Missing AAF Bomber Generation

I have always wondered about the large gap in performance of US heavy bombers in WW2. There seems to be a generation missing.

1st generation
B-17G
Gross weight 55,000 lbs
Range 2000m w/6k bombs
Max speed 287mph at 25k ft
Cruise speed 182 mph
Ceiling 35,600 ft
Operational altitude 20-25k
Engines turbocharged R-1820 1200 hp at 25k
Original operations Apr 38

B-24H
GW 56,000 lbs
Range 2100m w/5k bombs
Max Speed 290 mph at 25k ft.
Cruise speed 215 mph
Ceiling 28,000 ft.
Operational altitude 20-25k
Engines turbocharged R-1830 1200 hp at 25k
Original operations 1941


3rd Generation
B-29A
GW 140,000 lbs
Range 4100 mi w/16k bombs
Max Speed 357 mph
Cruise speed 220 mph
Ceiling 33,600
Operation altitude 30k
Engines turbocharged R-3350 2200 hp at takeoff
Original operations May 44


It seems to me the AAF jumped a capability level when they went directly to the B-29. The AAF did plan on developing a generation two, the XB-33A, but cancelled it to concentrate on the B-29. Risk could have been low in that it used the proven R-2600 and could have been designed without pressurization. The plane could ingress and egress at 242 mph and 25-30k (using pressure breathing?) and have a dash speed of 250-300 mph over the target area. Bombing error would have increased but this would be alleviated by a 10,000 lb bomb load. High altitude would reduce Flak coverage and speed would reduce exposure. For an eight hundred mile ingress-egress, exposure would have been reduced about 36 minutes. At the higher altitude and faster speeds, interceptors would have less closure speed and poorer maneuverability than when opposing B-17/24s. Technical difficulties hampered the B-29 continuously such that the obsolete B-17 and B-24 labored on until the end of the war.


Proposed 2nd Generation
B-33A
GW 95,000 lbs
Range 2,000 mi w/10k bombs
Max speed 345 mph
Cruise speed 242 mph
Operational altitude 25-30k non-pressurized, 30+ pressurized
Engines four Wright R-2600-15, 1800 hp each
Proposed Operational early Summer, '44

In 1944, the bomber could be updated with turbocharged R2800-21(water injection), flat rated 2300 hp (combat) to 27,000 ft, 2000 hp (Mil) and 1625 hp (normal) to 25,000 ft., and pressurized with a top speed of 370+ mph and a cruise speed of 255 mph cruise, and operational altitude 30-35k.


I guess my question is how many lives could have been saved had something like the B-33A been fielded in mid-43. Another question would be was the B-33A a possible threat to the B-29 such that it was terminated for political purposes?

IIRC, the B-29 was a far superior aircraft vs the B-29, heavier firepower, larger bomb load and a greater range. I do however love the way the B-33A looked.

I think the performance of the Lancaster would have closed that gap

Interesting thread and proposition Dave.
While I do not have a definite answer, I would hazard a guess that the superior range, highly advanced weapons system and pressurization that the B-29 offered on paper had some influence on the USAAF selection.
I believe it's worth noting that while the B-29 was being developed and rushed into production, there was a belief among the USAAF High Command that Germany and Japan would have to be bombed from far greater distances than they actually were.

i don't understand as B-17G and B-24H can be a 1st generation

Vincenzo said:

i don't understand as B-17G and B-24H can be a 1st generation

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I see it as the definitive versions of both aircraft which were in fact America's first generation of strategic bombers.

vikingBerserker said:

IIRC, the B-29 was a far superior aircraft vs the B-29, heavier firepower, larger bomb load and a greater range. I do however love the way the B-33A looked.

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The B-29 was a major jump in technology; however the risk was very high and indeed came to fruition primarily with the engine. The AAF backed up the B-29 with the B-32 but not too wisely kept the same engine.

The point in this is that the proposed generation two bomber would be similar in technology to the gen one to keep the risk low but improvements in aero and a much more powerful engine that was proven with the purpose of fielding a faster, higher flying bomber in mid '43.

FLYBOYJ said:

I think the performance of the Lancaster would have closed that gap

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It had about a 12000 lb advantage in empty to max weight, cruise is no better than the B-17 and 25 mph less than the B-24, and max speed is similar. Ceiling of 19k is pretty bad. I don't think this will do what I want it to do, go faster and higher with a better bomb load than the B-17/24. Bringing it up to defensive levels and adding another pilot would make it not much better than the AAF bombers.

Upgrading the engines in the Lancaster, B-17, and B-24 would have helped, but I think aero could have been improved. I also wonder why this did not happen.

TheMustangRider said:

Interesting thread and proposition Dave.
While I do not have a definite answer, I would hazard a guess that the superior range, highly advanced weapons system and pressurization that the B-29 offered on paper had some influence on the USAAF selection.
I believe it's worth noting that while the B-29 was being developed and rushed into production, there was a belief among the USAAF High Command that Germany and Japan would have to be bombed from far greater distances than they actually were.

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No doubt the AAF rolled the dice and bet everything on the B-29 and B-32. Unfortunately, snake eyes came up for the engine and nothing came available to improve the performance of the slow B-17s and 24s, which made 1943 a bloody time for American airmen.

Vincenzo said:

i don't understand as B-17G and B-24H can be a 1st generation

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The AAF started the war with the B-17 and 24, which I consider the first generation US heavy bomber. It finished the war with these same aircraft upgraded. The last versions of these aircraft had basically the same engine as they started with and, while self-protection armament went up, performance generally went down.

I'm finding service cieling for lanc as 24500ft, down to 22000ft?

It might be helpful to point out that the B-29 and B-32 were based on a USAC request issued in Dec 1939, i.e. I don't really see a "generational gap".

The Lanc could haul alot because it was lacking a lot the B17,24 took for granted ..Co Pilot , Icing Equipment lower protection and much less armour to name some

IMO the new B24 bomber should have been powered by 1,600 hp R2600 engines. That would have given the U.S. AAF a second generation heavy bomber.

Kryten said:

I'm finding service cieling for lanc as 24500ft, down to 22000ft?

I'm finding service cieling for lanc as 24500ft, down to 22000ft?

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Possibly, I just lifted the number from wikipedia. Still not great.

Muscogeemike said:

It might be helpful to point out that the B-29 and B-32 were based on a USAC request issued in Dec 1939, i.e. I don't really see a "generational gap".

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Conceptionally, IMO, it was a generational jump in performance. The AAF could have upgraded the B-17 and B-24 with better engines as Davebender states below, or developed a new bomber, like the B-33A, incorporating advances with minimum risk and a normal generation advancement in performance. The B-29 was over twice the weight, twice the range, and four times the bomb load of the B-17/24. This stretch of capability depended on the development of an entirely new engine. The AAF gambled heavily on the success of the B-29 at the expense of the next generation bomber.

Davebender said:

Engines jumped from 1,200 hp to 2,200 hp
IMO the new B24 bomber should have been powered by 1,600 hp R2600 engines. That would have given the U.S. AAF a second generation heavy bomber.

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Yes! That would have helped a lot. While upgrading the B-17 was experimented with using the XB-38, I could not find any effort to up-engine the B-24, which could probably use it to good advantage in that it had an advanced wing.

I believe there was two reasons the next generation bomber was not developed, one, when the bomber needed to be developed for operations in 1943 there was a basic belief that the B-17 and B-24 could fight its way to the target and back, and wouldn't need higher performance, and second, the B-29 was going to work, so, no need for the bomber upgrade. When belief one was decimated by the guns of the Luftwaffe and belief two was upset by the faulty engine, it was too late to do much except develop a long range fighter. Even with the long range fighter, better performing bombers would be more effective with lower losses and fewer missions, or more damage. A better cruise speed would allow fighters better flexibility, no more essing.

davebender said:

IMO the new B24 bomber should have been powered by 1,600 hp R2600 engines. That would have given the U.S. AAF a second generation heavy bomber.

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The initial B-17 and B-24 did not have turbo superchargers. With turbo superchargers they had as much or more power than a non-turbo R-2600 would have had at 20-25,000ft.

For some reason the the R-2600 was never turbo-ed in a production version.

The R-3350 was a R-2600 with two more cylinders per row, what could go wrong?

there was the Boeing Y1B-20 project.

Shortround6 said:

The initial B-17 and B-24 did not have turbo superchargers. With turbo superchargers they had as much or more power than a non-turbo R-2600 would have had at 20-25,000ft.

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With a service ceiling of 39,000 ft. they must have had something on their mind and I'll bet it was not nitrous.

Factsheets : Martin XB-33A

The R-3350 was a R-2600 with two more cylinders per row, what could go wrong?

there was the Boeing Y1B-20 project.

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Not much.

I've been reading up on Boeing history lately and it seems that by 1943 they were pretty confident the war was won. The next generation bomber was going to be a swept wing jet. The initial design for the B-47 was concieved in 1943, which eventually evolved from a straight winged piston airplane to the 1946 swept wing prototype. The B-52 was on the drawing board in 1948. The leap in technology...aided by German research was remarkable. The above information comes from the Boeing website.

As for the B-24 being built around the R-2600, while it seems like a simple solution the fuel burn is considerably greater than an 1830. The wing would also have to be re-engineered to handle the stress of upgrading to the larger engine. When the B-24 was being designed the 1830 was readily available while the 2600 was still under development. With proper testing and design the Turbo system could have been adapted to the 2600 but that engine was relagated to the medium bomber force as well as the TBF. The same GE turbo was universally used in the P-38, P-47, B-17, B-24 and B-29.

jim

IMO that would be time well spent as the B-24 had a very short development period prior to mass production. In addition to more powerful engines the initial model B-24 might have gotten self sealing fuel tanks, powered gun turrets and controls with better balance. Mass production starts a year later (1942 ILO 1941) but you get a much better aircraft. Perhaps good enough that the very expensive and problem plagued B-29 program gets cancelled.

the B-17 was a 1934 design
the B-24 was a 1939 design
the B-29 was a 1940 design
the B-32 was a 1940 design
the XB-33 was a 1940 design
the XB-30 was a 1940 design
the XB-31 was a 1940 design

So i don't think that XB-33 was un intermediate generation design within B-24 and B-29
and i do not think that B-17 and B-24 are of same generation, they are same class (similar capability).

if i wrong design time here first flight time
B-17 first flight 1935
B-24 first flight 1939
B-29 first flight 1942
B-32 first flight 1942
XB-33 not built
XB-30 not built
XB-31 not built

You might want to sandwich in the B-19 as an indication of a 2nd generation and why they skipped to the 3rd so quickly.

Shortround6 said:

You might want to sandwich in the B-19 as an indication of a 2nd generation and why they skipped to the 3rd so quickly.

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maybe
B-17 first generation
B-24 2nd
B-29 3rd

actuallly the 2nd was not successfull like the first that developed go to similar capability

XB-33 was not a design for heavy bomber was designed for high altitude bomber he was four engined but others challengers were twin engined (XB-27 and 28 )

so quickly because the war in europe

davebender said:

IMO that would be time well spent as the B-24 had a very short development period prior to mass production. In addition to more powerful engines the initial model B-24 might have gotten self sealing fuel tanks, powered gun turrets and controls with better balance. Mass production starts a year later (1942 ILO 1941) but you get a much better aircraft. Perhaps good enough that the very expensive and problem plagued B-29 program gets cancelled.

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If you didn't need a bomber the size of the B-29, possibly. Even with these improvements compare the size of the two and the bomb carrying capability of the B-29. The B-24 wasn't going to be stretched any further.