Flying the Missed Approach with a GPS 175 and GNC 255

[donkaye]

I posted this to BeechTalk and so far have gotten NO responses, so maybe the question is not so obvious.  Personally, I  think you have to manually switch Sources on the G5 after pushing the TOGO button before engaging NAV on the GFC 500, as part of the procedure, unlike the GTN where it is automatic.

"I had the following question posed to me and I couldn't give a definitive answer because I've not had any students with this combination of equipment, ie the GPS and ILS radios being different pieces of equipment.  With the GTNs the sequence is simple, since the radios are combined in a single unit and work together. I think I know the procedure, but would like confirmation from someone who has actually used the given equipment.
 

Equipment: 2 G5s, GPS 175, GNC 255, GFC 500

If flying an ILS approach with the GNC 255 and going missed, what is the sequence of button pushes that would be necessary to accomplish this task in combination with the GFC 500?
Thanks."

 

[JimB]

Don,

I have the same equipment in my F plus a GNX 375 but to be honest I am not sure either since all I have done are practice GPS approaches. I believe if you are monitoring the ILS/VOR approach with the GPS, you would push the TOGO button (commanding the nose up/wings level) and switch nav sources on the G5 and it would fly the missed per the established procedures loaded in the GPS. I could go try it tomorrow and let you know exactly what works if you don't get a better answer before then. 

[donkaye]

2 hours ago, JimB said:

Don,

I have the same equipment in my F plus a GNX 375 but to be honest I am not sure either since all I have done are practice GPS approaches. I believe if you are monitoring the ILS/VOR approach with the GPS, you would push the TOGO button (commanding the nose up/wings level) and switch nav sources on the G5 and it would fly the missed per the established procedures loaded in the GPS. I could go try it tomorrow and let you know exactly what works if you don't get a better answer before then. 

I left out the important point, having the GPS 175 as the GPS to switch to, but the GNX 375 would b the same, since it is a GPS/Comm.

[PeteMc]

Guessing it's a GNC355 if GPS/Comm. 

But I'm curious why you'd be switching *AT* the Missed?  Seems to me that this would be a lot of button pushing and mental bandwidth to make sure everything is doing what it is supposed to be doing.  (And not flying you into that hill or tower just off to the right....)

If the autopilot is engaged (or you just want to follow the Flight Director) then I could see pushing the Go Around button to start the climb, then continue to fly the Missed by hand or heading if still on the AP.  Once well established on the Missed and with some altitude, then you can confirm the GPS is really tracking the Missed (active leg, etc.) and switch over to follow the GPS.

[carusoam]

Trek Lawler should/may be available at BT..?

you might want to tag him on your request for information...

Best regards,

-a-

[David Lloyd]

Don,

I don't have an answer for you, but it is a great question causing a lot of thought.  I am picking up my airplane in another week or so with two new GI-275 to replace the failing vacuum AI and the King HSI with sticky flags. Existing avionics are a GNX375, KX165 with GS, and Stec 60-2.  I will be making a list of various scenarios to figure out what happens when.  Does the GPSS drop out when vectors for the approach is activated? Do I press the HDG and NAV buttons on the 60-2 before or after?  If GPSS was used before the approach, will it become active again when unsuspending the procedure at the MAP?  If doing an ILS with the 165 as the nav source, going missed, do I switch the source back to GPS?  Geez, I'm gonna have a 10 or 12 item list to figure out.  Better to find out now, in nice weather.  Thanks.

[carusoam]

See if Stec has a user handbook…

The BK book has a page for every aspect of flying their AP…

Each phase of flight, each type of approach, and what happens under various circumstances…

What changes at each step, why pushing the APPR button on time does one thing, and being late may not do something important…

This way you have a list of expectations while you test the validity of the install….

PP thoughts only, not a CFI…

Best regards,

-a-

[David Lloyd]

I have the original Stec pilot guide from 1990, when it was installed, matches the current offering on their website.  It tells in detail how to fly an ILS, only mentions GPS and LORAN as capabilities, no detail.  When it was written, I don't think an LPV approach was even a dream.  Yes I am good with using pushing the buttons at the appropriate time, getting vectors for an ILS, following the heading bug, and intercepting the localizer, then the glideslope.  But using GPSS or just GPS to the approach course and then switching the nav source to ILS, well that is something they didn't foresee.  I'll work it out with a little trial and error in clear air.

A lot of us that upgrade one piece of equipment or another, frequently from different manufactures need to find out how each piece interfaces with others.  Don's question illustrates the problem, how is this used with that when doing whatever, and Don is as or more knowledgeable than about anyone here.  How does a new display or navigator work with an old autopilot or a new one is something that needs to be sorted thru before an approach in the murk.

[donkaye]

6 hours ago, David Lloyd said:

I have the original Stec pilot guide from 1990, when it was installed, matches the current offering on their website.  It tells in detail how to fly an ILS, only mentions GPS and LORAN as capabilities, no detail.  When it was written, I don't think an LPV approach was even a dream.  Yes I am good with using pushing the buttons at the appropriate time, getting vectors for an ILS, following the heading bug, and intercepting the localizer, then the glideslope.  But using GPSS or just GPS to the approach course and then switching the nav source to ILS, well that is something they didn't foresee.  I'll work it out with a little trial and error in clear air.

A lot of us that upgrade one piece of equipment or another, frequently from different manufactures need to find out how each piece interfaces with others.  Don's question illustrates the problem, how is this used with that when doing whatever, and Don is as or more knowledgeable than about anyone here.  How does a new display or navigator work with an old autopilot or a new one is something that needs to be sorted thru before an approach in the murk.

Regarding the GFC 500 and different Nav source boxes, I confirmed with Garmin that the Nav source needs to be manually switched on the missed approach.  So, for example, with the GPS175 and GNC 255, after going missed from an ILS approach using the GNC 255:

1. Push the TOGA Button

2. Verify GA/GA

3. Add Power and properly configure for the go around

4. Verify missed approach altitude

5. Switch input source on the G5 to GPS 175 and verify GPS on the G5

6. Reengage NAV Mode on the GMC 507 to fly the missed approach

7. Reengage IAS or V/S

8. Verify AFCS Modes

[midlifeflyer]

4 hours ago, donkaye said:

Regarding the GFC 500 and different Nav source boxes, I confirmed with Garmin that the Nav source needs to be manually switched on the missed approach.  So, for example, with the GPS175 and GNC 255, after going missed from an ILS approach using the GNC 255:

1. Push the TOGA Button

2. Verify GA/GA

3. Add Power and properly configure for the go around

4. Verify missed approach altitude

5. Switch input source on the G5 to GPS 175 and verify GPS on the G5

6. Reengage NAV Mode on the GMC 507 to fly the missed approach

7. Reengage IAS or V/S

8. Verify AFCS Modes

That's good to know. I didn't contribute because I know there are various TOGA/GPS/AP combinations, even with similar avionics. Some auto-switch, some don't. Some engage AP; others only the FD.

I like that checklist. The only thing I'd add is to #2 (actually insert after #3) is to verify whether the AP is engaged (and to engage if not). I might also reverse #2 and #3. You actually end up with an almost universal template which can be easily modified depending on the specific set up.

some might also argue that your #3 should be #2. That "aviate" (power and climb configuration) has priority over "navigate" (are the avionics doing what they should?).

[David Lloyd]

9 hours ago, donkaye said:

Regarding the GFC 500 and different Nav source boxes, I confirmed with Garmin that the Nav source needs to be manually switched on the missed approach.  So, for example, with the GPS175 and GNC 255, after going missed from an ILS approach using the GNC 255:

1. Push the TOGA Button

2. Verify GA/GA

3. Add Power and properly configure for the go around

4. Verify missed approach altitude

5. Switch input source on the G5 to GPS 175 and verify GPS on the G5

6. Reengage NAV Mode on the GMC 507 to fly the missed approach

7. Reengage IAS or V/S

8. Verify AFCS Modes

Yes, something similar for the 275/165/375/60-2 combination.  I've always been a listmaker/listfollower.  It's just a matter of making a list, trying it out, adjusting the list and then running thru it a couple times.  I've never had GPSS before so there will be a checklist or two involving that also.

[PT20J]

On 6/13/2021 at 11:07 PM, donkaye said:

Regarding the GFC 500 and different Nav source boxes, I confirmed with Garmin that the Nav source needs to be manually switched on the missed approach.  So, for example, with the GPS175 and GNC 255, after going missed from an ILS approach using the GNC 255:

1. Push the TOGA Button

2. Verify GA/GA

3. Add Power and properly configure for the go around

4. Verify missed approach altitude

5. Switch input source on the G5 to GPS 175 and verify GPS on the G5

6. Reengage NAV Mode on the GMC 507 to fly the missed approach

7. Reengage IAS or V/S

8. Verify AFCS Modes

Thanks for getting the correct info and posting. Eight memory items happening at a critical time! Since real missed approaches don’t happen that often, it’s good to practice this every so often.

The TOGA button is generally mounted so that you can hit it with the index finger of your right hand as you push the throttle in. So for me, items 1 and 3 occur together with item 3 slightly leading item 1. 

Also, I always keep my left hand lightly on the yoke (and near the autopilot disconnect button) so that if anything doesn’t go right, I can instantly take back control. I do this whenever I in a critical condition: FAF inbound, initiating missed approach, low altitude, leveling off.

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[donkaye]

54 minutes ago, PT20J said:

Thanks for getting the correct info and posting. Eight memory items happening at a critical time! Since real missed approaches don’t happen that often, it’s good to practice this every so often.

The TOGA button is generally mounted so that you can hit it with the index finger of your right hand as you push the throttle in. So for me, items 1 and 3 occur together with item 3 slightly leading item 1. 

Also, I always keep my left hand lightly on the yoke (and near the autopilot disconnect button) so that if anything doesn’t go right, I can instantly take back control. I do this whenever I in a critical condition: FAF inbound, initiating missed approach, low altitude, leveling off.

Skip

I think the TOGA button needs to be pushed 1st with the power being applied almost simultaneously, the reason being that you don't want to be continuing down past DA before the button is pushed.

[PT20J]

Just now, donkaye said:

I think the TOGA button needs to be pushed 1st with the power being applied almost simultaneously, the reason being that you don't want to be continuing down past DA before the button is pushed.

Good point. I’ve noticed a lot of students tend to continue down hill because the engine is making a lot of noise so they think they are climbing. For me, the airplane doesn’t accelerate fast enough for that to be an issue, and I can push the throttle and the TOGA button without taking my eyes off the attitude indicator. Really the best set up is with a quadrant and the TOGA button on the throttle so you can activate it with your thumb.

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