VNAV capability on Avidyne/G450 Avionics

Hi Guys,

My apologies if this is an old subject…

My 2007 G3 is equipped with a Avidyne/2xG450w’s/Stec55X

It appears that this avionics suite is not capable of Vnav on RNAV approaches.

Am I missing something?

Is there a simple upgrade to Vnav an if so what is required?

Many thanks!


It can fly a glidepath (GS). It cannot do true VNAV. only Perspective and R9 can do VNAV. The autopilot requires a VNAV mode. The STEC55X and DFC90 don’t have that mode


I presume you have Garmin 430’s. I do not believe there is a Garmin 450. What Trip told you is correct. But the last page on the right of the NAV pages allows you to calculate a desired VNAV. But it has to be flown in VS mode and , as ground speed changes, the exact VSR (vertical speed required) will change. But you can use it as a rough calculation and follow the VSR.

The other thing to clarify is that the 430W does have a means to do an advisory glide slope on a standard RNAV(GPS) approach called LNAV+V. Unfortunately, it’s only available in 49 of the 50 United States, so no vertical navigation for you (or me).

This type of advisory guidance IS available with the Avidyne IFD series of navigators, and may be provided with the Garmin GTNs in a future software release.

It does depend on whether the RNAV approach is correctly aligned with the runway’s final approach course, and on how the procedure is coded in the database.

It can be coupled to the AP in GPS APPR mode, although I don’t know if that is supported with your S/Tec; it does work with the DFC90.

You should check with pilots in your country to see if this capability is available and operates on the approaches you’re interested in. It isn’t listed in any given approach chart.

Note to Garmin: it’s really disappointing that you won’t provide this capability on the 430W, especially since it requires simply relaxing an arbitrary constraint.


Yes, my typo…G430w

Many thanks for your input, your assistance is much appreciated!

The Cirrus instructor at the local flight school says that some of the Avidyne installations do have Vnav and some don’t, on similarly equipped G3’s. If this is true, I wonder if there isn’t just a software mod/upgrade on the G430 that accounts for this.

Thanks again for the interest.