Coupled approach - GTN650Xi & GFC500

[RussR]

It is practically standard procedure to remain at the higher altitude (3100 at TIRRO in this example) rather than further descend and level off at 2600 just to wait for the glideslope/path, for all the reasons @midlifeflyer enumerates.

However, you can't necessarily do it blindly, there must be some thought put into it, and quick math. While the IF will always (at least 99% of the time) be below the glidepath (so staying at that altitude will work), it can get trickier if there is a turn at the IF (like a standard T configuration).

Let's say the altitude at TIRRO was 4100 instead. Since the intermediate segment is 6.3 NM long, a quick estimate of the glidepath altitude at TIRRO is 6.3 x 300 + the 2600 FAF altitude = 4490. So being at 4100 at TIRRO is still below the glidepath, that's good.

However, if we're coming from one of the T's, that turn is going to roll out onto the intermediate segment somewhere inside TIRRO. Will that roll-out point still be below glidepath? Depends on the speed of the aircraft and how well you're set up and flying. If it's not, then the glidepath needle will start to come down as you're in the turn. Will your autopilot capture it in the turn, or in this scenario should you try to intercept it from above, or try to descend back beneath the glidepath before engaging Approach mode? Not necessarily one right answer, just something to think about and brief if you ever have the situation where the glidepath is below, but not THAT MUCH below the altitude at the IF.

 

[midlifeflyer]

Ah ok that makes sense if you have vertical guidance. My old avionics, the Garmin GNC300XL, only provides lateral guidance. There was no vertical guidance with GPS approaches. Only my King KX155 provided vertical guidance on LOC and ILS approaches.

The basic concept is that, by design, the descent from an IF to an FAF is supposed to be no worse than 3°. Think about it. On this approach, crossing TIRRO at 3100 you have over 6 nm to lose only 500”. You already noted that you would start a slow descent, so you realize this. But it also means that as you cross TITTO, the glidepath or ILS glideslope or +V advisory is way above you. At 3100 you’d be traveling level for about 4 miles past TIRRO before intercepting it. As I mentioned earlier, you would see the same with an ILS.


You mention earlier that you were glad you didn’t have an instructor there to see how bad you were doing. I have to disagree. Your transition to modern WAAS based capabilities is more reason to have one, not less.

 

[midlifeflyer]

It is practically standard procedure to remain at the higher altitude (3100 at TIRRO in this example) rather than further descend and level off at 2600 just to wait for the glideslope/path, for all the reasons @midlifeflyer enumerates.

However, you can't necessarily do it blindly, there must be some thought put into it, and quick math. While the IF will always (at least 99% of the time) be below the glidepath (so staying at that altitude will work), it can get trickier if there is a turn at the IF (like a standard T configuration).

Let's say the altitude at TIRRO was 4100 instead. Since the intermediate segment is 6.3 NM long, a quick estimate of the glidepath altitude at TIRRO is 6.3 x 300 + the 2600 FAF altitude = 4490. So being at 4100 at TIRRO is still below the glidepath, that's good.

However, if we're coming from one of the T's, that turn is going to roll out onto the intermediate segment somewhere inside TIRRO. Will that roll-out point still be below glidepath? Depends on the speed of the aircraft and how well you're set up and flying. If it's not, then the glidepath needle will start to come down as you're in the turn. Will your autopilot capture it in the turn, or in this scenario should you try to intercept it from above, or try to descend back beneath the glidepath before engaging Approach mode? Not necessarily one right answer, just something to think about and brief if you ever have the situation where the glidepath is below, but not THAT MUCH below the altitude at the IF.

Were we literally typing similar answers at the same time?

 

[RussR]

Were we literally typing similar answers at the same time?

Once again!

It happens with creepy regularity.

 

[iamtheari]

There are two things going on with your descent planning. The glide path is a straight line from the runway that you can intercept at or before the FAF depending on your altitude. It is represented by a magenta diamond next to the G3X Touch altitude tape. You can follow it using APR mode on the autopilot. The other is VNAV, which is a straight line from some point on your flight plan with a planned altitude. It is represented by a non-diamond (horizontal chevron?) next to the altitude tape and a TOD marker in the map view. You can follow it using VNAV mode on the autopilot, at least up until you begin an approach (it won’t dive and drive inside the IAF for you). I don’t believe that there is any scenario in which the TOD marker has any connection to the glide path, other than coincidence.

 

[flyingcheesehead]

My confusion here was that I was originally focused on getting lined up with 32 prior to TIRRO.

Not sure you really meant "lined up with 32 prior to TIRRO"? It sounds like you meant you wanted to go down to 2600 after TIRRO? Flying the left base to TIRRO, I'm not sure how you could get lined up with the runway prior to TIRRO.

Pushed APR and the white GP appeared, then past TIRRO it’s still white, I know that JODER is at 2600, so I’m thinking what’s going on, between TIRRO we need to descend from 3100’ to 2600’.

*Can* descend to 2600. You don't "need to".

What I learned is that at your TOD or top of descent, that is when the autopilot will start to descend you, at that point, the GP changes from white to green and then the airplane starts to descend.

Bingo.

I’m happy that I’m doing this myself because sometimes with an instructor, they just do it for you and you kind of know how to do that particular approach but you don’t necessarily understand the brain thinking behind the Garmin to apply in all cases.

If the instructor is doing it for you, you might want to get a different instructor.

On the way back, I went in for the KUGN ILS 23 via WAUKE, winds were 250 at 15 gusting 23-25, the autopilot was having a hard time lining up with the runway, it was basically lined up with the taxiway. I do think the winds felt a lot stronger than 25 but I asked tower for a wind check and the 15-25 was confirmed from 250. I’d guess they were closer to 35-40 kts based upon how my hangar was making noise and past experiences. I don’t understand how that wind pushed me that much off track though.

Was this after you turned inbound, or on vectors? It should not be able to be "blown off course by the wind". Can you download and post your data file for that leg? That would probably show what was going on and let us give you better info.

I expected the autopilot to start a slow descent at TIRRO, GP remained white, I thought I didn’t intercept it so I did a 360 to intercept TIRRO a few more times. Finally I just went with it and after the TOD (about midway from TIRRO to JODER) it started to descent and the GP changed to green. So it was set up properly all along, it just didn’t act as I predicted it would have. If I was hand flying, I would have started descending at TIRRO with plans to cross JODER at 2600’. If that makes sense?

That's a thing that's often done in instrument training but not the real world. On a vertically guided approach, there's no reason to go to the minimum altitude if you're already below glideslope/glidepath. Just maintain altitude and you'll only need to change configuration once. Makes for a much easier approach.

There are two things going on with your descent planning. The glide path is a straight line from the runway that you can intercept at or before the FAF depending on your altitude. It is represented by a magenta diamond next to the G3X Touch altitude tape. You can follow it using APR mode on the autopilot. The other is VNAV, which is a straight line from some point on your flight plan with a planned altitude. It is represented by a non-diamond (horizontal chevron?) next to the altitude tape and a TOD marker in the map view. You can follow it using VNAV mode on the autopilot, at least up until you begin an approach (it won’t dive and drive inside the IAF for you). I don’t believe that there is any scenario in which the TOD marker has any connection to the glide path, other than coincidence.

I don't see any evidence that VNAV was in operation here - No carrot, no VNAV modes. And it appears that the TOD is where the glidepath meets the current altitude.

I went looking to see if there's any reason TOD wouldn't appear for an approach glidepath and didn't find anything. It sounds like the TOD on the G3X Touch comes from the GTN Xi, but the Xi manual is a bit vague about such minutiae.

 

[midlifeflyer]

That's a thing that's often done in instrument training but not the real world. On a vertically guided approach, there's no reason to go to the minimum altitude if you're already below glideslope/glidepath. Just maintain altitude and you'll only need to change configuration once. Makes for a much easier approach.

That’s true and a little weird. For several years now, the FAA has been pushing CDFA. GPS navigators, even using analog equipment, have it built in.
It's what "+V" guidance is all about. The ILS “false glideslope” first appears (inverted) when you are twice as high (AGL) over the PFAF as the published intercept altitude, so it’s pretty much eliminated by procedure design. Yet, flight schools are still teaching dive and drive rather than stabilized descents as though it were a necessity.

There are times a dive is appropriate. Icing conditions. Mandatory crossing altitudes that might not be met by following a 3° vertical path. I have a friend who uses dive and drive as a technique to keep his speed up on approaches to busy airports. But not as SOP.

 

[mandm]

Not sure you really meant "lined up with 32 prior to TIRRO"? It sounds like you meant you wanted to go down to 2600 after TIRRO? Flying the left base to TIRRO, I'm not sure how you could get lined up with the runway prior to TIRRO.


*Can* descend to 2600. You don't "need to".


Bingo.


If the instructor is doing it for you, you might want to get a different instructor.


Was this after you turned inbound, or on vectors? It should not be able to be "blown off course by the wind". Can you download and post your data file for that leg? That would probably show what was going on and let us give you better info.


That's a thing that's often done in instrument training but not the real world. On a vertically guided approach, there's no reason to go to the minimum altitude if you're already below glideslope/glidepath. Just maintain altitude and you'll only need to change configuration once. Makes for a much easier approach.


I don't see any evidence that VNAV was in operation here - No carrot, no VNAV modes. And it appears that the TOD is where the glidepath meets the current altitude.

I went looking to see if there's any reason TOD wouldn't appear for an approach glidepath and didn't find anything. It sounds like the TOD on the G3X Touch comes from the GTN Xi, but the Xi manual is a bit vague about such minutiae.

I was trying to do straight in to TIRRO (i.e. lined up with 32) without the base leg.

For the KUGN ILS 23, I was between WAUKE and the runway. I need to figure out how to download the data and from which source (G3X or GTN650Xi). It was showing (the diamond) as off the lateral path as well, which I thought would attempt to correct but it didn’t. Now don’t get me wrong, I had date night scheduled so I came in and pulled a tight 180 to intercept WAUKE and I didn’t start the approach lined up either, I was too close to the FAC. See photos below.

 

[iamtheari]

I don't see any evidence that VNAV was in operation here - No carrot, no VNAV modes. And it appears that the TOD is where the glidepath meets the current altitude.

I went looking to see if there's any reason TOD wouldn't appear for an approach glidepath and didn't find anything. It sounds like the TOD on the G3X Touch comes from the GTN Xi, but the Xi manual is a bit vague about such minutiae.

The first picture in post #35 above (level at 3100 MSL between TIRRO and JODER, AP GPS and ALT in green and GP armed in white) shows the plane approaching the TOD with a white carat shown beneath the magenta glidepath diamond, and I think a carat shown on the VS tape for around a 300fpm descent. My experience with G3X Touch is limited to the experimental application, so in a certified plane things may be different. I think I can set mine to show a TOD from the G3X or from the GTN Xi, but I always keep it set to the latter. I think that it generates a TOD anytime you have an altitude coming up ahead of you in the flight plan. Arming the VNAV autopilot mode isn't necessary to get the TOD, the cues, or the audible "vertical track" alert one minute before TOD.

 

[Fracpilot]

Mark provided the answer, though I can see that it's not intuitively obvious what exactly VTF is going to do in this case.

As an alternative, for vectors to intercept the intermediate leg you could load the full procedure (from FGT) and then activate the leg from VEYNY (IF) to FATAR (FAF). Same result as VTF, but you don't have to think about what course VTF is going to apply since it's explicit in the leg you activate.

Regards,
Martin

VTF will extend the runway center out 28nm. It will also put the flight plan in SUSP. One the APR button is selected and your within the Garmin parameters of intercept at 2nm from the FAF, the SUSP button needs to be de-selected or the airplane will fly right through the course.

 

[flyingcheesehead]

That’s true and a little weird. For several years now, the FAA has been pushing CDFA. GPS navigators, even using analog equipment, have it built in.
It's what "+V" guidance is all about. The ILS “false glideslope” first appears (inverted) when you are twice as high (AGL) over the PFAF as the published intercept altitude, so it’s pretty much eliminated by procedure design. Yet, flight schools are still teaching dive and drive rather than stabilized descents as though it were a necessity.

Unfortunately, it seems that in this industry a large majority of instructors simply parrot back what their instructor taught them rather than teaching the state of the art, unless they're forced to do otherwise.

I was trying to do straight in to TIRRO (i.e. lined up with 32) without the base leg.

Aaaaahhhh, OK. In the first picture, the white line southwest of TIRRO that curves into the purple line at TIRRO indicates that you loaded the approach with WASOR as the IAF. I'm presuming that you were trying the vectors to final without activation technique (ie, you manually activated the leg from TIRRO to JODER)? @midlifeflyer does that technique allow you to intercept correctly? You're not hitting a purple line, so I guess I wouldn't expect it to. This is a situation where I would use the "Activate vectors to final" so I'm not completely sure of how it behaves when you aren't intercepting on the active leg.

The other option would be to use TIRRO as the IAF; in that case with the HPILPT the GTN should ask you whether you want to do a turn in the hold or proceed straight in. Oddly enough, despite being a normal-looking GPS "T" approach, it has an MSA instead of a TAA so you'll need to either get cleared for the approach "straight in" or do a turn in the hold.

For the KUGN ILS 23, I was between WAUKE and the runway. I need to figure out how to download the data and from which source (G3X or GTN650Xi). It was showing (the diamond) as off the lateral path as well, which I thought would attempt to correct but it didn’t. Now don’t get me wrong, I had date night scheduled so I came in and pulled a tight 180 to intercept WAUKE and I didn’t start the approach lined up either, I was too close to the FAC. See photos below.

Ah, I see. I'm not completely sure what was happening there, but it does look like you got the approach successfully activated and the autopilot was on and in the correct modes.

You are *close* to on course, but not quite. I do see that the FPM appears to be on the runway so it was probably doing a slow correction.

TBH, I pretty much don't bother with ILS approaches any more. A vertically guided GPS approach will be smoother and not subject to any of the issues that come along with radio wave propagation. No bending beams, no false glideslopes, none of that... And these autopilots fly them rock solid.

As far as the data, the various Garmin boxes log things in a very similar format that is pretty nicely human-readable if you import it into a spreadsheet and make a few adjustments. You can also upload it to flysto.net for some REALLY great (and free!) post-flight debriefs with yourself! I've found that the boxes do communicate with each other and log what they get from the other boxes to some extent, but it's not completely 100% interchangeable. Luckily, Flysto will let you just upload all the files and it will merge the ones from the same flights together. I highly recommend doing so, you'll learn a lot!

On the GTN, go to Utilities -> Logs to export the data, you'll find the files on the SD card in a folder called data_log. On the G3X, I believe it logs automatically, you'll find the files in the same place on its card. Same with the G5, I believe - On my GI 275 I need to hook up a USB thumb drive and I don't recall whether I've pulled the data from a G5 before. Its manual is a bit vague as well, just says it logs it on the MicroSD card, but that data_log folder is where you find the files on the SD cards for all of the other Garmin hardware I've worked with that logs to a card.

The first picture in post #35 above (level at 3100 MSL between TIRRO and JODER, AP GPS and ALT in green and GP armed in white) shows the plane approaching the TOD with a white carat shown beneath the magenta glidepath diamond, and I think a carat shown on the VS tape for around a 300fpm descent. My experience with G3X Touch is limited to the experimental application, so in a certified plane things may be different. I think I can set mine to show a TOD from the G3X or from the GTN Xi, but I always keep it set to the latter. I think that it generates a TOD anytime you have an altitude coming up ahead of you in the flight plan. Arming the VNAV autopilot mode isn't necessary to get the TOD, the cues, or the audible "vertical track" alert one minute before TOD.

This is the part where my wife (or my mother) would pipe up with a story of me not seeing something that I'm looking directly at that's right in my face. Facepalm.

Now that I go back to the first picture, I see the (white) carrots. I was looking for purple ones. Derp.

VTF will extend the runway center out 28nm. It will also put the flight plan in SUSP. One the APR button is selected and your within the Garmin parameters of intercept at 2nm from the FAF, the SUSP button needs to be de-selected or the airplane will fly right through the course.

I don't think I've ever flown a plane with Garmin stuff where VTF required me to un-suspend???

 

[midlifeflyer]

Aaaaahhhh, OK. In the first picture, the white line southwest of TIRRO that curves into the purple line at TIRRO indicates that you loaded the approach with WASOR as the IAF. I'm presuming that you were trying the vectors to final without activation technique (ie, you manually activated the leg from TIRRO to JODER)? @midlifeflyer does that technique allow you to intercept correctly

In the first picture in the post you are responding to, the active GPS leg is from the FAF to the runway, and the airplane is on a 2.5 mile final. It is also in green needles, so GPS is informational, feeding neither CDI nor AP (nor even +V advisory guidance).



With vectors to final, you are flying a vector - an assigned heading to intercept - to the extended FAC. In green needles, APR will continue that assigned heading until interception and turn unbound. Just like before GPS existed.

In my VTF SOP, green needles are on the CDI and the leg to the FAF activated on the GPS flight plan when I receive the first vector. If I recall correctly, @mandm was self vectoring. They could have been “bad” vectors, pointing at the FAF rather than a point outside the approach gate. I can’t tell from the pictures what was activated before green needles.

 

[mandm]

Thank you for all of the comments.

Went flying last night and heading east I turned on the autopilot and it started to do a 180 turn, I’m like no, that’s not what I want so I take over and hand fly and turn on the autopilot with heading mode on.



Duh, I look at the screen, the KUGN ILS 23 NAV frequency is loaded in, the green lines are present on the heading indicator and the LOC mode is active. Flip up the GTN650Xi to NAV page and press CDI to adjust from LOC / VLOC to GPS (ground based vs satellite based).



Now the green changes to magenta, in the direction I want to go, press direct to and then activate the autopilot under NAV mode. VLOC / LOC changes to GPS. Good to go!

Played with the settings and organization of the G3X and went through most of the options. Cool! Traffic in the smaller right box, awesome. Engine instruments on the right, awesome.

Landed at 66G, called the restaurant shuttle, and wah la, all you can eat with take home boxes, eating the leftovers right now as I’m typing this message. Met another guy at the airport who taught me how to turn the runway lights on, 122.95 instead of the CTAF, good to go.



On the way back, a short soft field runway, airspeed was building slowly, a tight climbing right turn to stay clear of trees. Called up flight following and turned on the autopilot. Beautiful!



We crossed the pond and I loaded and activated the KUGN RNAV 23 with LIRIC as the IAF with no course reversal. Look at that 67mph headwind, literally dead on!! So now I’m NAV mode A/P with an altitude hold ALT at 6500’. I want to keep some altitude over the pond, but now the question is can the A/P automatically descend? What mode is needed for that? So I’m wondering about this, I know I can manually set the desired ALT with a IAS or VS descent. I haven’t tried VNAV yet. I’m also thinking ALT mode would be overriding any other settings and keeping me at 6500’. So I press ALT and now ALT changes to PIT with a white GP. What does PIT mean and what do those mean together? I adjusted to 2300’ to get where I needed to be at LIRIC. Once at LIRIC I figured I’m on the approach so I pressed APR. While the autopilot flew this approach perfectly down to minimums, it does open a number of questions for me. Such as when you load and activate an approach, can you at this point just press APR and will the autopilot fly you down to minimums? Imagining I have nothing in the way from 66G to KUGN RNAV 23 via LIRIC (which you don’t when above 4800’), the autopilot could in theory fly the airplane from just after clearing the trees at 66G down to minimums at KUGN without any inputs needed from the pilot (minus fuel, gear, flaps, and throttle/prop/mixture controls).

 

[RussR]

Thank you for all of the comments.

Went flying last night and heading east I turned on the autopilot and it started to do a 180 turn, I’m like no, that’s not what I want so I take over and hand fly and turn on the autopilot with heading mode on.

View attachment 138947

Duh, I look at the screen, the KUGN ILS 23 NAV frequency is loaded in, the green lines are present on the heading indicator and the LOC mode is active. Flip up the GTN650Xi to NAV page and press CDI to adjust from LOC / VLOC to GPS (ground based vs satellite based).

View attachment 138948

Now the green changes to magenta, in the direction I want to go, press direct to and then activate the autopilot under NAV mode. VLOC / LOC changes to GPS. Good to go!

Played with the settings and organization of the G3X and went through most of the options. Cool! Traffic in the smaller right box, awesome. Engine instruments on the right, awesome.

Landed at 66G, called the restaurant shuttle, and wah la, all you can eat with take home boxes, eating the leftovers right now as I’m typing this message. Met another guy at the airport who taught me how to turn the runway lights on, 122.95 instead of the CTAF, good to go.

View attachment 138950

On the way back, a short soft field runway, airspeed was building slowly, a tight climbing right turn to stay clear of trees. Called up flight following and turned on the autopilot. Beautiful!

View attachment 138949

We crossed the pond and I loaded and activated the KUGN RNAV 23 with LIRIC as the IAF with no course reversal. Look at that 67mph headwind, literally dead on!! So now I’m NAV mode A/P with an altitude hold ALT at 6500’. I want to keep some altitude over the pond, but now the question is can the A/P automatically descend? What mode is needed for that? So I’m wondering about this, I know I can manually set the desired ALT with a IAS or VS descent. I haven’t tried VNAV yet. I’m also thinking ALT mode would be overriding any other settings and keeping me at 6500’. So I press ALT and now ALT changes to PIT with a white GP. What does PIT mean and what do those mean together? I adjusted to 2300’ to get where I needed to be at LIRIC. Once at LIRIC I figured I’m on the approach so I pressed APR. While the autopilot flew this approach perfectly down to minimums, it does open a number of questions for me. Such as when you load and activate an approach, can you at this point just press APR and will the autopilot fly you down to minimums? Imagining I have nothing in the way from 66G to KUGN RNAV 23 via LIRIC (which you don’t when above 4800’), the autopilot could in theory fly the airplane from just after clearing the trees at 66G down to minimums at KUGN without any inputs needed from the pilot (minus fuel, gear, flaps, and throttle/prop/mixture controls).

Literally every question you have asked in this thread would be covered with a little training with a competent CFI - AND would be far better answered in person while operating the exact equipment you have, even trying things on the ground, followed by scenarios in the air. Knowing how your autopilot works is not only a useful skill, but an important safety consideration as well. Many pilots I've worked with over the years have no idea what capabilities their autopilot system has, and when we do a flight review or other training, I often hear "wow, I had no idea it would do that" - because they never got good, thorough training. "New autopilot operation" was a staple of my work for years with pilots who upgraded their avionics.

You have implied before in this thread that you don't want a CFI along (for reasons I don't understand), but really, that's the answer here. Find one that's good with the equipment you have and develop a relationship with them - just a few hours with them now will pay off many times over in the future.

 

[iamtheari]

We crossed the pond and I loaded and activated the KUGN RNAV 23 with LIRIC as the IAF with no course reversal. Look at that 67mph headwind, literally dead on!! So now I’m NAV mode A/P with an altitude hold ALT at 6500’. I want to keep some altitude over the pond, but now the question is can the A/P automatically descend? What mode is needed for that? So I’m wondering about this, I know I can manually set the desired ALT with a IAS or VS descent. I haven’t tried VNAV yet. I’m also thinking ALT mode would be overriding any other settings and keeping me at 6500’. So I press ALT and now ALT changes to PIT with a white GP. What does PIT mean and what do those mean together? I adjusted to 2300’ to get where I needed to be at LIRIC. Once at LIRIC I figured I’m on the approach so I pressed APR. While the autopilot flew this approach perfectly down to minimums, it does open a number of questions for me. Such as when you load and activate an approach, can you at this point just press APR and will the autopilot fly you down to minimums? Imagining I have nothing in the way from 66G to KUGN RNAV 23 via LIRIC (which you don’t when above 4800’), the autopilot could in theory fly the airplane from just after clearing the trees at 66G down to minimums at KUGN without any inputs needed from the pilot (minus fuel, gear, flaps, and throttle/prop/mixture controls).

Breaking it down a bit...

Did you ever use a Garmin GPS that had a VSR (vertical speed required) readout? VNAV is that but on steroids. Here's how to use it:
1. Put a flight plan into the GTN Xi. Don't just use Direct To. Instead, go to the flight plan page and put your waypoints in order. The substitute for Direct To is just to put your departure and destination airports into the plan. You can use Direct To toward a waypoint in the flight plan later on, but the prerequisite of having a flight plan entered will pay dividends later. (Shortcut to go direct somewhere, if it's not what pops up when you hit the Direct To button: Flight plan page, tap the waypoint, then hit the Direct To button, then tap Activate or whatever it offers.)
2. On the flight plan page, enter a desired altitude for some future waypoint. For example, tap the destination waypoint's altitude box, choose AGL instead of MSL, enter 1000 feet, optionally choose an along-track offset like 3nm (after choosing AGL and entering the altitude), and then save it. Don't use the VNAV Direct To or whatever that option is called.
3. The avionics will show a top of descent (TOD). When you are 1 minute from it, they should also alert "vertical track" into your headset. At some point before reaching the TOD, assuming you are in altitude hold mode, do two things: Set a lower altitude preselect (such as that 1000 AGL altitude you entered earlier, unless ATC restricts you), then push the VNAV button on the autopilot controller (or the G3X Touch Flight Controls page). That will arm VNAV mode and, when you reach TOD, activate it with a descent angle to reach your desired bottom altitude, leveling off at a preselected altitude if your preselect is set higher than the bottom altitude from the flight plan.

PIT means Pitch mode, and it just holds a pitch relative to the horizon. This is the default vertical mode, just as ROL (roll) is the default lateral mode. ALT, IAS, VS, VNAV, GS, and GP are the other vertical modes. When you turn the autopilot on without having selected a vertical mode, it defaults to PIT. When you turn off a vertical mode (such as pressing ALT when it was in ALT mode), it defaults back to PIT. When in PIT mode, using the wheel on the autopilot controller will change the desired pitch of the airplane, just as in IAS and VS modes it will adjust the desired indicated airspeed or vertical speed.

APR mode is mostly for ILS and LPV approaches. I think it will follow the advisory vertical guidance from non-precision approaches but I haven't experimented with that. You can arm APR mode basically anytime before you intercept the glideslope/glidepath diamond. I think most people arm it at some point between being cleared for the approach and glideslope/glidepath intercept. Keep in mind that APR arms a vertical mode, and that you should already be on an appropriate lateral mode (which could be a variety of things, but most often will be an active GPS navigation mode or an active HDG mode with GPS or LOC armed). You also need to program the avionics appropriately to the approach, including switching the CDI to green needles for an ILS (unless your GPS auto-switches, which you would want to babysit even if it were set to do that).

I hope some of that helps.

Literally every question you have asked in this thread would be covered with a little training with a competent CFI. Knowing how your autopilot works is not only a useful skill, but an important safety consideration as well. Many pilots I've worked with over the years have no idea what capabilities their autopilot system has, and when we do a flight review or other training, I often hear "wow, I had no idea it would do that" - because they never got good, thorough training. "New autopilot operation" was a staple of my work for years with pilots who upgraded their avionics.

You have implied before in this thread that you don't want a CFI along (for reasons I don't understand), but really, that's the answer here. Find one that's good with the equipment you have and develop a relationship with them - just a few hours with them now will pay off many times over in the future.

This will help even more. Even if you don't go flying with a CFI, you should find a pilot who is familiar with these avionics to ride along with you. I've picked up some tricks from other G3X Touch pilots even in short VFR flights.

 

[RussR]

Landed at 66G...

Met another guy at the airport who taught me how to turn the runway lights on, 122.95 instead of the CTAF, good to go.

That concerns me - I don't see any mention of runway lights in the Chart Supplement or anything about pilot-control being on a different frequency. Nothing on the chart indicating lights either. Did you get any sense of why they're not shown in the usual sources?

 

[midlifeflyer]

What does PIT mean and what do those mean together?

PIT mean “pitch,” it’s the default vertical mode. Holds whatever pitch the airplane was in when you released ALT. When you turned off ALT and didn’t tell the autopilot what to do (like VS, IAS, OF APR, it returns to the default.

 

[Hang 4]

I'd echo @RussR comments. You're making it harder than it needs to be. Note on your first picture the "from/to" arrow is pointing opposite of your heading and there's a white "BC" annunciation. Pretty sure that's "back course" and it was expecting you to fly the localizer for the opposite runway. Also note on the last picture that your heading bug is opposite your course. It's a real good habit to keep it set to your heading in case NAV mode does something unexpected or you get vectors from ATC. Just push heading vs turn the bug and then set heading.

 

[mandm]

Literally every question you have asked in this thread would be covered with a little training with a competent CFI - AND would be far better answered in person while operating the exact equipment you have, even trying things on the ground, followed by scenarios in the air. Knowing how your autopilot works is not only a useful skill, but an important safety consideration as well. Many pilots I've worked with over the years have no idea what capabilities their autopilot system has, and when we do a flight review or other training, I often hear "wow, I had no idea it would do that" - because they never got good, thorough training. "New autopilot operation" was a staple of my work for years with pilots who upgraded their avionics.

You have implied before in this thread that you don't want a CFI along (for reasons I don't understand), but really, that's the answer here. Find one that's good with the equipment you have and develop a relationship with them - just a few hours with them now will pay off many times over in the future.

While that is one avenue that could be taken, I’m learning and understanding here just fine from the many posts above. I have trained with a 650/500/5 combo, and while flying or in student mode, I just don’t have the mental capacity to ask these questions. Here is a safe space for me to think about my questions and ask them here albeit your post saying go get a CFI is more of a toughen up and do it my way approach which may be off putting for some people who are trying to learn. You don’t know peoples situations, time to airport, scheduling, etc. It isn’t as simple as you put it. Your input is duly noted, hopefully you better understand my viewpoint from my response.

 

[mandm]

That concerns me - I don't see any mention of runway lights in the Chart Supplement or anything about pilot-control being on a different frequency. Nothing on the chart indicating lights either. Did you get any sense of why they're not shown in the usual sources?

Guessing because they are on a CTAF? Not sure.

 

[robin ardoin]

As @Hang 4 mentioned, it is good practice to periodically sync your heading bug with your current heading when in NAV mode. This reduces the chance of having the AP fly drastic heading changes if having to enter HDG mode if instructed by ATC to make a heading change. On the GFC 500, depressing the HDG knob will automatically sync the bug with your current heading. I do this as a matter of habit when a course changes or wind correction causes a heading change. Also, ALWAYS review your heading bug setting prior to engaging HDG mode.

 

[TCABM]

While that is one avenue that could be taken, I’m learning and understanding here just fine from the many posts above. I have trained with a 650/500/5 combo, and while flying or in student mode, I just don’t have the mental capacity to ask these questions. ….

The Garmin GTN trainer app in a 1G/0 airspeed environment is a great way to work through the various functions and capabilities while referencing the appropriate AFMS suppllement(s) and other references for the low, low cost of nothing except time.

If you’ve never used the trainer app, it’s really worthwhile.

 

[flyingcheesehead]

In the first picture in the post you are responding to, the active GPS leg is from the FAF to the runway, and the airplane is on a 2.5 mile final. It is also in green needles, so GPS is informational, feeding neither CDI nor AP (nor even +V advisory guidance).

View attachment 138936

With vectors to final, you are flying a vector - an assigned heading to intercept - to the extended FAC. In green needles, APR will continue that assigned heading until interception and turn unbound. Just like before GPS existed.

In my VTF SOP, green needles are on the CDI and the leg to the FAF activated on the GPS flight plan when I receive the first vector. If I recall correctly, @mandm was self vectoring. They could have been “bad” vectors, pointing at the FAF rather than a point outside the approach gate. I can’t tell from the pictures what was activated before green needles.

Sorry @midlifeflyer I created some more confusion there. I was talking about the first picture in the first post that had pictures, the RNAV 32 into KJVL. That one looked like it was loaded from the left base but the intermediate leg was active and the OP was trying unsuccessfully to line up on that leg from outside the IF. And now that I'm thinking about it, I think that should maybe work after all, but the leg does start with the second half of the base-to-final turn, so maybe not.

Maybe @mandm just needs to fly up to UES and pick me up so I can help him out in person.

Edit: @mandm This is a serious offer, I'd be happy to go flying with you. I don't have a CFI, but I do have a lot of time behind various Garmin boxes and recently helped my old flying club set up a training program for their new panel which looks an awful lot like yours.

 

[midlifeflyer]

While that is one avenue that could be taken, I’m learning and understanding here just fine from the many posts above. I have trained with a 650/500/5 combo, and while flying or in student mode, I just don’t have the mental capacity to ask these questions. Here is a safe space for me to think about my questions and ask them here albeit your post saying go get a CFI is more of a toughen up and do it my way approach which may be off putting for some people who are trying to learn. You don’t know peoples situations, time to airport, scheduling, etc. It isn’t as simple as you put it. Your input is duly noted, hopefully you better understand my viewpoint from my response.

Yes and no. Yes, some people can move to a different setup, but some of your questions reflect a lack of knowledge of a some basics that are identical regardless of specific Garmin system. I find that more often than I should when doing transition training - a pilot who never learned more than the bare minimum in their previous system. Btw, this has exactly zero to do with native intelligence.

Just two for example are when and how the GS becomes active and what PIT is. The first is practically universal whether GTN, GNS, G1000, Avidyne IFD, or Dynon HDX, and whether coupled to a Garmin, Aspen or other PFD, or for that matter, analog instruments. On the second, all autopilots have a default mode it reverts to when you don’t tell it what else to do.

We haven’t even gotten to the “gotchas.” You may think so, but you haven’t mentioned even one yet. Nothing but Level 101 basics so far, many of which I was frankly surprised you didn’t already know.

I don’t know what you are picturing, but when I do transition training, i incorporate flight, ground, and homework and some applicable YouTube videos. It’s not a one-shot deal. The client barely needs to know what questions to ask. In flight, I don’t correct every little thing in flight. Instead I make notes and, if the client agrees, I even video so they can see what I’m seeing. I’ve had client insist something happened or didn’t happen…until they watched the video.

Sorry, but from the discussion it really does seem you are making this much more difficult on yourself. Why, I don’t know.

 

[mandm]

Sorry @midlifeflyer I created some more confusion there. I was talking about the first picture in the first post that had pictures, the RNAV 32 into KJVL. That one looked like it was loaded from the left base but the intermediate leg was active and the OP was trying unsuccessfully to line up on that leg from outside the IF. And now that I'm thinking about it, I think that should maybe work after all, but the leg does start with the second half of the base-to-final turn, so maybe not.

Maybe @mandm just needs to fly up to UES and pick me up so I can help him out in person.

Edit: @mandm This is a serious offer, I'd be happy to go flying with you. I don't have a CFI, but I do have a lot of time behind various Garmin boxes and recently helped my old flying club set up a training program for their new panel which looks an awful lot like yours.

I usually fly later in the day but I’d be keen, any dinner or late lunch spots to fly into around you?

 

[mandm]

Yes and no. Yes, some people can move to a different setup, but some of your questions reflect a lack of knowledge of a some basics that are identical regardless of specific Garmin system. I find that more often than I should when doing transition training - a pilot who never learned more than the bare minimum in their previous system. Btw, this has exactly zero to do with native intelligence.

Just two for example are when and how the GS becomes active and what PIT is. The first is practically universal whether GTN, GNS, G1000, Avidyne IFD, or Dynon HDX, and whether coupled to a Garmin, Aspen or other PFD, or for that matter, analog instruments. On the second, all autopilots have a default mode it reverts to when you don’t tell it what else to do.

We haven’t even gotten to the “gotchas.” You may think so, but you haven’t mentioned even one yet. Nothing but Level 101 basics so far, many of which I was frankly surprised you didn’t already know.

I don’t know what you are picturing, but when I do transition training, i incorporate flight, ground, and homework and some applicable YouTube videos. It’s not a one-shot deal. The client barely needs to know what questions to ask. In flight, I don’t correct every little thing in flight. Instead I make notes and, if the client agrees, I even video so they can see what I’m seeing. I’ve had client insist something happened or didn’t happen…until they watched the video.

Sorry, but from the discussion it really does seem you are making this much more difficult on yourself. Why, I don’t know.

It’s on my to do list

 

[RussR]

Yes and no. Yes, some people can move to a different setup, but some of your questions reflect a lack of knowledge of a some basics that are identical regardless of specific Garmin system. I find that more often than I should when doing transition training - a pilot who never learned more than the bare minimum in their previous system. Btw, this has exactly zero to do with native intelligence.

Just two for example are when and how the GS becomes active and what PIT is. The first is practically universal whether GTN, GNS, G1000, Avidyne IFD, or Dynon HDX, and whether coupled to a Garmin, Aspen or other PFD, or for that matter, analog instruments. On the second, all autopilots have a default mode it reverts to when you don’t tell it what else to do.

We haven’t even gotten to the “gotchas.” You may think so, but you haven’t mentioned even one yet. Nothing but Level 101 basics so far, many of which I was frankly surprised you didn’t already know.

I don’t know what you are picturing, but when I do transition training, i incorporate flight, ground, and homework and some applicable YouTube videos. It’s not a one-shot deal. The client barely needs to know what questions to ask. In flight, I don’t correct every little thing in flight. Instead I make notes and, if the client agrees, I even video so they can see what I’m seeing. I’ve had client insist something happened or didn’t happen…until they watched the video.

Sorry, but from the discussion it really does seem you are making this much more difficult on yourself. Why, I don’t know.

Thank you Mark. You saved me a bunch of typing. I could just repeat literally everything in your post. We both see the same things over and over again.

 

[flyingcheesehead]

Went flying last night and heading east I turned on the autopilot and it started to do a 180 turn, I’m like no, that’s not what I want so I take over and hand fly and turn on the autopilot with heading mode on.

View attachment 138947

The "scoreboard" (the little window at the top that shows all of your autopilot modes) tells all. If you were trying to engage NAV mode, well, look at the scoreboard and the HSI. It was probably going to try and intercept the ILS localizer outbound, given your heading and the "BC" in the scoreboard.

Nav doesn't work 'til the HSI is doing what you want. It's worth adding a couple of items to your before takeoff checklist to get the flight plan entered and the HSI set up the way it should be. You noticed the green needles and VLOC instead of GPS, but that's the sort of thing that you want to ensure is set up and ready on the ground EVERY TIME so that you're in the habit. Taking off into IMC like this can kill you, so it's good to keep those habits VFR too.

We crossed the pond and I loaded and activated the KUGN RNAV 23 with LIRIC as the IAF with no course reversal. Look at that 67mph headwind, literally dead on!! So now I’m NAV mode A/P with an altitude hold ALT at 6500’. I want to keep some altitude over the pond, but now the question is can the A/P automatically descend? What mode is needed for that?

That, is VNAV.

You need to do three things to get VNAV to work:

1) Set the VNAV constraint on the GTN by setting an altitude for a fix in the flight plan. Since you had an approach already set up, the altitudes at the fixes on the approach should already be in there. It's also worth practicing manually putting in an altitude at a fix that's in your flight plan as well as creating an along-track offset fix - This function is REALLY useful when you get a clearance like "Cross 20 miles east of Farmington and maintain 4000" you can do it automatically.
2) Set the altitude bug to the new altitude. If you're holding altitude (ALT is green) just switching the bug won't cause the autopilot to deviate from where you are.
3) Hit the "VNAV" button on the autopilot mode controller.

If you miss any of those, nothing will happen.

So I’m wondering about this, I know I can manually set the desired ALT with a IAS or VS descent. I haven’t tried VNAV yet. I’m also thinking ALT mode would be overriding any other settings and keeping me at 6500’.

IAS and VS are "now" modes. VNAV is a "when we get to the TOD" mode, so it will not override ALT, nor will ALT keep it from working at the right time. If you hit VNAV when you don't have a VNAV constraint properly set up it'll do nothing, but if you did that part correctly you should see ALT in green and VNAV in white. When you get to TOD, ALT will go away and VNAV will turn green.

So I press ALT and now ALT changes to PIT with a white GP. What does PIT mean and what do those mean together?

PIT = Pitch. As previously mentioned, it's the default vertical mode just like ROL is the default lateral mode. If you're in ALT and you press ALT, you're turning ALT off so it'll switch to PIT. Same thing will happen in the other modes, for example, if you are in VS and you hit VS, it'll go into PIT.

The white GP stands for Glide Path, which refers to the vertical component of the approach you have loaded. GS and GP are analogous, GS is for GlideSlope on an ILS while GP is for GlidePath on an RNAV approach.

So, PIT in green and GP in white means that it'll maintain the set pitch until it intercepts the approach glidepath (as long as you don't intercept any terrain or obstacles first! )

I adjusted to 2300’ to get where I needed to be at LIRIC.

That explains why it also has ALTS in white... Which means it'd intercept 2300, though I must admit I've never tried arming modes "out of order" like that to see what happened.

Once at LIRIC I figured I’m on the approach so I pressed APR.

Remember that what APR means is "It's OK to go down when I get to the glidepath." You don't need to be on the approach to hit APR, nor do you necessarily want to hit APR even after you're on the approach (for example, ATC tells you to "Intercept the localizer" but doesn't clear you for the approach yet).

Such as when you load and activate an approach, can you at this point just press APR and will the autopilot fly you down to minimums?

Yes. But, the best practice is to hit APR when ATC clears you for the approach, with a few scenarios that are exceptions.

Imagining I have nothing in the way from 66G to KUGN RNAV 23 via LIRIC (which you don’t when above 4800’), the autopilot could in theory fly the airplane from just after clearing the trees at 66G down to minimums at KUGN without any inputs needed from the pilot (minus fuel, gear, flaps, and throttle/prop/mixture controls).

Kinda.

While it will probably work, "just clearing the trees" is likely below the minimum autopilot engagement altitude.

Also, VNAV is meant for descents and even then, only one. You can do a VNAV descent followed by an approach descent, but you can't just create a flight plan with multiple descending and climbing VNAV restrictions for something like the Chicago lakeshore and just hit "VNAV" and forget it.

For a flight like you took from 66G to KUGN, you can have the autopilot fly the whole flight from 800 AGL on climbout (minimum engagement altitude) down to minimums on the approach on the other end, but you'll still have a few buttons and knobs to deal with along the way.

For setup, you'd need to do the following:

* Set up your flight plan, including the approach, and ensure there's a vertical constraint included for VNAV, such as 2300 at LIRIC.
* Hit your TOGA button, which should put you in TO mode for both pitch and roll. (This is equivalent to PIT at the proper attitude for your plane and ROL with wings level.)
* Set your heading bug to runway heading
* Set your altitude bug to your desired cruising altitude.
* Ensure the HSI is showing the proper track for the first leg of your flight plan (it should do this automatically, just check it to be sure)

Then, take off, hand flying into the flight director. Hit IAS and set your desired climb speed, and HDG to maintain the runway heading you set earlier. At 800 AGL, hit AP to engage the autopilot. Adjust the heading to turn towards your course and then hit nav to arm an intercept, or just hit -D> and NAV.

When you get to cruise and ALT is green (and after doing your cruise checklist), hit VNAV and set the altitude bug down to the constraint you set in the flight plan. If that constraint is in a spot where you can intercept the approach glidepath without more than a single level-off at the constraint altitude, just hit APR when you're cleared for the approach and disconnect at minimums.

It's pretty cool, but it's definitely not set-it-and-forget-it, nor should it be. You still need to actively monitor your status for situational awareness.

While that is one avenue that could be taken, I’m learning and understanding here just fine from the many posts above. I have trained with a 650/500/5 combo, and while flying or in student mode, I just don’t have the mental capacity to ask these questions. Here is a safe space for me to think about my questions and ask them here albeit your post saying go get a CFI is more of a toughen up and do it my way approach which may be off putting for some people who are trying to learn. You don’t know peoples situations, time to airport, scheduling, etc. It isn’t as simple as you put it. Your input is duly noted, hopefully you better understand my viewpoint from my response.

Hopefully you're getting good info here. I think the concern is that you should be developing good habits right away, not stumbling into them a few at a time and needing to knock out the bad ones. On the other hand, I do keep coming up with situations where it's worth testing the system's behavior in edge cases, so there's some value to being in flight and learning as well.

The Garmin GTN trainer app in a 1G/0 airspeed environment is a great way to work through the various functions and capabilities while referencing the appropriate AFMS suppllement(s) and other references for the low, low cost of nothing except time.

If you’ve never used the trainer app, it’s really worthwhile.

It is, but they have separate apps for GTN Xi, G3X, and some others but they don't let you put together a full panel and learn how they interact with each other, so there are limits to what you can learn. They're a good way to start, but you really need to get into the airplane before too long.

 

[flyingcheesehead]

I usually fly later in the day but I’d be keen, any dinner or late lunch spots to fly into around you?

Bessie's at JVL, Jet Room at MSN, Several things walkable from OSH, courtesy car into town at 3D2, Flight Deck at RPJ, and lots of stuff that's kind of in the opposite direction from where you are (Lynnie Que's, Pilot Pete's, etc). Plenty of options!

 

[mandm]

Thank you for the replies, we will go flying together sometime. I’ll also try to find a CFII who is experienced in these avionics and do an IPC as well. Also going for my CFI ticket this year as well.

 

[Hang 4]

I'd suggest you simplify your "approach" to approaches. While this might be one of those differs by region things, I've rarely had a use case for VNAV in actual IMC. Usually get a "descend and maintain XXXX" and vectors to the approach. For descend - Bug new altitude and VS (Vertical Speed) set to -500 fpm (or whatever makes sense for your aircraft). For heading, bug the heading given and push HDG on the AP. When getting vectors, ATC will be having you join the course below the glide slope. Make sure the leg you are going to intercept is active. (or have VTF selected). Press APR when cleared and your done with button pushing til minimums. These two things are good to have as muscle memory items so you can reach for the knobs without looking and see the changes on screen.

Here's where I'll have to defer to others, I have a G500 and whatever I set for minimums only provides an annunciation, the AP doesn't know or care. It will gladly fly into the runway. If there was some way to do that, I don't trust the automation enough to do that anyways. I count down the last 500 feet above minimums by each 100 and am on a hair trigger to go missed if I don't clear.

 

[midlifeflyer]

Here's where I'll have to defer to others, I have a G500 and whatever I set for minimums only provides an annunciation, the AP doesn't know or care. It will gladly fly into the runway.

Even with a GFC autopilot, VS, IAS, and VNAV modes are the only descent modes that capture and level off at a target altitude. APR mode will happily fly you into the ground. There may be one out there (maybe one of the more advanced x1000 or FMS systems?), but I haven't come across of PFD that feeds the minimums reference to the autopilot as a hard altitude.

Besides, why would it level off? On a 3D approach (with official vertical guidance), you are either landing or going missed. You don't level off. On a 2D approach, you might level off if you dive and drive to an MDA rather than do a stabilized CDFA but, even then, most of the time the result is the same - land or go missed (unless you are circling).

If there was some way to do that, I don't trust the automation enough to do that anyways. I count down the last 500 feet above minimums by each 100 and am on a hair trigger to go missed if I don't clear.

If one is trusting any autopilot to the degree that they abdicate PIC responsibility by trusting without verifying - in any phase of flight - they are doing it wrong.

 

[bbchien]

Basically on the garmin systme you need to regard that it will only fly the coupled approach if you intereceipt at a less than acute angle and five miles outside the IAF. Itg's transparent- if the vertal guidance indicator doesn't appear it's nNOT going to descend.

In that case you engage NAV and and fly the altitudes.

 

[RussR]

Basically on the garmin systme you need to regard that it will only fly the coupled approach if you intereceipt at a less than acute angle and five miles outside the IAF. Itg's transparent- if the vertal guidance indicator doesn't appear it's nNOT going to descend.

In that case you engage NAV and and fly the altitudes.

5 nm outside the IAF? Did you mean FAF? Even then that's not correct, it should couple with an intercept well within 5 nm. In fact, the ATC vectoring minimum is 2 or 3 nm depending on type of procedure and some other factors.

 

[flyingcheesehead]

I'd suggest you simplify your "approach" to approaches. While this might be one of those differs by region things, I've rarely had a use case for VNAV in actual IMC.

While it is pretty uncommon in small GA, there are some cases where it might be used:

1) MSP sometimes uses crossing restrictions to keep you well clear of their Bravo. I've also gotten a crossing restriction from Houston in a piston single.
2) Pilot's Discretion descents - While you don't have to use the VNAV function to ensure compliance with anything here, it does allow you to set the boxes up to automatically begin the descent where you want to, maybe to arrive at the approach altitude at the IAF for example.

In VMC, of course, the old "pattern altitude at 3 or 5 miles before the field" is a great use for it as well.

Here's where I'll have to defer to others, I have a G500 and whatever I set for minimums only provides an annunciation, the AP doesn't know or care. It will gladly fly into the runway. If there was some way to do that, I don't trust the automation enough to do that anyways. I count down the last 500 feet above minimums by each 100 and am on a hair trigger to go missed if I don't clear.

The G3X allows you to set baro minimums and it gives you a minimums bug plus (if it's wired properly) a "Minimums, Minimums" audio alert:


But, as you noted, it will not level out here. If you're doing a dive-and-drive and want it to level out, you need to use the regular altitude bug and VS mode. If you're doing a vertically guided approach, when you hit minimums you're either going to continue and land or you're going to hit TOGA, increase throttle and get the heck outta dodge.

 

[flyingcheesehead]

As @Hang 4 mentioned, it is good practice to periodically sync your heading bug with your current heading when in NAV mode. This reduces the chance of having the AP fly drastic heading changes if having to enter HDG mode if instructed by ATC to make a heading change. On the GFC 500, depressing the HDG knob will automatically sync the bug with your current heading. I do this as a matter of habit when a course changes or wind correction causes a heading change. Also, ALWAYS review your heading bug setting prior to engaging HDG mode.

This. Other than possibly using the heading bug to mark your assigned runway (and thus be on runway heading) when you're taxiing out for takeoff, I can't think of a time where the heading bug should be anywhere other than straight up.

On almost all Garmin gear, pushing the knob you use to adjust the heading will put the heading bug at your current heading. Recognizing that the best practice is to always keep it where you are, some newer stuff such as the G3000 will actually engage a "heading sync" mode, where the heading bug always stays on your current heading, even through turns, unless/until you manually twist it to a new heading, and pushing the knob again turns the sync mode off. I kinda hope they make it work this way with more of their equipment via software updates - It certainly saves a lot of wear and tear on that button behind the knob!

 

[iamtheari]

VNAV is also convenient as a sanity check in case ATC forgets to descend you. When the calculated VSR creeps up on 1,000 fpm, you may want to check in. It also helps to decide when to exercise your pilot's discretion for a descent where you want to wait as long as reasonable before diving through a layer that could, for instance, deposit some ice on you.

As far as the heading bug pointed somewhere other than the nose of the plane, one more example comes to mind: Departures like "enter controlled airspace on heading 150" and similar heading-after-takeoff scenarios.

 

[mandm]

While it is pretty uncommon in small GA, there are some cases where it might be used:

1) MSP sometimes uses crossing restrictions to keep you well clear of their Bravo. I've also gotten a crossing restriction from Houston in a piston single.
2) Pilot's Discretion descents - While you don't have to use the VNAV function to ensure compliance with anything here, it does allow you to set the boxes up to automatically begin the descent where you want to, maybe to arrive at the approach altitude at the IAF for example.

In VMC, of course, the old "pattern altitude at 3 or 5 miles before the field" is a great use for it as well.


The G3X allows you to set baro minimums and it gives you a minimums bug plus (if it's wired properly) a "Minimums, Minimums" audio alert:

View attachment 138977
But, as you noted, it will not level out here. If you're doing a dive-and-drive and want it to level out, you need to use the regular altitude bug and VS mode. If you're doing a vertically guided approach, when you hit minimums you're either going to continue and land or you're going to hit TOGA, increase throttle and get the heck outta dodge.

I started reading the manual but frankly it’s so many options, it’s impossible to remember all of them. But I do want to play with VNAV, lean assist and minimums next time I fly.

 

[mandm]

This. Other than possibly using the heading bug to mark your assigned runway (and thus be on runway heading) when you're taxiing out for takeoff, I can't think of a time where the heading bug should be anywhere other than straight up.

On almost all Garmin gear, pushing the knob you use to adjust the heading will put the heading bug at your current heading. Recognizing that the best practice is to always keep it where you are, some newer stuff such as the G3000 will actually engage a "heading sync" mode, where the heading bug always stays on your current heading, even through turns, unless/until you manually twist it to a new heading, and pushing the knob again turns the sync mode off. I kinda hope they make it work this way with more of their equipment via software updates - It certainly saves a lot of wear and tear on that button behind the knob!

Very true, I was taught this but I do tend to forget to do this.

 

[TCABM]

Very true, I was taught this but I do tend to forget to do this.

I’m not sure why, but among my partner pilots, heading bug usage seems to be a very binary decision.

One of the guys I regularly fly with never uses the bug but recalls and holds his heading with amazing reliability. Me? If I’m not bugged, I’ll be all over the place, heading wise, and that’s even with lateral course guidance on the HSI and PFD G5s.