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G3X w/GPS175 minimums

Michael Henning

Well Known Member
Flying a coupled LPV approach with the G3X and the GPS175, with baro minimums set in the G3X, it seems the plane continues on the glide slope, below minimums, unless I disconnect the AP, or hit the TOGA button. Is that normal?
 
The 'Minimums' setting on the G3X is just a reminder, the AP will stay on the glide path until you do something (AP disc or TOGA).
 
Flying a coupled LPV approach with the G3X and the GPS175, with baro minimums set in the G3X, it seems the plane continues on the glide slope, below minimums, unless I disconnect the AP, or hit the TOGA button. Is that normal?

The alternative to what you describe would be breaking out right at minimums just for the autopilot to pitch up in go around mode. That seems less than ideal to me.
 
Mike,

I just did my first coupled ILS at ASH a few days ago and found I have a few things to learn about how the G3X and GTN/GPS do vertical steering on approaches. For normal VNAV, like an arrival procedure, the altitude selector should be set to the lowest altitude you expect. I'm wondering if that would be the case as well for an LPV or ILS - set the alt select to MSL minimums for the approach?

Maybe one of our G3X experts can chime in...

Dave
 
For what it's worth, when performing an LPV approach with my AFS/Dynon/GNC355 setup, I set minimums prior to beginning the approach. Once the glide slope is captured, I set missed approach altitude and continue to minimums. Unlike an ILS where the MAP (missed approach point) is determined by a baro altitude on the glide slope, LPV MAP is a waypoint (usually over the middle of the runway). My autopilot will level off at minimums and continue to MAP. Once reached, the Garmin navigator prompts you to execute a missed approach. If activated, my autopilot will begin a climb (at pre selected vertical speed) to the missed approach altitude. Additionally, the missed approach procedure and hold are activated.
I do not have a TOGA button.
Hope this helps.
 
For what it's worth, when performing an LPV approach with my AFS/Dynon/GNC355 setup, I set minimums prior to beginning the approach. Once the glide slope is captured, I set missed approach altitude and continue to minimums. Unlike an ILS where the MAP (missed approach point) is determined by a baro altitude on the glide slope, LPV MAP is a waypoint (usually over the middle of the runway). My autopilot will level off at minimums and continue to MAP. Once reached, the Garmin navigator prompts you to execute a missed approach. If activated, my autopilot will begin a climb (at pre selected vertical speed) to the missed approach altitude. Additionally, the missed approach procedure and hold are activated.
I do not have a TOGA button.
Hope this helps.

This is totally incorrect. The MAP for an LPV is the DA just like for an ILS and not, repeat not, the MAP waypoint depicted on the chart. That waypoint is there if you’re flying a degraded RNAV IAP like an LNAV vs an LPV.

My procedure for altitudes for my G3X is the same as for the G1000 that I learned behind. Once established on GS or GP I put the initial MAP altitude in the altitude select window. For a non-precision approach my selected altitude is the MDA and once I level off I change it to the MAP altitude.
 
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Todd,
You are correct as to DA on an LPV approach, which coincides with the VDP. My point was for the OP question regarding the Garmin 175/355/375. With LPV minimums set, the navigator will allow you to continue at the DA until the RNAV MAP, at which time the navigator will query the pilot regarding a missed approach.
 
Todd,
You are correct as to DA on an LPV approach, which coincides with the VDP. My point was for the OP question regarding the Garmin 175/355/375. With LPV minimums set, the navigator will allow you to continue at the DA until the RNAV MAP, at which time the navigator will query the pilot regarding a missed approach.

First the VDP does not coincide with the DA— VDPs are associated with non-precision MDAs. 2nd, while true the navigator will continue to sequence to the MAP waypoint on an LPV unless instructed otherwise,you are incorrect if you are waiting to execute the MAP until arrival at the MAP waypoint on a LPV or LNAV/VNAV instead of at the DA.

If you were flying an LPV coupled approach and did nothing at the DA the autopilot would fly you right into the ground just beyond the MAP waypoint.
 
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