Twin Commander

General Category => Avionics => Topic started by: donv on July 20, 2018, 12:40:08 pm

Title: GTN 750 VNAV
Post by: donv on July 20, 2018, 12:40:08 pm
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?
Title: Re: GTN 750 VNAV
Post by: Steve binnette on July 21, 2018, 12:08:18 am
What have you learned?  I have not heard anything, Vnav capability would be great.
Title: Re: GTN 750 VNAV
Post by: donv on July 21, 2018, 12:35:42 am
They just made an announcement...

Quote from: Garmin

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 If ATC issues an unpublished altitude restriction, pilots can enter those altitudes manually into the active flight plan under the VNAV field.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
Title: Re: GTN 750 VNAV
Post by: KenFlo on July 21, 2018, 08:32:31 am
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.
Title: Re: GTN 750 VNAV
Post by: donv on July 21, 2018, 09:41:31 am
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.
Title: Re: GTN 750 VNAV
Post by: Steve binnette on July 21, 2018, 10:11:58 am
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.
Title: Re: GTN 750 VNAV
Post by: KenFlo on July 25, 2018, 09:04:06 am
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?
Title: Re: GTN 750 VNAV
Post by: Steve binnette on July 25, 2018, 11:13:13 am
That is a interesting guestion,  I don’t know.
Title: Re: GTN 750 VNAV
Post by: donv on July 25, 2018, 11:47:15 am
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.
Title: Re: GTN 750 VNAV
Post by: Steve binnette on July 25, 2018, 01:25:48 pm
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.
Title: Re: GTN 750 VNAV
Post by: donv on July 25, 2018, 01:30:20 pm
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.
Title: Re: GTN 750 VNAV
Post by: KenFlo on July 25, 2018, 06:06:14 pm
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.
Title: Re: GTN 750 VNAV
Post by: donv on July 25, 2018, 10:38:28 pm
Do you guys with preselect on the 106 have to have a separate altitude alerter (in addition to the one built into the G600)?
Title: Re: GTN 750 VNAV
Post by: KenFlo on July 26, 2018, 08:26:44 am
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.
Title: Re: GTN 750 VNAV
Post by: Steve binnette on July 26, 2018, 01:24:22 pm
I have the 106 and G600 and have two alerts.  One is set 1000ft prior and the other is 200ft prior.
Title: Re: GTN 750 VNAV
Post by: donv on July 26, 2018, 01:45:58 pm
While I don't have preselect, I also only have to use one altitude alerter!

My G600 chimes at 1000 feet-- that was a setting. When I first got it, I think it was at 200 feet, but they were able to change that.
Title: Re: GTN 750 VNAV
Post by: Steve binnette on July 26, 2018, 06:05:07 pm
I like having two alerts.  I could always eliminate the one on the G600.

It is easy to get lazy and complacent with altitude preselect.  The extra alerts reminds me to watch it level.
Title: Re: GTN 750 VNAV
Post by: KenFlo on August 27, 2018, 08:11:34 am
The article said this was available in August...anyone had this done yet?  If so, anything to share about how the VNAV portion works and is displayed on the G600?
Title: Re: GTN 750 VNAV
Post by: donv on August 28, 2018, 01:13:14 am
That is certainly true, but I'd rather have them than not!
Title: Re: GTN 750 VNAV
Post by: donv on October 11, 2018, 12:54:12 pm
So I just got this update... I've only played with it on the ground so far, but it seems pretty good.

Unfortunately, then I had this forwarded to me by my avionics guy:

Quote

Hello everyone,
I know there has been a couple of threads on this issue, but I wanted to start a new one to consolidate this and pony up to the bar so to speak.

There has been some reports of the GTN blanking out periodically after the latest 6.50 software, we've been listening and taking data from some of these reports and have been able to verify exactly what the cause of this is. without getting way deep into the weeds on this it is a result of FIS B weather data and large amounts of weather data that the processor gets into a bad state and blanks the screen out momentarily. this does not affect any other function of the unit and it will continue to work correctly.

we are quickly working on a new patch to correct this issue and will have it released here as quickly as possible.

My apologies for this problem, please contact me with any questions on this, but I'll provide feedback as I receive it.

Title: Re: GTN 750 VNAV
Post by: KenFlo on October 12, 2018, 08:43:16 am
Yes, I will testify from personal experience that this does indeed happen.  It has happened to me about every other flight since updating the software.  Another problem I am having that apparently is unique to me is the Vertical Deviation indicator on the G600 is not functioning when an altitude constraint is selected on the GTN 750. Seems like every time I do updates a string of problems arise I didn't have before.  Makes you wonder.....
Title: Re: GTN 750 VNAV
Post by: donv on October 12, 2018, 01:44:20 pm
If you turn FIS-B off, does it solve the screen blanking problem? I have XM Weather as well, so no real need for FIS-B.
Title: Re: GTN 750 VNAV
Post by: donv on November 01, 2018, 03:37:11 pm
Apparently Garmin just released the fix. I'm supposed to get it installed tomorrow, since I have a trip on Saturday.
Title: Re: GTN 750 VNAV
Post by: donv on November 09, 2018, 02:27:56 pm
I did a nice trip with my GTNs with the fix, and everything worked fine. VNAV worked quite well, although I made the mistake of using the "VNAV Direct" feature, and then had a hard time changing the angle from 1.2 degrees back to 3 degrees.

Still, it's a massive improvement, and the integration with the G600 is really nice.
Title: Re: GTN 750 VNAV
Post by: donv on November 16, 2018, 11:35:22 am
I took a few pictures to show the VNAV working on the G600 and GTN. It's pretty neat. It both gives you a glidepath indicator and puts a bug on the vertical speed to show you what descent rate you need. I don't have a GFC600, so I can't couple it, but that's probably just as well.

On the GTN, it shows you altitude constraints. One annoying thing is that with the VNAV feature, you always have a column taken up in the Flight Plan page for altitudes. I used to like to have cumulative time there, and it would be nice if I could hide the altitude column when I wasn't using the VNAV.

Title: Re: GTN 750 VNAV
Post by: donv on November 16, 2018, 11:48:45 am
This was something cool which I didn't expect. I had an LPV approach set up in the GTN, and was cleared direct to an initial fix. The VNAV started giving me vertical guidance to cross the initial fix at the proper altitude, and then, while I was descending, it showed a preview of the LPV glide path as well. You can see that in the little diamond in the upper half of the vertical path indicator.

Title: Re: GTN 750 VNAV
Post by: KenFlo on November 17, 2018, 08:31:32 am
Don...I have the same set up.  My GTN 750 works perfectly in VNAV but for some unknown reason the G600 doesn' display any of the cues.  I have had the avionics shop look at it three times after speaking with Garmin but no success yet.  Frustrating, as it would be a nice cue to have the VNAV cue.  I am glad you like it and hopefully soon I can share in that delight!
Title: Re: GTN 750 VNAV
Post by: SKYFLYER on November 17, 2018, 10:13:05 am
I have heard that just uploading the latest update will cause this issue and that the unit software has to be deleted and reloaded from scratch using the newest update.

I do not have that Garmin system but the two that I know that do have it... said pretty much the same thing.

I would think that your shop should know this.  Maybe Don can inquire with his shop as to how they made his work and you can get yours up to speed as well.
Title: Re: GTN 750 VNAV
Post by: donv on November 17, 2018, 11:33:08 am
Does your G600 have the latest update?

The avionics guy did the update in my hangar, and he just followed the step-by-step instructions from Garmin. Maybe he had some notes scribbled on there that I didn't see, I suppose.
Title: Re: GTN 750 VNAV
Post by: donv on November 17, 2018, 11:36:11 am
When I did my recurrent training last January with Barry Lane, he made a comment about my G600 having the "Baro Minimums" setting that he hadn't seen before... he implied that required some additional box or connection-- does your G600 have that?
Title: Re: GTN 750 VNAV
Post by: Steve binnette on November 17, 2018, 11:57:24 am
Don, that looks great I need to get that update.  Thanks for showing us.
Title: Re: GTN 750 VNAV
Post by: KenFlo on November 18, 2018, 08:15:42 am
I will ask about both of those items.  I use Carpenter Avionics in Smyrna TN.  They have a great rep and have done excellent work for me so far.
Title: Re: GTN 750 VNAV
Post by: donv on November 18, 2018, 10:33:41 am
I was looking at my AFM supplement, and all of the various boxes in the system (and there are a lot of them!) have software versions that need to be up to date. It may be that they just missed updating one of the other boxes or something.
Title: Re: GTN 750 VNAV
Post by: KenFlo on November 19, 2018, 07:57:59 am
Thanks Don.  They reloaded all of the software to include the latest patch from Garmin that fixes the screen blackout issue on the GTN 750/650.  They also verified and updated again all of the systems in that loop.  They are working with Garmin on it.  So far its a real head-scratcher for them and Garmin.  It shouldn't make a difference but my G600 was one of the very early ones...they are looking into that as well.  I really appreciate everyone's feedback.  Will pass along updates as I have them.
Title: Re: GTN 750 VNAV
Post by: donv on November 19, 2018, 12:30:27 pm
My experience with avionics systems is that if either a software version or a database is out of sync, it won't work. Maybe there is also some sort of hardware issue, but my bet is something is not in sync in terms of software.

Depending on how old your GTNs are, there was also a change in the databases a few years ago where you had to use a different navigation database after a certain version upgrade on the GTN. It required telling Garmin or Jeppesen that you had the new OS for the GTN... I'm sure your guys thought of that, but it's one more thing.
Title: Re: GTN 750 VNAV
Post by: donv on December 13, 2018, 06:34:19 pm
I just had an interesting discovery, which is almost certainly related to the G600 update... the course needle on my copilot HSI (mechanical) no longer responds to turning the course knob on the HSI. The pointer still moves, but the needle doesn't respond, at least in VOR mode. It is instead slaved to the course needle on the G600... very weird.

Garmin suggested a fix, which involves losing the ability to display the #2 VOR on the G600, and I guess that is the best answer, from a redundancy point of view, but it is annoying to lose capability that I used to have. I used to use the #2 VOR on the bearing pointer on the G600 all the time... now I'll have to use the #1, which again, isn't the end of the world, but it is annoying to have to change.
Title: Re: GTN 750 VNAV
Post by: KenFlo on December 14, 2018, 08:19:35 am
Don, I continue to have issues with mine as well.  I have given up.  This software update did nothing but cause issues for me....frustrating.
Title: Re: GTN 750 VNAV
Post by: SKYFLYER on December 14, 2018, 08:49:55 am
Umm maybe time to get the new G900 (G1000) to go with the new clear view windshield... then maybe the MT 5 blade props


Wallet... what wallet 8)
Title: Re: GTN 750 VNAV
Post by: donv on December 14, 2018, 01:16:37 pm
I'm not ready to give up. I really like the VNAV functionality.

Garmin did helpfully point out that if I bought a second G600, or upgraded my existing G600 to a TXi, the problem would magically go away. Not doing that at this time! Of course, a G950 would also solve the problem...