VNAV function

[porterjames]

I have checked the previous posts and seen several videos of the use of the VNAV function when selecting the Direct TO a selected runway.  When using the Skyview only (no other source) the display shows a magenta line from the runway threshold to approximately the FAF. 
I attempted two intercepts using the track and ALT hold and then selecting Direct To the selected runway.  On the first attempt I attempted to intercept the extended runway center line outside of the magenta course line.  The autopilot flew through the center line and did not switch or capture the VNAV or change the aircrafts direction.
On the second attempt I intercepted the magenta line and the autopilot changed to VNAV and tracked the magenta line as well as descending along the prescribed glide-path.
My question is are you required to intercept the magenta course line?
Is there a way to extend this runway center line and have the autopilot intercept it?
Since this was my first attempt I obviously may have not had the autopilot properly set up on my first attempt.
Thanks.

 

[Dynon]

So for the VNAV function to activate, it needs to be armed. So if you're not seeing it on the AP top bar status area after the arrow (ie ALT XXXX>VNAV, it's not armed). The other is that you need to approach that glidepath from below for the AP to sequence. On the roll axis, similarly, NAV needs to be armed, so you need to see either HDG>NAV or TRK>NAV in the status area. Once you intercept the course, it should transition.

 

[porterjames]

Thanks for the reply. I was aware of that but don't recall if those indications were present when I made my first attempt.
Still I have my original question.
Can you accomplish all of that when attempting to intercept the course outside the magenta course line?
Thanks.

 

[Dynon]

For course guidance purposes, that extended centerline leg extends invisibly forever. In other words, if you aim angularly towards an extension of that leg, the needle will center, and as long as you're armed in HDG>NAV or TRK>NAV modes, you'll transition onto the lateral guidance in NAV mode when you get close.

 

[porterjames]

Thanks again for the reply.

 

[Jrskygod]

If I'm reading this right are you trying to do VNAV without the proper IFR navigator? If so the autopilot wont have the steering information available to utilize the VNAV function. Skyview itself wont do what I think you are trying to do without a certified WAAS navigator.

 

[Dynon]

We actually now have a very basic VNAV function that will set you up on an X degree glideslope to a runway. It is NOT suitable as an IFR approach aid.

 

[William_Ince]

We actually now have a very basic VNAV function that will set you up on an X degree glideslope to a runway. It is NOT suitable as an IFR approach aid.

In Dynons opinion, how well does the Garmin GTN 625 function with Skyview? Specifically, LPV approaches and missed approach functionality?

 

[Dynon]

Very well! At least we think so. You can fly LPV approaches under AP-control.

 

[William_Ince]

Very well! At least we think so. You can fly LPV approaches under AP-control.

Thank you for the prompt answer.

 

[porterjames]

Again, thanks for the response.
I flew the VNAV procedure several days ago and everything went according to plan. I found that the auto pilot elevator response was very active and got a pitch slip message more than once.

 

[William_Ince]

We actually now have a very basic VNAV function that will set you up on an X degree glideslope to a runway. It is NOT suitable as an IFR approach aid.

. . . . .

 

[woodmanrog]

We actually now have a very basic VNAV function that will set you up on an X degree glideslope to a runway. It is NOT suitable as an IFR approach aid.

I read the above on the July 5th reply. Is this still true today? We are trying to fly approaches using a Garmin 650 and not having much luck.
Thanks, Roger

 

[airguy]

The 650 is an IFR navigator, it should be feeding data directly into the ARINC-429 module and displaying on the Dynon HSI, and will drive the autopilot for a coupled approach as well. Are you receiving anything on the HSI from the 650? This is going to be completely separate from the basic VFR-only VNAV function that was discussed earlier here.

 

[kellym]

The 650 is an IFR navigator, it should be feeding data directly into the ARINC-429 module and displaying on the Dynon HSI, and will drive the autopilot for a coupled approach as well. Are you receiving anything on the HSI from the 650? This is going to be completely separate from the basic VFR-only VNAV function that was discussed earlier here.

As mentioned, the GTN 650 works fine for LPV and ILS approaches, IF you set it up correctly. It must be connected via ARINC 429 module, not serial connection. It must be selected as the HSI source. It should also be selected as the flight plan source. VNAV needs to be selected before intercepting the glide slope. In that case the GTN650 is supplying the vertical navigation.
Using Skyview as your flight plan source and the Skyview as your HSI source is required to fly the Skyview VNAV.
Two completely different navigation methods. The Skyview navigation and VNAV is strictly for VFR. The autopilot will only follow what the HSI and flightplan are calling for.