Fast bombers alternatives for 1939-40

[SplitRz]

Most of the photos of Ju88s that I have seen show bombs carried on external racks. Is the internal bomb bay absolutely necessary? A Spitfire bomber that carries its load externally, is smaller, and faster on the way home, after the enemy gets pissed off.

Its a good question. Whats being described there are really fighter bombers. The downside of using a high performance non-bomber designed aircraft in this role is that you are immediately clipping its wings in terms of speed and manoeuvrability. The drag deficit caused by hanging external ordinance is pretty huge - and you're saddling the aircraft with the weight on the way to the target PLUS the drag of rocket rails and bomb-crutches on the way back too. It means what ever performance parity a fighter-bomber might have with opposing aircraft is at at its lowest on terms of range and speed at the most strategically important part of its mission - on its way to the target. That was probably fine in theatres where air superiority (and later supremacy) had been established - and when aircraft were deployed not too far from the front line. But early war? A Hurricane with hardpoints, crutches plus 2 x 500lbs bombs is just barely capable of 300mph. A Spitfire won't be much better off - and with its less forgiving undercarriage is going to have to make do with 250lb bombs. Either option means nearby and likely light targets requiring shallow dive bombing for any kind of accuracy- with little margin for indirect routes to and from. Internal bomb bays offer much better streamlining and therefore potential range and speed, to as well as from the target.

This 'what if' isn't an easy circle to square. Once again it outlines how special and uniquely 'right' de Havilland got the Mosquito.

 

[Shortround6]

A Hurricane with hardpoints, crutches plus 2 x 500lbs bombs is just barely capable of 300mph.

and that is at around 19-20,000ft.
What happened at 5,000ft or under? The same 10% reduction in speed or are things a little worse?

 

[SplitRz]

and that is at around 19-20,000ft.
What happened at 5,000ft or under? The same 10% reduction in speed or are things a little worse?

I've got to presume its worse. I can't imagine 2 x 500lb bombs and crutches are going to produce less drag than 2 x 40mm cannons. I think Hurricane 2Ds were good for about 275mph at sea level.

Hanging munitions on fighters makes them into fighter bombers. But does it make them into 'fast bombers'? It seems to me an expedient move if you have semi-obsolescent and therefore relatively expendable aircraft (and/or desperation requires it), OR you have air superiority or supremacy. It also makes sense from a strategic economy perspective. But it seems to me that the general experience that the inherently more rugged fighters are the ones that stand the best chance of survival (ie Hurricane rather than Spitfire, P47 rather than P51 etc). And that's based largely in the face of the threat ground fire rather than aerial interception, as well.

 

[SplitRz]

The requirements for this thread are a bit too squishy. What exactly is considered "actually fast" in 1939, what is the minimum internal bombload, and what is a "useful" minimum range?

I'd posit the Martin Maryland would probably be a pretty good fast bomber in 1939-40, particularly if it could be outfitted with slightly more powerful engines that were available in this timeframe.

After pages and pages of cogitation, I think you have basically nailed it. A slightly ungraded Maryland (would benefit from twin defensive gun positions and more powerful engines) pretty much fits the bill to a T for 1940. Faster, more maneuverable and eminently more survivable than a Blenheim.

 

[Shortround6]

I've got to presume its worse. I can't imagine 2 x 500lb bombs and crutches are going to produce less drag than 2 x 40mm cannons. I think Hurricane 2Ds were good for about 275mph at sea level.

Hanging munitions on fighters makes them into fighter bombers. But does it make them into 'fast bombers'? It seems to me an expedient move if you have semi-obsolescent and therefore relatively expendable aircraft (and/or desperation requires it), OR you have air superiority or supremacy. It also makes sense from a strategic economy perspective. But it seems to me that the general experience that the inherently more rugged fighters are the ones that stand the best chance of survival (ie Hurricane rather than Spitfire, P47 rather than P51 etc). And that's based largely in the face of the threat ground fire rather than aerial interception, as well.

Basically the enclosed bomb/weapons bay thing came into being in the 1930s for drag reduction. They have been hanging bombs outside of planes since 1914-15 and they had a pretty good of idea of what that did to performance and some WW I planes tried interior stowage. Actual change in drag in WW I is questionable but by the early/mid 30s it was pretty much standard for bombers.
Fighter bombers get away with underwing racks for a number of reasons. Powerful engines is one. 2000hp Corsair vs 1200hp Japanese interceptors? Not saying the Corsair could carry it's bombs past the interceptors but the Corsair has a better chance of picking up speed and climb after dropping the bombs than a 1200hp fighter bomber would. Shorter range. Fighter bombers rarely operated several hundred miles from base. I said rarely, not never.
USN specified enclosed bomb bays for the SBD and TBD successors. That was not a choice by the makers/designers. If you want your design accepted for development contract it had to have a weapons bay. By 1944 the Navy didn't care. And they had 2000hp plus engines on the way (or 3000hp) and some assurance of air superiority so load carrying beat streamlining.
being able to swap bombs for drop tanks and having multiple hard points/pylons made things a lot easier for mission planners.

This thread is about 1939-40 aircraft and if we stray too far from that point in time we get answers that may not apply. Many an aircraft designer in 1938-39 would have loved to have an Allison engine from a P-40K available for his design. 50% more take-off power from the same engine weight (and size) could open a lot of doors. Not even getting into trick superchargers or other things

 

[Steamed_Banana]

I've got to presume its worse. I can't imagine 2 x 500lb bombs and crutches are going to produce less drag than 2 x 40mm cannons. I think Hurricane 2Ds were good for about 275mph at sea level.

Hanging munitions on fighters makes them into fighter bombers. But does it make them into 'fast bombers'? It seems to me an expedient move if you have semi-obsolescent and therefore relatively expendable aircraft (and/or desperation requires it), OR you have air superiority or supremacy. It also makes sense from a strategic economy perspective. But it seems to me that the general experience that the inherently more rugged fighters are the ones that stand the best chance of survival (ie Hurricane rather than Spitfire, P47 rather than P51 etc). And that's based largely in the face of the threat ground fire rather than aerial interception, as well.

Speed helps a lot in this. A-36s used to go on unescorted missions fairly deep into German held territory in Italy and drop their bombs and fly out, with fairly low losses. The egress seems to be maybe a bit more important for survival than the ingress, though they would drop their bombs if attacked by fighters before they hit their target.

 

[SplitRz]

There's the rub!

Some truths remain the same, regardless of time period however. In 1939, no one had (or could assume) air superiority. And like you say, for WW1 types, the speed penalty was a smaller percentage of a slower speed to begin with.

In 1939, the situation was much the same as it appeared '49 to '89: Bombers are going to have to make their initial strikes where opposition interceptors are going to be their primary threat. As in the OPs (IMO) correct observation, range is an issue - and one most impacted by external carriage. And in 1939/40, no one can simply assume that they're going to have an excess horsepower engine to offset compromised aerodynamics to give enough performance over what ever their opponents are employing. Once you know you CAN at least reach your target in range, you're remaining options on how to make the journey survivable are limited: enough excess range to make your route to your destination at least ambiguous helps throw off the plotters and fighter coordination. Enough speed to limit interception opportunity is a huge advantage. And a rugged enough and manoeuvrable airframe to not make yourself a sitting duck until an intercepting high performance but likely low endurance fighter give up, has got to help. Then there's the accuracy of your delivery - and again, as per the original OP, short of a dedicated dive-bomber, in 1939 this assumes a proper bomb sight (and presumably, bombardier.)

The desire for enclosed bomb bays was not just a USN sticking point post war. The advantages for strike aircraft were recognised and I remember a lot of eye rolling when it turned out that most of the impressive brochure performance stats for the lauded Tornado turned to dust when you actually hung anything like a useful load from it, because ALL ordinance apart from the guns were external. The reason was all that drag. And it was the reason why the 20 year older design of the Buccaneer actually and in practice ended up carrying more, further and at the same speed - because the performance penalty was smaller for a subsonic design AND it had that all important internal bomb-bay. RAF interceptor pilots on DACT have said that the Tornado was amongst the easiest strike bombers to intercept, and the Buccaneer one of the most difficult. Maybe I'm pulling to much assumption from all of that, but the observation stuck with me.

I don't think hanging one or two thousand lbs worth of bombs on external racks off of any 1939 era aircraft is going to create a 'fast bomber', is it? A slow bomber which can sprint away from the target quickly (if it can reach it), maybe. But is that on track for Tomos What If?

 

[Shortround6]

I know it is only 2-3 years but there were a lot of changes in those 2-3 years.
A-36 used an airframe that didn't exist (flyable prototype) until Sept/Oct 1940.
4 things here.
The wing was low drag compared to everything else. Not the laminar flow claimed but better than anything else.
The wing profile allowed for more volume inside for fuel compared to thin wing like Spitfire (even if Spitfire wanted to carry fuel in the wing)
The radiator system was lower drag than anybody else. Not going to argue about getting actual thrust. Just that it was lower drag.
NA figured out how to make a smoother airframe in general and do it in quantity.
Now engine
A-36 used a limited model of the Allison engine. Only used in the A-36. This was a low altitude engine that really hurt performance at high altitudes.
It did to two things for the A-36. Allowed for 1325hp for take-off instead of the 1150hp in the Mustang Is and the P-40Es. It also allowed for a max cruise at really low altitudes (3700ft) of 1100hp instead of 1000hp. SO a 10% boost in power at max continuous settings.
Needed 100+ octane fuel.

There were things that some countries could do in 1939-40 but not most of the ones used on the A-36.
British could have grabbed some Spitfires, stuffed Merlin VIIIs from the Fulmar into them, given them CS Rotol props, taken out 2-4 machine guns and fitted more fuel in the wing and slung a bomb underneath.
French are screwed. Using a low altitude HS 12Y engine doesn't by you much and you can't use much more boost even if you can get better fuel. Good luck trying to fit more fuel into the existing French fighter airframes.
Germans need to fit both fuel and bomb/s under a 109 size airframe. (and fix the canopy ;(

 

[Steamed_Banana]

You are unfairly fixated on the French! A few dozen Leo 451 would be very helpful for this Ceylon scenario

And let's not forget the French are basically the ones who saved the Boston, which would I think be very good in this situation, depending on the precise type(s) available.

I like the Bloch 174 (for high speed recon) and the Breuget 693 (for low level strike) for this too.

 

[yulzari]

Perhaps we have a glimmer of sense for the Heinkel He177 having a dive bombing capacity. If your intelligence can pinpoint the key buildings which have key machinery in them and you have a limited number of strategic heavy bombers then dive bombing precision will allow a more effective use of them. Key items are things like major machines that cannot be easily replaced or repaired. Ordinary factories can move out the rubble and the machinery will survive being covered in rubble etc. so the factory can soon get back to production even if it is working in the open air in winter. The allied approach for heavy bombers was to smother the whole factory area and anything nearby which needs far more bombers. Yes I do know that this concept has enough holes in it to form a fishing net but it does give dive bombing heavy bombers at least one reason to exist.

 

[Steamed_Banana]

Perhaps we have a glimmer of sense for the Heinkel He177 having a dive bombing capacity. If your intelligence can pinpoint the key buildings which have key machinery in them and you have a limited number of strategic heavy bombers then dive bombing precision will allow a more effective use of them. Key items are things like major machines that cannot be easily replaced or repaired. Ordinary factories can move out the rubble and the machinery will survive being covered in rubble etc. so the factory can soon get back to production even if it is working in the open air in winter. The allied approach for heavy bombers was to smother the whole factory area and anything nearby which needs far more bombers. Yes I do know that this concept has enough holes in it to form a fishing net but it does give dive bombing heavy bombers at least one reason to exist.

The problem isn't that dive bombing wasn't a lot more accurate - I certainly agree it was. The problem is in making an aircraft that heavy be able to withstand high G pullout. Which makes them even heavier.

The Ju 88 ultimately was too heavy and they had to remove the dive brakes from them. There is no way a beast like the He 177 was going to manage.

 

[Shortround6]

Now for comedy

You are unfairly fixated on the French! A few dozen Leo 451 would be very helpful for this Ceylon scenario

Only if they kept the gun mounts retracted
A real choice, test the unarmed bomber theory and run or deploy air brakes (gun mounts) and allow even Claudes to attack.

And let's not forget the French are basically the ones who saved the Boston,

No they didn't. The US ordered A-20s in the summer of 1939. They allowed the French and British to take first deliveries or perhaps we should say they delayed taking their own places on the production line while the French planes were built.

I like the Bloch 174 (for high speed recon)

One of the few bright spots. But it points out how hard building fast bombers was in 1939-40. It was fast but eight 50kb bombs is not a good return on investment for a bomber.

Breuget 693 (for low level strike) for this too.

Just set fire to these things on the runway and save the pilots.
It looks cool and they tried to fit bigger engines but it's actual growth potential is suspect. Using two 14 cylinder radials to carry the same warload (guns) as the MS 406 seems more than a little wasteful
Stick a low altitude HS engine in the MS 406, give it ejector exhausts and hang racks for four 50kg bombs under the wing. Presto, ground attack mission taken care of
Now if we could just figure out what to do about the German AA guns????

 

[Shortround6]

Yes I do know that this concept has enough holes in it to form a fishing net but it does give dive bombing heavy bombers at least one reason to exist.

 

[Steamed_Banana]

Now for comedy

Only if they kept the gun mounts retracted

Hmmm

A real choice, test the unarmed bomber theory and run or deploy air brakes (gun mounts) and allow even Claudes to attack.

You have data to back that up? I see 300 mph with guns including that big 20mm, range 1802 miles at 231 mph. 3,300 lb bomb load.

The Germans rated it.

No they didn't. The US ordered A-20s in the summer of 1939. They allowed the French and British to take first deliveries or perhaps we should say they delayed taking their own places on the production line while the French planes were built.

Maybe worthy for another thread. The Americans were losing interest in the design (and the British were decidedly lukewarm) until they noticed the French loved it.

One of the few bright spots. But it points out how hard building fast bombers was in 1939-40. It was fast but eight 50kb bombs is not a good return on investment for a bomber.

It was really a recon plane, but probably could have been made into a proper bomber.

Just set fire to these things on the runway and save the pilots.
It looks cool and they tried to fit bigger engines but it's actual growth potential is suspect. Using two 14 cylinder radials to carry the same warload (guns) as the MS 406 seems more than a little wasteful

Payload may have been smallish but it carried bombs internally mate 882 lb bomb load plus a 20mm cannon for strafing.

And managed 300 mph with those leetle engines you hate so much!

Stick a low altitude HS engine in the MS 406, give it ejector exhausts and hang racks for four 50kg bombs under the wing. Presto, ground attack mission taken care of
Now if we could just figure out what to do about the German AA guns????

Kido Butai is Japonais mate. You know the ones you are always going on about how little AAA they had?

 

[Howard Gibson]

and that is at around 19-20,000ft.
What happened at 5,000ft or under? The same 10% reduction in speed or are things a little worse?

A Hurricane IID with the two Vickers 40mm cannon did 250mph at 5,000ft. Don't forget though that everybody was slower down low. The Hurricane could do 320mph at 18,000ft, but any German tanks it found at that altitude probably were not in good shape.

Even late in the war, the really hot superprops were doing around 380mph at sea level.

 

[Howard Gibson]

Speed helps a lot in this. A-36s used to go on unescorted missions fairly deep into German held territory in Italy and drop their bombs and fly out, with fairly low losses. The egress seems to be maybe a bit more important for survival than the ingress, though they would drop their bombs if attacked by fighters before they hit their target.

Versatile aircraft during WWII and at other times at gobs and gobs of extra performance. People could hang stuff on the aircraft to perform extra missions. The performance would be degraded, but not enough the render the aircraft not functional. The Mustangs and Apaches illustrate this point perfectly. You can add bombs for ground attack, or big fuel tanks for long range escort, without slowing the planes to the point that the enemy can manage them.

In 1939, the closest thing to a high speed bomber was the Ju88. Under certain circumstances, these could be very difficult for fighters to catch. The Battle of Britain was not one of those circumstances.

Let's design a high speed bomber for 1939. The successful radial engines in WWII were big, and not available in 1939. We need power by Rolls Royce Merlins, Daimler Benz DB601s, or Junkers Jumo 211s. With a reasonable amount of fuel and an enclosed bomb bay, we need a larger aircraft, and we need two engines to maintain performance. The aircraft do not need to by fully aerobatic, so we can reduce weight by not stressing the wings as much. Maybe dive bombing is a bad idea. We still need self sealing tanks and armour, although I don't know how common this was in 1939.

 

[Shortround6]

You have data to back that up? I see 300 mph with guns including that big 20mm, range 1802 miles at 231 mph. 3,300 lb bomb load.

Ok, no data........................but

Leo 451 with guns retracted, very slippery. Now deploy the 20mm

now lower the belly gun

Granted it was a lot skinner than it was long but what happens to the 300mph speed?
You may also want to check that 3300lb bomb load. You can fit it in the bomb bays but one old book claims range of 1430 miles with 1100lbs of bombs, you can carry 3300lbs of bombs easy, you just have leave 2200lbs of fuel at home

Maybe worthy for another thread. The Americans were losing interest in the design (and the British were decidedly lukewarm) until they noticed the French loved it.

Orders and actual use often were spaced out over a year or more.
French ordered 100 DB-7s and 115 Martin 167s in Feb 1939. The US ordered 186 A-20s and A-20As on May 20th 1939. The First French DB-7 flew Aug 17th 1939. First A-20S flew in Sept 1940. British don't get into the act until Nov/Dec 1939 when they start negations for A-20 equivalent of the DB-7. Douglas built two French DB-7 in California but the rest of the first order were built as sub assemblies and crated and shipped to France (actually North Africa) for final assembly after much confusion about the legaties of shipping aircraft and parts from natural US to belligerent France. It take from Jan though April first 1940 for the 98 planes from the first order to be put on ships and start sailing. By the 10th of May 1940 33 planes had been issued to 3 squadrons. I/19, II/19 and II/61 in Morocco. The British had ordered 150 DB-7Bs (with R-2600 engines) in Feb 1940. Sorting out how many of the several French orders wound up in British hands is difficult. If the plane had R-1830 engines it is ex French, but the French had ordered a batch with R-2600 engines and those batches intermingled as did the US A-20A/A-20 built in the later parts of 1940 and 1941.

It was really a recon plane, but probably could have been made into a proper bomber.

Maybe. It is a plane about the size of a DB-7 and with about 80% of the wing of a Martin 167 and using engines not much better than single speed R-1830s.
Maybe with a little pulling/pushing you can get Six 100kg bombs in the thing.

Kido Butai is Japonais mate. You know the ones you are always going on about how little AAA they had?

French had really screwed this one up. They guess the Germans army would have about the same AA capability as the French Army had, which was close to zero. They guessed wrong and French air units of many types suffered large losses trying to support the French army.

 

[Howard Gibson]

Ok, no data........................but
View attachment 854819
Leo 451 with guns retracted, very slippery. Now deploy the 20mm
View attachment 854835
now lower the belly gun
View attachment 854836
Granted it was a lot skinner than it was long but what happens to the 300mph speed?
You may also want to check that 3300lb bomb load. You can fit it in the bomb bays but one old book claims range of 1430 miles with 1100lbs of bombs, you can carry 3300lbs of bombs easy, you just have leave 2200lbs of fuel at home

They were investigating Wright R2600 engines for this thing.

 

[Steamed_Banana]

Ok, no data........................but
View attachment 854819
Leo 451 with guns retracted, very slippery. Now deploy the 20mm
View attachment 854835
now lower the belly gun
View attachment 854836
Granted it was a lot skinner than it was long but what happens to the 300mph speed?

Oh I think it's fine, to be honest. No worse than moving a pair of .50 cal machineguns around or a quad .303 turret - as with those the drag depends on how it's pointed. I think that tall Boulton-Paul turret on a lot of Allied aircraft like the Hudson or the Blenheim IV is likely a good bit draggier (not to mention the chin gun position on the latter).

Hmmm.....

In 'stowed' position like in the drawing at the bottom, I don't think it's dragging much at all. It will only be deployed if the aircraft is engaged and it doesn't traverse that widely - though it does have a nice field of fire with the twin-tail. And I bet it's pretty intimidating.

That said, if it did turn out to be a problem how hard do you think it would be to just replace that gun with a .303, or a pair of them, or a .50. I think they could manage that in the field if they thought they needed to.

The ventral turret is of course, deployable and it's appearance during flight is therefore optional. By default it stays within the aircraft, and it too could in fact be deleted which saves a fair bit of weight.

You may also want to check that 3300lb bomb load. You can fit it in the bomb bays but one old book claims range of 1430 miles with 1100lbs of bombs, you can carry 3300lbs of bombs easy, you just have leave 2200lbs of fuel at home

I think you'll find it out-ranges the other bomber types with an equivalent bomb load

This is why the Germans liked it so much they allowed Vichy France to resume production and build a bunch more.

Orders and actual use often were spaced out over a year or more.
French ordered 100 DB-7s and 115 Martin 167s in Feb 1939. The US ordered 186 A-20s and A-20As on May 20th 1939. The First French DB-7 flew Aug 17th 1939. First A-20S flew in Sept 1940. British don't get into the act until Nov/Dec 1939 when they start negations for A-20 equivalent of the DB-7. Douglas built two French DB-7 in California but the rest of the first order were built as sub assemblies and crated and shipped to France (actually North Africa) for final assembly after much confusion about the legaties of shipping aircraft and parts from natural US to belligerent France. It take from Jan though April first 1940 for the 98 planes from the first order to be put on ships and start sailing. By the 10th of May 1940 33 planes had been issued to 3 squadrons. I/19, II/19 and II/61 in Morocco. The British had ordered 150 DB-7Bs (with R-2600 engines) in Feb 1940. Sorting out how many of the several French orders wound up in British hands is difficult. If the plane had R-1830 engines it is ex French, but the French had ordered a batch with R-2600 engines and those batches intermingled as did the US A-20A/A-20 built in the later parts of 1940 and 1941.

So what? The French interest preceded their order (in spite of one of the French purchasing agents dying in a prototype crash while illegally onboard). It was in fact the French interest which caused the US and British to take another look.

Maybe. It is a plane about the size of a DB-7 and with about 80% of the wing of a Martin 167 and using engines not much better than single speed R-1830s.

Au contraire mon frere. It's nowhere near the size of a DB-7 or a Martin 167. I have scale models of all three I can show you if you like. It's about 70% the size of a DB-7, maybe 80% the size of the 167.

Maybe with a little pulling/pushing you can get Six 100kg bombs in the thing.

I think it could carry a good bit more but who knows. It's clearly a good high-speed recon plane for the era, and could have been useful in that role.

French had really screwed this one up. They guess the Germans army would have about the same AA capability as the French Army had, which was close to zero. They guessed wrong and French air units of many types suffered large losses trying to support the French army.

They had some bad missions with high-losses in low-level attacks against well defended German positions, but so did just about any other Allied aircraft which tried that. I don't think it really means that much.

Which would you rather fly into action against the KB, a Fairey Battle or that little Breuget? Be honest We know which one has better food in the galley...

 

[Steamed_Banana]

They were investigating Wright R2600 engines for this thing.

They had ordered 200 with R2600s but the war ended that