Prop disc thrust uniformity in turns vs wing position

[WrathofAtlantis]

TL;DR Summary

Does a low wing position, plus a turn's angle of attack (and curvature), affect the prop disc thrust uniformity?

I would like to know what is the current consensus on the effect of the position of the wing relative to a tractive propeller disc's uniformity of thrust (the focus configuration would be WWII fighters).

 

[russ_watters]

I would like to know what is the current consensus on the effect of the position of the wing relative to a tractive propeller disc's uniformity of thrust (the focus configuration would be WWII fighters).

This is vague yet seems to be similar to the thread you created a 9 months ago. Could you be more specific or try to attach this to/differentiate it from the previous thread?

 

[berkeman]

Looks like your previous thread was deleted because you were trying to present your personal theory. Is that your intent again, or are you just asking for help understanding the mainstream science now? Thanks.

I have this theory that, as a turn is entered and sustained at a 6-7 degrees Angle of Attack, the propeller disc's outflow spiral is raised relative to the low wing, causing the spiral's rearward flow to "dogleg" towards being (largely) above the wing. This, I theorize, would depressurize the bottom of the propeller disc ("bottom" being relative to the fuselage).

 

[WrathofAtlantis]

Yes I would like to hear what the science actually says about a low wing's effect on the prop disc's thrust uniformity at changing AoA.

To clarify, this is about the wing's presence in the prop's airflow, in horizontal turns, at constant high prop load, but at changing angles of attack, during a steeply banked turn.

If the P-factor was all there was, you would then expect extra power to fasten the turn rate.

What I wonder is, how would a vertical (to fuselage) prop load variation be detected, since, on take-off, the tendency would be held by the ground one way, and the airplane's weight the other? The exact same holds true in straight level flight or vertical pull-outs, wing lift being substituted to the "ground"...

In turning flight, a vertical prop load variation would be more easily detectable by a "nose light" tendency (need to push on the stick to maintain the turn, which would otherwise "self tighten") or a "nose heavy" tendency (need to pull back). "stick pushing" does happen on some types, but only in low speed sustained turns... Horizontal turns would be more sensitive to vertical prop load variations, it seems to me.

WoA

 

[jedishrfu]

I don’t think we can answer this. However, NOVA had a show sometime ago about WW2 plane restoration and perhaps those guys could answer your questions better.

https://www.kcet.org/shows/blue-sky...tory-a-hand-with-vintage-aircraft-restoration

Your question is too specialized for any of us to give a proper answer,

 

[cjl]

I still maintain my position from your earlier thread - I don't think there will be a significant vertical prop load. Before we speculate on what a vertical prop load would do, I'd still want to see some evidence that it exists in the first place.

 

[jrmichler]

Summary:: Does a low wing position, plus a turn's angle of attack (and curvature), affect the prop disc thrust uniformity?

I would like to know what is the current consensus on the effect of the position of the wing relative to a tractive propeller disc's uniformity of thrust

There is a discussion of this in Aerodynamics, Aeronautics, and Flight Mechanics, by Barnes W. McCormick. The author states that Propellers in Yaw, NACA R 820, by H.A. Ribner, 1945 presents a different method of calculating forces. The figure below is from the first edition of McCormick, published in 1979. The 2nd edition of this book is available from Amazon.

I bought this book back when I had ideas of designing my own airplane. Reading the book convinced me to not do that. And please do not ask me to interpret the above graph.