See this document. Am I understanding the document correctly, that “Cd0” =
0.021 for a Boeing 737-800? Is the value likely to be correct?
Is this document something I
can use to get the correct values on a flight model? How do I match the MSFS
flight model to the table above? Is it even possible? Aircraft Drag Polar
Estimation.pdf I have looked at the
Is drag_coef_zero_lift of many “flight models”. PMDG 737-800 = 0.018066 FBW
A320 = 0.0187 Salty 747 mod = 0.02300 CJ4 = 0.02010 Since PMDG is considered
to be the best in the industry, one could assume that they can get hold of
values from Boeing that are more correct than a random document that I find
online. If we assume that the values in the document are correct, i.e. Cd0 =
0.021 for a Boeing 737, then the question arises why would PMDG have such a
different value compared to reality? Another theory is that they have exactly
the right values from Boeing but that they intentionally made the aircraft
“better”? But now I’m starting to end up in speculation, and that’s where I
don’t want to end up. I want to use as correct values as possible. What is
most likely? That the document is wrong? That PMDG is wrong? That MSFS
calculates wrong? None of it? What do they compensate for? That MSFS does not
have correct simulation? Edge case? Or am I simply misreading that Cd0 is not
the same as Is drag_coef_zero_lift. In that case how do you arrive at
drag_coef_zero_lift?
Found this page:
<Basic Aerodynamics
yKjMv-RjOKY1LXkZyQUpDQ7a3gC5v-wajxGCasUGdY2peuxk> This suggest to me that
“drag coef zero lift” and Cd0 is the same thing. Can someone please confirm.
This then suggest that I should use the Cd0 = 0.021?
I think you are correct, that the drag_coef_zero_lift and Cd0 would be the
same. I had the assumption that this would be the drag coefficient at the
point of lowest lift which should be the same thing anyway. Is 0.021 vs.
0.0181 a significant difference? Maybe not so much. But I also find that the
induced drag calculation in the sim turns out different that I expect, so
lower values of Cd0 may end up working better.
Nice thank you! It woulkd be nice if someone from MSFS, ASOBO could confirm
this.
No it is not the same in MSFS. A non-zero value for drag_coef_zero_lift moves
the entire Cl-Cd polar vertically up and down. It allows for the minimum drag
to not coincede with zero-lift, and thus allows for effects of fuselage drag
or others.
So if I were to use the data from the document, CD0, Clean, As in this case is 0.021, where would I put this value in MSFS?
Sorry my bad, that is the correct parameter. I got confused with lift_coef_at_drag_zero = 0.
Eric