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If a plane with a propeller, e.g., a Spitfire, does a constant barrel roll in the same direction as the propeller, will the plane travel faster as impractical?

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    $\begingroup$ "will the plane travel faster as impractical" ??? Can you re-word that? "impractical" is not the correct word here, I'm guessing you want to know if the roll rate is helped/hindered by the torque effects of the engine? $\endgroup$ – Ron Beyer Dec 28 '17 at 3:53
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for a propeller rotating at 2400RPM = 40 rev/second and a roll rate of 0.3 rev/second, the roll rate will not measurably affect the prop rotation speed and the plane will neither travel faster (if the rates are additive) nor slower (if the rates are opposite).

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    $\begingroup$ Well, it's almost a difference of a whopping 1% $\endgroup$ – Koyovis Dec 28 '17 at 7:42
  • $\begingroup$ I do not think the airspeed indicator would resolve that difference. this is why I said "measurably affect". $\endgroup$ – niels nielsen Dec 28 '17 at 7:45
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The plane will fly slower

If the plane is constantly rolling, then both ailerons are extended into the slipstream, causing drag.

During approximately 1/2 the roll, the plane is in knife-edge flight. In that condition, the aircraft's fuselage is providing lift. It's a very inefficient way to fly and usually involves a significant nose-high attitude (more drag).

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  • $\begingroup$ The fuselage produces lift when the aircraft fuselage angle-of-attack (AOA) angle is non-zero. And any lift that it produces would be in the direction of this AOA. i.e., if the aircraft maintains a zero sideslip angle, will always be perpendicular to the plane of the wings. The aircraft roll angle or attitude has nothing to do with it. $\endgroup$ – Charles Bretana Dec 28 '17 at 17:32
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    $\begingroup$ @CharlesBretana What happens when the aircraft has rolled 90 degrees and the wings are no longer contributing to lift? $\endgroup$ – Dan Pichelman Dec 28 '17 at 17:35
  • $\begingroup$ You are confused by the multiple and overly simplistic uses of the term Lift. Lift is not only "the force that holds the aircraft up". It is "the force generated by the flow of airstream". - this is especially relevant if you wish to discuss the Lift produced by parts of the airframe other than the wings. So, to answer your question, the Wings are always producing Lift, even if you are upside down. In 90 degrees of bank all this lift is turning the aircraft sideways, changing its heading. $\endgroup$ – Charles Bretana Dec 28 '17 at 17:42
  • $\begingroup$ If the aircraft AOA is zero, the "Lift" points backwards, parallel to the flight path, and slows the aircraft down without changing its flight path direction. One "artificial" definition of Lift (redefined to allow us to split it up into lift and drag, is to define it as only that component of the total force that is perpendicular to the flight path, and the drag is that component parallel to he flight path. Another common redefinition (which you are assuming) is to use the horizon as the frame of reference or orientation. But all these are artificial, and used only for convenience. $\endgroup$ – Charles Bretana Dec 28 '17 at 17:47
  • $\begingroup$ And to answer the last question (implied) in your comment, at 90 degrees of bank, the aircraft will not maintain level flight, it would fall, since (as you correctly surmise), the lift which is still being generated by the wings is not pointed up, and so can no longer keep the aircraft from falling. $\endgroup$ – Charles Bretana Dec 28 '17 at 17:50

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