B25 or B26, which was the better bomber?

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On the other hand, the B-24 has better payload-range characteristics than the B-17, so it had uses, such as maritime patrol, that the B-17 could not do as well.

The B-26 had worse payload-range than the B-25, so there would seem very little advantage to the B-26.
 
A text book from 1942/43 claimed that an estimated 10 cubic feet of space was needed for an intercooler installation for a 1000 HP engine. Due to economy of scale you don't need 20 cubic feet for a 2000 HP engine but you do need a lot more than ten. This makes it rather difficult to add 2nd stages and intercooler to existing designs.
Please look at the B-24 for an extreme example. Originally designed and built without the turbo with a round cowling, when the turbo was added the cowling was changed to the oval shape with large scoops/intakes on both sides. One side is the combined intake air and oil cooler. The other side is entirely cooling air for the air cooler.
Adding 2 stage supercharger to an airplane will improve it's performance above 15,000 ft or so but hurt it under that height, unless your fuel/engine will allow for lots over boost.
Most radials were severe duty engines for fuel and did not tolerate over boost well without water injection.
 
The B-26 had better internal payload. The B-25 could only surpass the B-26 payload by carrying ordnance externally.
The B-25 did have better range once its internal tankage was upped to 975 US gal. R-2600s having far better fuel economy than R-2800s.
 
I read recently that in 1943 the USAAF made the decision to use the B-25 as its primary multi-engined trainer, replacing the AT-9, AT-11, AT-21, etc. It was considered to be so easy to fly and so reliable that it made a better trainer than did the trainers, and of course it was good for other things, too, and often served as a hack both during and after the war. The B-25 continued to be a trainer after the war, all the way until the late 1950's. Gen Doolittle had a B-25 as his personal transport until well after the war, one modified to use the much quieter collector ring exhausts of the early models.

A book by a B-26 navigator in the ETO revealed that they avoided losses by following the recommendations of the RAF and making frequent course changes when flying over occupied territory, every 3 minutes or so, preventing the Germans from setting up an AAA barrage. The only units I know of that used a B-26 as a hack were those that transitioned to A-26's and kept one of their old B-26's since it had more room for cargo and people.
 
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Greg Boeser said:
The B-26 had better internal payload. The B-25 could only surpass the B-26 payload by carrying ordnance externally.
The B-25 did have better range once its internal tankage was upped to 975 US gal. R-2600s having far better fuel economy than R-2800s.
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R-2600-13, as found on B-25s, consumed between 90 and 100 USG/hr at 2100 rpm, lean mixture*; 115 USG/hr at rich mixture. The R-2800 of 1850 HP, as found on early B-26, was consuming between 70 and 80 USG/hr at 2150 rpm**. The smallest consumption figure I was able to find is 38.5 USG for the R-2800 (at 1480 rpm), and 31 USG/hr for the R-2600-13, however that was listed under 'conditions to avoid' (that particular consumption was for 1600 rpm, 29.5 in Hg, at sea level).

* making 1005 or 905 HP, 1st or 2nd S/C gear
** making 900 or 975 HP, 1st gear only
 
OK, but only the B-26 MA (201 made), the B-26A (139 made) and the first 80 or so B-26Bs used the lower rated engine. All B-26Bs, Cs, Fs & Gs used in NA and Europe used the more powerful, and thirstier, R-2800-41(B-26B and B-2) and R-2800-43 (B-26B-3 and later).
By the way, I have copies of several B-26 manuals and each presents the fuel consumption numbers differently. So there is no single answer.
 

There might not be a single answer, but per each HP made, the R-2800 was not a fuel junky when compared with R-2600. Eg. the R-2800-43 was to use less than 100 USG per engine at 15000 ft, 2200 rp, full throttle, auto-lean.
The highest actual figure for the -43 I was able to find is 199 gph, per engine, for 2400 rpm operation (max continuous setting, max 1550 HP, low gear); the R-2600-13 making 1500 HP max at 2400 rpm, low gear, again max cont setting, 180 gph. Both engines using rich mixture here.
 
tomo pauk said:
Intercooler was present there from day one.
Click to expand...
I know most all twin-stage superchargers had them, but the B-26 with a single-stage twin-speed supercharger would not have one. If it were switched to twin-stage, it would then require them.

It was kind of a hypothetical...


Shortround6 said:
A text book from 1942/43 claimed that an estimated 10 cubic feet of space was needed for an intercooler installation for a 1000 HP engine. Due to economy of scale you don't need 20 cubic feet for a 2000 HP engine but you do need a lot more than ten.
Click to expand...
How much would you need, if you were to make a guesstimate?

Do you think one could have designed enough room to fit an intercooler inside the engine nacelle, the wing, or both?
Adding 2 stage supercharger to an airplane will improve it's performance above 15,000 ft or so but hurt it under that height
Click to expand...
The horsepower differences in the F4U seem to cover things at lower altitudes
 

The intercooler can be also fitted in front of the leading edge of the wing. I am of opinion that a) it would've been possible to outfit the B-26 with a 2-stage R-2800 and b) that it would've improved performance above 7-8 thousand feet.
But then, deficiences of the B-26s were not in it's powerplant, but rather in it's fuselage (designed around big crew compartments rather than around bomb bay and fuel tanks, and not a single galon of fuel) and wing (no advantage taken from latest airfoil knowledge, nothing new either in high lift devices installed, earswhile too small a wing).


The difference in power, 1-stage vs. 2-stage B series R-2800 at 8500 ft was 200 HP, mil power, and 150 HP for max continous power. So I don't think that we'd see any drop of performance in any altitude.
BTW - I don't think that 2-stage R-2800 needed even 15 cu ft of space (nor that a 2-stage V-1650 needed even 10 cu ft), and even so it is easy to find that space on a bomber, let alone outside of a bomber.
 
 
Maxwell Sparks, who flew on the Operation Jericho raid, said that changing from the Boston to the Mosquito was like going from Del Boy's 3 wheeler to a Ferrari (or something similar),

Not quite sure what Bostons or Venturas have to do with the topic of B-25 vs B-26.
 
tomo pauk said:
The intercooler can be also fitted in front of the leading edge of the wing.
Click to expand...
So it would be put on the wings leading edge or on the engine nacelle?
I am of opinion that a) it would've been possible to outfit the B-26 with a 2-stage R-2800
Click to expand...
I'm surprised that they didn't agree for a single-staged blower for the time being with the intent to go to a twin-speed blower when the time came. It might sound silly, but it would have left the aircraft with considerable growth potential.
it would've improved performance above 7-8 thousand feet
Click to expand...
How much would you suggest it would have increased the short and long-winged variants in terms of cruise and top-speed?
But then, deficiences of the B-26s were not in it's powerplant, but rather in it's fuselage (designed around big crew compartments rather than around bomb bay and fuel tanks
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Why did they build it that way?

As for the wings: Why was their aerodynamic knowledge fairly primitive? As for lift-devices, the aircraft had flaps...
The difference in power, 1-stage vs. 2-stage B series R-2800 at 8500 ft was 200 HP, mil power, and 150 HP for max continous power. So I don't think that we'd see any drop of performance in any altitude.
Click to expand...
Yeah, it would be faster all around. At higher altitudes, with the speed increasing, you have to consider exhaust thrust too.
I don't think that 2-stage R-2800 needed even 15 cu ft of space
Click to expand...
Fascinating...

MIflyer said:
An RAF crewman that transitioned from Venturas to B-25's said that when they got the Mitchells they had an airplane that was better in every respect.
Click to expand...
That does raise an interesting question: You think the war would have really worked out much different if the B-26 wasn't built at all, or built and then cancelled after it's low speed problems were brought up?
 

Actually It's the opposite, the B-17 had the superior range/payload characteristics. Early B-24s had ~15% greater useful load available for fuel and bombs and a somewhat greater installed fuel capacity over contemporary B-17s. This allowed the B-24 trade off more bombs for fuel and this gave the B-24 a longer range. When the overload tanks were add to the B-17, it's overall better aerodynamics gave it ~10% greater range.
 
The B-17 was originally designed for attacking ships at sea...this was because the USAAC envisioned that any enemy attacking the U.S. had to come by sea, so the B-17 was designed with that in mind.

So the B-17 had the ability both in range and warload to conduct maritime duties and the USN did in fact, have several B-17s serve in that role as the PB-1.

But the B-17 was in high demand from the USAAF, and the B-17 was only being manufactured at three plants: Boeing Seattle, Douglas Long Beach and Vega Burbank, where the B-24 was being manufactured in larger numbers from more plants: Consolidated San Diego, Consolidated Ft. Worth, Ford Willow Run, North American Dallas and Douglas Tulsa.
 

Fuselage also included an extra crew compartment for two men seating side a side, with passage between them, the compartment being located between pilots' compartment and bomb bay. All said, there was plenty of space for 8 (9?) crew members - 5 in front of bomb bay, 3 (4?) aft. Indeed, worthy of a 4-engined heavy bomber. All of the volume alloted for men added weight and drag, despite the neat shaping of fuselage.
Bomb bay might be big per US standards, but not per RAF standards.
As for the wing, we have several things that matter when bombers are in question:
- how good is the symetrical air foil when it is about weight lifting?
- wing loading
- lack of Fowler flaps (or the like) - people at Martin knew well that those work, yet none was incorporated
- relatively thin wings (15%?) do work


Perhaps I went too far claiming that people at Martin were not using the most recent knowledge of airfoils. However, there wing airfoil choosen does not show any low drag vs. lift properties that one will need for a fast and heavy A/C. Flaps were 'simple', not Fowler or a variant, that both increase wing area and camber of the wing.
I'd put the intercoolers in front of leading edge of the wing.
Don't mix supercharger stages with speeds - 2-speed S/C was always on R-2800s of the B-26s, 2-stage was never. The greatest improvement in speed would've came at high altitudes, say above 20000 ft, probably comfortably above 350 mph.
Why did the built it that way? We need to ask Magruder.
 
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