Procedural question for KFC225+Garmin4/530 coupled approaches

[THill182]

I have a question for those of you flying the original KFC225 with a WAAS Garmin 4/530, as it was installed on the original pre-glass Ovations etc.:

 

I have never figured out how best to transition smoothly from the Approach mode on the autopilot to the coupled-glideslope Approach mode operation on RNAVS. So here is how it works, let's say on a T-layout RNAV with Glideslope guidance:

1. When I am cleared to the approach, and get close to the initial approach fix, I punch the APProach button on the KFC225. I then use the autopilot to descend to the respective altitudes along the approach.

2. Sometime closing in on the final approach leg of the approach, the Garmins warn me that Glideslope outputs are available. To enable them, I need to push the PROC button, and select Enable A/P Outputs. All that is described in the manuals I have.

3. BUT: when I do that, the autopilot disconnects and starts blinking. Usually, I can turn off and then on the autopilot and that fixes it (couples the approach). But I never figured out how to do that reliably. (For example, the last two approaches I flew, I ended up doing the final approach by hand because I didn't want to get distracted punching buttons).

 

How do others do this? What is the correct sequence to reliably couple the approach without disconnecting the autopilot ever (not that I don't practice by-hand approaches; but in the real soup  to minimums I prefer to be the backup and let the autopilot fly, while I scan the altitude and look out the window for signs of seeing the runway…).

 

PS: The last approach, I flew with the Nav BUG, and then when I enabled the A/P glideslope outputs, the autopilot didn’t disconnect. Maybe that is the technique? Fly the bug, until you get glideslope output?

[rgpilot]

I have the same autopilot connected to the Garmin 530/430 wass units. When flying an RNAV approach you have to fly in nav mode on the autopilot until the final approach fix. You have the Garmin in approach mode but wait to hit approach on the autopilot. You can fly the hold in nav mode without touching the controls and the autopilot will fly the entire hold. Than when you are lined up on final and pass the Final approach fix hit approach on the autopilot.

[THill182]

Thanks rgpilot; that is what occurred to me when I realized that while flying the bug, enabling the A/P outputs won't disconnect the autopilot; so it is the autopilot Approach Mode that is "incompatible" with the enabling of A/P outputs, and hence disconnects the autopilot. That actually makes sense given what I understand how this works logically.

 

Thanks, I will try that and adjust my procedure accordingly!