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

[tomo pauk]

What does a single engine bomber bring to the table?

As in what do 200 single bombers that can move 1000lbs apiece 400miles (radius) do for you that 100 twin engine bombers that can move 2000lbs each 400 miles (radius) at the same speeds?

Single-engined bomber was needed to replace the old single-engined bombers, in ever-increasing quantities. Eg. in the RAF, Battle was replacing the Hind, in Germany the Ju-87 was supposed to replace the Hs 123, Su-2 was also replacing biplane bombers in the VVS. New 2-, 3- and even 4-engined bombers were in pipeline to replace old, mostly 2- engined bombers.

There was a handful of 2-engined fast (or fast-ish) bomber types that were able to carry 2000 lbs before 1942, most prominent being the Tupolev SB. Blenheim carried 1000 lbs, while Beaufort was not fast. Early Do-17s (like the -E version) that were fast when compared with biplane fighters and French fighters were carrying 1100 lbs, while the later versions carrying 2000 lbs were no fast bomber anymore. French 2-engined bombers that managed more than 400 km/h, like the Potez 630, carried 900 lbs; 420-430 km/h was slow for 1939-40. Ki-48, that was supposed to be a 'better SB', was slow, with under 900 lbs bomb load - all despite using two engines. So there is a lot of air forces where a reasonably fast 1-engined bomber would've been a boon when compared with 2-engined bombers produced in many hundreds.

BTW the He 118 was a bad example. It used a wing about 96% of the size of a Battle's wing and since it first flew in 1936 it's aerodynamics were not any better than the Battle's.
You need a new wing

I haven't also suggested a 'big Bf 109' for nothing

 

[Shortround6]

Single-engined bomber was needed to replace the old single-engined bombers, in ever-increasing quantities. Eg. in the RAF, Battle was replacing the Hind, in Germany the Ju-87 was supposed to replace the Hs 123, Su-2 was also replacing biplane bombers in the VVS. New 2-, 3- and even 4-engined bombers were in pipeline to replace old, mostly 2- engined bombers.

in the RAF, Battle was replacing the Hind,

Should it have though? They were actually built for different jobs. The Hind had zero hope of hitting the German homeland (crossing the Rhine) from British bases unless on a suicide mission. Wiki says range of 460 miles, The Hind could have been used (in the early 30s) for interdiction behind the army front lines or for combat support.
The Battle was sold ( somewhat by politicians or RAF bomber advocates) as a 'strategic' bomber capable of hitting Germany.
The Ju-87 wasn't really a replacement for the Hs 123. This is sort of semantics but the Hs 123 was a temporary substitute for the Ju-87. They never intended the HS 123 to be built in large number and again the Hs 123 and the Ju 87 were tactical bombers. In the 1930s the conventional wisdom was that dive bombers needed heavier construction than regular light bombers and would be inferior in performance due to the higher structural weight.
The SU-2 was sort of a general purpose light bomber but let's use Russian numbers instead of Wiki, the SU-4 uses the M-82 engine out of LA-5.

There was a handful of 2-engined fast (or fast-ish) bomber types that were able to carry 2000 lbs before 1942, most prominent being the Tupolev SB. Blenheim carried 1000 lbs, while Beaufort was not fast. Early Do-17s (like the -E version) that were fast when compared with biplane fighters and French fighters were carrying 1100 lbs, while the later versions carrying 2000 lbs were no fast bomber anymore. French 2-engined bombers that managed more than 400 km/h, like the Potez 630, carried 900 lbs; 420-430 km/h was slow for 1939-40. Ki-48, that was supposed to be a 'better SB', was slow, with under 900 lbs bomb load - all despite using two engines. So there is a lot of air forces where a reasonably fast 1-engined bomber would've been a boon when compared with 2-engined bombers produced in many hundreds.

And we do have to be careful to compare years. Yes the Blenheim only carried 1000lbs, but it was faster by about 30mph than the Battle.
For the Do 17 the plane went through a succession of engines, so pick the right one. Put DB 601 engines in it and you have 290mph in 1939. Granted the range was extremely short.
The Ki-48 was a day late and dollar short Or way more than a dollar short. Example of how to bomb civilians on a budget?
It has Douglas DB-7 1940 performance in the summer of 1942. and Blenheim 1938 performance in 1940.
The Ki-48 had range and not much else. Using a pair of under 1000hp engines for a 4 man crew in 1940 was not a good idea.
But Sticking a licensed built DB 601 and retracting landing gear on one of these was not a good idea either.

We are also looking at different requirements. The Japanese navy wanted one large primary bomb to attack ships with.
The Japanese army wanted a crap load of small bombs for attacking cities with wooden (flammable) structures or large numbers of troops on the ground (not dug in).
You have different bomb storage problems. For the Ki-48 bomber the requested bomb load in 1937 was twenty four 15kg/33lb bombs or six 50kg/110lb bombs.
A bomb bay for a single 250kg HE or 500kg AP bomb can be much smaller.

 

[Shortround6]

Some of the twin engine types were supposed to offer better defense. The Ki-48 for instance offered both a top and bottom gunner and a flexible gun out the nose, Trouble is the Japanese Army 7.7mm machine gun wasn't very good.
Single engine bombers tried to use fixed gun/s out the front and a dorsal gun out the back.
British tried fixed guns out the front of several twins.

Which leads us to one of those "conflicts of theory" problems.
Light bombers of either type were suppose to keep a small tight formation to concentrate the fire of the rear guns, several gunners firing at one aircraft. However with fixed guns each bomber has to maneuver at least somewhat independently in order to get the gun/s on to (or even close to) the attacking aircraft, which is going to open up the formation and lessen defense to the rear.

 

[tomo pauk]

Should it have though? They were actually built for different jobs. The Hind had zero hope of hitting the German homeland (crossing the Rhine) from British bases unless on a suicide mission. Wiki says range of 460 miles, The Hind could have been used (in the early 30s) for interdiction behind the army front lines or for combat support.
The Battle was sold ( somewhat by politicians or RAF bomber advocates) as a 'strategic' bomber capable of hitting Germany.

You are right on these points.

In the 1930s the conventional wisdom was that dive bombers needed heavier construction than regular light bombers and would be inferior in performance due to the higher structural weight.

Ju 87 was of inferior performance due to it's big size (bith fuselage and wing), draggy flaps, and due to the fixed U/C. Before the D version, the cockpit was also blocky. Even the Battle was better streamlined. Engine power on the Ju 87 was always about one year behind what went into German or British fighters. It took 2 years for the Ju 87 to receive a 1000 HP engine when compared with Battle.
Nothing was preventing people from making streamlined tactical and/or dive bombers.

And we do have to be careful to compare years. Yes the Blenheim only carried 1000lbs, but it was faster by about 30mph than the Battle.

We can again take a look at Battle's portly appearance - it's deep and long fuselage and it's big wing. Wing area was 90% of what the Blenheim, Mosquito or DB-7 had - not good when the Blenheim has 2/3rds more HP ( even after the engine-related drag does it's number on it).

The Ki-48 had range and not much else. Using a pair of under 1000hp engines for a 4 man crew in 1940 was not a good idea.
But Sticking a licensed built DB 601 and retracting landing gear on one of these was not a good idea either.

I'm probably a wrong person to accept a Japanese aircraft to be powered with the Japanese copy of the DB 601
For them - a radial in the nose, 'ordinary' wing with a retractable U/C and there it is.

You have different bomb storage problems. For the Ki-48 bomber the requested bomb load in 1937 was twenty four 15kg/33lb bombs or six 50kg/110lb bombs.
A bomb bay for a single 250kg HE or 500kg AP bomb can be much smaller.

Here the 'bomb chambers' like on the XF4U-1 might come in handy to help out with the 15 kg bombs; the 50 kg bombs should probably fit in the 'main' bomb bay under the fuselage. Once these are proved bad, and engine power is up (needs more fuel), have on that place fuel tanks instead.

 

[Shortround6]

Nothing was preventing people from making streamlined tactical and/or dive bombers.

We can again take a look at Battle's portly appearance - it's deep and long fuselage and it's big wing. Wing area was 90% of what the Blenheim, Mosquito or DB-7 had - not good when the Blenheim has 2/3rds more HP ( even after the engine-related drag does it's number on it)

The Hind and Battle could have a man lying prone using a bomb sight though a hole/window in floor for better "accuracy". Again we are back to what do you want the plane to do.
You could cut down the Battles bulk by using only two men and eliminating the bomb aiming function (with required a steady speed and course (and altitude) for a number of seconds before bomb release. For the British (and some others early on) you have the airfield problem. For the British, they wanted to use the 3 man crew, carry four 250lb bombs, enough fuel for 1000 miles AND they wanted to get the plane out of the standard 500yd field. In 1936-38 that meant a big wing. In 1938 they started making some of the airfields bigger. They started fitting better props (better acceleration during the take-off run) and they had figured out how flaps worked so the plane could actually land back the same airfield.

I'm probably a wrong person to accept a Japanese aircraft to be powered with the Japanese copy of the DB 601
For them - a radial in the nose, 'ordinary' wing with a retractable U/C and there it is.

Well, you keep asking for fast The Kawasaki V-12 gave them 850hp for take-off in 1937-40 (30 less than the Merlin) and 950 hp at 12,470ft.
The Ki-32 was faster at 13,000ft than the Battle Problem for the Japanese was in 1937-1940 they needed really big radials to get big power. Hundreds of the early Ki-21 bombers used the same engine as the Ki-30

Not a lot to choose between the Ki-30 and the Ki-32. In 1940/41 the Radials with two speed superchargers (and other improvements) show up
And perhaps you could have your fast bomber then. The Japanese were not backwards. They had done experiments and calculations and retracting landing gear aircraft often did not show much advantage in the under 300mph speed range as long as due care was taken designing the landing gear. over 300mph it became a different story.

Here the 'bomb chambers' like on the XF4U-1 might come in handy to help out with the 15 kg bombs; the 50 kg bombs should probably fit in the 'main' bomb bay under the fuselage. Once these are proved bad, and engine power is up (needs more fuel), have on that place fuel tanks instead.

Just pointing out that Army requirements and Navy requirements are not the same.

For the US the requirements for the A-20 changed.
In the A-20, A-20A, and A-20B there were racks for eighty (80) 30lb fragmentation bombs in in vertical chutes/tubes.
Max load of sixteen 100lb bombs was provided for and since the US Army and the US navy didn't use the same bombs at this time the Army also wanted to hold four 300lb bombs, two 600lb bombs or one 1100lb bomb.

The British didn't want the small bomb storage but did want to carry 500lb bombs (only two ) but since their bomb was longer than the American bombs the bomb bay was lengthen by about a foot. The US got rid of the requirement for the little bombs while they were still sorting things out but the space in the upper bomb bay was used for first a 100 gallon fuel tank and later up to 325 US gallons could be put in the bomb bay with four US 500lb bombs below.
depending on year and country the intended bomb load could make quite a difference to an air plane even if the nominal weight was the same (A-20 bomb bay was 62.5 in in height as the 30lb bombs were required to fall free of the tube before the slipstream hit them.
And the eighty 30lb bombs were the max bombload of 2400lbs.

 

[Macandy]

Seems like the people at Yokosuka didn't gotten the memo, with their bomber doing 335 mph on 1 engine no better than the V-1710-39.

Ah yes, the Yokosuka Comet, Comet by name, blazing Comet by nature.
A disastrously bad design!

WW2 Wings of Glory Airplane Packs Preview – Yokosuka D4Y Suisei - Ares Games

The last article about our most recent WW2 Airplane Packs series presents the Yokosuka D4Y Suisei, probably the least familiar to many people. If the subject of “Japanese Dive Bomber” is mentioned, many people quickly think “Val” – the Aichi D-3, famous for its fixed landing gear (sort of the...

www.aresgames.eu

 

[tomo pauk]

Ah yes, the Yokosuka Comet, Comet by name, blazing Comet by nature.
A disastrously bad design!

WW2 Wings of Glory Airplane Packs Preview – Yokosuka D4Y Suisei - Ares Games

The last article about our most recent WW2 Airplane Packs series presents the Yokosuka D4Y Suisei, probably the least familiar to many people. If the subject of “Japanese Dive Bomber” is mentioned, many people quickly think “Val” – the Aichi D-3, famous for its fixed landing gear (sort of the...

www.aresgames.eu

Not having self-sealing tanks does matter.

 

[Shortround6]

They made the plane too light. It was unable to do it's intended role of dive-bomber/attack plane.
Which meant that the D3A had to soldier on for a considerable time.

If the plane had lost 5-10mph of speed and 100 miles of range for stronger structure it still would have been ahead of the D3A2.

Everything is a trade off.

Now if you want protected tanks plus the ability to dive (and pull out) we start getting into even shorter range or perhaps a slightly bigger wing. The D4Y couldn't use the smaller carriers as it was which lead to the A6M7 which didn't show up in time to really change anything.

 

[Macandy]

Not having self-sealing tanks does matter.

Yes, it does, but this 'fast single engined bomber' only achieved the 'fast' by deleting basics like self sealing tanks and armour, that made it a flying torch that lit up with a single strike.
Its no good being fast if you aren't survivable. Which is back to the lessons learned from the Spanish Civil War, light single engined bombers simply didn't have the performance to survive on a modern battlefield. See the Battle and Devastator for good examples.

 

[GrauGeist]

What bomber (Allied or Axis) possessed survivability beyond that of any other, self-sealing tanks or not?

Fighter/bombers could drop their ordnance and turn to fight.

A dedicated bomber did not have that advantage. So to simply wave off a certain type solely based on what type of fuel tanks it was designed with, is missing the bigger picture.

ANY bomber will burn if hit hard enough, regardless of it's fuel tank protection.

 

[tomo pauk]

Yes, it does, but this 'fast single engined bomber' only achieved the 'fast' by deleting basics like self sealing tanks and armour,

Source for this claim?

Its no good being fast if you aren't survivable. Which is back to the lessons learned from the Spanish Civil War, light single engined bombers simply didn't have the performance to survive on a modern battlefield. See the Battle and Devastator for good examples.

Neither Battle nor Devastator were fast.

 

[Shortround6]

Which is back to the lessons learned from the Spanish Civil War, light single engined bombers simply didn't have the performance to survive on a modern battlefield. See the Battle and Devastator for good examples.

Neither Battle nor Devastator were fast.

Neither the Battle or the Devastator were designed with the lessons of the Spanish civil war. They (and a number of other single and twin engine bombers) were designed before the Spanish Civil war and produced during it.

Indeed the Battle would have been a speed demon in the Spanish Civil war. Or at least part of it.

From Wiki,
17 July 1936 – 1 April 1939 (2 years, 8 months, 2 weeks and 1 day)

It is easy to see the lessons now, but some countries actually drew the wrong lessons , like 3 rcmg's were adequate defense for a "fast" medium bomber and yes, the Germans considered the He 111 fast. Or at least not as slow as Ju 52s.

There are at least two standards of "fast".

Can you runaway from a fighter that has a visual on you? Or at least make him chase you long enough to run into fuel or temperature problems before he gets to shoot. A 12mph speed advantage means the fighter can make up 1 mile of distance in 5 minutes.

Depending on ground control, how fast does the bomber formation (or even single planes) have to be make actual interception difficult? As in how many miles off the bomber/s track before the fighters cannot be vectored to bomber formation. Without radar and good ground control gets a lot harder. However in some cases in the Pacific it was easy. If a coast watcher reported a formation of planes 1/2 way between Guadalcanal and Rabaul there weren't a lot of possible target's/destination.

Faster planes will make the inception more difficult but not make surviving the inception any better.

Fighter/bombers could drop their ordnance and turn to fight.

Which then counts as a successful intercept. The defending fighters have succeeded in stopping the enemy from bombing the target, at least for that day.

 

[GrauGeist]

Which then counts as a successful intercept. The defending fighters have succeeded in stopping the enemy from bombing the target, at least for that day.

Agreed.

However, the intercepted "bombers" have a higher chance of surviving the bounce and will be available to try again another day.

 

[Shortround6]

Agreed.

However, the intercepted "bombers" have a higher chance of surviving the bounce and will be available to try again another day.

yes, most of the time.
Some air forces had an easier time with providing more fuel and bombs for repeat strikes.
Sometimes the weather prevented repeat strikes for a few days.
For tactical targets, Sometimes the enemy ground troops (or ships) weren't there a few days later.

 

[delcyros]

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.

 

[Shortround6]

For the Allies the fighter bomber may have been a better option.

We are also (maybe?) comparing unescorted fast bombers and unescorted fighter bombers.

The idea that fighter bombers were "self-escorting" is rather false. Once the intercepting fighters see bombs drop (and they have to be close to see it) the interceptors can turn around and go home without firing a shot. They have defended the target
The allies usually had enough fighters to send one or more squadrons as escorts/ top cover.
And in some cases as the war went on the Axis didn't have enough fighters to intercept every (or even very many ) raids anyway.
There were always exceptions which makes it had to come up with short generalities.

 

[Shortround6]

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.

It had a few problems, it was way too big for the job.

It was a 4-5 seat airliner meant to compete with the Lockheed Orion 9

trying to use 1932-33 aircraft for a 1936 or later warplane is not going to work, There was a lot of stuff going on under the "hood". Better materials, better construction methods, more time in wind tunnels, flaps designed in rather than added on.

 

[delcyros]

A narrower body design then. More alike the He-270.

 

[SaparotRob]

All these "build a better.." threads have shown me what a great job all those original designers did back back then. Different tech trees advancing at different rates. Designers working at putting stuff together with stuff never having been put together before. Insane government specifications for a contract that will make or break their firms. We here still haven't topped those guys.

 

[tomo pauk]

There are at least two standards of "fast".

Can you runaway from a fighter that has a visual on you? Or at least make him chase you long enough to run into fuel or temperature problems before he gets to shoot. A 12mph speed advantage means the fighter can make up 1 mile of distance in 5 minutes.

We can take a look at I-16 Type 5 (750 HP engine) from 1936 vs. Battle I from 1937. Fighter is 15-20 mph faster than the bomber, similar result is when Bf 109A or B are compared with the Battle. Not that much of a speed demon, despite having the world's most powerful military engine in service before 1939. Battle's problem - and that is not going away by some nip & tuck - is it's huge drag.
P-35 (no suffix) is also faster, by 20-25 mph.
The P-30 will also be faster, but at greater altitude, allowing a shallow dive to pick up speed.

Indeed the Battle would have been a speed demon in the Spanish Civil war. Or at least part of it.

Pitted against biplane fighters, yes.
Pitted against Hurricane I, Bf 109B/C/D, late I-16s, Fokker D.XXI, MS.406 or He 112B - not so much.