27

I was watching some footage of the Enola gay

I was interested in the part where the plane was backing up over the bomb (starts around 18:27). It appears to be doing this under its own power with the propellers running. Could the B-29 reverse some propellers to do this?

Machavity
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  • https://aviation.stackexchange.com/questions/7689/why-dont-planes-have-a-reverse-propeller-as-air-brakes – BowlOfRed May 17 '19 at 16:16
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    @BowlOfRed: Having checked two B-29 declassified manuals, neither mention reversible pitch props, only that they are full-feathering. –  May 17 '19 at 16:34
  • @ymb1 Check out Mike's answer. He actually found a video with the props shown reverse pitching, along with landings done using only reversible props. I'm guessing it was to facilitate them landing on those shorter south Pacific SeaBee runways – Machavity May 17 '19 at 18:48
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    @Machavity: Nice. And here's a bit of trivia, the B-29 development cost more than the Manhattan Project. –  May 17 '19 at 23:31
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    @ymb1: Most B-29s didn't have reversible-pitch propellers. The Silverplate B-29s (the nuclear-weapon-delivery version), however, did. – Vikki May 19 '19 at 00:25

3 Answers3

39

Some B-29s had reversible pitch propellers. All the B-29s used for the Atomic bomb missions had reversible pitch propellers.

Wikipedia B-29 Variants

Moreover, engine packages changed; including the type of propellers and range of the variable pitch. A notable example were the eventual 65 airframes (up to 1947's end) for the Silverplate and successor-name "Saddletree" specifications; built for the Manhattan Project with Curtiss Electric reversible pitch propellers.

Army Air Forces tests reversible propellers for B-29 bomber

Machavity
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Mike Sowsun
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19

Although I can't find direct hard documentary evidence, I'll make the case that that B-29 has Curtis Electric reversing propellers thusly:

  1. We know that Curtis had a reversing version of its electric propeller during WWII because the Consolidated had them for the inboard engines of the Coronado flying boat.
  2. The B-29 in the video is clearly backing up under its own power, and you can tell at least two engines are higher RPM from the blade strobing. It's not the wind blowing it back. The B-29 had a free castering unsteerable nose wheel and you can see that steering is being done by ground crew manhandling a towbar for fine steering, probably assisted (or hindered) by bits of braking by the pilot. Looks like a pretty tricky task.
  3. There were many field mods done on the B-29 and things like installing reversing props in the field as an upgrade would certainly have been done late in the war. And you can bet that Enola Gay had all of the latest and greatest field mods. As field mods they were probably covered by Flight Manual Supplements and that sort of documentation can be very hard to track down.
John K
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    I suspect that your answer is basically correct except that the steering is being caused not by the pilot braking but rather by the people that we see in front of the nose from 18:40-18:47 pushing sideways on a towbar attached to the nosewheel to cause the nosewheel to castor. The tail might rise and fall more if the pilot were actually braking. – quiet flyer May 17 '19 at 17:18
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    Very good observation @quietflyer thanks. I've revised my post. – John K May 17 '19 at 17:39
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Many planes have props that can be set to a negative angle, for braking during landing. So, that could also be used to reverse under its own power.

Vikki
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pnauta
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