Prop disc thrust uniformity in turns vs wing position

In summary, the current consensus is that the position of the wing relative to a propeller disc's uniformity of thrust is not as important as was once thought.
  • #1
WrathofAtlantis
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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).
 
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  • #2
WrathofAtlantis said:
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?
 
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  • #3
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).
 
  • #4
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
 
  • #6
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.
 
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  • #7
WrathofAtlantis said:
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.
Prop.jpg


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.
 
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What is prop disc thrust uniformity?

Prop disc thrust uniformity is a measure of the evenness of thrust distribution across the propeller disc of an aircraft. It determines how efficiently the propeller can generate thrust and affects the aircraft's performance and stability.

How does prop disc thrust uniformity differ in turns compared to straight flight?

In turns, prop disc thrust uniformity is affected by the position of the wings. This is because the wings create a disturbance in the airflow that can impact the distribution of thrust across the propeller disc. In straight flight, the wings do not play a significant role in prop disc thrust uniformity.

Why is prop disc thrust uniformity important?

Prop disc thrust uniformity is important because it affects the aircraft's performance and stability. If the thrust is unevenly distributed, it can lead to increased drag, reduced efficiency, and potential loss of control during flight.

How does the wing position affect prop disc thrust uniformity in turns?

The wing position can have a significant impact on prop disc thrust uniformity in turns. If the wings are positioned in front of the propeller, they can create a blockage in the airflow, causing uneven thrust distribution. However, if the wings are positioned behind the propeller, they can help to smooth out the airflow and improve prop disc thrust uniformity.

What factors can influence prop disc thrust uniformity in turns?

Aside from wing position, other factors that can influence prop disc thrust uniformity in turns include airspeed, angle of attack, and propeller design. These factors can all affect the airflow around the propeller disc and impact the distribution of thrust.

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