Garmin TO/GA functionality during missed approach

[Bavafa]

I tried the search function but it does not like the word TO/GO as it finds it too short even if other words are included.

I was wondering what is the expected behavior of the A/P when this button is pressed during a missed approach. My understanding was that it will set the A/P to the NAV mode and also give a pre determined pitch command to go to the selected altitude bug.

I tried this function yesterday and while my navigator (650XI) functioned as expected, the A/P did not and I had to manually press the NAV mode and VS with a desired rate of climb in order to get to my altitude and way point.

 

[georgemohr]

Was the AP engaged prior to the TO/GA press?

 

[Bavafa]

Was the AP engaged prior to the TO/GA press?

Yes.

 

[georgemohr]

Interesting, what mode was it in?

 

[Walt]

Normal unless you're on an RNAV.

 

[Bavafa]

Normal unless you're on an RNAV.

I was on LPV approach and the A/P was in the armed mode (APR)

 

[Phil Sprang]

It does not stay in or activate NAV. Lateral mode will be GA and the vertical mode will be GA. It will sequence the missed approach but to follow it, you'll need to press NAV.

 

[georgemohr]

Very interesting. I assume the vertical guidance is a fixed pitch climb. What is the lateral guidance for GA?

 

[Pat Hatch]

When you hit the TO/GA button, the autopilot should pitch up to the preset pitch (I have mine set to 5°), and follow the missed approach procedure, which could be a heading or a course to the missed approach fix. If it's a holding pattern, the autopilot will do the correct entry into the holding pattern. All you need to do is add power, raise the flaps and reset your altitude to the missed approach altitude if you haven't already done so. I usually set the missed approach altitude before I start the LPV approach. The autopilot will then level off at your missed approach altitude. As for pitch control during the missed approach, the intial 5° pitchup gets you going in the right direction, but then you need to select either an IAS or a rate of climb to continue to your MAP altitude.

As for doing a search, use TO/GA instead of TO/GO, you'll get lots of responses.

This assumes that you have the G3X paired with a GTN, which it sounds like you do. Also, you can set your TO/GA go-around pitch in the Flight Director setup menu. Check the wiring for your TO/GA switch, this could be your problem.

 

[Richard Connell]

I went and shot 4 RNPs and an ILS yesterday as it happens. 2 manually and two full coupled. These were all LNAV+V for me. no SBAS here FWIW. but the +V is certainly very helpful.

For an RNAV/RNP TOGA puts the AP into GA/GA which is PIT and ROLL and then arms NAV laterally and ALT capture - so GA (GPS) / GA (ALTS) It seems to take 5-6 sec for the Lateral mode to transition to NAV (GPS). I usually then change Vertical mode to VS (ALTS). From what I've observed, it does not matter when you GA, NAV (once it recaptures) will fly you to the MAPt then the missed approach.

For an ILS TOGA puts the AP into GA/GA which is PIT and ROLL but only arms the ALT capture. so GA / GA (ALTS). Here Im in the habit of transitioning it manually to TRK shortly after GA assuming I've bugged the final approach course like a good boy.

One thing I haven't tried is the GPS published missed approach off an ILS. we rarely get that. But Id be curious as to whether Id see GA (GPS) if I hit the "use GPS missed approach" on the navigator.

 

[Bavafa]

I went and shot 4 RNPs and an ILS yesterday as it happens. 2 manually and two full coupled. These were all LNAV+V for me. no SBAS here FWIW. but the +V is certainly very helpful.

For an RNAV/RNP TOGA puts the AP into GA/GA which is PIT and ROLL and then arms NAV laterally and ALT capture - so GA (GPS) / GA (ALTS) It seems to take 5-6 sec for the Lateral mode to transition to NAV (GPS). I usually then change Vertical mode to VS (ALTS). From what I've observed, it does not matter when you GA, NAV (once it recaptures) will fly you to the MAPt then the missed approach.

For an ILS TOGA puts the AP into GA/GA which is PIT and ROLL but only arms the ALT capture. so GA / GA (ALTS). Here Im in the habit of transitioning it manually to TRK shortly after GA assuming I've bugged the final approach course like a good boy.

One thing I haven't tried is the GPS published missed approach off an ILS. we rarely get that. But Id be curious as to whether Id see GA (GPS) if I hit the "use GPS missed approach" on the navigator.

This is interesting and contrary to what Garmin support just told me. According to Garmin support, pushing the TO/GA during an approach will pitch up to the preselected pitch setting in the FD settings and level in Roll. For any guidance (i.e. published Miss) one need to press the appropriate selection manually, NAV for the published miss or Heading for the instructed heading. The climb will be based on the pitch setting till the pre selected altitude (altitude bug) is reached.
My flight yesterday behaved as above. It is possible that I did not wait long enough for the NAV mode to get activated automatically but my guess it was more than 5-6 seconds. Only after I manually selected the NAV mode, the autopilot started following the publish miss.

For ILS approach and expecting to follow the publish missed based on GPS, we would need to manually change the navigator to the GPS mode instead of VLOC and of course NAV on the A/P.

 

[Bavafa]

As for doing a search, use TO/GA instead of TO/GO, you'll get lots of responses.

I tried it again and same result. It complains that is too short.

 

[Richard Connell]

First one is the TOGA hit well before the MAP
Second is the TOGA hit just a few secs before the MAP
Third is the ILS

 

[Richard Connell]

This is interesting and contrary to what Garmin support just told me. According to Garmin support, pushing the TO/GA during an approach will pitch up to the preselected pitch setting in the FD settings and level in Roll. For any guidance (i.e. published Miss) one need to press the appropriate selection manually, NAV for the published miss or Heading for the instructed heading. The climb will be based on the pitch setting till the pre selected altitude (altitude bug) is reached.
My flight yesterday behaved as above. It is possible that I did not wait long enough for the NAV mode to get activated automatically but my guess it was more than 5-6 seconds. Only after I manually selected the NAV mode, the autopilot started following the publish miss.

For ILS approach and expecting to follow the publish missed based on GPS, we would need to manually change the navigator to the GPS mode instead of VLOC and of course NAV on the A/P.

I think Garmin do a good job generally, but so much keeps changing with the functionality - especially in experimental that I think the manuals don't keep up.
Nobody really publishes good guides to buttonology and every CFI has a different opinion on when to push what buttons.
Some of the functionality available to us is bleeding edge compared to 90% of the fleet.
Some of the garmin videos still online from only a few years back are incorrect now.
Who here knows you can now concurrently arm VNAV and APR while in alt hold for example? That got snuck through in a software change relatively recently for GFC500 in a G3X system. I can't find anything in the pilot guide about it.

That said, now you have me second guessing whether I did press NAV!

Edit - found this:

Go Around button

I have a GTN 650, an AFS 5500 touchscreen EFIS and a Dynon autopilot control panel. The current method of activating a missed approach has too many button pushes. I have to execute the Go Around on the GTN 650 for lateral tracking guidance to the MAP but ALSO engaging a vertical mode with the...

vansairforce.net

 

[Pat Hatch]

Try using TOGA without the /, the diagonal seems to be the problem.

Here is the quote from the Pilot's Guide:
TO/GA Button (Takeoff/Go Around) Selects flight director Takeoff (on ground) or Go Around (in air) Mode When properly configured with a GTN, if an approach procedure is loaded, this switch also activates the missed approach when the selected navigation source is GPS or when the navigation source is VOR/LOC and a valid frequency has been tuned.

I don't believe you have to select NAV, not sure if it automatically goes to NAV, I'll have to check next flight to see, but I'm pretty sure it stays in the APR mode until you tell it otherwise. The statement from the Pilots' Guide appears to imply that you do not have to select NAV.

 

[Ed_Wischmeyer]

I strongly agree with the comment about the Garmin manuals, but I have completely worn out my welcome with them on this topic. 'nuff said.

It's truly amazing to have all that functionality in our little toy airplanes, but some of the bugs and design decisions are just as frustrating.

“Any clod can have the facts; having opinions is an art.” Charles McCabe

 

[Bavafa]

I apologies for the incorrect reporting earlier, I just went back to the airport and tried the same approach and missed approach and the A/P behaved as Richard and Pat have reported but it took some seconds to go from a pitch up to the 'NAV' mode to follow the GPS guidance. It also followed the climb to the preselected altitude without needing to touch any other buttons other than the TO/GA.
It is possible that in my yesterday flight, I did not wait long enough for the 'NAV' to kick in.

As for the Garmin support, since she did not find much explanation in the experimental document, she went and read from the certified document and it is possible that in the certified world this behavior is different and need to be deliberate.

I hope this clarifies it.

 

[mburch]

it took some seconds to go from a pitch up to the 'NAV' mode to follow the GPS guidance.

You might observe that it waits for the aircraft to establish a positive vertical speed.

As for the Garmin support, since she did not find much explanation in the experimental document, she went and read from the certified document and it is possible that in the certified world this behavior is different and need to be deliberate.

That's correct, this behavior is different in certified installations.

 

[Richard Connell]

You might observe that it waits for the aircraft to establish a positive vertical speed.



That's correct, this behavior is different in certified installations.

Thanks that’s a helpful snippet re VS. might be worth putting that in the pilots guide.

Bit of a backstory but I went out to test some other functionality yesterday and what precipitated it was exactly this divergence. CFIs and pilots of certified aircraft adamant that they know how the system in my plane works when in fact the airframes they are flying (documented properly or not) are literally a decade behind and bear only a passing resemblance to the capability we enjoy. Especially wrt VNAV, APR, transition to approach.

The Garmin documentation is ambiguous, out of date, or just doesn’t address it. So the only way to test it is to fly. Which isn’t ideal.

I’m glad I’m not going crazy about letting the TOGA transition to NAV. The reality is I don’t tend to do many practice missed approaches. Yesterday I didn’t get visual at the MAP and that’s probably the first missed from the minima in IMC I’ve done in maybe a year so I was busy. I could easily see myself having been impatient to see the NAV transition automatically and pushed the button if I was unsure about what it was going to do.

Again if anyone has a good reference material recommendation I’d be interested. I’m shredding the flows I was taught with 10y ago and going to write new ones.

 

[Ed_Wischmeyer]

At one Oshkosh, I asked the Garmin representative what the differences were between the experimental and certified versions, and where that was written down. "Go ask your CFII," they said. "I am the CFII." Clumsy end of conversation...

 

[Richard Connell]

You might observe that it waits for the aircraft to establish a positive vertical speed.

First example from above the transition took 7 seconds from TOGA to GPS NAV (re)capture. or 2 seconds from sustained 500fpm or greater climb


In the second example from above, the transition took 18seconds from TOGA to GPS NAV (re)capture, or 12seconds from 500fpm sustained or greater.



So while it makes sense that a positive vertical speed could be a variable in the logic to transition. there must be something else at play.
12seconds is a heck of a long time to be sitting there wondering "what's it doing" while you're 500' AGL in cloud.
Thats got a high chance of getting a nervous pilot intervention (even if its unnecessary).
This comes back to the same points made above.
Im sure there's a sensible answer. I just want to know.
The manual should state what to expect. why it may be near instantaneous in one example and why it might feel like a lifetime and/or need positive rectification in another.
Id even be happy with "the GMC500 relies on a variety of conditions to be satisfied before transitioning from GA (GPS) to GPS. This could take anywhere from 2-20 seconds. If these conditions are not met within 20seconds then the PIC should engage an appropriate lateral mode manually via the mode controller or touch screen"

 

[Waiex-guy]

First example from above the transition took 7 seconds from TOGA to GPS NAV (re)capture. or 2 seconds from sustained 500fpm or greater climb
View attachment 57118

In the second example from above, the transition took 18seconds from TOGA to GPS NAV (re)capture, or 12seconds from 500fpm sustained or greater.

View attachment 57116

So while it makes sense that a positive vertical speed could be a variable in the logic to transition. there must be something else at play.
12seconds is a heck of a long time to be sitting there wondering "what's it doing" while you're 500' AGL in cloud.
Thats got a high chance of getting a nervous pilot intervention (even if its unnecessary).
This comes back to the same points made above.
Im sure there's a sensible answer. I just want to know.
The manual should state what to expect. why it may be near instantaneous in one example and why it might feel like a lifetime and/or need positive rectification in another.
Id even be happy with "the GMC500 relies on a variety of conditions to be satisfied before transitioning from GA (GPS) to GPS. This could take anywhere from 2-20 seconds. If these conditions are not met within 20seconds then the PIC should engage an appropriate lateral mode manually via the mode controller or touch screen"

Perhaps the exact wording of the missed approach procedure in question says something like climb to 478 MSL, then climbing right turn via…blah blah blah to 3000 and hold.

 

[Bavafa]

First example from above the transition took 7 seconds from TOGA to GPS NAV (re)capture. or 2 seconds from sustained 500fpm or greater climb
View attachment 57118

In the second example from above, the transition took 18seconds from TOGA to GPS NAV (re)capture, or 12seconds from 500fpm sustained or greater.

View attachment 57116

So while it makes sense that a positive vertical speed could be a variable in the logic to transition. there must be something else at play.
12seconds is a heck of a long time to be sitting there wondering "what's it doing" while you're 500' AGL in cloud.
Thats got a high chance of getting a nervous pilot intervention (even if its unnecessary).
This comes back to the same points made above.
Im sure there's a sensible answer. I just want to know.
The manual should state what to expect. why it may be near instantaneous in one example and why it might feel like a lifetime and/or need positive rectification in another.
Id even be happy with "the GMC500 relies on a variety of conditions to be satisfied before transitioning from GA (GPS) to GPS. This could take anywhere from 2-20 seconds. If these conditions are not met within 20seconds then the PIC should engage an appropriate lateral mode manually via the mode controller or touch screen"

I couldn't agree more and I would also love to fully understand the condition it needs to be met before it transition to the NAV. My practice flight yesterday seemed to be a short duration before it went to the NAV whereas the prior day which I was in IMC seemed forever hence I pushed the NAV manually. The only difference in the system configuration is that I change the GA rate of climb to 5degree from the previous that was set to 4degree. I am thinking of changing it even higher as 5degree for a RV is a shallow climb rate

If I get a chance, I may go out and practice this more with both shallow climb rate and higher climb rate

 

[PilotjohnS]

I went and shot 4 RNPs and an ILS yesterday as it happens. 2 manually and two full coupled. These were all LNAV+V for me. no SBAS here FWIW. but the +V is certainly very helpful.

For an RNAV/RNP TOGA puts the AP into GA/GA which is PIT and ROLL and then arms NAV laterally and ALT capture - so GA (GPS) / GA (ALTS) It seems to take 5-6 sec for the Lateral mode to transition to NAV (GPS). I usually then change Vertical mode to VS (ALTS). From what I've observed, it does not matter when you GA, NAV (once it recaptures) will fly you to the MAPt then the missed approach.

For an ILS TOGA puts the AP into GA/GA which is PIT and ROLL but only arms the ALT capture. so GA / GA (ALTS). Here Im in the habit of transitioning it manually to TRK shortly after GA assuming I've bugged the final approach course like a good boy.

One thing I haven't tried is the GPS published missed approach off an ILS. we rarely get that. But Id be curious as to whether Id see GA (GPS) if I hit the "use GPS missed approach" on the navigator.

Wow, i am just restarting my IFR training after 10 years. This is all Greek to me. I guess I need to find a good instructor..... (sigh)

 

[Breezy]

I tried the search function but it does not like the word TO/GO as it finds it too short even if other words are included.

I was wondering what is the expected behavior of the A/P when this button is pressed during a missed approach. My understanding was that it will set the A/P to the NAV mode and also give a pre determined pitch command to go to the selected altitude bug.

I tried this function yesterday and while my navigator (650XI) functioned as expected, the A/P did not and I had to manually press the NAV mode and VS with a desired rate of climb in order to get to my altitude and way point.

Gents,
I'm not ruling out a CONFIG, system, or wiring problem. But, It could be everything is working. You asked about what to expect, I am offering this.

There is a very good book by Max Trescott; "GPS WAAS Instrument Flying". The info is based on the G1000 paired with 430/530 navigators. The G3X is a G1000 "light" system. Setting aside the touch screen, 430/530 navigators function sequence is nearly the same as the GTN650. This may clear up what you are observing.

When on the ground pressing the TOGA button will raise the FD command bars to the default pitch for climb. If HEADING is engaged there will be commands to the BUGed heading, as well as level off if an altitude is pre-selected. An engaged AP will follow the FD commands.

In APPROACH mode the navigator is programed to keep the aircraft on course in the protected corridor. At low altitude there can be lateral obstructions that prevent turning until altitude clearance. If so, missed approach procedures have a minimum altitude based on the area past the Missed Approach point and height clearance of the lateral obstruction. The Navigator will not initiate a missed approach turn until at or above the "Climb to ___then..." altitude. If in the Approach Mode on the final leg the navigator will not begin a turn until past the DA/MISSED fix and above the "Climb to" altitude.

There are distinct differences in the NAV corridors of VHF and GPS approaches. Be sure to use a GPS chart. The missed procedure can be very different.

Make sure you have current NAV data in the navigator. If expired the navigator will not desend beyond the FAF. After entering the terminal area of an approach the navigator automatically checks GPS/WAAS signal integrity. If below minimum requirements, again it will not desend beyond the FAF.

Additionally, while on the final leg to either DA/MISSED, or inbound to a Hold fix, on the lower GTN status bar a square with "SUSP" will appear. This means auto leg sequencing is SUSPended. If not cancelled before reaching the fix the navigator will continue on the current track.

I hope this helps.

Cheers!

 

[RWoodard]

As Waiex guy mentioned above, one consideration is whether the missed approach procedure immediately *requires* a turn at the moment the TO/GA button is pushed. ”Climb straight ahead until reaching xxxx altitude, then turn right…” The other missed approach gotcha that has claimed more than one life is that you should not initiate any turns until you reach the missed approach point. Climb, yes, but an early turn might have you flying into an obstacle or terrain.

I fly an Airbus at work and one of the things we have hammered into us in all phases of training is to pay attention to what Airbus calls FMA’s. Flight Mode Annunciation. Selecting something using the autopilot control panel doesnt become reality until you see it via an FMA. When the hope versus the reality doesn’t match, it could be as simple as missing a button with your finger or it could be that you’ve asked the autopilot to do something that it can’t (or won’t) do at that moment.

Push a button or turn a knob and then look to the appropriate display to make sure it Really happened.

I can’t wait to fly the G3x system I’m installing in my Glasair!

 

[g3xpert]

It does not stay in or activate NAV. Lateral mode will be GA and the vertical mode will be GA. It will sequence the missed approach but to follow it, you'll need to press NAV.

This is true for Certified Installations and reflected in the associated GFC 500 AFMS. In non-certified installations, the flight director will automatically sequence from GA (Lateral Mode, wings level) to GPS once a positive climb away from the ground has been established. As with all other cases where GPS is armed, it will not become active if significantly off course for the missed approach course.

First example from above the transition took 7 seconds from TOGA to GPS NAV (re)capture. or 2 seconds from sustained 500fpm or greater climb
View attachment 57118

In the second example from above, the transition took 18seconds from TOGA to GPS NAV (re)capture, or 12seconds from 500fpm sustained or greater.

View attachment 57116

So while it makes sense that a positive vertical speed could be a variable in the logic to transition. there must be something else at play.
12seconds is a heck of a long time to be sitting there wondering "what's it doing" while you're 500' AGL in cloud.
Thats got a high chance of getting a nervous pilot intervention (even if its unnecessary).
This comes back to the same points made above.
Im sure there's a sensible answer. I just want to know.
The manual should state what to expect. why it may be near instantaneous in one example and why it might feel like a lifetime and/or need positive rectification in another.
Id even be happy with "the GMC500 relies on a variety of conditions to be satisfied before transitioning from GA (GPS) to GPS. This could take anywhere from 2-20 seconds. If these conditions are not met within 20seconds then the PIC should engage an appropriate lateral mode manually via the mode controller or touch screen"

The other variable is height from the ground at the time of activation. Per the report here, you pressed the TO/GA button just prior to the missed approach waypoint. The flight director holds wings level (GA Lateral Mode) until you have begun to fly away from the ground, before the system will activate GPS course guidance. Please feel free to email us your full datalog (with a reference to the approach you are flying) as this screenshot only includes a few of the parameters necessary to tell the whole story here.

We will update the EAB Pilot's Guide to better describe the lateral mode transition when the TO/GA input is activated.

Thanks,

Justin

 

[Bavafa]

This is true for Certified Installations and reflected in the associated GFC 500 AFMS. In non-certified installations, the flight director will automatically sequence from GA (Lateral Mode, wings level) to GPS once a positive climb away from the ground has been established. As with all other cases where GPS is armed, it will not become active if significantly off course for the missed approach course.

The other variable is height from the ground at the time of activation. Per the report here, you pressed the TO/GA button just prior to the missed approach waypoint. The flight director holds wings level (GA Lateral Mode) until you have begun to fly away from the ground, before the system will activate GPS course guidance. Please feel free to email us your full datalog (with a reference to the approach you are flying) as this screenshot only includes a few of the parameters necessary to tell the whole story here.

We will update the EAB Pilot's Guide to better describe the lateral mode transition when the TO/GA input is activated.

Thanks,

Justin

I just did one more approach test (all in the same airport and runway) and the transition from lateral to GPS seemed to be based on positive rate of climb.

 

[Richard Connell]

Gents,
I'm not ruling out a CONFIG, system, or wiring problem. But, It could be everything is working. You asked about what to expect, I am offering this.

There is a very good book by Max Trescott; "GPS WAAS Instrument Flying". The info is based on the G1000 paired with 430/530 navigators. The G3X is a G1000 "light" system. Setting aside the touch screen, 430/530 navigators function sequence is nearly the same as the GTN650. This may clear up what you are observing.

When on the ground pressing the TOGA button will raise the FD command bars to the default pitch for climb. If HEADING is engaged there will be commands to the BUGed heading, as well as level off if an altitude is pre-selected. An engaged AP will follow the FD commands.

In APPROACH mode the navigator is programed to keep the aircraft on course in the protected corridor. At low altitude there can be lateral obstructions that prevent turning until altitude clearance. If so, missed approach procedures have a minimum altitude based on the area past the Missed Approach point and height clearance of the lateral obstruction. The Navigator will not initiate a missed approach turn until at or above the "Climb to ___then..." altitude. If in the Approach Mode on the final leg the navigator will not begin a turn until past the DA/MISSED fix and above the "Climb to" altitude.

There are distinct differences in the NAV corridors of VHF and GPS approaches. Be sure to use a GPS chart. The missed procedure can be very different.

Make sure you have current NAV data in the navigator. If expired the navigator will not desend beyond the FAF. After entering the terminal area of an approach the navigator automatically checks GPS/WAAS signal integrity. If below minimum requirements, again it will not desend beyond the FAF.

Additionally, while on the final leg to either DA/MISSED, or inbound to a Hold fix, on the lower GTN status bar a square with "SUSP" will appear. This means auto leg sequencing is SUSPended. If not cancelled before reaching the fix the navigator will continue on the current track.

I hope this helps.

Cheers!

Thanks for the suggestion. ill check it out.
However... and please dont take this the wrong way - you have neatly provided another example of what caused me all my issues.
A G3X Touch connected to a GTN Xi and GFC500 in an experimental is an integrated system that is FAR more advanced and capable than any non NXi G1000 or 430/530 with autopilot X. Its the complete reverse of being a G1000 "light" and many people - including instructors - incorrectly assume that they are somehow feature limited but the button pushing is the same.
Sure the buttons have the same names and do similar things, but the devil is in the details - and the details aren't documented and/or they are hard to find. See my comment above about having GP and VNAV armed concurrently in ALT Hold mode.

This whole odyssey of frustration started when I did my renewal last year. The instructor was adamant that the AP would capture the GP at the IF while in ALT mode and all would be good. Needless to say - It obviously didn't - and his response was basically, well that's how the G1000 in the 2008 cirrus (G2 or G3 don't know what AP) does it so your config is wrong or you avionics aren't as good a the 15yo cirrus - so I'm going to make you fly it in VS mode until you capture the FAF alt sometime before the FAF then it'll transition yada yada.
Completely oblivious to the existence of enhanced VNAV or Transition to approach that would take you right to the FAF on a 3 degree path and seamlessly transition you to GP.
So in a nutshell - the problems all stem from being taught with the old stuff, with procedures for the old stuff, that don't work with the new stuff or ignore their capabilities. I did my IR 10y ago with a 430. Dont miss that box at all.

There are subtle but important differences in how all the current iterations of the Garmin suites operate between Certified and experimental installs. Let alone legacy avionics
G1000NXi/GFC700, G500TXi/GTNXi/GFC600, G3XT/GTNXi/GFC500 in an STC, G3XT/GTNXi/GFC500 in an experimental all have subtle feature differences.
Mehrdad found this out when he asked support. Even they didn't know. So how are Instructors or pilots supposed to?

As Waiex guy mentioned above, one consideration is whether the missed approach procedure immediately *requires* a turn at the moment the TO/GA button is pushed. ”Climb straight ahead until reaching xxxx altitude, then turn right…” The other missed approach gotcha that has claimed more than one life is that you should not initiate any turns until you reach the missed approach point. Climb, yes, but an early turn might have you flying into an obstacle or terrain.

I fly an Airbus at work and one of the things we have hammered into us in all phases of training is to pay attention to what Airbus calls FMA’s. Flight Mode Annunciation. Selecting something using the autopilot control panel doesnt become reality until you see it via an FMA. When the hope versus the reality doesn’t match, it could be as simple as missing a button with your finger or it could be that you’ve asked the autopilot to do something that it can’t (or won’t) do at that moment.

Push a button or turn a knob and then look to the appropriate display to make sure it Really happened.

I can’t wait to fly the G3x system I’m installing in my Glasair!

Good reminder to double check the mode on every button push.
Bringing it back to the OP question at hand-
Lets assume that everyone is following the procedure as its designed. The database is current, nobody early turning before the MAP etc. the modes have all been selected properly and verified.

Yes do think that the proximity of a turn after the MAP could be a factor. There was no "course to altitude" legs in either missed approach.
In the 12 second delay example the missed procedure is runway heading and climb to 3000 AGL. No great urgency. No real chance of getting too far off the missed approach course.
In the 2 second example there is an immediate right turn at the MAP. however there was no great rush there either as I went missed 1.5NM before the MAP and crossed the MAP 30seconds later - but there would have been if I flew level at the MDA for 1.5NM first before pushing TOGA.

But logically, if you are climbing and you are on the inbound course to the MAP still or on the missed course, why wait. Just transition the lateral mode from GA straight back to GPS. 12 seconds just makes you sweat unnecessarily IMHO. Unless there's a decent reason.

Edit...didnt see Justins reply ahead of me. AGL sounds sensible!
Ill email the flight file through. Would be great to get some more insight. Much appreciated.

 

[DCBrown198]

I have Dynon Skyview HDX as the driving autopilot, with a Garmin GPS175 guiding the Dynon on IFR approaches.

I have a G/A remote button on the panel. It is wired to both the Dynon Skyview and the Garmin GPS 175. Anytime I push the button on the approach the Dynon pitches up towards a climb rate target. Before the MAP the Garmin ignores the G/A button and continues to laterally follow the approach course to the MAP (as it should). After MAP the Garmin goes into SUSPend and wants me to either press my G/A button on the panel again, or select UNSUSPend.

Has anyone had luck with the remote G/A button activation before the MAP causing the GPS175 to set up for automatic waypoint sequencing for the missed approach course? In other words, a pressing of the remote GA button prior to the MAP will prevent the Garmin from going into SUSPend at the MAP.

 

[Ed_Wischmeyer]

I couldn't agree more and I would also love to fully understand the condition it needs to be met before it transition to the NAV. My practice flight yesterday seemed to be a short duration before it went to the NAV whereas the prior day which I was in IMC seemed forever hence I pushed the NAV manually. The only difference in the system configuration is that I change the GA rate of climb to 5degree from the previous that was set to 4degree. I am thinking of changing it even higher as 5degree for a RV is a shallow climb rate

If I get a chance, I may go out and practice this more with both shallow climb rate and higher climb rate

When I was figuring out approach techniques in the -9A, I initially was flying at 70 knots. I found the pitch up at 2°/sec to be too much, too soon, (speed loss) especially if I didn't already have the power in. Nowadays I aim to be at 80 kt at minimums, and GA pitch is only 2°. This stops the descent and as I get the power in, flaps up, etc, then I can engage the desired vertical mode. And since I fly at an airport with Class C airspace, I go out of my way to make friends with the controllers by keeping my speed up. As I once wrote, the question is not whether approaches should be stable, but rather, how long they should be stable. In a responsive RV, the stable part of the approach can be lots shorter... not to mention that many gusts will exceed many stable approach criteria.

 

[Longez]

I have Dynon Skyview HDX as the driving autopilot, with a Garmin GPS175 guiding the Dynon on IFR approaches.

I have a G/A remote button on the panel. It is wired to both the Dynon Skyview and the Garmin GPS 175. Anytime I push the button on the approach the Dynon pitches up towards a climb rate target. Before the MAP the Garmin ignores the G/A button and continues to laterally follow the approach course to the MAP (as it should). After MAP the Garmin goes into SUSPend and wants me to either press my G/A button on the panel again, or select UNSUSPend.

Has anyone had luck with the remote G/A button activation before the MAP causing the GPS175 to set up for automatic waypoint sequencing for the missed approach course? In other words, a pressing of the remote GA button prior to the MAP will prevent the Garmin from going into SUSPend at the MAP.

Yes, pressing the TO/GA button at any point after the FAF causes my G3X Touch system with GNX 375 to automatically transition both systems to the missed approach with no "popup message" or operator interaction required on the GNX 375.

At the point the GNX 375 receives the missed approach activation signal from the TO/GA button, the green LPV annunciator at the bottom left turns immediately to a green MAPR annunciation indicating that the missed approach is active.

On a recent flight I was established on the LPV glidepath inside the FAF on a practice approach and pressed the TO/GA button 4 nm from the runway to execute the missed approach early and the transition was automatic just as if the button had been pressed at the normal missed approach point.

It sounds like the missed approach signal is not properly connected or configured on your GPS 175.

Steve

 

[rsultzbach]

First example from above the transition took 7 seconds from TOGA to GPS NAV (re)capture. or 2 seconds from sustained 500fpm or greater climb
View attachment 57118

In the second example from above, the transition took 18seconds from TOGA to GPS NAV (re)capture, or 12seconds from 500fpm sustained or greater.

View attachment 57116

So while it makes sense that a positive vertical speed could be a variable in the logic to transition. there must be something else at play.
12seconds is a heck of a long time to be sitting there wondering "what's it doing" while you're 500' AGL in cloud.
Thats got a high chance of getting a nervous pilot intervention (even if its unnecessary).
This comes back to the same points made above.
Im sure there's a sensible answer. I just want to know.
The manual should state what to expect. why it may be near instantaneous in one example and why it might feel like a lifetime and/or need positive rectification in another.
Id even be happy with "the GMC500 relies on a variety of conditions to be satisfied before transitioning from GA (GPS) to GPS. This could take anywhere from 2-20 seconds. If these conditions are not met within 20seconds then the PIC should engage an appropriate lateral mode manually via the mode controller or touch screen"

Is it possible the GA function is looking for an altitude prior to engaging NAV?

 

[Richard Connell]

Is it possible the GA function is looking for an altitude prior to engaging NAV?

Yes. I think that’s likely.
I’ve emailed the data from flight in question to Garmin. Will see what they say.

 

[dmattmul]

Make sure you have current NAV data in the navigator. If expired the navigator will not desend beyond the FAF. After entering the terminal area of an approach the navigator automatically checks GPS/WAAS signal integrity. If below minimum requirements, again it will not desend beyond the FAF.

I hope this helps.

Cheers!

I recently tried an approach with a 5 month expired NAV data in my GTN750 (Non-Xi) and it flew the approach past the FAF and descended down below minimums without an issue. Maybe it was with the type of navigator or RNAV type that made the difference but performed fine. I typically buy a subscription every 2 or 3 years and obviously don't fly IFR (practice approaches only) but in an emergency feel if needed I could use it. Thanks

 

[newt]

Yes. I think that’s likely.
I’ve emailed the data from flight in question to Garmin. Will see what they say.

This might be a dumb question --

How is your TO/GA button wired?

The G3X Touch manual allows it to be set up in several ways:

• Connected to one of the discrete inputs on the GEA-24 configured for AFCS TO/GA
• Connected to one of the discrete inputs on the GSU-25 configured for AFCS TO/GA (if you have a GSU-25, which you probably don't)
• Connected to the TO/GA input on a GMC-507.
• Connected to one of the discrete inputs on a GTN or GNX via a double-pole switch also connected to the one of the others.

I'm looking at 190-01115-01 rev AM figure 27-1.7, figure 27-1.8, figure 27-2.17. Probably more, but I gave up looking.

So I'm now wondering what happens if the GTN/GNX is connected to a TO/GA button but the rest of the G3X Touch system is not.

In theory, the navigator should be able to execute a missed approach without the assistance of the rest of the system. What is the purpose of the provision for connecting a TO/GA button via the GEA, GSU or GMC?

(executing a go-around while navigating in nav source "internal" mode, perhaps?)

- mark

 

[mburch]

What is the purpose of the provision for connecting a TO/GA button via the GEA, GSU or GMC?

You still need to be able to tell the flight director to change modes, hence this connection.

(by the way, the references to "GSU 25" here should be references to the discontinued GSU 73... just in case someone attempts to connect a button to their GSU 25, which has no discrete inputs)

 

[Bavafa]

This might be a dumb question --

How is your TO/GA button wired?

The G3X Touch manual allows it to be set up in several ways:

• Connected to one of the discrete inputs on the GEA-24 configured for AFCS TO/GA
• Connected to one of the discrete inputs on the GSU-25 configured for AFCS TO/GA (if you have a GSU-25, which you probably don't)
• Connected to the TO/GA input on a GMC-507.
• Connected to one of the discrete inputs on a GTN or GNX via a double-pole switch also connected to the one of the others.

I'm looking at 190-01115-01 rev AM figure 27-1.7, figure 27-1.8, figure 27-2.17. Probably more, but I gave up looking.

So I'm now wondering what happens if the GTN/GNX is connected to a TO/GA button but the rest of the G3X Touch system is not.

In theory, the navigator should be able to execute a missed approach without the assistance of the rest of the system. What is the purpose of the provision for connecting a TO/GA button via the GEA, GSU or GMC?

(executing a go-around while navigating in nav source "internal" mode, perhaps?)

- mark

Mine is connected to Pin 10 of the 507 and another pigtail that goes to the 650xi via a double pole push button.

 

[dmattmul]

Mine is connected to Pin 10 of the 507 and another pigtail that goes to the 650xi via a double pole push button.

Here is how mine is wired. It's been a while and don't remember the exact details but initially had an issue with using this function as the incorrect switch was installed. From what I understand (limited) the diode is important. If using a DPDT seems a diode not needed and a SPDT can be used? This function can be tested on the ground.

 

[Bavafa]

DPDT is correct. This function can be tested on the ground.

Yes, with the Garmin setup, if you go to the system page --> 507 you can observe the status of the TO/GA and if you push it you should see the status changing to "closed"

 

[dmattmul]

Yes, with the Garmin setup, if you go to the system page --> 507 you can observe the status of the TO/GA and if you push it you should see the status changing to "closed"

In addition, on the ground when the TOGA button is pushed the FD command bar pitches up to your pre-set pitch up attitude and the FD button on the 507 lights up. (If it was not lit already) I think this is a valid test of the TOGA button.

 

[Richard Connell]

This might be a dumb question --

How is your TO/GA button wired?

The G3X Touch manual allows it to be set up in several ways:

• Connected to one of the discrete inputs on the GEA-24 configured for AFCS TO/GA
• Connected to one of the discrete inputs on the GSU-25 configured for AFCS TO/GA (if you have a GSU-25, which you probably don't)
• Connected to the TO/GA input on a GMC-507.
• Connected to one of the discrete inputs on a GTN or GNX via a double-pole switch also connected to the one of the others.

I'm looking at 190-01115-01 rev AM figure 27-1.7, figure 27-1.8, figure 27-2.17. Probably more, but I gave up looking.

So I'm now wondering what happens if the GTN/GNX is connected to a TO/GA button but the rest of the G3X Touch system is not.

In theory, the navigator should be able to execute a missed approach without the assistance of the rest of the system. What is the purpose of the provision for connecting a TO/GA button via the GEA, GSU or GMC?

(executing a go-around while navigating in nav source "internal" mode, perhaps?)

- mark

My TOGA is wired into the GMC (and the GTN)
It all functions as expected.
I’d be confident that if your TOGA wasn’t connected to the G3X system that the navigator would still function as designed for a missed approach. The TOGA would unsuspend it and it would continue to provide lateral guidance.
You’d then need to manually change vertical and lateral modes on the FD/Autopilot to NAV and some form of climb. It’s possible that APR may either keep lateral GPS or transition to NAV(GPS) past MAP but I wouldn’t be sure.
It would be quite a bit of button pushing though at a busy time.

The TOGA input to the FD/AP is to get it into a guaranteed PIT mode to get you climbing ASAP wings level all with one button push.
While at the same time re-arming the NAV for missed lateral guidance. Else you have to do that all mode control manually.

I’m 99% sure after all this that the conditions required for recapture of NAV laterally from GA (GPS) / GA to GPS / GA is 500’ AGL and a 500fpm ROC. (more or less)
I’ll report back when Garmin confirms.

 

[Dugaru]

I did my IR 10y ago with a 430. Dont miss that box at all.

How dare you!! 430 lovers unite!!

 

[Longez]

I’m 99% sure after all this that the conditions required for recapture of NAV laterally from GA (GPS) / GA to GPS / GA is 500’ AGL and a 500fpm ROC. (more or less)

Richard,

You certainly do not have to be at or above 500 ft AGL before NAV mode is captured on a missed approach activation. In this example from one of my flights, the airport altitude is ~1000 ft MSL.

The TO/GA button was pressed at 1220 ft MSL (220 ft AGL). The lateral GA to NAV mode capture was completed 7 secs later at 1188 ft MSL (188 ft AGL).

You will notice that my missed approach pitch setting is only 3 degs. A higher pitch setting would probably result in a faster NAV mode capture. In watching the video for this flight it appeared to capture very fast, perhaps in 2-3 seconds, but the data shows that it was a bit longer. This is typical for what I have seen in flying LPV missed approaches for over a decade. The capture is so fast that I never have the concerns you have voiced.

While the capture occurred after reaching a rate-of-climb of 500 fpm, I suspect we will see that the requirement is for an established positive rate of climb, not a hard number like 500 fpm.


Steve

 

[Richard Connell]

Richard,

You certainly do not have to be at or above 500 ft AGL before NAV mode is captured on a missed approach activation. In this example from one of my flights, the airport altitude is ~1000 ft MSL.

The TO/GA button was pressed at 1220 ft MSL (220 ft AGL). The lateral GA to NAV mode capture was completed 7 secs later at 1188 ft MSL (188 ft AGL).

You will notice that my missed approach pitch setting is only 3 degs. A higher pitch setting would probably result in a faster NAV mode capture. In watching the video for this flight it appeared to capture very fast, perhaps in 2-3 seconds, but the data shows that it was a bit longer. This is typical for what I have seen in flying LPV missed approaches for over a decade. The capture is so fast that I never have the concerns you have voiced.

While the capture occurred after reaching a rate-of-climb of 500 fpm, I suspect we will see that the requirement is for an established positive rate of climb, not a hard number like 500 fpm.

View attachment 57424
Steve

Hi Steve.
Yep and therin lies the question both Mehrdad and I had from the start of the thread. Which nobody has answered. If it’s not an AGL constraint then what is it?
The data above of mine clearly shows one example of almost 12sec from positive rate of climb (18s from toga press) to NAV recapture. The RNP immediately after it was like yours. Only a few seconds.

It seems too long - feels like an eternity in the plane. My toga pitch is set at 5. Which is absolutely plenty. Probably too much. I could easily wind it down to 3 or 4 like you and be happy.
cheers

 

[Bavafa]

I agree that 500' AGL is not a requirement as my last test confirmed that. At this point, I am leaning towards a positive rate of climb that will cause it to go switch to NAV but I have not tested it yet with a shallow/delayed rate of climb to see if that is the reason.
If it is a positive rate of climb, I don't know the specific of that (i.e. what sort of climb rate it needs to see before transitioning) . It is however conceivable that it needs to see the pitch level that it has been configured for, 5 degree for my setup.

 

[Pat Hatch]

I put up a short video of the missed approach sequence on an LPV approach this morning to runway 23 at Okeechobee, FL. Missed approach altitude is 315' msl. As you can see, approaching minimums I push the TO/GA button and the annunciator on the GMC 507 switches immediately from APR to NAV. The aircraft pitches up to the GA attitude and begins to climb. The lateral side of the autopilot annunciator on the attitude indicator goes from a steady GPS to GPS GA, and the pitch mode goes from GP to GA & ALTS immediately. GPS begins to flash on the lateral side untill a positive climb is indicated and then goes to steady GPS. A few seconds later the missed approach fix (FINLO) and holding pattern pop into view on the NAV page. I ended the video at about 1,200 feet as the aircraft was climbing to the missed approach altitude of 2,000' with the autopilot flying the missed approach procedure.

 

[Bavafa]

I put up a short video of the missed approach sequence on an LPV approach this morning to runway 23 at Okeechobee, FL. Missed approach altitude is 315' msl. As you can see, approaching minimums I push the TO/GA button and the annunciator on the GMC 507 switches immediately from APR to NAV. The aircraft pitches up to the GA attitude and begins to climb. The lateral side of the autopilot annunciator on the attitude indicator goes from a steady GPS to GPS GA, and the pitch mode goes from GP to GA & ALTS immediately. GPS begins to flash on the lateral side untill a positive climb is indicated and then goes to steady GPS. A few seconds later the missed approach fix (FINLO) and holding pattern pop into view on the NAV page. I ended the video at about 1,200 feet as the aircraft was climbing to the missed approach altitude of 2,000' with the autopilot flying the missed approach procedure.

Thank you Pat, this is nice as we can see it over and over again to see exactly what it does as oppose to real life which all happens quickly. I guess my next test is going to be what climb rate I will get at 5degree and whether I should adjust that or not.

 

[Richard Connell]

I put up a short video of the missed approach sequence on an LPV approach this morning to runway 23 at Okeechobee, FL. Missed approach altitude is 315' msl. As you can see, approaching minimums I push the TO/GA button and the annunciator on the GMC 507 switches immediately from APR to NAV. The aircraft pitches up to the GA attitude and begins to climb. The lateral side of the autopilot annunciator on the attitude indicator goes from a steady GPS to GPS GA, and the pitch mode goes from GP to GA & ALTS immediately. GPS begins to flash on the lateral side untill a positive climb is indicated and then goes to steady GPS. A few seconds later the missed approach fix (FINLO) and holding pattern pop into view on the NAV page. I ended the video at about 1,200 feet as the aircraft was climbing to the missed approach altitude of 2,000' with the autopilot flying the missed approach procedure.

Thanks Pat
Nice and smooth
That’s looks pretty much the same as the short recapture example of mine above.
I’m just going to park it for now. I’m pretty sure it’s working as it should. Maybe it’s something to do with the procedure design or some other esoteric factor unique to Antipodean airspace
It would just be nice to be definitive.
Cheers

 

[g3xpert]

Hi Steve.
Yep and therin lies the question both Mehrdad and I had from the start of the thread. Which nobody has answered. If it’s not an AGL constraint then what is it?
The data above of mine clearly shows one example of almost 12sec from positive rate of climb (18s from toga press) to NAV recapture. The RNP immediately after it was like yours. Only a few seconds.

It seems too long - feels like an eternity in the plane. My toga pitch is set at 5. Which is absolutely plenty. Probably too much. I could easily wind it down to 3 or 4 like you and be happy.
cheers

That variability in time to transition FD modes results from the AGL at which you pressed the TO/GA button. If you press the TO/GA button at LPV approach minimums, it is going to sequence flight director modes as soon as a positive rate of climb is achieved. If you press the TO/GA button just prior to actually reaching the runway (very low AGL), the system holds wings level (GA lateral mode) until you have both achieved a positive rate of climb, and flown away from the ground to a reasonable threshold.

I think you will find that pressing the TO/GA button at LPV approach minimums will lead to a very quick transition of flight director modes. If you are in a situation you are pressing the TO/GA button beyond approach minimums, the system will hold you wings level for a bit longer, before it begins any kind of lateral GPS course correction, even if it is very slight.

Thanks,

Justin