GTN 750 VNAV

[donv]

I see that Garmin is adding true VNAV capabilities to the GTN 750. That's something I'm looking forward to! That's really the one big thing it was missing.

That might even be enough to convince me to upgrade to one of the Garmin autopilots, once they are certified for the Commander. Or maybe I should offer to be the first?

[Steve binnette]

What have you learned?  I have not heard anything, Vnav capability would be great.

[donv]

They just made an announcement...

GTN 650/750 descent vertical navigation

To assist in descent planning and energy management, pilots can take advantage of VNAV profiles throughout the enroute and terminal phases of flight within the GTN 650/750 touchscreen navigators when they’re paired with the G500 TXi/G600 TXi, G500/G600 or G5. Within the GTN, pilots can easily enter altitude constraints on the flight plan page to set-up a vertical descent profile. Pilots also experience a near-seamless transition from VNAV to an arrival and instrument approach. Once an arrival or approach is loaded and activated, the GTN automatically populates step-down altitudes or any applicable altitude restrictions. If ATC issues an unpublished altitude restriction, pilots can enter those altitudes manually into the active flight plan under the VNAV field.

As part of the VNAV profile, top of descent (TOD) and bottom of descent (BOD) values are also calculated and displayed on the moving map. As the aircraft arrives at TOD, the GTN displays a visual annunciation prompting the pilot to begin the descent. When paired with a display such as a G500 TXi/G600 TXi, G500/G600 or G5, a vertical deviation indication (VDI) also populates on the display to provide vertical guidance for the descent. Additionally, when the GTN 650/750 series is paired with the GFC 600 or GFC 500 autopilot, pilots can select the VNAV button on the mode controller to fly a fully-coupled VNAV profile.

http://newsroom.garmin.com/press-release/featured-releases/garmin-provides-key-updates-txi-flight-displays-gtn-navigators-gfc%C2%A0a

[KenFlo]

This is a great addition!  Especially flying RNAV SIDS and STARS around larger airports.  Unfortunately my autopilot can't use the signal to fly that profile but more info is always better.  I am interested on how it will be displayed on the G600.  Now if only an AC90 could do 250-280 knots we could fly any RNAV STAR!  Thanks for passing this on...I had not seen this.

[donv]

I suspect it will display like a glideslope. That's how my old GNS-XLSs did it on the Collins setup.

As for speed, I'm leery of going much over about 210-220 unless it's perfectly smooth and going to stay that way. I do pay pretty strong attention to that placard about "180 knots in moderate turbulence." It would be nice if you could go a bit faster, though. The Merlin had a 265 kt Vmo, and that was nice.

[Steve binnette]

Very nice new feature, having an AP that could fly it would Really make the most of the feature.    Even still having a VNAV pointer for the profile really helps with situational awareness on descent. 

it would be nice to see the constraints on the G600 next to the waypoint.  I guess there is always more!  Seeing the constraints on flight plan page is good enough.

[KenFlo]

Probably a dumb question but....if you are on a RNAV STAR with defined crossing altitudes, with the new VNAV function, could your autopilot capture the altitudes if you flew the procedure in Approach Mode?  We all know that Approach Mode captures vertical guidance on a LPV approach.  Don't know enough about how it works to know the answer...anyone?

[Steve binnette]

That is a interesting guestion,  I don’t know.

[donv]

Probably a dumb question but....if you are on a RNAV STAR with defined crossing altitudes, with the new VNAV function, could your autopilot capture the altitudes if you flew the procedure in Approach Mode?  We all know that Approach Mode captures vertical guidance on a LPV approach.  Don't know enough about how it works to know the answer...anyone?

It depends on the autopilot setup. In the 695B that we used to have, with the Collins EFIS-85 and a UNS-1M, it would actually do this. However, it's a bad idea because it's very sensitive in approach mode, and at the speeds you would typically be descending at (200+), it's very, very nervous feeling. I tried it once, and I wouldn't do it again.

I think an AP106/G600 setup might do it, but it is hard to say. Even if it will do it, I wouldn't.

[Steve binnette]

My set up is the 106 and G600.

The 750 goes into approach mode when a approach is activated and intercepted.  As long as the 750 is in the enroute phase the sensitivity from the navigator should be the same as if you were navigating during cruise.

What I don’t know is if the AP gets more sensitive when selecting approach.  That’s what I think you are saying Don.  Is that correct.

It would be nice to set the altitude pre select to the bottom of the arrival when cleared to descend via.

[donv]

Yes, what I'm saying is that the autopilot itself gets much more sensitive in approach mode.

Furthermore, in approach mode you would no longer be getting roll steering.

[KenFlo]

Don, thanks for the answer.  I will be happy to use the altitude que in the G600 and just set the altitude capture on the autopilot for the crossing altitude.  I hope with a GTN 750 and G600 setup, they find some real estate on the G600 to give you those altitudes without have to go to flight plan page on the GTN 750.  Anyway you slice it, its a great addition.

[donv]

Do you guys with preselect on the 106 have to have a separate altitude alerter (in addition to the one built into the G600)?

[KenFlo]

Don,  I have a King 300 and yes, I have a separate altitude alert.  I have to set the altitude in both the G600 and King 300 and I get two chimes.

[Steve binnette]

I have the 106 and G600 and have two alerts.  One is set 1000ft prior and the other is 200ft prior.