I fly a Garmin bird - and have flown the PL21 in the sim. I have also grown up Garmin.

The downsides of the Garmin/Collins Interface:
- Garmin is not - yet - RVSM, so retain/use some oem avionics
- Use oem Altimeter for AP control/interface. Need to enter baro 2x (Garmin 1x, OEM 1x, and back-up/co-pilot if you choose)
- Use oem altitude pre-select. Would be nicer to use G600
- AP won't fly an altitude profile on a STAR - you are managing descent via altitude Vertical Speed

Sounds like a lot, in practice, it's not a big deal at all. Love the Garmin gear. I expect the pros will prefer FMS...

Very helpful. Thank you! When navigating between waypoints, is the AP in NAV mode or is the AP in heading mode and Garmin is constantly adjusting heading?

Can we bug the heading during navigation between waypoints?

Other than VNAV is there any functionality that’s lost?

Pretty sure all Avanti are RVSM. An Avanti without RVSM is just a weird looking King Air.
I am an admitted slow learner on any and all things computer. Took me a bit to get comfortable on Proline. Love it now. Avanti I guys with Garmin love it.

One of the bigger differences is empty weight. David has an earlier light II at 7915 pounds empty but does not have 66B engines.
I have a heavy II at 8248 and 66B engines. I rarely carry a full load but David does regularly. He would be a bit hamstrung with my bird.

My current believe right/wrong is the slight extra power in 66B just carries the extra ~300 lbs.

My G700 TXi (same as G600 TXi) is RVSM in my Citation. Why wouldn't it be RVSM in the Avanti? The panels support the altitude error correction tables needed for RVSM.

I enter baro only once for everything, and use the altitude preselect on the Garmin.


I don't have VNAV capability to the FD/AP, but you do get an indicator to track.

Someday, a new FD/AP will get me VNAV.

A Garmin setup will be a heck of lot cheaper for the database subscription and to get repairs. It should also be lighter.

Mike C.

The G600 provides GPSS so most of the time the autopilot thinks it is in heading mode. But it works flawlessly and follows waypoints, turns, holds, etc.

The heading bug is displayed in an outline so you can move it without it affecting the GPSS course.

I don’t know the VNAV capabilities of the PL21 so I can’t speak to whether it is more capable in VNAV. In Garmin, VNAV prompts generated by the GTN750Xi are displayed on the G600Txi, but the autopilot doesn’t follow them directly. Personally I have found I like to set the SPD hold mode of the autopilot and then use the power setting to track the required descent rate to meet the VNAV prompts. But it requires manually adjusting the power setting a little during the descent.

Piaggio has not released the correction tables to Garmin or any stc holders.

So it's an easy fix if Piaggio had the desire. But as of right now, Garmin birds rely on the old altitude select for rvsm.

Word on the street is that Piaggio won’t sell the SSEC data curves to allow Garmin to certify it for RVSM in the Avanti. I’ve heard rumors of discussions, but no announcement, so who knows.


I expect same.


Yes, both of these are true as well.

Those curves can be determined in other ways.

For example, take an Avanti with the stock system and an altitude test set, record the values you get as you climb the airplane. Make your own table.

Or, fly the airplane with both systems installed and match them up.

Or, fly the airplane with a trailing cone static measurement device and get the raw data to begin with. This is probably the best way.

https://en.wikipedia.org/wiki/Trailing_cone

I don't know where my SSEC came from for my Citation installation, but it would not surprised me if it wasn't from Textron.

Mike C.

I actually got my multi in the the DA62 and frankly find the Piaggio significantly easier to fly. I did a full Garmin retrofit in my Avanti I and have no regrets.

While the autopilot will not follow VNAV, it of course does approaches, and the Garmin equipment will tell you the required rate of descent in FPM to hit any crossing restriction and you get the "banana", which tells you where you will be at the altitude that's in the pre-selector. There are a couple other very minor annoyances, like you can't arm approach mode on the autopilot until you are aligned with the approach, as approach mode limits bank to 10 degrees.

Setting the various altitude preselects (Garmin & Collins & Backup) is also a little annoying, but not a big deal. I took my Piaggio to Europe for the summer, where controllers are automatically alerted if the Garmin pre-select mismatches with your assigned altitude (pre-select is transmitted in ADSB, but US contorllers don't see it), so I have gotten very good at quickly changing both.

The Collins autopilot is fine. It's not as good as Garmin's. With Garmin's, I know in half a second if the plane isn't doing what I want. With Collins, I have to wait a few seconds to figure it out.
I suspect that in time Garmin EIS and autopilot will come to the Piaggio. There is a good amount of demand. And I have heard a rumor a deal for the information was struck. We shall see.

Another factor you might want to consider is corrosion in the Vertical Stabilizer Assembly. I've been told anecdotally that this is a bigger issue with II's than I's, but I haven't confirmed it. See https://ad.easa.europa.eu/ad/2023-0122R1.

Re approaches. If you can’t arm the approach before you get on the localizer, then how do you get aligned?

Normally I would be on a ~30deg heading to the localizer (vectors to final) in heading mode and hit APR to arm and let the autopilot make the turn when it’s time to get fully established.

If this is not how you do things with Garmin on Avanti I, then how?

Thanks,

Talmon

I think this is how the Collins autopilot does it as well - while in heading mode, you can press HDG and APR simultaneously and it'll fly the heading but arm the approach mode such that when it captures it'll turn to the approach.

I think this is how the Collins autopilot does it as well - while in heading mode, you can press HDG and APR simultaneously and it'll fly the heading but arm the approach mode such that when it captures it'll turn to the approach.

Yeah, that makes sense. I guess I have gotten used to hitting the Approach button before getting established. Garmin spoils us

Yeah, that makes sense. I guess I have gotten used to hitting the Approach button before getting established. Garmin spoils us

How does Garmin spoil you in this context?
I don't have too much Garmin experience and nothing more sophisticated than a 530