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In this book, The Making of the Atomic Bomb by Richard Rhodes (p. 705), I read:

[Paul Tibbets] eased the brakes [of Enola Gay] at 0245, the four fuel-injected Wright Cyclone engines pounding. “The B-29 has lots of torque in take-off,” he notes. “It wants to swerve off the runway to the left. The average mass-production pilot offsets torque by braking his right wheels. It's a rough ride, you lose ten miles an hour and you delay the take-off.” Nothing so rude for Tibbets. “Pilots of the 509th Group were taught to cancel torque by leading in with the left engines, advancing throttles ahead of the right engines. At eighty miles an hour, you get full rudder control, advance the right-hand engine to full power and, in a moment, you're airborne.”

I am not especially knowledgeable in aviation matters, but I believe that the torque is due to the B-29's four propellers all rotating in the same direction. Is that right? If so:

  1. Why did this problem only arise during take-off?
  2. Why did all propellers rotate the same way? Is this true for all propeller-driven aircraft with more than one engine? Why?
  3. If the 509th Group's technique was so good (and apparently not especially complex), why did only they use it?
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    $\begingroup$ Although this particular technique was not, in fact, unique to the 509th (as per @JonStory's answer), one response for as to why, hypothetically, the 509th might adopt some technique not used by other B-29 crews could be that the 509th operated Silverplate/Saddletree (nuclear-capable) B-29s, which were rather extensively modified for nuclear delivery, whereas most B-29 crews flew non-nuclear-capable aircraft. $\endgroup$ – Sean Aug 7 at 22:57
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  1. It didn't arise ONLY during takeoff, but it is most noticeable then for several reasons

    • The engines are at maximum power, therefore producing maximum torque
    • You've got a very good reason to need to be travelling in an exactly straight line (the runway)
    • You're travelling at fairly slow speed, so your vertical stabilizer is less effective - at higher speeds, the tail counteracts the torque more effectively (for this B-29 this occurs at 80mph, as mentioned). As soon as you get above 80mph, you can just input a little right rudder to counteract it.... B-29's only travelled below 80mph on takeoff and landing, so it wasn't a problem during flight, and during landing the throttles were at idle or very low power.
  2. It isn't true for all aircraft with more than one engine now (although it is true for some), but it does still happen and was much common back in WWII - they didn't want the extra supply line complexity of two different sets of otherwise identical engines, when it could be solved with a bootfull of right foot. Note also that the B-29 had 4 engines, most modern multi-props only have two, and they're closer to the fuselage, which reduces the effect

  3. I think you're misinterpreting the source: he's not saying this technique was unique to the 509th, just that they were taught the technique. The very fact he says they were taught it, rather than "came up with" it, suggests it was known elsewhere. The 509th are only referenced here because that's the group Tibbets was part of, it's unrelated.

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  • $\begingroup$ P-factor is actually something different, that comes into effect on rotation and climb out due to the prop blades hitting the air stream at an angle. On the takeoff run you're only looking at torque and perhaps prop slipstream. $\endgroup$ – falstro Feb 20 '15 at 10:03
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    $\begingroup$ @DaG That means one of the instructors of the 509th knew of using diff-thrust for yaw control at low speeds and passed it on to his students $\endgroup$ – ratchet freak Feb 20 '15 at 10:14
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    $\begingroup$ It's likely that different units would have independently arrived at the same technique, it's just common sense. $\endgroup$ – GdD Feb 20 '15 at 10:32
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    $\begingroup$ @JonStory "The average mass-production pilot" I read as the average B-29 pilot, who was always a bomber pilot. The thing I read is "average people are taught that in flight training, but the good pilots know to use diff thrust. The 509th only had good pilots, so we used diff thrust." $\endgroup$ – cpast Feb 20 '15 at 15:59
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    $\begingroup$ Very minor point: Placing the engines close to the fuselage has no effect on the torque due to engine rotation. It does, however, make a big difference to the engine out behaviour. $\endgroup$ – copper.hat Feb 23 '15 at 17:50

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