Non-Precision Approach using Garmin G430W

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Hop Harrigan
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Non-Precision Approach using Garmin G430W

Unread post by Hop Harrigan » Wed Jan 12, 2022 8:20 pm

I wonder if one of you guys can give me some advice here pls?
I fly non-precision approaches in the Cirrus using the Garmin 430 WAAS (VOR and RNAV (LNAV only)). The problem I have is the following:
I fly the vertical profile using ROD on the autopilot. Set the MDA into the system and an appropriate ROD of around 800'/min at 130kts. This arrangement holds the 'glide slope' nicely but I always wind up too high, too close to the touchdown point because the G430 automatically reduces the set ROD as the aircraft approaches the set altitude which causes a too-early rounding out and reduces the 'glide slope' angle. I am loathe to set a lower altitude into the autopilot for fear over of undershooting the MDA.
Anybody got a solution for this problem?
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Re: Non-Precision Approach using Garmin G430W

Unread post by foxbat » Thu Jan 13, 2022 12:10 am

The altitude pre select needs to be set to the missed approach altitude at an appropriate point depending on the systems logic. I'm not familiar with the Garmin but most approaches 1000' AAL should be OK, I've only seen a few with very high MDAs where that wouldn't work.
Your MDA should be "converted" to a DA by adding a margin appropriate to the aircraft type so that a go around will not lead to descent below the MDA.
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Re: Non-Precision Approach using Garmin G430W

Unread post by a7abw » Tue Jun 07, 2022 3:31 pm

Hop, just logged on after quite some time and saw your post.

As Foxbat said, the altitude pre-select should be set to the missed approach altitude upon intercepting the vertical profile and not the MDA which is most likely why it's doing what you describe.

I'm assuming that your flight director/autopilot can be used in the APPR mode for these non-precision approaches in which case it will follow the lateral and vertical guidance on the HSI down to the MDA (and beyond) until you disconnect the autopilot.

Another method is to use the NAV mode for the inbound track and VS mode for the vertical profile; keep adjusting the vertical speed in order to maintain the indicated vertical profile or 'glide slope' shown on the HSI.

Hope this helps.

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