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chipmeisterc
14th Jun 2012, 16:19
Hi guys,

I am currently coding up a little flight simulator to try and better understand the physics of flight.

I have the lift/drag equations implemented, and have curves defining Cl / Cd for each surface.

I am noticing however that when the aircraft comes in to land, the tailplanes AoA is very close to that of the wing and as such sometimes stalls before the wing, not giving me enough control authority to flare correctly. Good job its not a real aircraft otherwise I think the results would be a bit painful!

Here is a video of it in action..sadly Youtube has down resed it so you can't really clearly read the debug text shoing the AoA for each surface.

Lunchtime coding - Flight Dynamics - YouTube
5YEQmi-JV7s

My current thinking is that either the elevator isnt big enough..to produce enough lift, or has too smaller moment again resulting in the same effect? But then the proportions are modelled closely on that of the cirrus so I would have thought it would behave in a similar manner?

Maybe my cg is in the wrong place? Maybe I need to learn more about pitch/thrust coupling etc.

Any words of wisdom?

What is the expected difference in aoa between the wing and tailplane in terms of aoa both in cruise and also during the flare? How close does the tailplane come to the stall when flaring?

Do I need to take into consideration the down wash from the wings, which will have an effect on the tailplane aoa?

Armchairflyer
14th Jun 2012, 16:31
Is this of any help?

Angle of Attack Stability, Trim, and Spiral Dives [Ch. 6 of See How It Flies] (http://www.av8n.com/how/htm/aoastab.html)

chipmeisterc
14th Jun 2012, 16:38
Thanks Armchairflyer! Will have a read and let you know :)

NITRO104
14th Jun 2012, 19:23
I am noticing however that when the aircraft comes in to land, the tailplanes AoA is very close to that of the wing and as such sometimes stalls before the wing

Often, FBWless aircraft have elevators'/canards' angle of incidence set in such a manner, that they stall sooner (at lower alphas) then the main wing, as a handling safety measure.

chipmeisterc
14th Jun 2012, 20:34
Edit - Had lots of questions about that link, but then answered them by reading a bit futher :) will see what happens with my new found knowledge tomorrow lunch time!