Simviation Forums

Is there anyway to set the pitch trim in the AIR or CFG files so that the aircraft loads with the correct takeoff trim setting? Right now, the aircraft rotates when it gets to 120 (757) and tries to leave the ground at 140 and stalls.

This happens when I switch planes while at a stopover, and not when I load a saved flight.

I need to know how to set the trim settings in either the CFG or the AIR file to fix this.

Scott

You can't preset trim in the cfg file... You can adjust it's effectiveness (sensitivity)... though.

What you might wanna try (and do it in small steps backing up the original) is play with the CoG..

Sounds like you need to move it forward a bit. It will probably make the whole performance envelope a little better.

Brett, I'm interested in this one.    How do you go about playing with the CG?

I'm in Fargo, ND ... far away from a sim-equiped computer...

Someone will be along shortly with specifics..

If I remember correctly... Here's the aircraft.cfg paragraph..

--------------------------------------------------------
[WEIGHT_AND_BALANCE]
max_gross_weight= 2750.000
empty_weight= 2100.000

reference_datum_position=2.56, 0, 0      
empty_weight_CG_position=-1.0, 0, 0      
------------------------------------------------------


The

Rather than adjusting the CG in the Weight & Balance section, I go to [Airplane_geometry] and adjust the: wing_pos_apex_lon=.  That doesn't alter the weight, but changes the 'location' of the wing (I think).  Anyway, I set the CG slightly foward, and flight characteristics improve.  It's a lot less confusing than adjusting the weight & balance and it works just fine.

Bob

Very interesting..........how far forward do you put the wings?

Really interesting.     Nearly every aircraft I've downloaded has had the CG at about the forward limit.  Even after adjusting the 'pitch moment-trim change' value in the primary aerodynamics section of the .air file, most of these aircraft run out of trim power at low speeds.    

The problems start when designers just "adapt" an existing air/cfg file to the model at hand.

If you take your time, build those files carefully, use exact distances for apexes, etc..  it doesn't take much tweaking..

Be careful if you change W&B in a small (fighter) aircraft. I was A.F. & Lockheed certified in W&B and weighed well over 600 acft in my days. CG in a small plane is measured in inches so be careful with the .cfg value change. Tom F.

Sorry for the delay.  When I adjust the wing position, I base it on the CG shown in FS9, and go from there.  In the aircraft config file, I remark out the orig wing pos line (showing it as the original), then I add another wing pos line and insert the new settings.  Increasing the original number will move the wing pos to the rear.  Sometimes it takes quite a change:  Some orig wing positions show 0.0000 and I've had to change to 30.0000 to move the CG mark to the proper location.  A little practice plus trial and error seems to pay big dividends.  It's made a world of difference in some aircraft; others require little or no adjustment.
Note:  SOME aircraft will require further minute tweaking of the trim sensitivity, but it's rare.  Also, I've noticed payload weight and distribution do litte to affect the wing pos, so that's one less monkey wrench to toss into the equation.

Good luck,

Bob

Thanks, Bob.