Jump to content

Heading Instabilty


mverlin

Recommended Posts

I'm experiencing repetitive unexpected shifts in compass and GPS headings. The only method I'm using is to set the the HSI and autopilot set to heading. If I try to use the Nav and GPS the aircraft will display frequent unexpected course changes.

 

Any suggestions to deal with this is welcome.

 

Michael Verlin

Link to comment
Share on other sites

Different places in the "world" have different magnetic off sets. Thus, a magnetic heading of 245° in California is different when compared to true North, than in Hawaii, just for example. Also, and along the same lines, the magnetic heading will be totally different, in most of the world, from the GPS heading, which orients to true North.

 

Does this help at all?

Pat☺

[sIGPIC][/sIGPIC]

Had a thought...then there was the smell of something burning, and sparks, and then a big fire, and then the lights went out! I guess I better not do that again!

Sgt, USMC, 10 years proud service, Inactive reserve now :D

Link to comment
Share on other sites

If I understand your problem correctly, the heading changes occur when you use NAV mode to hold the aircraft on a VOR radial. There are 10 control variables (called PID feedback controllers) in the autopilot section of the aircraft.cfg file that can be revised to improve this. My own analysis several years ago came up with the following values that work well for me in most cases:

 

nav_proportional_control= 20.0

nav_integrator_control= 0.45

nav_derivative_control= 0.0

nav_integrator_boundary= 0.50

nav_derivative_boundary= 0.0

//

gs_proportional_control= 14.0

gs_integrator_control= 0.65

gs_derivative_control= 0.0

gs_integrator_boundary= 0.70

gs_derivative_boundary= 0.0

 

Give it a try and see what happens.

 

Regards,

JerryH

Link to comment
Share on other sites

Thank you for all of your kind assistance. I've tried it with some improvement. The real puzzle its the fact that the compass reading is unstable. With a fixed heading on the autopilot, the compass won't hold the proper heading. It swings wildly at times 180 degrees, sometimes not as large a setting, but if I try to use the GPS, the aircraft will not follow the intending course. The only way I can fly is to keep the autopilot in HDG, and ignore the compass and GPS.

 

I'm at the point where I am considering abandoning flight simulation after almost 18 years.

 

Any help is appreciated.

 

Michael Verlin

Link to comment
Share on other sites

Perhaps your magdec.bgl file is corrupted? Try replacing it from the FS9 CDs.

 

Is it worse near the poles but OK at the equator? If so, your magdec.bgl file may not be being read correctly? Try moving it from its default location to a new folder (and scenery subfolder) listed at the top of the Scenery Library.

 

Hope this helps,

Tom Gibson

 

CalClassic Propliner Page: http://www.calclassic.com

Link to comment
Share on other sites

Michael,

 

Now that you've described the compass swings of as much as 180 degrees, it's obvious that my PID controller changes are not the solution.

 

If anyone knows the answer, Tom Gibson will be the one. Don't give up.

 

Regards,

JerryH

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...