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GX-Pilot RNAV - missed approach question

BillL

Well Known Member
I have the Gx-Pilot with two G3X non-touch + GTN650

For the IFR RNAV LPV approach and getting to the MAP, the 650 gives "guidance" as altitude XXXX following the MAP.

Since approaches take a while and one can not linger to try different scenarios for actions, here are some options and I am looking for better ones pilots might have developed with this specific hardware.

Option 1 - as the MAP is reached the 650 goes into suspend mode. I disconnect the AP with the CWS button with a tap, pitch/power/climb on RWY HDG, turn and then at the missed altitude, unsuspend the approach and set to the AP to "AP-NAV" and "ALT ALT" .

I would like to use the CWS feature to do the following:

Option 2 - I could hold the CWS until established in the climb and release the CWS so the AP is in "PIT" mode and HDG "ROLL" mode. (At least I think that is what it will do.) Then when at the turn altitude (in my home approach) Unsuspend the 650 and engage HDG - "AP NAV" mode for tracking followed by ALT- "AP ALT" hold mode.

Option 3 - Please post

Note: I can not find any mode resembling a TOGA for this AP.
 
Bill, I have a similar setup, just with the 430 instead of 650. Prior to the MAP I dial in the missed altitude. And set HDG bug to runway heading. At the map I disconnect A/P and pitch up to 500 FPM climb. I re-engage ap in VS mode, undo suspend and hit engage NAV. I suspect that if you add a TOGA switch to the 650 all it would do for you is to re-establish the lateral guidance, but not vertical guidance. The G3X touch with the Garmin A/P will fly the missed both lateral and vertical assum8ng you have installed a TOGA switch.
 
Bill,
I don't know this for sure but as I understand it, pushing and holding CWS will suspend the pervious mode of operation and when released, it returns back to that mode. For example, if you are in a "NAV" mode and push the CWS for a period of time and release, it will go back to NAV mode and tries to capture the pervious course.
It is a good thing to test and verify to see how it behaves.

The other day I was trying my new toys in the new plane (G3X touch with 650 and OTGO button) on a GPS LPV approach with my altitude bug at 4000. Prior to arriving at MAP, I pushed the TOGO and the A/P pitched up and followed the runway heading and climbed to 4000 but never followed the miss approach. On 650 I had the option of suspend or missed approach which I had selected missed approach and was expecting the A/P go to the NAV mode and follow the miss approach but it did not.

I wonder if this will follow the course to missed approach only if the TOGO button has been pushed after arriving the MAP?

One of the Garmin youtube video clearly shows that it should do that but mine did not go to NAV mode automatically.

Thoughts?
 
Bill, I have a similar setup, just with the 430 instead of 650. Prior to the MAP I dial in the missed altitude. And set HDG bug to runway heading. At the map I disconnect A/P and pitch up to 500 FPM climb. I re-engage ap in VS mode, undo suspend and hit engage NAV. I suspect that if you add a TOGA switch to the 650 all it would do for you is to re-establish the lateral guidance, but not vertical guidance. The G3X touch with the Garmin A/P will fly the missed both lateral and vertical assum8ng you have installed a TOGA switch.

Thanks, Bill, I did set the HDG bug and the missed altitude and at the map disconnected the AP via a tap to the CWS. Then did pitch-power-climb by hand. I tried to reengage the AP with another tap of the CWS, but did not behave as expected. I understand your process and will try that. I know what it will do.

Steve, at G3XExpert, said I could wire a TOGA to my 650 and G3X non-touch, I'll have to research what guidance is provided by the 650 and when, to be sure, but don't think vertical guidance is included.

Bill,
A) I don't know this for sure but as I understand it, pushing and holding CWS will suspend the previous mode of operation and when released, it returns back to that mode. For example, if you are in a "NAV" mode and push the CWS for a period of time and release, it will go back to NAV mode and tries to capture the pervious course.
It is a good thing to test and verify to see how it behaves.

B) The other day I was trying my new toys in the new plane (G3X touch with 650 and TOGO button) on a GPS LPV approach with my altitude bug at 4000. Prior to arriving at MAP, I pushed the TOGO and the A/P pitched up and followed the runway heading and climbed to 4000 but never followed the miss approach. On 650 I had the option of suspend or missed approach which I had selected missed approach and was expecting the A/P go to the NAV mode and follow the miss approach but it did not.

I wonder if this will follow the course to missed approach only if the TOGO button has been pushed after arriving the MAP?

One of the Garmin youtube video clearly shows that it should do that but mine did not go to NAV mode automatically.

Thoughts?

Bavafa, you answered one question,(B) as to what the TOGA will do, it apparently picks up the altitude limitation. As to the NAV - try what Bill stated above, touch hdg-AP-NAV for the 650 guidance, as long as the approach has been unsuspended. I have done that and it works. What happens before that has me seeking options.

To your A comment, my documentation does not precisely address the CWS commands, and results (integrated autopilot). I have found that a tap will release the AP, a second tap reengages the AP to the previous vert and nav mode. But must determine exactly what vertical and nav modes do after the CWS is held for a few seconds, while the 650 approach is suspended. I may have to make a video of this to see what the screen is telling me. I get kinda focused on the altitude at the MAP with the altitude AGL being so small.
 
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The other day I was trying my new toys in the new plane (G3X touch with 650 and OTGO button) on a GPS LPV approach with my altitude bug at 4000. Prior to arriving at MAP, I pushed the TOGO and the A/P pitched up and followed the runway heading and climbed to 4000 but never followed the miss approach. On 650 I had the option of suspend or missed approach which I had selected missed approach and was expecting the A/P go to the NAV mode and follow the miss approach but it did not.

I wonder if this will follow the course to missed approach only if the TOGO button has been pushed after arriving the MAP?

One of the Garmin youtube video clearly shows that it should do that but mine did not go to NAV mode automatically.

Thoughts?
Hello Mehrdad,

A couple of comments on this.
  • When you use the TO/GA button to execute the missed approach with a GTN, you should not have to interact with the GTN in any way. It will automatically execute the missed approach and will not wait on you to answer the "Suspend" or "Execute Missed Approach" question. It sounds like you either don't have the GTN discrete wired correctly to your button, or the discrete is not properly configured for "Remote Go Around".
  • On an LPV approach, the autopilot will automatically convert the GA lateral mode to GPS and couple laterally to GPS NAV to fly the missed approach.
  • On an ILS approach, the GA lateral mode will not automatically switch to GPS mode. Since flying the missed approach requires switching nav sources from VLOC to GPS, you have to simply press the NAV button on the control panel to couple laterally to fly the missed approach. Two pilot actions on ILS. Push TO/GA button, then push NAV button on ILS. On an LPV, just push TO/GA button.
  • After you push the TO/GA button, the vertical flight director (autopilot) mode will stay in GA (fixed, preset pitch angle) unless you push a button and convert to another vertical mode such as PIT, VS, or IAS for the climb.
  • You do NOT have to wait until arriving at the MAP to push the TO/GA button to have all of this work automatically. I frequently push the TO/GA button early on an LPV practice approach when traffic at the airport makes it prudent to do so. It works the same.

Thanks,
Steve
 
Hello Mehrdad,

A couple of comments on this.
  • When you use the TO/GA button to execute the missed approach with a GTN, you should not have to interact with the GTN in any way. It will automatically execute the missed approach and will not wait on you to answer the "Suspend" or "Execute Missed Approach" question. It sounds like you either don't have the GTN discrete wired correctly to your button, or the discrete is not properly configured for "Remote Go Around".
  • On an LPV approach, the autopilot will automatically convert the GA lateral mode to GPS and couple laterally to GPS NAV to fly the missed approach.
  • On an ILS approach, the GA lateral mode will not automatically switch to GPS mode. Since flying the missed approach requires switching nav sources from VLOC to GPS, you have to simply press the NAV button on the control panel to couple laterally to fly the missed approach. Two pilot actions on ILS. Push TO/GA button, then push NAV button on ILS. On an LPV, just push TO/GA button.
  • After you push the TO/GA button, the vertical flight director (autopilot) mode will stay in GA (fixed, preset pitch angle) unless you push a button and convert to another vertical mode such as PIT, VS, or IAS for the climb.
  • You do NOT have to wait until arriving at the MAP to push the TO/GA button to have all of this work automatically. I frequently push the TO/GA button early on an LPV practice approach when traffic at the airport makes it prudent to do so. It works the same.

Thanks,
Steve
Hello Steve,
I appreciate the info here, it looks like something is not setup correctly on mine.

I did an LPV approach two days ago to test the TOGO function and prior to reaching the MAP, I pushed the TOGO button which caused it to pitched up and flew runway heading. The NAV button on the A/P never got engaged.

Today I did the same LPV approach, setup my minimum and waited till I arrived at my minimum and then I pushed the TOGO button. This time, the NAV button on the A/P was lit and it flew the published miss but I had to interact with the 650 to tell it to do the miss approach (had two options, suspend or miss)

When I wired my TOGO button, I had two discrete and ran them together to a single poll switch. I know this is not the recommended way to run them to a single poll switch but do you think this is part of the issue or is it a configuration missing on the 650?

I don?t recall any configuration on the 650 for this discrete.

Much appreciate the feedback here.
 
Hello Steve,
I appreciate the info here, it looks like something is not setup correctly on mine.

I did an LPV approach two days ago to test the TOGO function and prior to reaching the MAP, I pushed the TOGO button which caused it to pitched up and flew runway heading. The NAV button on the A/P never got engaged.

Today I did the same LPV approach, setup my minimum and waited till I arrived at my minimum and then I pushed the TOGO button. This time, the NAV button on the A/P was lit and it flew the published miss but I had to interact with the 650 to tell it to do the miss approach (had two options, suspend or miss)

When I wired my TOGO button, I had two discrete and ran them together to a single poll switch. I know this is not the recommended way to run them to a single poll switch but do you think this is part of the issue or is it a configuration missing on the 650?

I don’t recall any configuration on the 650 for this discrete.

Much appreciate the feedback here.

Hello Mehrdad,

Wiring the two inputs to a SPST button is likely not the problem.

Step 1 is to identify which GTN input discrete is wired to the TO/GA button.

Step 2 is to configure the GTN input discrete wired to the TO/GA button to "Remote Go Around".

We always use P1002, pin 11 in our planes and kiosks since few EAB aircraft have a GSR 56 installed and "GSR Status In" is the default configuration for this input discrete and can be changed to "Remote Go Around".

Thanks,
Steve
 
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Hello Mehrdad,

Wiring the two inputs to a SPST button is likely not the problem.

Step 1 is to identify which GTN input discrete is wired to the TO/GA button.

Step 2 is to configure the GTN input discrete wired to the TO/GA button to "Remote Go Around".

We always use P1002, pin 11 in our planes and kiosks since few EAB aircraft have a GSR 56 installed and "GSR Status In" is the default configuration for this input discrete and can be changed to "Remote Go Around".

P.S. I read one post that running both discrete to single SPST switch could cause some issues. I have ordered a DPDT momentary switch to replace this if you can confirm it is needed. Logically, I can't think of a reason that it would make a difference.

Thanks,
Steve

Good Morning Steve,
Again, thank you for chiming in so quickly.
Looking at my wiring diagram, I see that I have pin 38 of P1001 of the 650 as well as pin 10 of P5071 of GMS-507 connected to my TOGO button.

Is the pin 38 of P1001 not correct or can it be configured to use for this purpose thru discrete settings?
 
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I forgot to mention that I had read one post that running both TOGO wire lead to a SPST switch could cause some issues. Last night I ordered a double pole momentary switch to replace this but logically, I can't think of how different that would be since both get grounded at the same time in either case.
 
Good Morning Steve,
Again, thank you for chiming in so quickly.
Looking at my wiring diagram, I see that I have pin 38 of P1001 of the 650 as well as pin 10 of P5071 of GMS-507 connected to my TOGO button.

Is the pin 38 of P1001 not correct or can it be configured to use for this purpose thru discrete settings?

Hello Mehrdad,

Yes, the GTN P1001, pin 38 discrete input that defaults to an "Air/Ground" input can be reconfigured for the "Remote Go Around" input connected to the TO/GA button.

We prefer to see a DPST button (e.g. Apem 4743 series) used in lieu of a SPST button since it provides good isolation between the two inputs on the two devices.

Thanks,
Steve
 
Hello Mehrdad,

Yes, the GTN P1001, pin 38 discrete input that defaults to an "Air/Ground" input can be reconfigured for the "Remote Go Around" input connected to the TO/GA button.

We prefer to see a DPST button (e.g. Apem 4743 series) used in lieu of a SPST button since it provides good isolation between the two inputs on the two devices.

Thanks,
Steve
Hi Steve,
This is really good news as I was dread having to move wires around. Do you mind sharing how this reconfiguration is done or should I contact Garmin support.
On the DPST switch which I ordered one, I was planning on running my ground to both poles and then connect each TOGO lead to each leg of each pole. Sounds about right?
 
Hello Mehrdad,

A couple of comments on this.
  • When you use the TO/GA button to execute the missed approach with a GTN, you should not have to interact with the GTN in any way. It will automatically execute the missed approach and will not wait on you to answer the "Suspend" or "Execute Missed Approach" question. It sounds like you either don't have the GTN discrete wired correctly to your button, or the discrete is not properly configured for "Remote Go Around".
  • On an LPV approach, the autopilot will automatically convert the GA lateral mode to GPS and couple laterally to GPS NAV to fly the missed approach.
  • On an ILS approach, the GA lateral mode will not automatically switch to GPS mode. Since flying the missed approach requires switching nav sources from VLOC to GPS, you have to simply press the NAV button on the control panel to couple laterally to fly the missed approach. Two pilot actions on ILS. Push TO/GA button, then push NAV button on ILS. On an LPV, just push TO/GA button.
  • After you push the TO/GA button, the vertical flight director (autopilot) mode will stay in GA (fixed, preset pitch angle) unless you push a button and convert to another vertical mode such as PIT, VS, or IAS for the climb.
  • You do NOT have to wait until arriving at the MAP to push the TO/GA button to have all of this work automatically. I frequently push the TO/GA button early on an LPV practice approach when traffic at the airport makes it prudent to do so. It works the same.

Thanks,
Steve

Hi Steve,
I have read this a few times and request a clarification, but in addressing, lets choose an RNAV-LPV approach where the missed requires a climb to a specific altitude before making the turn to the holding point. You can look at the RNAV 18 to 3MY as the example.

I think your description indicates there is no vertical guidance nor altitude consideration for the lateral guidance while executing the missed. Meaning, if the TOGA is engaged at or just before the MAP, then the climb will commence immediately as well as the turn to course for the hold point (without consideration for altitude and/or obstacle clearance).

The answer may come down to what guidance is provided by the 650 for all approach procedures. The LPV has vertical guidance for approach, as it is part of the procedure, why wouldn't the guidance for the missed procedure also contain the same vertical guidance? Is that not considered part of the FAA procedure?
 
Hi Steve,
I have read this a few times and request a clarification, but in addressing, lets choose an RNAV-LPV approach where the missed requires a climb to a specific altitude before making the turn to the holding point. You can look at the RNAV 18 to 3MY as the example.

I think your description indicates there is no vertical guidance nor altitude consideration for the lateral guidance while executing the missed. Meaning, if the TOGA is engaged at or just before the MAP, then the climb will commence immediately as well as the turn to course for the hold point (without consideration for altitude and/or obstacle clearance).

The answer may come down to what guidance is provided by the 650 for all approach procedures. The LPV has vertical guidance for approach, as it is part of the procedure, why wouldn't the guidance for the missed procedure also contain the same vertical guidance? Is that not considered part of the FAA procedure?

Hello Bill,

While there is no vertical guidance provided by the GTN on the LPV missed approach, the GTN does honor altitude constraints such as the one in the 3MY LPV RWY 18 approach.

The missed approach instructions for this approach are: "Climb to 1200 then climbing right turn to 2700, direct WETEV and hold."

When you go missed and push the TO/GA button, you should already have the selected altitude set to 2700. The system initially shows GA GA in the autopilot mode bar on the PFD, but quickly transitions to GPS GA with lateral GPS coupling following GPS roll steering (bank angle) from the GTN.

Since the missed approach instructions call for climbing to 1,200' before beginning the right turn, the GTN provided lateral guidance will keep you flying straight ahead, as long as it takes, until you reach 1,200'. Then, and only then, will the GTN lateral guidance turn the aircraft right on a standard rate turn and fly direct to WETEV for the hold.

As mentioned in my previous write-up, it is up to you what vertical mode is used in the climb to both 1,200' and ultimately 2,700'. You can leave the vertical mode set to GA which is a fixed pre-defined pitch angle until it captures 2,700' and automatically changes to ALT mode, or you can switch to PIT, VS, or IAS (all controlled with GMC wheel) to perform the climb to the hold altitude.

When you think about it, it only makes sense to work this way. Every airplane can descend on the glide path coded in these approaches, but the climb performance of each aircraft is different, so you wouldn't want the instrument approach to specify vertical path guidance on the climb to the missed approach hold, since it wouldn't always be safe to do so for all aircraft unless that climb path was extremely shallow. The way it is now, all aircraft can climb as fast or as slow as they choose.

Let us know if you still have questions.

Thanks,
Steve
 
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Hello Bill,

While there is no vertical guidance provided by the GTN on the LPV missed approach, the GTN does honor altitude constraints such as the one in the 3MY LPV RWY 18 approach.

The missed approach instructions for this approach are: "Climb to 1200 then climbing right turn to 2700, direct WETEV and hold."

When you go missed and push the TO/GA button, you should already have the selected altitude set to 2700. The system initially shows GA GA in the autopilot mode bar on the PFD, but quickly transitions to GPS GA with lateral GPS coupling following GPS roll steering (bank angle) from the GTN.

Since the missed approach instructions call for climbing to 1,200' before beginning the right turn, the GTN provided lateral guidance will keep you flying straight ahead, as long as it takes, until you reach 1,200'. Then, and only then, will the GTN lateral guidance turn the aircraft right on a standard rate turn and fly direct to WETEV for the hold.

As mentioned in my previous write-up, it is up to you what vertical mode is used in the climb to both 1,200' and ultimately 2,700'. You can leave the vertical mode set to GA which is a fixed pre-defined pitch angle until it captures 2,700' and automatically changes to ALT mode, or you can switch to PIT, VS, or IAS (all controlled with GMC wheel) to perform the climb to the hold altitude.

When you think about it, it only makes sense to work this way. Every airplane can descend on the glide path coded in these approaches, but the climb performance of each aircraft is different, so you wouldn't want the instrument approach to specify vertical path guidance on the climb to the missed approach hold, since it wouldn't always be safe to do so for all aircraft unless that climb path was extremely shallow. The way it is now, all aircraft can climb as fast or as slow as they choose.

Let us know if you still have questions.

Thanks,
Steve

Thanks Steve, your description does make perfect sense. It would be odd if it didn't but I wanted a definitive statement that it did do this. Very very helpful,
Bill
 
I wanted to resurect an old post, if I may.

When I press my TOGA switch it disconnects the autopilot (G3X Autopilot and GTN750) and commands a pitch up attitude and wings level.

Is there a way to change what the TOGA button commands the Autopilot to do? I'm hoping upon pressing the button it would become a case of add power and the AP flys the Missed approach.
 
Autopilot Configuration

I wanted to resurect an old post, if I may.

When I press my TOGA switch it disconnects the autopilot (G3X Autopilot and GTN750) and commands a pitch up attitude and wings level.

Is there a way to change what the TOGA button commands the Autopilot to do? I'm hoping upon pressing the button it would become a case of add power and the AP flys the Missed approach.

In configuration mode, select Autopilot, and then the Pitch tab. What value do you have set for Min Airspeed Limit?

Thanks,

Justin
 
Steve or Justin, can you please explain the difference between the TOGA on the GMC507 compared to the GTN?

From the G3X manual: "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."

Is there an advantage or improved functionality of wiring the TOGA to the GTN over the GMC507? Thanks
 
TO/GA Input

Steve or Justin, can you please explain the difference between the TOGA on the GMC507 compared to the GTN?

From the G3X manual: "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."

Is there an advantage or improved functionality of wiring the TOGA to the GTN over the GMC507? Thanks

Grounding the TO/GA input on the GMC 507 transitions the flight director modes to GO AROUND (GA) both laterally and vertically. Activating a TO/GA input on the GTN cycles the flight plan to the missed approach procedure on your navigator. You want your TO/GA button (ideally located near the throttle) to activate both inputs at the same time, this is shown on the right hand side of page 27-10 of the G3X Touch Installation Manual (rev AQ).

Please let us know if you have any other questions.

Thanks,

Justin
 
Grounding the TO/GA input on the GMC 507 transitions the flight director modes to GO AROUND (GA) both laterally and vertically. Activating a TO/GA input on the GTN cycles the flight plan to the missed approach procedure on your navigator. You want your TO/GA button (ideally located near the throttle) to activate both inputs at the same time, this is shown on the right hand side of page 27-10 of the G3X Touch Installation Manual (rev AQ).

Please let us know if you have any other questions.

Thanks,

Justin

Looking for a little guidance on use with a 430W. If I hit the TOGA button, both go to GA mode, which I assume is PIT mode to the preset pitch angle setting and then ROL mode on the lateral. If I un-suspend on the 430, will it switch to NAV mode or do in need to press the NAV button or do I need to use HDG mode until the phase where an actual nav direction is specified on the plate? Lets say I set the ALT bug to the final alt and go into VS mode, will the AP correctly use the altitudes in the missed procedure before executing turns like you described in a previous post for the GTN series or do I need to do that?
 
The Min Airspeed Limit and Max is not set. All I see is _____kt on both.

It stands to reason that the autopilot requires a valid configuration for Minimum Airspeed in order to remain engaged when go-around mode is selected. If this wasn't the case, you might not like the results. You just need to follow the configuration instructions on page 35-68 of the current installation manual (revision AQ):

Go to the Autopilot Configuration page and set the proper min/max airspeed limits for the pitch servo. The pitch servo will lower or raise the nose of the aircraft to try and keep it inside these airspeed limits.
a) The min airspeed limit should be set above the stall speed of the aircraft with some margin.
b) The max airspeed limit should be set below the never exceed speed of the aircraft with some margin.
 
TO/GA

Steve wrote.
You do NOT have to wait until arriving at the MAP to push the TO/GA button to have all of this work automatically. I frequently push the TO/GA button early on an LPV practice approach when traffic at the airport makes it prudent to do so. It works the same.
More a procedural point with an early G/A particularly, on LPV or RNP approach, although, technically on all approaches were a MAP is defined. No lateral manoeuvres should be commenced prior to reaching the MAP. In specific cases this can be overridden in the G/A procedures. In the airline world this was ensured by an over-fly at the MAP in the data base or a crew entry of an over-fly at the MAP.
 
Steve wrote.
You do NOT have to wait until arriving at the MAP to push the TO/GA button to have all of this work automatically. I frequently push the TO/GA button early on an LPV practice approach when traffic at the airport makes it prudent to do so. It works the same.
More a procedural point with an early G/A particularly, on LPV or RNP approach, although, technically on all approaches were a MAP is defined. No lateral manoeuvres should be commenced prior to reaching the MAP. In specific cases this can be overridden in the G/A procedures. In the airline world this was ensured by an over-fly at the MAP in the data base or a crew entry of an over-fly at the MAP.

Interesting point. If I went missed, at say 4 miles until the MAP, I assume the Autopilot would climb to the Alt set on MCP, fly the LOC until at the MAP then turn as per the procedure?
 
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