I've gone soft - need help on some aero

[Marc Zeitlin]

I need some guidance on an aerodynamic calculation (and not a particularly complex one, but I'm still flummoxed). I'm actually looking for the math to use here - not handwaving or qualitative arguments - I need the actual quantification .

Here's the question.

Assume I have two airplanes - identical in all ways (weight, surface area, airfoils, engine, etc.) EXCEPT that one has lower parasitic drag than the other one, due to <magic reasons> implemented by the builder of that plane.

Assume that the lower drag plane uses the same exact amount of power to fly at 200 KCAS as the higher drag plane uses to fly at 160 KCAS.

Assume that the higher drag plane has a best L/D of 13:1.

What is the best L/D of the lower drag plane (assumedly higher than the higher drag plane) and how did you arrive at the answer?

'm just confusing myself with the math - getting old and senile, apparently...

Thanks.

 

[oriol]

 

[jl_s]

 

[HoHun]

 

[addaon]

 

[Marc Zeitlin]

 

[plncraze]

 

[addaon]

 

[Marc Zeitlin]

 

[addaon]

 

[proppastie]

 

[addaon]

 

[proppastie]

 

[addaon]

 

[proppastie]

 

[addaon]

 

[proppastie]

 

[Marc Zeitlin]

 

[Marc Zeitlin]

 

[Flatiowa]