# Is there a way to calculate the lift curve slope vs aspect ratio?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by rtfm, Sep 26, 2018.

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1. Sep 26, 2018

### rtfm

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Hi,
I am trying to find a way to calculate the lift curve slope of a wing depending on its aspect ratio. Is there such a beast? Basically the slope value * some factor based on AR.

Duncan

2. Sep 26, 2018

### lr27

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Ok. A tiny bit of algebra on a formula found in Hoerner* for "lift angle" gives:

dCl/d alpha = 1/ (10 + (20/A))

This is supposed to be a rough approximation for straight wings of at least moderate aspect ratio, and may still be a little different depending on planform shape. Units are degrees.

*Fluid Dynamic Lift Don't know if you can still get it.

3. Sep 26, 2018

### lr27

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Was poking around the web about something else and found a reference to a way of calculating lift curve that's supposed to be in NACA TR-665. You can probably find that on NASA's technical report server or on the Magic NACA Archive. Appears to be more complicated.

4. Sep 26, 2018

### rtfm

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Thanks mate

5. Sep 26, 2018

### lr27

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BTW, I bet if it's for a Pou, it's more complicated.

6. Sep 26, 2018

### dwreck

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General Aviation Aircraft Design by Snorri Gudmundsson has a short section in Chapter 9 listing various methods for estimating wing lift-curve slope. Inbox me if you want screenshots.

7. Sep 26, 2018

### pictsidhe

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1/(pi*(1+(2/A)*(1/e)))
where e is span efficiency. Angle in radians

8. Sep 30, 2018

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