Boeing XB-47D: Two turning, two burning

"ttyymmnn" (ttyymmnn)
03/23/2020 at 12:35 • Filed to: wingspan, planes you've (probably) never heard of, Planelopnik

(US Air Force)

In 1944, the US Air Force began work to field a jet-powered bomber to keep pace with developments taking place in Nazi Germany. A number of manufacturers responded with traditional straight-wing designs, but Boeing got the jump on everybody else by using data on swept-wing aircraft that had been captured from the Germans. The result was the !!!error: Indecipherable SUB-paragraph formatting!!! , a groundbreaking aircraft with wings swept at 35º and engines slung beneath the wings in pods, a design that essentially set the standard for bombers and civilian airliners of the future.

(US Air Force)

However, early jet engines were notoriously thirsty, and the Air Force needed to find a way to extend the range of the jet bombers while not sacrificing speed. So Boeing took two B-47C Stratojets and replaced each inboard pair of jet engines with one 8,500 horsepower Wright YT49 turboprop engine that complemented the single outboard General Electric J47 turbojet engine. The turboprops were fitted with Curtiss reversible pitch props that measured 15 feet in diameter.

Following delays in the development of the turboprop engines, the first XB-47D took its maiden flight on August 26, 1955, followed by the second prototype six months later. The flights marked the first time such a hybrid turboprop/turbojet arrangement had ever flown. The XB-47D did manage to reach 600 mph, but only when going flat out at full power. As a result, the hoped-for fuel savings never materialized, though the reversible props did shorten the landing roll. With performance that was no better than the standard all-jet-powered Stratojet, the project was abandoned after the construction of the two prototypes.

(US Air Force)

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For more stories about aviation, aviation history, and aviators, visit !!!error: Indecipherable SUB-paragraph formatting!!! . For more aircraft oddities, visit !!!error: Indecipherable SUB-paragraph formatting!!! .

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DISCUSSION (12)

user314 > ttyymmnn
03/23/2020 at 12:57

Shame neither was retained:

Even though both aircraft accumulated a good many flying hours, no prototypes were ordered. Having served its basic purposes, the program never went beyond the experimental stage. At the conclusion of the program, the AF asked Boeing to ferry the two aircraft to Tinker AFB, where they would be converted back to bombers. Boeing replied that such a flight would need one or two stops to replace the engines and/or propellors. The AF forgot about the plan and the aircraft were instead scrapped at Seattle.

In addition to the B-47D, Boeing also looked at replacing the B-47 with the XB-55, which would have used four Allison T40s driving counter-rotating three bladed props:

Kinja'd!!!

JawzX2, Boost Addict. 1.6t, 2.7tt, 4.2t > user314
03/23/2020 at 13:15

The American Bear! Though the TU-95 was(is) a bit bigger and more powerful, the similarities are striking.

AlfaCorse > user314
03/23/2020 at 13:23

Huh interesting, l ooks like a smaller Tu-95

ttyymmnn > JawzX2, Boost Addict. 1.6t, 2.7tt, 4.2t
03/23/2020 at 13:25

The Tu-95 has a much more radically swept wing. Also this .

ttyymmnn > user314
03/23/2020 at 14:16

W here did you find that info?

user314 > ttyymmnn
03/23/2020 at 14:26

Wiki and Global Security .

ttyymmnn > user314
03/23/2020 at 14:40

Thanks. I keep forgetting about GS. I found those manual pages there, but didn’t read the article.

user314 > ttyymmnn
03/23/2020 at 15:25

I was really hoping one of them was still extant, either out at Pima or in crates at the USAFM awaiting restoration, but t’was not to be.

Looking to see if there’s a kit or conversion parts to build a B-57D, just for shiggles. Looks like there is a resin kit to add the turboprops to a 1/144 kit, which is doable. I’m not quite interested enough to ape Joe Martin and build my own 1/10th scale R/C model...

Kinja'd!!!

Also of interest was 53-2104, redesignated as an NB-47E and bailed to the Navy to test the TF34 engine for the S-3 Viking:

Kinja'd!!!

jminer > user314
03/23/2020 at 15:37

This was really an interesting read - thank you . I love this phase of R&D where new tech is being grafted onto existing old tech. It always leads to interesting things being learned.

ttyymmnn > user314
03/23/2020 at 16:18

So weird seeing “NAVY” on a B-47.

f86sabre > ttyymmnn
03/23/2020 at 20:04

Well, that’s an odd one.

ttyymmnn > f86sabre
03/23/2020 at 20:29

Indeed. Stumbled across it on the SDASM Flickr last night. I’d never heard of it.