posted 01-11- 10:10 PM               

I guess that by editing these values you can change the performance of the plane somewhat. I changed the horsepower on one of the planes and it seemed to go faster in level flight.

But does anyone have a list of ALL the data values that go into a given flight model? I.E. where is every number that you need to have the "real" data for to create the most realistic performance?

I would think even an abbreviated list of the most "critical" numbers would go a long way towards approximating the aircraft's actual performance.

posted 01-12- 03:16 AM               

http://firelight.dynip.com/oppforum

posted 01-12- 06:26 AM               

For any airfoil object (wings, tails):

1. Airfoil: this points to an airfoil file that holds the data for that airfoil including lift coef, drag coef,and moment coef at all AOA for the wing. You can edit airfoils with the WingExtractor tool. Also I gather that there is an "up" and "down" version in addition to then main chart that represents the wing with trailing edge (ailerons, etc) up or down. I would guess that an interpolated value is used depending on how far up/down the control surface is.

2. Area: area of the wing in square feet.

3. AR: aspect ratio of the wing

4. Airpoint: Where the lift/drag force will be appllied - you can see this as an arrow in OPS.

5. Chord length - width of wing from leading edge to trailing edge.

Weight distribution and CG are very important as well:

1. Total plane weight is set at the parent object level - usualy the fuse... This weight will trickle down to the parts to define weight distribution.

2. There is usualy a hidden engine LOD that is for the purpose of damage detection and inertia - it most often has its own weight set (phyLbs I think). To seeit in OPS, delete the obHidden property on it, then save and reload the SM file. You can easitly add it back when you are done. Because it is a child of the main plane, it takes weight from the main plane weight - leaving the rest of the weight to be ditributed to the rest of the plane. Move the engine into the correct postion and make it the correct size. I have noticed that the engine is usualy a bit bigger than the fuse - I think this is to make engine damage more likely.

3. You will probably see an airfoil type "cylinder" for the fuse - this gives the fuse drag. You can set the area just like it was a wing.

4. Other parts of the plane do not usualy have weight specified like the engine. Instead the have inertia boxes with densities. This works cool - you set the weight per size (density) - then just match the inertia box size to that part's size. This object will take weight from the over-all plane weight setting depending on the size and desity compared to all the other objects defined. You can see/edit inertia boxes in OPS (thanks Bryan!)

Weight distribution will effect CG and such things as roll rate, nimbleness, and ground handling - just like a real plane!

CG tip: To check your Center of Gravity, just let the AI fly the plane. They seem to trim for level flight real good. If your CG is too far forward then the AI will trim down elevator. If the CG is to far rearward, the AI will trim up elevator. To see this, let the AI fly, then take control of the plane. Now center your stick - where is the elevator?

I found this out by mistake - I feared a bug when I noticed that my SE5a (I knew the CG was off) had no elevator through - it was all the way up and I could not move it with the joystick!!! This was because the trim was set full up by the AI due to the plane being sooo nose heavy (I moved the engine forward) It looked at the time like the evelator DOF was broken. But why did the planes parked have the elevator in the right oreintation? It stumped me for like an hour LOL

Also note that the force of lift will be perpendicular to the orientation of your wing LOD in OPS. It has NOTHING to due with the shape of your LOD So DO rotate your LOD in OPS to implement dihedral in your FM.

You can also set a incidence angle for any airfoil object. This is cool. Using this you can leave your wing/tail LOD level (a good idea) and simply add the small incedence angle to the FM.

I am not sure yet how the level of damge of an airfoil part affets its performance.

Of course the OpenPlane document mentions all of these properties in detail if you want to edit/add them. It is fun, and once you start fidling it gets quite easy. You can see the results very well.

Things I dont know: How to best set up an engine/prop. How to best edit an airfoil to get certain results.

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-Sv =FC=

WWI in SDOE!

posted 01-12- 08:53 AM               

I know Jane's usually has a lot of detailed physical info, but not necessarily for every plane or the varient you're doing. Any online sites for airplane nuts that have this stuff?

I think my approach is going to be mainly: use an existing plane from the game that's "close" to what I'm building, performance-wise, modify its appearance, and then change the physical properties of whatever aspects I can find data for. That way it will seem different from the model I started with, but probably not "precisely" correct for the "real" plane. I guess that might make it kinda questionable for online use tho...

And no, I'm not building a C-47

posted 01-12- 09:25 AM               

You can find airfoil data for many planes here including the C-47! (NACA 2215):
http://amber.aae.uiuc.edu/~m-selig/ads/aircraft.html

Generally we asume the airpoint to be 25% back behind the leading edge. (I think that is it)

A good guess at engine weight should do.

The best data seems to be stuff like climb rate, turn rate, max speed at atl. X - etc. Then tweek your plane to match these specs. This is the time consuming art that is FM.

I just go for as close as I can get with a reasonable amount of effort (my SE5a is not done FM wise) For fun flying on-line the best thing IMO is to match your new plane against the other existing planes. For example make sure your plane can not out climb a plane that has a better climb rate than your plane. Stuff like this makes flying the planes together more fun and realistic - even if the numbers are not exact. At least this is what I am doing for the WWI planes...

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-Sv =FC=

WWI in SDOE!