COG or COM understanding? Flight dynamics

[JoeJ]

You can use real world values, like kg or lbs, but you need to keep the same convention for all objects.
In my simulation nothing changes if i scale each mass by factor 100, because i take mass into relation when computing forces or torques.
If you have example real world force values given in joule, and joule relates to metric system, i'd recommend to use kg.

[andygib]

hi Joe, thanks for that. I thought that would be the case and was only looking for idea excuses to why my simulator still wasnt working as it should. BUT after some more looking and searching i figured another method i was doing incorrect and since implimenting it correctly it is really acting much better!

Thanks
Andy

[andygib]

Im still not sure how i impliment the rudder part though, i think this is causing me issues.

The reason is, all airfoiles are in a loop calculating lift & drag forces.

For main wings i calculate the AOA and then check if the AOA is above 0 and below Stall Angle. BUT for rudder that has a symetrical airfoil the AOA can be + & minus, as the lift can be left or right, as apposed to the main wings where we assume if AOA is 0 there is 0 or very little lift?

Or put another way, we know the lift vec for main wing airfoil is the cross product of the airfoil up and airfoil velocity. But what about rudder? The lift vec can be lift or right?

Thanks
Andy

[Adversus]

Hi,

For the last couple of days I've been trying to implement something similar so this thread has come in very useful.

At the moment I have the wings and elevator airfoils cycling through a loop to generate the resultant force and torque as described by Julio

However I still have a few questions but I'll start with this one.

What I am looking for is to be able to have a plane be able to travel at level flight unless I change the elevator airfoil flaps however I don't know how I can initialize it so that the elevator airfoils don't cause it to flip over if all the flaps are set at 0.0f.

I've tried moving the elevators and the wings but nothing has worked.

Is there an equation that allows me to determine the position of it and/or do I have to change the flaps on the elevator automatically depending on air speed?

Sorry for the basic questions, I'm not a big flight sim guy and ultimately this will be used for an arcade style game so I want the control to be as straight forward as possible.

[Adversus]

Regarding the coefficent of drag and lift.

Andy what do you do if your angle of attack is less than 0.0f or greater than the stall angle?

If I simply just give it no lift or drag then if the plane is climbing without an elevator the plane will reach the max aoa before it gets no lift from the airfoil i.e. for my curve the stall angle is 16 and this angle is 32.

If I then try to bank it this will push the aoa over this and stall the plane causing it to fall.

Should we be implementing these curves instead?

http://www.aerospaceweb.org/question/ai ... 150b.shtml

[Adversus]

From a bit of research online I think it's actually working however and I have concluded that I will have to write a control routine that will automatically balance the forces by changing the flaps on the airfoils to allow for level flight i.e angle of attack is zero and steady thrust.

Which seems like it will be straightforward enough however would the best way to do this be with a PID or simply by deriving the flaps from the force equations?