Garmin GPS 175 didn't give me a procedure turn when it should have. Help.

bcg-63M20C

Filing Flight Plan
Joined
Sep 15, 2022
Messages
22
Display Name

Display name:
bcg
I recently replaced an old GPSS system with a dual G5 and GAD29 in my plane. Previously, if I had a very tight turn to begin an approach, the GPS would automatically put in the procedure turn at the IAF and direct the AP accordingly. Today, the first time I tried it on the new system, it tried to make the turn from a 270 heading to a 120 heading directly instead of using a PT. Before I get deep into this, does anyone have any idea what I should be looking at? I'm sure it's either a configuration or programming error.

Thanks.



Sent from my Pixel 6a using Tapatalk
 
Way too little info. What GPS navigator and autopilot are in play?
 
Way too little info. What GPS navigator and autopilot are in play?
Garmin GPS 175, I had it in the title. The AP is an S-Tec 50 but it doesn't really matter, it just does what the GPS tells it to do and the GPS didn't tell it to do a PT.

Sent from my Pixel 6a using Tapatalk
 
Last edited:
Was it a HILPT? If so, the box should have asked you if you want to fly it.
 
What mode did the G5 show for the active autopilot mode?
 
I suspect the gps asked you if you wanted the procedure turn and you answered no. That's really the only time I've been burned by this, I was in a rush to get the procedure loaded and clicked no without thinking about it.
 
I suspect the gps asked you if you wanted the procedure turn and you answered no. That's really the only time I've been burned by this, I was in a rush to get the procedure loaded and clicked no without thinking about it.

I’ve been burned there too, and it really reinforced verifying what’s in the flight plan matches what’s in my brain.
 
I suspect the gps asked you if you wanted the procedure turn and you answered no. That's really the only time I've been burned by this, I was in a rush to get the procedure loaded and clicked no without thinking about it.
I don't think it's ever asked me that. We actually removed the approach and reloaded it with the same result. It was odd, in the past I remember it always just doing it if it was needed. That said, I've had the plane down for 3 months for annual and avionics so I could be misremembering. This is the first approach I've flown in it since late August.

Sent from my Pixel 6a using Tapatalk
 
Then it’s most likely the PT was not loaded in the sequence.
Correct, that's my question. Why wasn't it loaded when the GPS loaded/activated the approach? It always has in the past.

Sent from my Pixel 6a using Tapatalk
 
Do you load the approach while you’re headed to the iaf and check to see if the if the procedure turn is shown in gray and the procedure name appears in the flight plan page after the iaf? If I remember right, that’s how I was taught. Then we didn’t activate the approach till the atc clears us and we’re passed the Iaf.
 
Do you load the approach while you’re headed to the iaf and check to see if the if the procedure turn is shown in gray and the procedure name appears in the flight plan page after the iaf? If I remember right, that’s how I was taught. Then we didn’t activate the approach till the atc clears us and we’re passed the Iaf.
I did load and verify it was there but did not look for the PT on the map until we got closer.

Sent from my Pixel 6a using Tapatalk
 
Correct, that's my question. Why wasn't it loaded when the GPS loaded/activated the approach? It always has in the past.

Sent from my Pixel 6a using Tapatalk

It likely did not load because you were likely presented the option to fly a PT/HILPT or not and chose not to.

Without a video replay though, the only thing we have to rely on is memory. If you share the approach and the transition you flew, I’ll put it thru Garmin’s GTN trainer and see if the option was presented or not.
 
Last edited:
It likely did not load because you were likely presented the option to fly a PT/HILPT or not and chose not to.

Without a video replay though, the only thing we have to rely on is memory. If you share the approach and the transition you flew, I’ll put it thru Garmin’s GTN trainer and see if the option was presented or not.
RNAV12 via OBUCO into ERV

We deleted and reloaded the approach, it didn't give an option that I saw...

Sent from my Pixel 6a using Tapatalk
 
RNAV12 via OBUCO into ERV

We deleted and reloaded the approach, it didn't give an option that I saw...

Sent from my Pixel 6a using Tapatalk

Heh. I know that approach well. I’m based out of SSF and 5C1. Just flew it last month. Give me a bit and I’ll run it thru the trainer.
 
Heh. I know that approach well. I’m based out of SSF and 5C1. Just flew it last month. Give me a bit and I’ll run it thru the trainer.
I used to fly out of 5C1 a lot and know quite a few people over there, wouldn't be surprised if we've met at some point. What do you fly? I've got a 63 Mooney M20C.

We were heading back to ERV from HYI after flight testing a new NAV radio on the ILS. That worked great.

Sent from my Pixel 6a using Tapatalk
 
So, loading the approach and selecting OBUCO presents the 4NM hold.
b257df6221195c6ee7e3f5c440b76b6e.jpg


If you select VTF for the transition (intentionally or otherwise), the hold does not present and you’re sequenced to OBUCO since it’s the IAF.

6acde6ab50decaf5436f4edbab0a971f.jpg

But, what I found interesting is if you load the approach with OBUCO as the transition, the when you activate the approach, if you select Activate VTF, the hold is removed, even though it was loaded in the sequence when OBUCO was chosen. I can understand Garmin’s logic behind that since a course reversal isn’t required for VTF. OBUCO is left in the sequence, but the active leg is set to LAVIC.

My best guess is there was a buttonology error or VTF was selected at some point.

ETA: I’m a partner in a 172 at Stinson and we may be adding a 182 shortly. I’ve been renting Cirrus and TAA 172s at 5C1 since I live across 10 near FOR and wanted some TAA time with a variety of avionics configurations.

If you Joe Cabe, we have a mutual friend.
 
Last edited:
So, loading the approach and selecting OBUCO presents the 4NM hold.
b257df6221195c6ee7e3f5c440b76b6e.jpg


If you select VTF for the transition (intentionally or otherwise), the hold does not present and you’re sequenced to OBUCO since it’s the IAF.

6acde6ab50decaf5436f4edbab0a971f.jpg

But, what I found interesting is if you load the approach with OBUCO as the transition, the when you activate the approach, if you select Activate VTF, the hold is removed, even though it was loaded in the sequence when OBUCO was chosen. I can understand Garmin’s logic behind that since a course reversal isn’t required for VTF. OBUCO is left in the sequence, but the active leg is set to LAVIC.

My best guess is there was a buttonology error or VTF was selected at some point.

ETA: I’m a partner in a 172 at Stinson and we may be adding a 182 shortly. I’ve been renting Cirrus and TAA 172s at 5C1 since I live across 10 near FOR and wanted some TAA time with a variety of avionics configurations.

If you Joe Cabe, we have a mutual friend.
I did Direct To KERV then loaded the RNAV12 with OBUCO. It only gave me OBUCO or VECTORS as choices.

I'll play with it some more.and see if I can figure out what's going on.

I know the name.buy, can't put a face to it. I did some of my early flight training at Texas Skies.

Sent from my Pixel 6a using Tapatalk
 
Was it a HILPT? If so, the box should have asked you if you want to fly it.
Nope. Coming from that direction, it wont ask. It will load the hold automatically.

@bcg-63M20C, like @TCABM, I ran it in the trainer. Created the HYI-ERV flight plan and loaded the RNAV 12 via OBUCO.
1701343571205.png
Unless something is wrong with the unit, it will always load the hold coming from that direction with that transition. Unless something is wrong with the unit, the only three things I can think of offhand that would remove it while retaining the extended FAC are VTF, activating the OBUCO-LAVIC leg, or using the “Remove” option.
 
when you activate the approach, if you select Activate VTF, the hold is removed, even though it was loaded in the sequence when OBUCO was chosen
Thread creep...

So is any T IAF you loaded

I would expect that behavior. When you hit VTF you are basically telling the navigator, "I don't need all that other stuff." I don't have an inside line, but I think the retention of the waypoints along the extended final approach course in this series of GTN-based units may be related to the penchant of ATC to begin by giving vectors to final and then give direct to the some fix on the extended FAC, most commonly the IF with a straight in clearance. It may also be related to the regulatory "thou shalt make no course reversal" when being vectored to final in 91.175.

Parenthetically, I think IF-straight-in clearances are going to increase just because of increasing RNAV point-to-point availability. Coming from the arrival side of the airport, direct to the IF is less workload than vectors to intercept the FAC for both pilot and controller. Even from the departure side, I can see a 90° intercept "vectors to the IF" even without a charted T configuration.

But in any event, we need to remember that the only thing retained with VTF are those extended FAC waypoints. For another example, this is the RNAV 5R Y into RDU. Load the approach with OTTOS as the transition. Switch to VTF, and OTTOS will be gone; the ones from BEICH inbound will be retained.

1701367339255.png
 
I'm at the plane working on something else and tried it again just a minute ago. It shows the PT now with the expected teardrop. I guess it's possible I hit Vectors instead of OBUCO yesterday but, I'm fairly confident I told it to use OBUCO. Oh well, I'll see what happens next time I fly.

Sent from my Pixel 6a using Tapatalk
 
…But in any event, we need to remember that the only thing retained with VTF are those extended FAC waypoints. …
All good info; I think this bit of creep is actually the most useful part for me right now.
 
I'm at the plane working on something else and tried it again just a minute ago. It shows the PT now with the expected teardrop. I guess it's possible I hit Vectors instead of OBUCO yesterday but, I'm fairly confident I told it to use OBUCO. Oh well, I'll see what happens next time I fly.

Sent from my Pixel 6a using Tapatalk
I think it's a bit less of an issue with a touch system than a a button system, but many of us (me included) have a bad habit of touching things without really looking at them.
 
Nope. Coming from that direction, it wont ask. It will load the hold automatically
Right. That direction was not a part of the original post. I was under the impression that it might have been from a different direction.
 
I guess it's possible I hit Vectors instead of OBUCO yesterday but, I'm fairly confident I told it to use OBUCO. Oh well, I'll see what happens next time I fly.
Next time, maybe you can take a picture of the GPS screen anytime you cross a waypoint or something else changes. That will help confirm what's going on.
 
Back
Top