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Questions about FSDS

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i have some questions about a model (piper cherokee) i made with fsds. i assigned it the cessna 182 skylane airfile (and i have no idea, just yet on how to tweak air files).1. added all the scrape and gear points and the model sinks into the ground and crashes. 2. how do you center your model...the documentation says drag it to 0,0,0. i have tried this and can't seem to get it correct. any tips would be appreciated.3. when i did manage to slew the model up to about 5000ft (before it had a chance to crash) it flew very unstable and was all but uncontrolable.any help would be greatly appreciated

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First off, which sim? FS2000 or FS2002?Let's assume you are doing an FS2000 ac. To start off with, set your center (front to back) at 1/4 of the cord back of the leading edge of the wing then the up/down center thru the center of the engine. If you are designing for FS2000, be sure and create the gear.center, gear.left and gear.right reference polys and place them directly under the tires and centered to the tires lowest point, so that FSDS can modify the gear heights in the air file. To get the Center Of Gravity in section 301 set, open the air file with AirEd or other similar program and look at the main gear height. Multiply that by 1500 and enter it in for the COG. This should get your aircraft to sit on the ground close to right.The handling problem I find is usually caused by something like the fuel tank positions and center of lift on the wing. So you may need to mess with those. Be sure and write down your beginning figures before you change something so you can get back to square one if need be.If your flying this ac in FS2002, well you just have to do a lot of manual entering of location figures in the aircraft.cfg file as far as getting it to sit on the ground properly. With the model open in FSDS, move your cursor around in the various views and jot down the locations or in the case of the tire, change to point mode and not the locations of the lowest points on the tires. This also applies for wing, engine, horizontal and verticle stabalizers. One other thing, the y and z axis are switched in FS2002 so you have to shift gears for that.Give it a try and see what happens. If you still have problems and want someone to give it a look, let me know.

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I like Lou's approach also...My first suggestion would be for you to dowload a similar Piper Cherokee to use as reference air file. In FSDS, one of the things that may be overlooked is the use of the airparms.fsc file on which to build your model. This file provides you with the basic reference parts to locate your gear, etc., moving them to the correct locations. Note that you don't have to use the airparms file. It just makes it easier and you don't have to redo the reference disks. Note that these parts should be tagged as "reference parts only" so they do not get compiled. Your COG will typically be the 0,0,0 point around which you build your aircraft. In FSDS, to move the complete model, in part mode (F5) select all parts (A) the move the whole assembly so the that 0,0,0 corresponds to where you want. By using the reference parts when compiling the model, the reference part locations are correctly transferred to the air file. I believe that when using FFDS to compile in FS2002, if using an FS2002 *.air file, you may want to recheck your aircraft.cfg points (gear, etc.) against the corresponding *.air file values, to make sure they correspond.Hope this helps

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when you say "set your center (front to back) at 1/4 of the cord back of the leading edge of the wing" what do you mean by "cord back"?btw, i'm building for fs2002thanks for your help

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The cord is the measure of the distance from the leading edge of the wing to its trailing edge. If the cord is 20 feet, then you would set the leading edge 5 feet in front of 0,0,0. This way the Absolute Center is 1/4 of the cord.

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