GFC500 IAS Climb oscillations: post gain addendum

[201Steve]

I know there’s a million page thread out there on this, but since Garmin released the gain addendum to supposedly correct this issue, what’s everyone’s result?

I have found very little change. Everything works great on my AP except climbing through turbulence in ias mode. It will chase the speed by 10 knots. If bumpy, I initially climb in VSP. 
 

I had my avionics guys update the gain ad per the Garmin SB. No noticeable change. 

[PT20J]

I have the original gain settings. It holds airspeed well in smooth air. It chases it a little in turbulence, but I have a hard time holding a constant airspeed in turbulence manually. I use PIT if it’s bumpy. Tightening the pitch servo bridal cables to max spec helped. 

[mhrivnak]

My understanding is that it's common for the GFC 500 to do a poor job of maintaining IAS during a climb in turbulence, even on other airframe types. For example my flying club has 5 Piper Warriors and sees that same issue. IMO, pitch mode is the right tool for the job in that scenario. I like to climb at around 100kts IAS in my J, so in turbulence I'll establish that, and then turn on pitch hold. Then just keep an eye on your IAS to keep it in a desirable range, and adjust pitch if needed. It's a much more comfortable ride that way.

Even if the GFC 500 could do a perfect job of maintaining IAS in turbulence, it would still be doing significant pitch changes, and I think I'd prefer to just maintain pitch and accept the fluctuations in IAS.

[Pinecone]

My K had pitch oscillations with the original gain settings.  My shop did the SB gain setting change and that solved the issue.

But I started having some unexplained auto pilot disconnects (others have reported this also).  So my shop thought maybe go back to the original gain settings.  But they found that Garmin had changed the settings in the STC, so they put those in and so far, minimal pitch oscillations (1 - 2 knots) and no disconnects.

So it appears that there are 3 sets of gain settings.  The Original STC ones. The SB ones.  And the New STC ones.

[201Steve]

4 hours ago, Pinecone said:

 

So it appears that there are 3 sets of gain settings.  The Original STC ones. The SB ones.  And the New STC ones.

For crying out loud!!!!

[201Steve]

7 hours ago, PT20J said:

I use PIT if it’s bumpy.

What’s your method for this? Set up to desired speed manually, and then just click on the AP without any preselections, then select the desired horizontal source?

pitch vertical and selected horizontal?

(I wish pitch could be selected with its own button like any of the other settings)

[Emmet]

5 hours ago, Pinecone said:

My K had pitch oscillations with the original gain settings.  My shop did the SB gain setting change and that solved the issue.

But I started having some unexplained auto pilot disconnects (others have reported this also).  So my shop thought maybe go back to the original gain settings.  But they found that Garmin had changed the settings in the STC, so they put those in and so far, minimal pitch oscillations (1 - 2 knots) and no disconnects.

So it appears that there are 3 sets of gain settings.  The Original STC ones. The SB ones.  And the New STC ones.

Can you post the new STC settings?

[PT20J]

39 minutes ago, 201Steve said:

What’s your method for this? Set up to desired speed manually, and then just click on the AP without any preselections, then select the desired horizontal source?

pitch vertical and selected horizontal?

(I wish pitch could be selected with its own button like any of the other settings)

PIT is the default setting if no other vertical modes are selected. When the AP is first engaged it will hold the current pitch attitude unless you select another vertical mode. You can use the thumbwheel to adjust the attitude. If another vertical mode is selected, cancelling it will revert the AP to PIT.

[Pinecone]

14 hours ago, Emmet said:

Can you post the new STC settings?

They are available to Garmin dealers.  My dealer may give them to ME, but I would not distribute them