V

vasrv7a

Well Known Member
Can anyone please explain how the Garmin G3X works in approach mode with respect to capturing the glidepath... Garmin's video shows that when an approach has been activated using an external navigator (Garmin 4XXW) and pressing the G3X approach softkey, the video shows that it then becomes NECESSARY to select a vertical speed to capture the glide path (GP).
questions:
1. Is it required to select a vertical speed (AP VS softkey) to capture the GP in approach mode?
2. If not, how early in the approach do you select the approach mode softkey so that it will capture the GP?
3. If it's required to select a vertical speed (AP VS softkey) to capture the GP, at what point in the approach (exactly at the FAF inbound?) do you choose a vertical speed, and what if you select a vertical speed that's different from what's necessary to stay on the GP? Will the G3X then change and adjust the vertical speed to match the GP?

The Garmin Documentation as well as Garmin phone support was of little to no help in answering these questions.

Assistance with this issue will be very much appreciated.

Thanx.

Victor
 
Hi Victor,

Not sure who you talked to or which version of the G3X pilot's guide you looked at, but I thought I'd point out that the newest version is Rev E, dated earlier this month (you can find it here).

Maybe I did a bad job narrating those autopilot videos, but you don't need to select a vertical speed before using the autopilot to capture an ILS glideslope or a WAAS GPS glidepath. As long as you have the appropriate vertical mode armed (GS for an ILS glideslope or GP for a WAAS GPS glidepath) and you are approaching the glideslope/glidepath from below, it will capture regardless of which vertical mode was previously active. That is to say, you can capture a glideslope/glidepath from ALT (altitude hold), PIT (pitch hold), or VS (vertical speed hold) modes, and the system will do all the work. If you'll let me know which sequence in which video you found to be ambiguous, I can go take a look.

For an ILS approach, you can press the APPR softkey to arm for an ILS approach any time you have a a VLOC nav source selected and an ILS frequency tuned. The APPR softkey will also be available even before the external navigator is switched to VLOC mode, if you have the ILS approach procedure loaded into the external GPS navigator's flight plan. This allows you to arm for the ILS approach while still following GPS guidance inbound to the final approach fix. This is not shown in the videos but it's pretty cool to do - you can arm for the ILS fifty miles out, let the autopilot fly through the procedure turn and then capture the localizer and glideslope automatically, and all you have to do is manage the throttle.

For a WAAS GPS approach, the APPR softkey is available any time the WAAS GPS navigator is in LPV, LNAV+V, or LNAV/VNAV modes. It's also generally possible to arm for a WAAS GPS approach any other time you have one loaded in the external GPS navigator, as long as you're not also using VNAV at the same time.

By the way, if you've ever flown in an airplane equipped with a G1000 system and the GFC 700 autopilot, you might find this to be pretty familiar, since the G3X integrated autopilot interface is designed to work the same way!

cheers,
mcb
 
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Matt,

Thanx VERY much for you kind and PROMPT assistance, and I appreciate your link to the latest docs for the G3X as I am currently using Rev D.

In glancing breifly through the latest manual, I am encouraged to see several improvements. This weekend I intend to further test out and learn more about my new all glass panel in my 5 year old RV-7A:

Dual Garmin G3X with battery backup, TruTrak Pilot GX Autopilot, 1 Garmin 420W, 1 Garmin SL40, Dynon D10A backup EFIS with backup battery, B&C 60amp alternator and B&C 20amp backup alternator... transponder, audio panel, etc.

Your videos are great, they are extremely helpful. I was studying the GPS approach video, and upon further review, you set the vertical speed to 700FPM to go from 4500 down to 3800, and just as the aircraft got down to and captured 3800 it then captured the approach glidepath. This is the source of my confusion, initally it appeared to me that you had to set a VS with the autopilot in order to capture the GP on the final approach segment. It is now clear to me that had you been flying level at the captured altitude of 3800, the autopilot would have then captured the GP automatically with no need to set a VS. I will definitely test this function over the weekend.

Thanx again for everything.

Victor
 
Victor,

Glad I could help. If you're talking about this video, if you fast forward to about 2:35 you can see that I didn't actually bother to arm GP mode for the approach until after the autopilot had leveled off at 3800 feet, although I could have done it quite a bit earlier since the WAAS glideslope indication was valid quite a ways from the airport (although the needle was off the top of the scale, of course). Starting at about 3:30 in the video, the autopilot captures and tracks the WAAS glidepath down to the runway. In actuality there were several extra minutes of us cruising level at 3800 with GP mode armed, on the way to intercept the glidepath, but that got edited out in the interest of brevity. Good luck and enjoy your new panel - let me know if you have any other questions.

cheers,
mcb
 
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