want to call Supermarine's people here, their 13% t-t-c (root)wing Spitfire is a great start, area increased to perhaps 270-270 sq ft. Bombs go in the bomb bay.
De Havilland also comes to the mind as a company to design this.

We can take a look on the D4Y. On the equivalent of the Merlin III, DB 601A, V-1710 or M 105, it was good for 330 mph. Great fuel load (230 imp gals) was possible because there was no thought on the self-sealing tanks, something that non-Japanese will take care by 1940-41.
On a better V12 engine (when it worked, it was comparable with Merlin XX, DB 601E or the de-rated DB 605A, it was good for 363 mph.
D4Y was dive-bombing capable, as well as navalized (no folding wings, though).

Again, timing and other requirements. Put your 270-280 ft wing on a plane that is several thousand pounds heavier than a Spitfire in 1937/38 and you might not pass the field requirements. Even giving you a constant speed prop.

It turns out the early D4Ys were NOT dive bomber capable, they broke.

 

[GrauGeist]

Perhaps we can look to the Antanov An-2 to get an idea of what it would take to solve the issue of a single engine bomber.
What's interesting (aside from it being a biplane) is that it's powered by a nine cylinder engine (ASh-62).

 

[Shortround6]

The problem isn't making a single engine bomber, the problem was making a fast single engine bomber.

Fast enough to make interception difficult.

 

[Shortround6]

Vickers had attempted to improve the speed of the single engine bomber went they went from this,

to this

A lot of the fuselage was the same. in attempt at low drag the bombs were carry in the under wing panniers instead under the wings.
Perhaps they could have used in the wing bomb cells but the loading of the bombs by men standing on the ground

was not considered a good solution

This is just a bit of fun with the Vickers machines.

Basically for a high speed single engine bomber you are taking the same engine as you are using in your interceptor fighters, adding 50-100% more fuel, adding a fatter or longer fuselage for internal bomb stowage. You are taking out some of the guns (in 1936-40 that may not be that much, eight .303s and 2400 rounds was 440lbs) ). If you need a rear seater (2nd crewman) for radio/navigation/bomb aimer/ rear gunner we have an even longer fuselage. You may or may not need to get the plane out of the same size airfield as the fighters (depends on each country/air force) so you need a bigger wing.
You don't need to be as fast as the interceptors using the same engine, you do need to be fast enough to make interception difficult. You also need to carry at least 50% of the bomb load as a twin engine plane using the same engines or what is the point?

 

[Tom Graham]

Basically, Germans don't accept the dive-bombing doctrine so there is no Ju 87 as we know it, while British make a fast bomber instead of Battle or Henley (yes, the last one never bombed anything beyond the target range, but still). Italians make something much better than the Ba.65, Polish got something more streamlined than the PZL.23. Americans, Soviets and Japanese can also compete here. Ditto for Yugoslavia, Romania, Sweden, Czechoslovakia, Belgium, Netherlands, Australia...
These alternative bombers still have at least 2 crew members; they should use engines, guns and aerodynamics of the day, and start without a meaningful protection. Preferably designed with bomb bay, or at least with a recess to house the payload. Range needs to be good (Battle was carrying double the fuel when compared with Hurricane), bomb load should be at least at 500 kg or 1000 lbs. Max two MGs forward, at least one MG in defensive position.

Please note that this is not about fighter bombers, and also this is not about carrier-borne types.

Possible pointers might be the Ca.335, Ca.355, as well as the D4Y (late for this thread, but even with modest power was good for ~330 mph in it's 1st versions).

If R.R. had done what Dowding hoped, and produced a de-rated "R" engine with the same HP/litre output as the Merlin 111 (1480 vs 1080HP) how fast could a Fairey Battle been?

 

[tomo pauk]

If R.R. had done what Dowding hoped, and produced a de-rated "R" engine with the same HP/litre output as the Merlin 111 (1480 vs 1080HP) how fast could a Fairey Battle been?

A 40% power increase nets what, 10-15% of speed increase (before compressibility kicks in)? On 257 mph basis, it is ~290 mph with 1480 HP?
If the same engine is on the Henley, with 'under 300mph' speed figure (290? 295?) we'd get ~330 mph?

Griffon will necessitate a bigger radiator than the Merlin.

 

[Shortround6]

Some of this depends on what altitude you want to fly at (what the actual mission profile/requirements are) and if your "what if" allows for different propellers.
Sticking a two pitch prop on an adolescent Griffon seems a bit much

Using a lower supercharger gear or cropped impeller on the Merlin III will give you several hundred more HP around 6-8000ft if you are going low level.
Having a prop that allows you to open the throttle up at less than 14-15,000ft also increases low level speed a bit.
Flying at low level does increase fuel consumption a bit but if the goal is NOT to hit the Ruhr from a base in England by over flying the low countries than a 1000 mile range may not be a consideration anyway.

If you can steal Merlin X engines (and CS props) from bomber command it may not do much for high altitude (17,000ft ) but may add 20-30mph at low altitude.

If you have adolescent Griffons then sticking them in Whitley's or Wellingtons may be much more beneficial.

If you give up on the long range you could probably just put four 250lbs bombs or two 500lb bombs under a developed P.4/34

We also need to use caution with speeds from prototype aircraft. A service aircraft would not have made it with shown windscreen/canopy.
Of course switching to ejector exhaust would have helped. But ejector exhaust works better at higher altitude than at low altitude.

 

[Wild_Bill_Kelso]

This is yet another thread that really shows the merits of this forum. The above P4/34 is the second very interesting pre-WW2 aircraft I had never heard of previously and learned about as a result of this discussion (the other being the wonderful and strange Italian / Belgian Reynard R.36).

Humbling, as I'd thought I'd seen 'em all at this point. A nice reminder that there is always more to learn about WW2 aviation.

So a few thoughts after reading the thread. The challenge of making a bomb carrying aircraft that can survive encounters with interceptors

Engines
Probably limited options there, as better engines may go to higher priority aircraft, as already stated.

Speed
To improve speed, better streamlining is always possible, (that R.36 is a nice example of the possibilities in 1937, as is the Spitfire), features like retractable landing gear, and using an inline instead of radial engine all also help, but that will only get you so far. You are still dealing with drag and weight with limited engine power. You have fighters which are capable of 300 mph and more, so 'fast' bombers will need to at least approach that speed.

First I'd say, again taking a page from Fairey here (can't believe I'm sayin that) is that assuming you have to carry more fuel, crew, defensive guns and bombs, maybe length is better than width when it comes to the fuselage. Longer aircraft seem ('anecdotally' so to speak, based on specific aircraft I'm familiar with rather than any particular engineering knowledge) to often be a bit more stable, and not necessarily slower than shorter. I assume greater length does increase drag because the air is moving over more surface area, but fuselage lengthening seemed not to slow down several aircraft types I'm familiar with. It seems like a wider fuselage is usually much more draggy.

We also know that weight seems to matter much less than drag when it comes to top speed. Weight may affect acceleration but that doesn't necessarily matter as much for a bomber as for a fighter.

Shorter wings
One way that perhaps could have been tried would be to use aircraft with a higher wing loading. Shorter wings are a good way to reduce drag. Most 1930s single engined bombers had large to enormous wingspans to help improve range and weight carrying capacity. Pilots in the 1930s were just getting used to things like retractable undercarriage and generally would not love an aircraft with a high takeoff and landing speed. And many airfields in England were grass fields made with biplanes in mind.

But there were longer airstrips available, and pilots did learn to cope with higher wing loadings through the war. So long as the fuselage was well streamlined, It should be possible to make a light bomber with say, a 38' wingspan. This could improve speed though altitude performance and range may be affected. Still, I see this as an opportunity where with some organizational / logistical shifting and training, they might be able to find some room for significant improvement in performance. The A-36 bomber, granted it was really a fighter bomber, but it gives a template as it only had a 37' / 11.28 m wingspan.

Bomb load
I have often felt, and argued here (with little traction) that bomb load often gets too much importance placed on it. To me, other factors like bombing accuracy, mission survival rate, actually matter more. If you have an aircraft which carries 6,000 lbs of bombs but drops bombs from higher altitudes and rarely hits anything, and flies at 200 mph and with a loss rate of 1 per 20 missions, is that better than a more accurate bomber (with a smaller CEP, say) that flies at 300 mph, & only carries 1,000 lb of bombs but has a loss rate of 1 in 50 missions?

But perhaps we can look to the historical record to answer this question of how much of a bomb load does a 'fast' single engined bomber need to carry. At least some 'fast' twin-engined bombers like the A-20, Pe-2, Tu-2, P1Y1, Br 693, Martin Maryland and Baltimore all carried fairly small bomb loads, as did other contemporaneous light or 'medium' twin engined bombers which weren't that fast, like the Do 17. And yet these were considered relatively effective types. The A-36 Mustang, actually quite an effective mid war 'fast bomber', typically only carried a 1,000 load. And yet it played a very useful role in Italy, from what I've read.

Other similar fighter bombers carried between 250 lbs in the early war to as much as 1,500 or 2,000 lbs, but were still considered effective, even pivotal to the outcome of land battles and even in Operational interdiction campaigns against supplies and troop movements, such as in the South Pacific, China /Burma and North Africa.

So I don't think a theoretical early or pre-war 'fast bomber' needs to carry that much payload weight. Start with even as low as a 250 lb to 500 lb load and then increase it as engine power improves. This is another area where you can give yourself a little breathing room with the design.

Crew / Defensive guns
This is another area where you need something, but the speed (and escort fighters) may matter more. With the benefit of hindsight we now know that very few bombers indeed, maybe the Mosquito, the A-36 and some jets? could operate without fighter escort during WW2 if there were considerable numbers of enemy fighters around. Putting together a single engined 'fast bomber' that could outrun fighters may be impossible. But higher speed, say in the ballpark of 300-330 mph / 480-530 kph, seemed to be enough to enable some twin engined bombers to survive at a little bit better rate than the slower types, and it didn't matter that much how many guns they had.

But a bomber should have longer range, and therefore may need a navigator and at least one defensive gunner is a good idea. I'd say put one navigator / radio man / gunner with a retractable heavy machine gun or 20mm cannon for defense.

 

[Wild_Bill_Kelso]

If by some miracle you made a bomber that could fly 350 mph or more you could maybe do without the guns.

 

[K5083]

With the sole exception of the D4Y we haven't found a succesful operational single used as a bomber. It isn't that it can't be done, it's that it is not a logical use of resources. Two engines get you a far better bomber, and if you want a tactical aircraft you can use a current or slightly older fighter. Tactical aircraft don't need the range. Range and bombload involve trade-offs for a single which leave you in Battle, Ki-30, Ki-32 territory. Where singles had to be used, at sea, even the bigger engines didn't give the TBM or SB2C the kind of speed that beat a pursuing fighter.


Things I've found looking around at what could be done;

Ki-30 and Ki-32, with their fixed gear, were just as fast, or do I mean slow, as the Battle.

The proposed Ju187 with it's Jumo 213 was no faster than Ju87D. And every Jumo could have powered a 190D or half a Ju88G

Once jabos came in the idea of single-engine specialist bombers disappeared except for tactical aircraft and carrier-borne types. And the F-105.

 

[Shortround6]

Engines
Probably limited options there, as better engines may go to higher priority aircraft, as already stated.

If you don't use the best engines you have got you are already screwed.
Bomber with best engines vs smaller fighter with 2nd best engine????
Bomber with 2nd best engine vs fighter with best engine?????

But there were longer airstrips available, and pilots did learn to cope with higher wing loadings through the war. So long as the fuselage was well streamlined, It should be possible to make a light bomber with say, a 38' wingspan. This could improve speed though altitude performance and range may be affected. Still, I see this as an opportunity where with some organizational / logistical shifting and training, they might be able to find some room for significant improvement in performance. The A-36 bomber, granted it was really a fighter bomber, but it gives a template as it only had a 37' / 11.28 m wingspan.

The A-36 was great airplane, but it does point to a few problems.
1, it arguably one of the most streamlined planes around and maybe the most streamline. A bomber with enclosed bomb stowage has little chance of being as good.
2, the A-36 used a 1325hp engine for take-off which it puts 20-30% more powerful than any V-12 engine in 1939-40, let alone before. It is 15% more powerful than the Allisons used in the P-40D & E or even the Mustang Is.
3, and that brings us to one of my hobby horses, Field Length. The A-36 with its 1325hp engine needed 3150ft at 10,000lbs (full internal fuel and two 500lb bombs) to clear 50ft .
And that is at 0 degrees C or 32 degrees F Add 20% more length for 20 degrees C or 72 degrees F. This is on a hard runway.
You can operate a Halifax or Lancaster out of the same size airstrip.
4. now figure out the operational radius. with 180 US gallons. And any other plane you can make without a trunk load of NA drawings/documents won't have the same range.
How close you come is subject to question.

If you have an aircraft which carries 6,000 lbs of bombs but drops bombs from higher altitudes and rarely hits anything, and flies at 200 mph and with a loss rate of 1 per 20 missions, is that better than a more accurate bomber (with a smaller CEP, say) that flies at 300 mph, & only carries 1,000 lb of bombs but has a loss rate of 1 in 50 missions?

Ok, lets start doing the math. If we want 120,000lb of bombs on target (area) we need 20 big bombers and so we are going to loose 1 bomber for every mission.
If we use the 1000lb load bomber we need 120 planes and we are going to loose 2.4 bombers per mission. Adjust for imagined crew size.
The only advantage is the increase accuracy of the small bomber. How much of that is training?
Now you may be able (with increased losses and smaller bomb load) attack targets further away with the big bomber.
You can't attack targets much further away with the small bomber at all.

The A-36 Mustang, actually quite an effective mid war 'fast bomber', typically only carried a 1,000 load. And yet it played a very useful role in Italy, from what I've read.

A lot depends on the theater of operations.