Menu Sign In Contact FAQ
Banner
Welcome to our forums

No GS on LPV approach (IFD540 LPV)

I wonder if I do something wrong when flying an LPV approach. I have now flown a number of these approaches into EDTM and twice the GS did not show up. The base leg to the final approach course is perpendicular and my Avidyne boxes auto-switch very late. The approach was activated and the box was in gps-vloc auto switch mode. I decided to manually switch to vloc. The box did not give me a lead in turn indication like it did from downwind to base (there I was still in gps mode) so I slightly overshot. I had no GS was in IMC and went missed to finally divert to Karlsruhe.

On the same approach a few weeks ago the GS was working just fine but I can’t remember whether I manually switched from gps to vloc or if I let the box do it. Either way why would one be different than the other. I am 100 % positive that the last time the GS worked the box was in vloc.

Does it really make a difference if vloc is selected manually, was this the reason the box gave no turn indication? how could one recover from this? what could I have done to the box afterwards to get the GS while on the final approach course?

Placido

LSZH

With a GPS approach you fly it in GPS not VLOC. It never switches.

VLOC means VOR/Localiser. It is only used for VOR, Localiser, ILS and LOC BC approaches. ie approaches that use the selected VHF navaid.

Last Edited by JasonC at 14 Feb 00:21
EGTK Oxford

I think I found out what my mistake was. When you activate an RNAV approach on the Avidyne in the top right corner you see the gps-lpv auto sequence mode. When on an ILS you can manually switch to vloc by twisting the knob as the box auto switches very late for my gusto. If you do this enough times during conventional ILS approaches you develop a routine. Unfortunately, during a RNAV approach twisting the knob does not yield the expect switch from gps-lpv to lpv but it goes to vloc. My brain did not realize the difference, also because I have flown 99% ILS and just a handful of RNAVs so I am stuck in that routine.

My mistake also caused by a lack of understanding of the technology hence my brain did not elaborate.

LSZH

Interesting… thanks for posting this Placido.

We have many past threads on the GNS430/540 ILS auto switching and loads of people are confused. The internal logic is nontrivial and very few people know the criteria which the box uses to switch over, and sometimes it doesn’t…

Administrator
Shoreham EGKA, United Kingdom

Peter, The GNS430/530 autoswitch is well defined in the Garmin Pilot Guide.

There is no autoswitch required for LPV or RNAV with vertical guidance. That is one reason I gave up doing those last century approaches, aka ILS.

KUZA, United States
5 Posts
Sign in to add your message

Back to Top