Contact points VS scrape points

S

Sid2008

Charter Member
Hi everybody,
In the process of making my first airliner with a full VC in FSDS 3.5. It is a de Havilland Hercules, biplane trimotor airliner.

I got the exterior model done and have been working on the full VC lately. In my initial attempt, I am using stock Cessna and Beech gauges. Last weekend was my first revenue flight, where I used this old bird to haul some pipes across Washington state in FS Cargo.

I have read the previous threads in this forum about how to alter the contact points of my tail dragger in the aircraft.cfg file so that all 3 points sit snugly on the runway.

I have been experimenting with mixed results. Currently, the base model sits several feet above the runway (although the Y coordinate is negative for all 3 contact points). By incresing the "Y" coordinates on the 3 contact points (i.e., bringing the coordinate values closer to zero), I was able to get the plane closer to the runway, but never on the runway. In fact, if I try to get the plane nearer the runway, it always exhibits a tendency to somersault and crash.

So for contact point and scrape point gurus, can you please assist me with this, using lay-terms, so that I can get the main gears and tail skid on the runway?

Thank you,
Sid2008
 
Sid,

In FSDS, Set the model up at centerline, thrustline, and 25% MAC of the wing before doing this. In the cfg, ensure the CoG and Ref are all zeroes.

You can get the contact point data directly (coordinates) out of FSDS by selecting a vertice at the bottom of the tires, end of the wing tips, tail, and nose, as well as find the precise locations for your lights, crash points, etc.

Comment out your crash points (class 2 points) until you get your class 1 points set up.

This might help although using gmax: http://www.sim-outhouse.com/sohforums/showthread.php?t=944
 
Thank you for such a prompt response

Dear Mr. Shupe that your for your prompt response. I would like to try your suggestions tonight. However, I am requesting that you please take a moment to describe your instructions more fully, because I don't understand them clearly.
1) "In FSDS, Set the model up at centerline, thrustline, and 25% MAC of the wing before doing this" how does one does this?
2)"Comment out your crash points (class 2 points) until you get your class 1 points set up." What does this mean, and how does commenting out crash points affect a model?
Thank you for your help.
Sid2008
 
By setting out the contact points, wheels etc and not the crash (scrape points etc) you will insure that you can check the positioning without having a crash. There was a great addon program that is no longer available, called Aircraft Container Manager, which showed the position of all points in relation to a wire frame of the 3 D model. Some use temporary lights at the contact point position to show their external location.

Make sure that you have set the verticle velocity of the landing gear at a sufficently high value to avoid unintentional crashing. Typical values are 1600-2200. Also the compression and dampening values can cause problems such as the aircraft dancing around on the ground, or even flubber effects.

Cheers: T.
 
I wish I had gotten into simming earlier. I seem to have missed out on some nice software for developers. I can however add my recommendation on using lights set at contact points to visualize contact point locations. I also agree with Milton on setting a practical 0/0/0 point to start with. I am too often frustrated trying to improve flight dynamics via the CFG when I find the 0/0/0 point has been placed way toward the nose or tail. For these I rarely get the gear to contact the ground at a believable location leading to strange visual behavior, say on a rotation. If you have the time to fiddle a bit, I also borrow CP sets from similar aircraft that I know are close to the mark then I adjust them to suit.
 
"Firestriker" has a nice site that gives you examples of aircraft placement in your design program.

Also adding some screenshots to show how the model might appear in the design program.

If you are working with meters, then convert your coordinares to feet for the aircraft.cfg contact points.

The grid, or crosshairs represent the FS Reference point at 0,0,0, and by default the CoG if you have it set to 0,0,0.

http://www.oregon-coast.net/Tutorials/CofG/index.htm
 
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