Aerodynamics queries

[seanmcleod]

@Octal450 do you have a list of the sources you used to build the aerodynamic model?

How come you're using density altitude to vary the Cl vs Alpha curve? Shouldn't you be using Mach instead?

https://github.com/legoboyvdlp/A320-family/blob/afc6db9d236f5211039a70e5b50e6cb7f1cdf104/FDE/Config/a320-aerodynamics.xml#L54-L87

In terms of the drag modelling I'm curious why you've used both drag due to alpha and drag due to Cl squared. Typically I'd expect to see one of the other used.

[Octal450]

@Warning39

Just saw about the account issue, so wanted to ping you here as well.

Thanks, Josh

[Warning39]

Just saw about the account issue, so wanted to ping you here as well.

Yep, real pain, still waiting for an answer from Github. I'm also trying to resolve it via a separate Microsoft contact. How did you notice I had an account issue?

[Octal450]

I saw your post in the JSBSim issue. Best of luck getting resolve

Btw please see my above question.

Thanks, Josh

[Warning39]

So in terms of slats and drag with the A320. So there are there 6 configurations (0, 1, 1+F, 2, 3, Full).

FLAP Lever has five positions : 0, 1, 2, 3 and FULL.

Two configurations correspond to position 1 : Config 1 and Config 1 + F.

If you move lever from 0 to 1 and airspeed is less than/equal to 100 kts then Slats as well as Flaps are deployed (Config 1 + F). If speed is more than 100 kts then only Slats deploy (Config 1)

If you move lever from 2 to 1 and airspeed is less than 210 kts then Slats as well as Flaps are extended (Config 1 + F). If speed is more than 210 kts then only Slats extend (Config 1).

When in Config 1 + F and speed more than equal to 210 kts, flaps automatically retract to 0 and you get into Config 1.

When in Config 1 and speed less than/equal to 100, flaps automatically extend and you get into Config 1 + F.

Ref : FCOM DSC-27-30-10

So you could simply have 6 configs for the CD-alpha table and not have to worry about adding slat drag separately.

[Octal450]

Well I can't do that.

Because it's a full simulation, it accounts for "unusual" situations, where failures can cause actuators to not move. So I need to be able to account for slat and flap position separately.

Also, the 320 isn't my current focus right now (see here if you want to know why), so the other planes I am working on have a stow function for slats which means it have more configuration options.

Kind Regards, Josh

[Warning39]

So for the Boeing 737 simulator this is what they do.

[Octal450]

You'll have to pardon me for any stupid question, but as a dyslexic sometimes my understanding of these charts is not immediate because of how similar many of the letterings are.

So there are two tables which the gain KDAS is used to slew between them based on the position of slat.

At this point, maybe what I should do is compute the basic alpha curves and then produces tables for delta slat and delta flap drag based on the difference between alpha table with flap/slat and the basic alpha curve.

That would make it slightly easier to maintain.

Kind Regards, Josh