Fast bombers alternatives for 1939-40 (2 Viewers)

[Shortround6]

The problem with the B-26 was that it was so wide, it was designed for ten (!!!) crew. The Martin 187 Baltimore, made by the same company but sold to the French (abortively) and British, was much thinner and therefore also faster (over 300 mph) with (I think?) the same engines.

Martin Baltimore used about the same engines as the B-25. R-2600 B series engines. It also carried about 1/2 the bomb inside the bomb bay.

 

[Steamed_Banana]

Martin Baltimore used about the same engines as the B-25. R-2600 B series engines. It also carried about 1/2 the bomb inside the bomb bay.

How much sortie loss ratio percentage points is another 2,000 lbs of bombs worth?

 

[Shortround6]

How much sortie loss ratio percentage points is another 2,000 lbs of bombs worth?

That may depend on how far you have to go or how often.

Most of the Aircraft designers were pretty smart and at a given point in time they would give similar answers to the same question/s (requirements).
But even 2-3 years in the late 30s and early 40s meant big changes in knowledge, engines, fuel and so on.
The Baltimore was sort of souped up, bigger fuselage Maryland. Which means even with a higher gross weight and a bigger fuselage, somethings have to go, like range.
I was wrong and only the last batches of the Baltimore got the 1700hp engines, the early ones got the 1600hp version much like the A-20 had. A Baltimore had an overload Gross weight close to the B-26 when at normal weight and the B-26s could add thousands of pounds to that.

Now the original ASAAC requirement for the B-25 and B-26 turned out to be fantasy stuff. 2000lb bomb load carried over 2000 miles (slowly) with a high speed dash. But one can see where the large crews came from. A 9-10 hour mission needed more men than a 4-5 hour mission. Navigators (especially over water) need more room to work their charts and use their instruments. The co-pilot could come in very handy at times and so on. But this was 1939 and early 1940 and just like bombing from 25-30,000 the practical problems hit hard and really long ranges were rarely used.

And if you do want to go long range, having bombers that can carry 2000lbs over the same distance as the smaller bomber can only carry 1000lbs may be important. The smaller bomber may be a bit faster but they need almost the same ground crew to take off the planes and the ground crew has to be feed and watered. The larger medium bomber needs more fuel but not twice as much so the logistics load per ton of bombs dropped is smaller. A small formation of 2000lb capacity bombers may be (or might not) be more accurate than a larger formation of 1000lb capacity bombers. A lot depends on if each plane (or small group) bombs independently or or uses the master bomber technique with planes that are hundreds if not thousands of feet away from the master bomber all dropping at the same time.
The B-26 offered a lot more options to the bomber commanders. Now we can question wither they used those options wisely at times but at least the airplane designer gave them options.
You usually cannot out run flak so using a smaller number of bombers to deliver the same tonnage of bombs was generally seen as a good thing. Yes fast bombers spend less time in the flak zone but this also depends on which theater. Over Germany (and France) bomber formations had to zig-zag across the map avoiding flak hot spots. In the far east there was very little flak outside the actual target zone. Mid east was lot closer to the Far East.

British were just happy they weren't flying Bleneims

 

[wuzak]

How much sortie loss ratio percentage points is another 2,000 lbs of bombs worth?

If it is half the bomb load then you need twice the missions to deliver the same amount of bombs.

And if you are doing twice the missions, then you woudl want a loss rate less than half, or better.

But the bombs themselves are important.

The B-26 could carry 2 x 2,000lb bombs, which tend to be more effective than smaller bombs for many targets. Presumably could carry 4 x 1,000lb?

What could the Baltimore carry?

Could it carry a single 2,000lb bomb, or 2 x 1,000lb bombs?

Or was it stuck with 4 x 500lb maximum? Like the Mosquito used for much of the war. Then again, the Mosquito could carry those bombs 50-100mph faster.

 

[wuzak]

There was, at one point, a proposed version of the B-26 fitted with Allison V-3420s.

Early V-3420s would have given a sizeable power boost, going from 1,800hp (in early B-26s) or 2,000hp to 2,300hp.

Later V-3420s would have produced 2,600hp.

The B-26 also missed out on more advanced and powerful versions of the R-2800, which would have helped performance.

 

[yulzari]

Mention of the Martin Maryland made me take a quick comparison between a 1050bhp Maryland and 1,600 Beaufighter rather than to a period medium bomber. It reminded me of the virtues of the Maryland and the still puzzling change to the Baltimore which seems to do no more but does it with more power. Still a 2,000lb bombload. The Beaufighter doing little more than the Maryland also on more power

What might a Maryland have done with 1,600bhp engines? Could it also replace the navigators position with nose guns and free a little more wing space for fuel in the existing wing machine gun bays?

Essentially I am wondering if the fast bomber we seek is more a heavy fighter bomber than a speedy bomb truck. When victims are sent out in Blenheims with half the power and half the bomb load in 1943 what if they were up graded Marylands with twice the power and twice the bomb load? Maybe Martin sending motorless airframes to the UK to be fitted with Hercules and nose cannons if larger US engines were not available to Martin. World a bulged bomb bay allow larger bombs than the usual 4x500lb bombs?

The OTL Maryland has the wing area of a Beaufighter, at least the bomb load of the same yet the loaded weigh of the Maryland is about the same as the empty weight of the Baltimore or Beaufighter. The Maryland has a shorter range than the Beaufighter but more than the later Baltimore. Whilst not being an especially thin wing the Maryland wing is significantly thinner than the thick Beaufighter wing which will allow the extra power of a 2x1,600bhp Maryland to gain more speed from the power. Not to mention the standard Maryland had an impressive rate of climb and far lower wimg loading that the Baltimore If there is a fly in the upgraded Maryland ointment it may be where do you put the navigator/bomb aimer in a solid nosed Maryland?

As to air to air fighting quality, I do note that the Beaufighter gained seventy pilots ace status and even the Maryland in standard form gained one.

 

[Steamed_Banana]

That may depend on how far you have to go or how often.

Most of the Aircraft designers were pretty smart and at a given point in time they would give similar answers to the same question/s (requirements).
But even 2-3 years in the late 30s and early 40s meant big changes in knowledge, engines, fuel and so on.
The Baltimore was sort of souped up, bigger fuselage Maryland. Which means even with a higher gross weight and a bigger fuselage, somethings have to go, like range.
I was wrong and only the last batches of the Baltimore got the 1700hp engines, the early ones got the 1600hp version much like the A-20 had. A Baltimore had an overload Gross weight close to the B-26 when at normal weight and the B-26s could add thousands of pounds to that.

Now the original ASAAC requirement for the B-25 and B-26 turned out to be fantasy stuff. 2000lb bomb load carried over 2000 miles (slowly) with a high speed dash. But one can see where the large crews came from. A 9-10 hour mission needed more men than a 4-5 hour mission. Navigators (especially over water) need more room to work their charts and use their instruments. The co-pilot could come in very handy at times and so on. But this was 1939 and early 1940 and just like bombing from 25-30,000 the practical problems hit hard and really long ranges were rarely used.

And if you do want to go long range, having bombers that can carry 2000lbs over the same distance as the smaller bomber can only carry 1000lbs may be important. The smaller bomber may be a bit faster but they need almost the same ground crew to take off the planes and the ground crew has to be feed and watered. The larger medium bomber needs more fuel but not twice as much so the logistics load per ton of bombs dropped is smaller. A small formation of 2000lb capacity bombers may be (or might not) be more accurate than a larger formation of 1000lb capacity bombers. A lot depends on if each plane (or small group) bombs independently or or uses the master bomber technique with planes that are hundreds if not thousands of feet away from the master bomber all dropping at the same time.
The B-26 offered a lot more options to the bomber commanders. Now we can question wither they used those options wisely at times but at least the airplane designer gave them options.
You usually cannot out run flak so using a smaller number of bombers to deliver the same tonnage of bombs was generally seen as a good thing. Yes fast bombers spend less time in the flak zone but this also depends on which theater. Over Germany (and France) bomber formations had to zig-zag across the map avoiding flak hot spots. In the far east there was very little flak outside the actual target zone. Mid east was lot closer to the Far East.

British were just happy they weren't flying Bleneims

Totally disagree.

Lets compare Baltimore and Boston to Marauder

A-20A - Crew 3, max speed 350 mph, cruise speed 250-295 mph, range 2,000 (ferry), 675 miles with 1,200 lb bomb load, 525 miles with 2,400 lb bomb load. Two fixed .30 guns in nose, two or three flexible guns for defense. Light armor, partial / simple SS tanks. Fuel 205 US gallons
Boston III - Crew 3, max speed 337 mph at 12,500 ft, 311 mph at sea level, cruise speed 240-273 mph, range 1,240 miles, 745 miles with 1,000 lb bombs, 525 miles with 2,000 lbs bombs. Initial climb rate 2,420 fpm, 4 fixed .303, 2 flexible .303, max bomb load 2,000 lbs (four 500 lb bombs) normal 1,000 lbs. Fuel 394 US gallons
A-20C - Crew 3, max speed 342 mph at 13,000 ft, 314 mph at sea level, cruise speed 240-280 mph, Range 2,300 miles (ferry), 745 miles with 1,000lb bomb load, 400 US gallons fuel (could carry 300 additional gallons with external tanks)
A-20G - Crew 3, max speed 317 mph at 10,000 ft, cruise speed 230-270 mph, max bomb load 4,000 lbs, range 1,025 miles with 2,000 lb bombs, fixed guns 6 x .50, defensive 3 x .50 including power turret, armor, SS tanks, fuel capacity 725 gallons, capacity for an additional 374 gallon drop tank.

311-314 mph at Sea Level is pretty telling. Can a Bf 109E7 make that? Can an F2 or F4? I'm pretty sure neither a Zero nor a Ki-43 can.

Baltimore III - Crew 3, max speed 305 mph, cruise speed 225 mph, four fixed .303 guns in wings, four .303 guns in Boulton paul turret, range 950 miles with 1,000 lbs bombs
Baltimore IV - Crew 3, max speed 305 mph at 11,500 ft, cruise speed 220 mph, four fixed .303 guns in wings, two .50 in Martin power turret, bomb load 2,000 lbs, range 2,800 miles ferry, 1082 miles with 1,000 lb bombs, 617 US gallons fuel carried.

B-26C Marauder - Crew 6-8 (?), max speed 282 mph at 10,000 ft, cruise speed 214 mph, "combat" range 1,150 miles, twelve .50 machine guns, max bomb load 3,000 lbs.
B-26C Marauder - Crew 6-8 (?), max speed 283 mph at 5,000 ft, cruise speed 216 mph, range 1,150 miles with 3,000 lbs of bombs, eleven .50 machine guns, max bomb load 4,000 lbs, fuel load 1,153 US gals

These Marauders could carry more bombs if the aft bomb bay was used, but this usually had fuel tanks.

B-25C/D Mitchell - Crew 6, max speed 284 mph at 15,00 ft, cruise speed 230 mph, range 1,300 miles with 3,000 lbs bombs, six to eight 0.50 machine guns
B-25J Mitchell - Crew 6, max speed 272 mph at 13,000 ft, cruise speed 220 mph, range 1,350 miles with 3,000 lbs bombs, ten 0.50 machine guns, 974 - 1,194 US gallons of fuel.

So here are some questions:

What is the survival rate per sortie (escorted and unescorted)
What is the mission versatility (level bombing, low alt bombing, strafing, torpedoes, night fighter, intruder)
What is the time to target (and time on target, and time back to base)
How much fuel is used in each mission? (this one has at least a partial answer - Looks like 204 gals for the A-20A, 394 for the Boston III, 725 gallons for the A-20G, 1,153 for the B-26, and 974 - 1,194 for the B-25 Mitchell)
How many crew are lost / at risk if one is shot down (again, here we have an answer - 3 for the Boston and the Baltimore, 6-8 for the Marauder and Mitchell)
What is the max range and bomb load (675 with 1,200 lbs for A-20A, 745 with 1,000 lbs A-20C, 1,025 with 2,000 lbs A-20G, 1082 miles with 1,000 lbs Baltimore, 1,150 miles with 3,000 lbs Marauder, 1,350 miles with 3,000 lbs Mitchell)

So I guess, depending on the environment, you have a tradeoff.

A-20A is an economical short range (675 miles) bomber with a very fast cruise speed and low fuel use. You can fly four missions in this for the same fuel as one in the B-26. But the B-26 carries almost three times as many bombs. But the A-20A is hard to catch...
A-20C is closer, range still pretty short (745 miles) still with a small bomb load (1,000 lbs). Cruise speed still fast. Fuel is now enough for three missions vs one in the A-26, but bomb load is still 1/3
A-20G is now medium range (1,025 miles) with a bit more bombs (2,000 lbs). Cruise speed still fast. Fuel is 725 gallons, now 60% of that of the B-26. But how good of a competitor is it?
Baltimore is medium range (1,000 miles) but with only 1,000 lbs bombs. It could carry 2,000 and did, but I couldn't figure out how much range that left it with. Cruise speed is better than the B-26 but only a little. But fuel is still close to half.

More bomb weight is good. But is it everything?

The B-26 ultimately had, allegedly, the lowest mission loss rate in the war. But that is only part of the story. Initially it seemed to be a versatile aircraft, being used as a torpedo bomber in the Pacific and by the British (I think South Africans?) in the Med. It was fitted with guns for strafing and could attack at low level. But fairly or unfairly, it was moved out of the Pacific in favor of the B-25 and the A-20. In North Africa, the B-26 was relegated to the (admittedly important) role of maritime commerce raiding. It was considered too vulnerable to attack Axis and in particular German bases and military ground targets. It also used a lot of fuel which mattered in places like the South Pacific and North Africa, where the supply chains were long. The Marauder ended up being used by the Americans in Theater but strictly as a medium altitude level bomber with a heavy fighter escort- usually P-40Fs from one of the US fighter groups, as the Spitfires didn't have the range to stay with them.

From reading the combat history of the B-26 in both the South Pacific and Aleutian campaigns, I think it actually seemed to have some merits. There were some accidents but it brought the to me interesting capacity to carry torpedoes. But US torpedoes didn't work very well, and the plane did have some accidents. If they had asked me, I'd have said keep it and figure out a way to use British torpedoes.

But I suspect the reason they transferred them out of the Theater (or de-emphasized them, shall we say) might have been the fuel use. Early on, those dinky A-20As were more economical on what was a limited logistics capacity. Later when there seemed to be plenty of fuel, they had settled into using the B-25 and the heavy bombers... and still the later versions of the A-20 'light' bomber. A concept the US planners were never really in favor of, but one which seemed to work really well in actual practice. For them, for the British, for the Russians, the Aussies, everyone who used them.

 

[Shortround6]

I have issues with some of the specifications you list.
A-20A's either had 500 gallons in four unprotected tanks or 400 gallons in protected tanks.
A-20A's do have few differences to DB-7A & Bs which also used R-2600 engines.
The early A-20s were not magic. At 278mph they sucked 199 gallons of fuel an hour. If you putzed around at 183mph you could get the fuel burn down to 72-73 gph.
If you had to run fast you could burn almost 300gph or 5 gallons per minute.
the 374 gal external tank was pretty much ferry use only. It also did not show up until the A-20G-20

It may have been jettison-able in flight. Needs more research. The 540 gal combination was the normal wing tanks and a 140 gallon tank in the rear of the upper bomb bay.
The 725 gal combination had three tanks in the upper bomb bay. It may have possible to take one out but since there were not useable bomb racks/chutes there any more it doesn't change the bomb load.
The A-20 did use less fuel but not enough less to reach the results you think. At certain combinations of speed the B-26 may be burning twice the fuel but carrying 50% more bombs.
The 140 bomb bay/fuselage tank did not show up until the A-20G and the 725 gal capacity showed up on the A-20G-20 model. These tanks were self sealing, the external belly tank was not.
The A-20Gs started to leave the factory/s in March of 1943. Several months before combat?
There were never any underwing fuel tanks. There were ferry tanks that could fit in the lower bomb bay where the bombs were carried. Up to 4 metal, not self sealing tanks.
Any bombload above 2000lbs required carrying the extra bombs on underwing racks outboard of the engines and a reduction in the fuel load.
Just adding the extra fuel in the upper bomb bay was just under 2000lbs without the weigh of the tanks.

 

[tomo pauk]

The DB-7 up-engined with the V-1710s would've been pretty fast for the time.
It's bigger sibling, the A-20, would've been even faster with the turboed V-1710s. Yes, Americans were not keen for having turboes in the 'attack' category aircraft, but still.
The turboed R-1830s would've also been an interesting powerplant for this lineage.

 

[Steamed_Banana]

I have issues with some of the specifications you list.
A-20A's either had 500 gallons in four unprotected tanks or 400 gallons in protected tanks.
A-20A's do have few differences to DB-7A & Bs which also used R-2600 engines.

I believe the A-20A does have R-2600, though I may have misunderstood you here

The early A-20s were not magic. At 278mph they sucked 199 gallons of fuel an hour. If you putzed around at 183mph you could get the fuel burn down to 72-73 gph.

In certain Theaters, they simply couldn't putz around at 183 mph at all (North Africa, notably, where German fighters could show up almost anywhere, and A-20s were usually on close-to-the-front-line fields). In the South Pacific, they also faced potential fighter attack at any point, but would sometimes putz around a bit to form up until they crossed to the Japanese side of the mountains. Then it was up to fast cruise speed. And I do think that the A-20 had a much lower drag than either the B-26 or B-25.

A-20 wingspan 61' 3.5"
Maryland wingspan 61' 4"
Baltimore wingspan 61' 4" (later marks of these incidentally had four crew rather than 3, I was wrong on that)
Early B-26 wingspan 65' - fuselage about twice as thick as an A-20 or Baltimore
Later (most) B-26 wingspan 71' - fuselage about twice as thick as an A-20 or Baltimore
B-25 wingspan 67' 7" - fuselage about twice as thick as an A-20 or Baltimore

Dash speed was used during attack and (especially) egress immediately after releasing bombs. Baltimores apparently had a particularly high available mach number (they were used in late and postwar research on compressibility and high speeds) and could get going very fast, well over 400 mph in a high speed dive, which they did to survive Axis fighters while egressing from bomb missions. Shores mentions this a couple of times in MAW. They often flew in with heavy escort, but flew out on their own as their escort got engaged with the Axis fighters, but usually keeping their formations (the fighters often also got separated and flew home alone too - often individually- sometimes getting in trouble on the way).

In the South Pacific, A-20s were able to operate independently except in the most dangerous raids like right over Japanese fighter bases, and even then sometimes did so 'solo'. With a 311 - 314 mph top speed at Sea Level I can understand how this worked. Often they would just dash to the nearest cloud, sometimes they had to run at near full speed near sea-level half way back to base being chased by Ki-43s or A6Ms, but they seem to have been rarely caught.

In the early difficult days in the Western Desert as the British called it, Axis fighters and (especially German) AAA was extremely lethal. Allied bomber life span was pretty low. The Blenheims got wrecked, Wellingtons were quickly relegated to commerce raiding, as was the (I think one squadron of) Marauders, though both did well in this important role, it's worth noting. Initial bomber units were mainly the Boston III's and the Marylands, and almost always flying with fighter escorts, mainly Tomahawks and then Kittyhawks, sometimes Hurricanes too for shorter trips. Both carried light loads but had a relatively good survival rate. I don't know what it was exactly but you are talking one or two lost on a bad raid, vs five or six of the Blenheims. Obviously more sustainable. The only limitation of the Bostons was they were short ranged, while the Marylands could go further. A bit later the British got the Baltimores in which largely replaced the Marylands for the longer ranged strikes and equipped several units. When they tried to use the Baltimores unescorted, they too got wiped out, incidentally, but with escorts I believe they had the lowest loss rate in Theater.

When the Americans showed up in some numbers around the third quarter of 1942 they brought B-24s, a few B-17s, B-25s, and B-26s... and a bunch more A-20s. Quite early mark ones with limited fuel protection and so on, but they proved very useful during the clusterf***k of Kasserine pass for example, where they sometimes flew raids unescorted. Once fighter capacity ramped up, the B-24s were usually flying with P-38 escort at around 20 - 25,000 ft, but sometimes lower, the B-25s were doing a lot of the heavy strikes against Axis airfields, often with B-24s as well, the B-26s were usually flying a bit further afield and hitting ports, landing depots, and Italian air bases like at Pantelleria and later Sardinia and Corsica.

The heavy bomb load of the B-24s was ultimately telling in the destruction of Axis airfields in early 1943, by which time the Allies had tons of fighters including Spitfire Mk IXs and some mk VIII (I think). But they (B-24s) took fairly heavy losses. The B-25s did fairly well but were in trouble if their escorts got away from them.

If you had to run fast you could burn almost 300gph or 5 gallons per minute.
the 374 gal external tank was pretty much ferry use only. It also did not show up until the A-20G-20
View attachment 852523
It may have been jettison-able in flight. Needs more research. The 540 gal combination was the normal wing tanks and a 140 gallon tank in the rear of the upper bomb bay.
The 725 gal combination had three tanks in the upper bomb bay. It may have possible to take one out but since there were not useable bomb racks/chutes there any more it doesn't change the bomb load.
The A-20 did use less fuel but not enough less to reach the results you think. At certain combinations of speed the B-26 may be burning twice the fuel but carrying 50% more bombs.
The 140 bomb bay/fuselage tank did not show up until the A-20G and the 725 gal capacity showed up on the A-20G-20 model. These tanks were self sealing, the external belly tank was not.
The A-20Gs started to leave the factory/s in March of 1943. Several months before combat?
There were never any underwing fuel tanks. There were ferry tanks that could fit in the lower bomb bay where the bombs were carried. Up to 4 metal, not self sealing tanks.
Any bombload above 2000lbs required carrying the extra bombs on underwing racks outboard of the engines and a reduction in the fuel load.
Just adding the extra fuel in the upper bomb bay was just under 2000lbs without the weigh of the tanks.

It's hard to assess the relative merits, but it seems like both in North Africa and in the South Pacific, the A-20s / DB-7s were more useful than the B-26. However in the Aleutians where the distances were longer I'd give the nod to the B-26. I'd have to go back and look carefully at the B-25 missions, though overall I think they did fairly well in terms of sortie / loss, and this is true in China and Burma / India as well.

However, if your supply chain is a bit strained, as it certainly was in China, in the South Pacific, and at least intermittently in North Africa (probably until after Torch), even if we are saying it's 400 or 700 gallons of fuel per sortie vs 1200 gallons, mission after mission, that adds up. If you also have even a little bit higher survival ratio with the lighter plane, that also makes a difference over time, day after day. These planes were flying strikes sometimes 15-20 days per month. And if your lighter plane turns out to be a bit more flexible in terms of the types of missions it flies, that also matters. I'd also note that billeting, feeding and training 3 or 4 crew vs 6-8 could also make a difference over time.

Range makes a difference and the early Bostons were clearly out-matched by the B-26 or B-25 in that regard, though the Baltimore is much closer and seems to have similarly high survival ratios and also used a lot less fuel.

 

[Steamed_Banana]

I would also add that while the B-24s did seem to really wreck some Axis airfields, they usually seemed to miss targets like ports, shipping, rail and tactical military targets, whereas the smaller bombers (Boston, Baltimore, and Mitchell) were more effective against these. Fighter bombers probably best of all.

 

[Jugman]

The V-1710 offers weight savings and drag reduction compared to the R-2600.

The V-1710 was paired with the B-series turbo in the P-38, as was the R-1820 in the B-17.

Could an R-2600 use the B-series turbo, or would it need an upgrade to the larger C-series (as was paired with the R-2800 in the P-47)?

The V-1710-89/91 should add around 1,400 to 2,00lbs. Even for single-engine fighters the drag advantage of liquid-cooled engines is not that significant. For large multi-engine aircraft even less so.

A type B could be used but critical altitude would be reduced. Above ~25,000ft power would start to drop off and by around 30,000ft be about the same. A type D or C would be a better fit.
The designed rated altitudes for some type B models
B-2 110 lb/min @ 25,000ft @ 21,300RPM Used in early B-17, B-24, and some early P-38s. Replaced by the B-13 in the P-38
B-22 120 lb/min @ 28,000ft @ 24,000RPM Replaced the B-2 in later B-17s and B-24s
B-33 130 lb/min @ 27,500ft @ 24,000RPM Replaced the B-13 in the P-38H-5 and later.

I don't have figures for the type C or D.
The CH-5 was rated for 265 lb/min @ 20,000RPM @ 35,000ft. The C-23 and CH-5 had an overspeed rating (aka Military rating) of 22,000RPM for 15 minutes. I don't know if and of the B models did.

My weight estimates assumed a type C for the upper limit. Thinking on it a little more, I think my weights are a little light. Four R-2600Bs should weight ~3.200-4,300lbs.

 

[Dimlee]

It's a good discussion; however, I don't think that most bombers mentioned in the latest posts are relevant to this thread. B-26 is not ready for 1939-1940. Baltimore, Maryland and B-25, in my opinion, could not be considered as "fast bombers" at all in 1940, being much slower than the fighters already in mass production.
Up-engined DB-7 suggested by Tomo is the most interesting option.

 

[bf109xxl]

Up-engined DB-7 suggested by Tomo is the most interesting option.

The most interesting option would have been to provide Merlin engines to Tupolev in 1940. I think that even with their takeoff power the "58" would have outperformed all fighters in terms of speed at altitudes of 5-6 km. The only question is how much bomb load it could carry. But it should definitely exceed 1,000 kg.

 

[wuzak]

The most interesting option would have been to provide Merlin engines to Tupolev in 1940. I think that even with their takeoff power the "58" would have outperformed all fighters in terms of speed at altitudes of 5-6 km. The only question is how much bomb load it could carry. But it should definitely exceed 1,000 kg.

The USSR was not an ally in 1939/1940.

 

[Steamed_Banana]

What if you put a bomb bay in a Ki-46

 

[bf109xxl]

The USSR was not an ally in 1939/1940.

Of course. This is a completely unrealistic alternative - rather an attempt to understand what the ideal high-speed bomber in the late 1940 might have been like. Tupolev developed an excellent airframe and generally designed the aircraft "around the bomb," but at that time, the USSR was experiencing a serious crisis with engines.

 

[GrauGeist]

What if you put a bomb bay in a Ki-46

The KI-46-III/B was designed for ground attack (cannon armed) but it's fuselage was such, that an internal bomb load modification would not work.

 

[Geoffrey Sinclair]

Sort of wondering what the missions are going to be, it is coming across as a type that would enable a 1944 replacement of Bomber Command Mosquito with A-20 and B-26, or the other way, as the design would do every mission. For long range beyond fighter cover supercharging becomes important, for within fighter cover then performance at 10 to 15,000 feet is more important, though this assumes the targets are not the big ones that will have lots of flak cover. A big internal bomb bay is what you need to carry a variety of ordnance but that makes for a bigger therefore more drag airframe. Similar for longer range. The speed bomber would enable escorts to be at their fast cruise (P-51 escorting Mosquito ideas) without having to weave very much. Next is what bomber top speed, 100% of fighter? 90%? In "mass production" terms in 1938 fighters were around the 320 to 330 mph mark, in 1939 it became 350 to 360 mph but also better altitude performance, enabling a better height for speed trade off. The fighter top speed stayed the same to the end of 1940, was around 370 to 380 mph with better again altitude performance in mid 1941, to pushing 400 mph by the end of the year. So any good enough speed bomber in 1940 is going to need a rapid update or be phased out or take a reputational hit during 1941.

No one uses all the fuel loaded onto a plane unless something has gone wrong. RAF Aircraft performance charts note, In these tables the ranges of all aircraft except fighter types are calculated after deducting fuel used in 50 minutes at maximum economic power a) 20 minutes at maximum economic cruising power, to allow for warming of engines, taxying, taking off and the climb to operational height b) 30 minutes at maximum economic cruising power, to allow for time over target, navigational errors and other emergencies. The above makes no allowance for - (i) The effect of wind, (ii), The effect of formation flying, (iii) The use of full throttle over enemy territory. The effect of these factors must be allowed for when flights are being planned.

Blenheim IV, top speed 266 mph at 11,800 feet, range with 1,000 pounds of bombs 1,160 miles at 225 mph at 15,000 feet (2.9 ampg), 1,457 miles at 170 mph at 15,000 feet (3.6 ampg)

Boston II, top speed 311 mph at 15,000 feet, range with 1,500 pounds of bombs 690 miles at 243 mph at 15,000 feet (3.3 ampg), 840 miles at 165-175 mph at 15,000 feet (4 ampg)

Maryland 167F3, top speed 292 mph at 13,000 feet, range with 2,000 pounds of bombs 1,250 miles at 242 mph at 15,000 feet (3.35 ampg), 1,450 miles at 160-170 mph at 15,000 feet (3.9 ampg).

The Halifax I with 9,250 pounds of bombs on board 1.03 ampg at 210 mph, 1.27 ampg at 190 mph. Is obviously the most efficient in terms of fuel and crew per ton of bombs despatched.

A-20 and B-25 in 9th Air Force, A-20 average bomb load 2,357 pounds, (bombs dropped on target divided by effective sorties), B-26 average bomb load 3,621 pounds, mission times A-20 3.31 hours (Operational hours divided by credit sorties), B-26 3.44 hours, given the two types were cruising at similar speeds unless one set of bases was further from the front than the other they were over enemy territory for about the same time. Losses on combat operations, rate is per 1,000 NOT 100 sorties.

A/C Type	Category	A-20	B-26
Flak	Lost	56​	204​
Flak	CAT E	36​	116​
Flak	Total	92​	320​
Flak	Rate	4.4​	4.1​
Enemy Aircraft	Lost	0​	47​
Enemy Aircraft	CAT E	0​	13​
Enemy Aircraft	Total	0​	60​
Enemy Aircraft	Rate	0.0​	0.8​
Other	Lost	34​	69​
Other	CAT E	43​	124​
Other	Total	77​	193​
Other	Rate	3.8​	2.5​
Totals	Lost	90​	320​
Totals	CAT E	79​	253​
Totals	Total	169​	573​
Totals	Rate	8.2​	7.4​

Another 2,774 A-20 and 9,425 B-26 recorded damage on operations. A-20 22,999 sorties airborne, 20,522 credit, 15,855 effective, B-26 85,706 sorties airborne, 77,785 credit, 62,686 effective. A-20 68.9% airborne sorties effective, B-26 73.1%.

The bombs dropped,

Bomb	Type	Class	B-26	B-26	A-20	A-20
Weight	Type	Class	On Target	Jettison/lost	On Target	Jettison/lost
Pounds	Type	Class	Number	Number	Number	Number
2000​	GP	HE	21,874​	875​
1600​	GP	HE	98​
1100​	GP	HE	359​	34​
1100​	Demo	HE	72​
1000​	GP	HE	61,160​	1,338​
1000​	Comp B	HE	40​	4​
1000​	SAP	HE	1,145​	9​
600​	GP	HE	1,341​	33​
500​	GP	HE	106,213​	3,331​	72,767​	1,978​
500​	Comp B	HE	3,872​	32​
500​	SAP	HE	0​	0​	528​	10​
300​	GP	HE	4,523​	184​	17​
250​	GP	HE	148,778​	3,954​	724​	52​
250​	Demo	HE	422​
150​	GP	HE	9,084​	142​	24​
100​	GP	HE	94,668​	3,793​
100​	Demo	HE	686​
100​	D/A	HE	56​	5​
500​		Frag	24​	0​	520​
500​	CL	Frag	0​	0​	395​	4​
260​		Frag	33,032​	980​	61​	4​
120​		Frag	3,629​	263​
6 x 20		Frag	1,900​	86​
100​		Frag	3,417​	203​
500​	IC	Incen	4,844​	68​
500​	IB	Incen	4,959​	109​	118​	4​
250​	TI	Incen	179​
100​	WP	Incen	24​
100​	IB	Incen	6,568​	182​
Totals	All	All	512,967​	15,625​	75,154​	2,052​

According to the War Production Board Report, July 1940 to August 1945 inclusive the US made 45,030x4000 pound, 213,000x2000 pound, 1,745,000x1000 pound, 7,397,000x500 pound, 355,000x300 pound, 2,455,000x250 pound, 450,000 150 pound TI, 4,132,000x100 pound HE/Demolition bombs. The 300 pound bomb program ended in September 1942.

DB-7 October 1939 to December 1940, DB-7A November 1940 to May 1941 (Santa Monica), August 1941 to January 1942 (Boeing), DB-7C May and June 1942, A-20A December 1940 to August 1941, A-20B and C from December 1941. A-20G starting February 1943.

B-26 starting February 1941, to B-26A in October, to B-26B in March 1942, to B-26F in August 1943, Omaha started B-26C production in AUgust 1942.

A-22/Maryland, first French order from September 1939, to second order in December, third order April to July 1940, British order from December 1940.

The US started exporting DB-7 and Maryland in 1939, all 100 from the first French DB-7 order to France, second order split 32 France 138 Britain, Britain took over the French DB-7A and 7B orders, which were ultimately split between Britain, Russia, US and Netherlands, while all but 1 DB-7C ordered by the Netherlands went to Russia. All 215 Maryland from the first two orders were exported for France, third order was 68 France, 62 Britain

The US kept all the A-20A for itself.

In the early difficult days in the Western Desert as the British called it, Axis fighters and (especially German) AAA was extremely lethal. Allied bomber life span was pretty low. The Blenheims got wrecked, Wellingtons were quickly relegated to commerce raiding, as was the (I think one squadron of) Marauders, though both did well in this important role, it's worth noting. Initial bomber units were mainly the Boston III's and the Marylands, and almost always flying with fighter escorts, mainly Tomahawks and then Kittyhawks, sometimes Hurricanes too for shorter trips. Both carried light loads but had a relatively good survival rate. I don't know what it was exactly but you are talking one or two lost on a bad raid, vs five or six of the Blenheims.

The Desert War started in June 1940, but presumably "early difficult" dates to some time in 1941 but could be well into 1942 given the aircraft types mentioned. Wellingtons did anti shipping operations and remained the primary strategic bomber in Egypt, supplemented by Halifax and then the USAAF B-24 units started to take over.

When it comes to bomber losses there is Bomber Losses in the Middle East and Mediterranean Volume 1 1939 to 1942, by David Gunby and Pelham Temple. Meant to include aircraft lost on ferry flights to the theatre as well as all causes losses, pages 17 to 36 the 1940 war losses, pages 37 to 114 for 1941, pages 116 to 211 for 1942. The most common way for a formation to take multiple losses was an anti shipping strike.

A quick leaf through for multiple losses on the one raid, 1941, Western Desert unless mentioned otherwise, 4 or more
13 April, 6 out of 6 Blenheim, Greece, fighters
23 May, 5 out of unknown number Blenheim, fighters
27 May, 6 out of unknown number, Blenheim, Crete, none to enemy action
9 July, 4 out of 7 Blenheim, causes not given
12 September, 4 out of unknown number Blenheim anti shipping, flak
1/2 November, 5 out of unknown number Wellington, fog.
20 November, 5 out of 9 Maryland, army co-operation, fighters
22 November, 4 out of 6 Blenheim, fighters
10 December, 5 out of 6 Boston, fighters
12 December, 5 out of unknown number Maryland, fighters
20 December, 4 out of 12 Blenheim, fighters

In 1942,
4 February, 4 out of unknown number Blenheim, low cloud
16/17 August 4 out of unknown number Wellington, none enemy action
13/14 September 4 out of unknown number Wellington, probably none enemy action
4 December 9 out of unknown number Blenheim (NW Africa), fighters

Interesting that from pre Gazala battle daylight bomber losses to enemy action drop away.

The heavy bomb load of the B-24s was ultimately telling in the destruction of Axis airfields in early 1943, by which time the Allies had tons of fighters including Spitfire Mk IXs and some mk VIII (I think). But they (B-24s) took fairly heavy losses. The B-25s did fairly well but were in trouble if their escorts got away from them.

To end May 1943, 9th Air Force, B-24 3,118 sorties airborne 30 lost, no more than 5 in a month, B-25 1,801 sorties, 20 losses, P-40 10,820 sorties, 70 losses. Over at the 12th Air Force mostly B-17 units, November 1942 to end May 1943, 3,497 sorties attacking (NOT airborne), 139 losses, monthly loss rates as a percentage of attacking 2.4, 6.9, 6.8, 4.6, 5.1, 3.9, 2.5, overall 4.0. No data for 12th AF light and medium bombers.

 

[bf109xxl]

The Soviets changed the bomb racks on the A-20 and increased the bomb load to 2,000 kg when taking off from a concrete runway. In general, Soviet aviation considered the nominal bomb load of the A-20 to be underestimated—the aircraft was capable of carrying much more.