Hello all,
We all know that the B-29 was chosen to enter service as the biggest, heaviest, and most sophisticated bomber of WWII. While it was under development the B32 was the alternative design, and only 118 were built.
However, another long-range model flew earlier - the Douglas XB-19. This model did not enter production. It was last flown in 1946 and scrapped in 1949.

Comparing the XB-19's spec to that of the B-29 shows that the former had a much better performance than the latter. This is true regarding the most important ones:
Ceiling
MTOW
Range
Bomb load

If that was the case, than why did the XB-19 was not chosen to enter service?
The reason stated in Wikipedia is that the design was regarded as obsolete before completed, but I can't figure why if the spec sheet is so impressive compared to those of other designs.

Thanks,

An225

Some thoughts:
The B-29 had a pressurised cabin, the XB-19 did not
The B-29 was significantly faster (165 vs 220 mph) (wikipedia)
It was likely more advanced systems wise, allowing for operation well into the korean war.
I am not entirely sure about aerodynamics and fuel consumption but a less thirsty plane is always useful - you never know how much fuel there is in war conditions. The round nose and sleek fuselage of the B-29 may have helped in that aspect.
Lastly, size is not everything. If the B-29 was smaller (better handling) and cheaper (easier to build) while being sufficient for the time's needs it was perhaps concluded that the larger XB-19 was unnecessary.

Thanks.
Sounds logical

According to Wiki, the XB-19 was obsolete technology-wise even before Douglas finished the first frame, so not surprising a more advanced design like the B-29 was chosen for general production.

In essence, it was not designed with as much attention towards mass production as later models were. It's lifting capacity was incredible for its time, but this came from very large and heavy wings, which led to lots of drag. As a result, to get its range, it traveled slower and still used more fuel. For the resources that it took to make one xb-19, almost two b-29s could be made (this figure includes man hours of labor as well as materials). Also, to achieve its final numbers, it needed the Allison V engines, which were in very short supply in the era (there was a b-17 prototype with them that showed significant performance gains, but the engines were never plentiful enough for them to be used there) which further cemented it's fate. Had things gone differently in europe, it's possible that you would have seen serial production start, but once the b-29 and the b-32 were in mass production, it would have been all over.

The 19 was never ahead of its time, it was just the logical extensign of what could be done with what was currently known. Given its large size and slow speed, it would have been quite vulnerable to defending fighters (assuming that they could have gotten up to it, FL39 is nothing to sneeze at, and few contemporary fighters were able to get up to it, and those that were had a very narrow operational envelope, making attack runs rather predictable) and it's accuracy would have suffered even more from level bombing from the even higher altitude. For its day, it was a big accomplishment, but it still wasn't a game changer.

It looks like a bomber out of the old Bugs Bunny cartoons.

The XB-19 design was never intended for production. It was a concept aircraft.

The designs which competed with the aircraft that became the B-29 were the Lockheed XB-30, the Douglas XB-31 and the Consolidated B-32

It was a bit more than just a concept. There was a bonafide desire to have a working design for a very long range heavy bomber to use in the event that there were no land bases available near Europe (and later Japan). However, as I said above, it was not designed with mass production in mind and would have required reworking to make that a reasonable possibility.

There was a book published on the XB-19 by William Wolf this past spring. I am unable to provide any kind of review since I have not seen a copy yet.

Douglas XB-19: An Illustrated History of America's Would-Be Intercontinental Bomber
https://www.amazon.com/Douglas-XB-19-Il ... glas+xb-19

An225 wrote:

Comparing the XB-19's spec to that of the B-29 shows that the former had a much better performance than the latter. This is true regarding the most important ones:
Ceiling
MTOW
Range
Bomb load

Think the XB-19 had a higher ceiling than the B-29? You think it had more range with the same bomb load?

After the war, a modified B-29 flew nonstop Honolulu to Cairo. Other? B-29s set payload-to-altitude records-- as I recall they climbed to 30000+ feet with 10000 kg payload. I'm guessing Douglas didn't hope to improve on that with the XB-19.

The B-19 had an internal bomb load of 18,700 lbs (it would not carry externals on long range missions). That makes its typical wartime bomb load around 15,000-16,000 lbs.
The B-29 typical wartime bomb load was 20,000 lbs. As mxaxai already mention, the B-29 was faster than the B-19, by a lot. Fighter pilots love big slow targets.
The B-19 required a crew of 18, while the B-29 had a crew of 10-11. There was also some doubt by Gen. Arnold and MGen. Groves the B-19 could take the Silverplate modifications. In 1943 the USAAF knew there were only two airplanes in the world that could deliver the two different Atomic Bombs that were then in development, the USAAF Boeing B-29 and the RAF Avro Lancaster Mk. I Special. Gen. Arnold wanted an American built bomber to deliver the A-Bombs, so the Lanc was out of consideration.
Silverplate (aka Saddletree) B-29s differed from their B-29 sisters by having most guns and armor removed, the two bomb bays converted into one long bomb bay, new bomb shackles, new bomb release system, provisions to arm the bomb after take-off, and the last batches of WWII built Silverplate B-29s had fuel-injected Wright R-3350-41 engines for improved performance.
Of the 46 Silverplate B-29s built during WWII, 29 were assigned to the 509th Comp Gr. and of those 15 were designated as combat airplanes that would be used to deliver the A-Bombs, the other 14 were flown on combat missions, just not involving the A-Bomb missions (the A-Bomb mission aircraft included Enola Gay, Bockcar, Great Artist, weather, and photo planes).