IAS mode sorta wonky.....

[carguy4471 19]

So I've got the local GTN mods, and v1.8 overhaul from the wonderful folks here at avsim.  

 

I'm really not thinking my IAS mode is working right though.

 

My routine is:  

Set FD and Nav or Hdg on runway

Takeoff, engage AP, clean up aircraft

Hold 130-140kts

Hit IAS, then dial altitude and hit arm

 

When I do the above the airspeed will continue to decrease until I take it out of IAS, gain more airspeed and hit it again.  The second time it will usually hold a steady speed at 10-25kts faster than I have set.  

 

Am I doing something wrong or is this typical behavior from the IAS mode??

 

 

[TPerson 15]

Did you read this forum post?

 

http://www.avsim.com/topic/452595-guide-correct-use-of-pc-12-autopilot-kmc321kac297/

 

Todd

[carguy4471 19]

I have read that thread, and that seems to be how I'm operating the AP.  I'm not quite sure mine seems to be a bit of a chore.  

[autogyro 18]

I haven't flown in awhile but I do recall the AP struggling to maintain the set IAS. It was never off by as much as you seem to be getting. Try trimming the airplane and set the target altitude before engaging AP. I don't recall if it was ever fixed.

[carguy4471 19]

I have noticed the PC-12 doesn't autotrim under AP.  Maybe that has something to do with it.  I'll try trimming it up before engaging IAS.