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GTN 650 vectors to final function


DXB

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Upon getting my IR, I am feeling danger of being reborn as a child of the magenta line, and a developmentally delayed one at that.  So I am working on resolving all my confusion with the GTN 650 to help focus on flying and not button pushing - particularly on approach .  Toward that end, I need a little more help on flying vectors to final. 

First a tentative observation that might generate discussion:

When loading (but not activating) an approach, it seems best to load  it with the most likely of the listed initial fixes and never as "vectors," even if anticipating getting vectors. That way if one is sent direct to an initial or intermediate fix to join the approach at the last minute, it increases the chances that the fix is already loaded. If sent to a fix, one can then simply hit that loaded fix in the flight plan and then "direct" to activate the approach.  Once certain of being given an intercept heading and not sent to a fix at the last minute to join, it is easy to hit the name of the approach in the flight plan and then "activate vectors to final" even if I loaded one of the available fixes to fly a full approach to a given runway.  Am I thinking clearly here??

Now two specific questions:

1. If I activate vectors to final, I see the extended magenta line of the final course and the FAF as the active waypoint, as expected. However if I am beyond a certain distance from the final course, an "unsuspend" button also appears in the lower right on the map and disappears at some point when I get closer (see recreation on ipad sim below). If I hit the button, then it activates the leg from the FAF to the runway before I intercept and I no longer see the FAF as the active waypoint - I just see distance to the runway.  My question is: Why does this button appear?  When would I ever use it??  I find no description of this functionality in the manual.  

2. Why do some airports offer an option to load visual approaches and others do not in their list of available procedures in the box?  I imagine a "visual" could be executed at any airport without navigational guidance (that's kinda the point of flying a "visual" approach once you see the field).  I understand the newest software version, which I do not have yet, creates a visual approach button for most any airport that provides advisory horizontal and vertical guidance.  Is that the point of selecting a visual approach from the procedures list??

image.thumb.png.b5cdd13a3ae5ed260608b606632c1698.png

 

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For question #1, from the GTN 725/750 Pilot’s Guide, 6.12 (page 6-18): 

If Vectors-to-Final is activated while on the “FROM” side of the FAF, automatic waypoint sequencing is suspended and the SUSP annunciation will appear. Automatic waypoint sequencing will resume once the aircraft is on the “TO” side of the FAF and within full-scale deflection.

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1 hour ago, Deb said:

For question #1, from the GTN 725/750 Pilot’s Guide, 6.12 (page 6-18): 

If Vectors-to-Final is activated while on the “FROM” side of the FAF, automatic waypoint sequencing is suspended and the SUSP annunciation will appear. Automatic waypoint sequencing will resume once the aircraft is on the “TO” side of the FAF and within full-scale deflection.

Ah thanks -  yes I see the same now in the GTN650 Pilot Guide 6.13.   I suppose it's to prevent it from prematurely activating the FAF to MAP leg.  I suppose it's best to  just ignore the button when it appears.     

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As to question number 2, from revision M of the manual:

"The availability of vertical guidance advisories for visual approaches is dependent on terrain and obstacle obstructions along the approach path.  If no known obstructions are within the approach path, vertical guidance is provided to a maximum distance of 28 NM from the runway. If there are known obstructions further than 3 NM, but within the 28 NM maximum distance from the runway along the approach, vertical guidance is limited to the approach path portion after crossing the known obstructions. This is indicated by the shortened magenta line on the map after loading the approach. If obstructions are within 3 NM to the runway, along the approach path, advisory vertical guidance is not provided. Lateral guidance is always provided for visual approaches. Published data is used to determine the visual approach GPA and TCH for the selected runway. If no published data is available, the default is 3° GPA and
50 FT TCH."

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The guidance to always load an initial fix rather than vectors is arguable.  I think new GTN owners are sometimes led astray by CFIIs who have been working with older navigators and/or older firmware for years.

First, with modern firmware, loading vectors on a GTN retains all fixes along the final approach course, including those prior to the FAF.  This is different from older navigators and GTNs with older firmware.  So if you're "surprise" cleared direct to a fix along the final approach course when you were expecting vectors, it's no more or less keystrokes to activate direct to that fix than if you'd loaded the full approach to start with.  Yes, it's possible the controller could clear you to a fix not along the final approach course when you were told to expect vectors, but this is uncommon, and not that big a deal anyway (see third point below).

Second, loading a full approach while actually being vectored has its own problems.  If you do this, the CDI is providing guidance along a leg you're not actually flying, and sometimes results in sequencing behavior that's hard to understand.  While it's true that controllers sometimes tell you to expect vectors and then clear you to a specific fix instead, this is less common than them actually giving you the vectors you were told to expect.  So by loading a full approach, you're accepting the risk of incorrect CDI guidance as a hedge against an event that's arguably not that likely to happen.  This is not an obviously good tradeoff.

Third, I've never really understood the mindset that loading a full approach somehow guarantees you're not going to have to push buttons in the middle of the approach in a way that might get confusing.  I do understand that with older navigators the number of button pushes may be different to switch in one direction vs. another.  But you should practice and understand how to re-sequence your GPS rapidly in either direction.  You're going to need this skill anyway for the "what's it doing now?" problem.  And on the GTN, it's pretty trivial to reload a VTF transition approach to select an IAF transition instead.  The five clicks are HOME -> PROC -> Approach -> Transition -> [desired transition].  Takes about 5 seconds.  If you find this especially distracting or confusing, I'd argue you need more practice and training.

Edited by Vance Harral
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Despite the GTN including fixes in a straight line to the FAC, I agree with the commentators who do not  see a good reason to avoid selecting and loading an appropriate IAF as part of the initial IAP loading/briefing process.

I guess I'm just one of  the bad CFIIs who leads pilots astray even though at this point I am more familiar with the GTN than the older navigators.

Edited by midlifeflyer
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Honest questions: how do you define "appropriate" IAF to load when the choice is ambiguous, and what do you teach your students about the behavior of the CDI during the interim period until you activate VTF?  I'm particularly interested in the scenario where you're approaching from the opposite direction of the final approach course (i.e. being vectored downwind), and the IAF is beyond the point you'll likely be vectored on a base and thence intercept leg.

To be clear, I'm not saying it's wrong to load an IAF when being vectored, and I'm not suggesting you're giving bad instruction.  I'm just saying the benefits aren't that clear.  I practice both methods as a form of mental pushups to stay comfortable with the navigator, and loading an IAF while being vectored seems like more of a distraction to me on the GTN.

Edited by Vance Harral
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On 7/3/2018 at 1:59 AM, Vance Harral said:

The guidance to always load an initial fix rather than vectors is arguable.  I think new GTN owners are sometimes led astray by CFIIs who have been working with older navigators and/or older firmware for years.

First, with modern firmware, loading vectors on a GTN retains all fixes along the final approach course, including those prior to the FAF.  This is different from older navigators and GTNs with older firmware.  So if you're "surprise" cleared direct to a fix along the final approach course when you were expecting vectors, it's no more or less keystrokes to activate direct to that fix than if you'd loaded the full approach to start with.  Yes, it's possible the controller could clear you to a fix not along the final approach course when you were told to expect vectors, but this is uncommon, and not that big a deal anyway (see third point below).

Second, loading a full approach while actually being vectored has its own problems.  If you do this, the CDI is providing guidance along a leg you're not actually flying, and sometimes results in sequencing behavior that's hard to understand.  While it's true that controllers sometimes tell you to expect vectors and then clear you to a specific fix instead, this is less common than them actually giving you the vectors you were told to expect.  So by loading a full approach, you're accepting the risk of incorrect CDI guidance as a hedge against an event that's arguably not that likely to happen.  This is not an obviously good tradeoff.

Third, I've never really understood the mindset that loading a full approach somehow guarantees you're not going to have to push buttons in the middle of the approach in a way that might get confusing.  I do understand that with older navigators the number of button pushes may be different to switch in one direction vs. another.  But you should practice and understand how to re-sequence your GPS rapidly in either direction.  You're going to need this skill anyway for the "what's it doing now?" problem.  And on the GTN, it's pretty trivial to reload a VTF transition approach to select an IAF transition instead.  The five clicks are HOME -> PROC -> Approach -> Transition -> [desired transition].  Takes about 5 seconds.  If you find this especially distracting or confusing, I'd argue you need more practice and training.

Further, if you load a full approach that has a required procedure turn and you end up getting a vector, it will not automatically switch to inbound leg.  You will be left with no final approach guidance if the gtn is left alone.   

If I fly to an uncontrolled field, I will clarify if ATC will provide vectors or not when they advise “expect...approach”.  If setup for vector, then they clear to a fix, it’s easy to direct to flt plan waypoint.  

Edited by Browncbr1
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On 7/3/2018 at 1:59 AM, Vance Harral said:

And on the GTN, it's pretty trivial to reload a VTF transition approach to select an IAF transition instead.  The five clicks are HOME -> PROC -> Approach -> Transition -> [desired transition].  Takes about 5 seconds.  If you find this especially distracting or confusing, I'd argue you need more practice and training.

I do appreciate the lively discussion among more experienced folks, and I think there's little doubt I need more practice and training as a brand new IFR pilot  ;).

My experience over the weekend illustrates some of the points made above. I tried loading an IAF for an RNAV approach that requires a procedure turn in a hold because I wanted to ask to fly the full approach later for practice.  Though I didn't "activate" the approach,  just loading it changed my course guidance to the IAF as opposed to the direct leg to the airport I had been assigned.  Loading VTF instead took care of this issue, and as noted by someone above, it retained the IAF because in this case it was on the final approach course.  I was later sent direct to that IAF and cleared for the approach, so I hit direct to that fix.  Unfortunately that gave me course guidance for a 150 degree hairpin turn  at that fix rather than the procedure turn in the hold I needed -  I thought the box would be smart enough to know I needed the procedure turn, but it wasn't.  Flying the hold without the magenta line was no biggie, but it certainly taught me that I haven't figured out the box yet.

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On 7/3/2018 at 11:09 AM, Vance Harral said:

Honest questions: how do you define "appropriate" IAF to load when the choice is ambiguous, and what do you teach your students about the behavior of the CDI during the interim period until you activate VTF?  I'm particularly interested in the scenario where you're approaching from the opposite direction of the final approach course (i.e. being vectored downwind), and the IAF is beyond the point you'll likely be vectored on a base and thence intercept leg.

To be clear, I'm not saying it's wrong to load an IAF when being vectored, and I'm not suggesting you're giving bad instruction.  I'm just saying the benefits aren't that clear.  I practice both methods as a form of mental pushups to stay comfortable with the navigator, and loading an IAF while being vectored seems like more of a distraction to me on the GTN.

It's as simple as it was before the GTN upgrade and as it still is in other navigators. I said "an" appropriate IAF. Not "the" appropriate IAF. I've seen very, very few "ambiguous" IAF choices and none causing any significant operational issue (perhaps you can point one out).  If I'm being vectored, I don't care too much about the CDI. In most any GPS navigator, it's going to send me somewhere I am not being vectored.

I don't really follow your "beyond the point" comment. If I am on a downwind I don't know how far downwind ATC is going to take me. Especially on a busy IFR day, I've been taken pretty far out. Now, at some point, it becomes obvious that, unless ATC decides to have me make a 180  and go off into Neverland, there are no longer any waypoints to send me to. Plenty of time for three taps on large buttons to activate VTF. I've never seen a workload issue manually changing to VTF on a GNS. It's even less workload on the GTN since its VTF function permits the pilot to make that decision significantly earlier.

Keep in mind that, like you, I am not saying your way is wrong. I wouldn't even consider trying to change someone who did it the your way* ; just that I have not seen a reason to treat this unit differently than others just because the GTN gives us  waypoints on the extension of the FAC. Now, that could very well be because of my environment. I deal with  pilots who fly multiple airplanes with multiple avionics. One day, it might be a GTN. Another say a 430; still another day a G1000. SOP consistency where it is reasonable is itself a value in that environment. Yes, one needs to understand each piece of equipment but there are far more important differences than this one.

[* I firmly believe attempting to change a pilot's procedure which works just because the CFI likes another one better is a cardinal sin.]

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2 hours ago, DXB said:

I do appreciate the lively discussion among more experienced folks, and I think there's little doubt I need more practice and training as a brand new IFR pilot  ;).

My experience over the weekend illustrates some of the points made above. I tried loading an IAF for an RNAV approach that requires a procedure turn in a hold because I wanted to ask to fly the full approach later for practice.  Though I didn't "activate" the approach,  just loading it changed my course guidance to the IAF as opposed to the direct leg to the airport I had been assigned.  Loading VTF instead took care of this issue, and as noted by someone above, it retained the IAF because in this case it was on the final approach course.  I was later sent direct to that IAF and cleared for the approach, so I hit direct to that fix.  Unfortunately that gave me course guidance for a 150 degree hairpin turn  at that fix rather than the procedure turn in the hold I needed -  I thought the box would be smart enough to know I needed the procedure turn, but it wasn't.  Flying the hold without the magenta line was no biggie, but it certainly taught me that I haven't figured out the box yet.

>>just loading it changed my course guidance to the IAF as opposed to the direct leg to the airport
That should not happen in the GTN just from loading an approach with an IAF. See the photos below. The fists is with no approach loaded. the second  and third are  with an approach loaded with an IAF. Notice the active waypoint is still the airport.

On theothers...

You specifically told the box you didn't need the procedure turn when you selected VTF.  You told it, in effect, "I'm being vectored to final. I don't need an IAF, so remove it." The box didn't retain "the IAF." It retained a waypoint which was on the extension of the FAC. That is was also the IAF of the procedure was no longer relevant.

GTN1.PNG.c37ff09238e07aac92a783f73f5eae12.PNGGTN2.PNG.4224468e696971547b67bdfa037140ef.PNGGTN3.PNG.99deb586e60c5c6692e42856130833e3.PNG

Edited by midlifeflyer
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1 hour ago, midlifeflyer said:

>>just loading it changed my course guidance to the IAF as opposed to the direct leg to the airport
That should not happen in the GTN just from loading an approach with an IAF. See the photos below. The fists is with no approach loaded. the second  and third are  with an approach loaded with an IAF. Notice the active waypoint is still the airport.

On theothers...

You specifically told the box you didn't need the procedure turn when you selected VTF.  You told it, in effect, "I'm being vectored to final. I don't need an IAF, so remove it." The box didn't retain "the IAF." It retained a waypoint which was on the extension of the FAC. That is was also the IAF of the procedure was no longer relevant.

GTN1.PNG.c37ff09238e07aac92a783f73f5eae12.PNGGTN2.PNG.4224468e696971547b67bdfa037140ef.PNGGTN3.PNG.99deb586e60c5c6692e42856130833e3.PNG

It depends on what version of the software you have.  If you have an OLD version, I mean several versions old, it will leave your airport in the list.  If you have any of the newer versions it will replace the airport with the approach... unless you are already direct to the airport.

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53 minutes ago, Bob - S50 said:

It depends on what version of the software you have.  If you have an OLD version, I mean several versions old, it will leave your airport in the list.  If you have any of the newer versions it will replace the airport with the approach... unless you are already direct to the airport.

And, yes,  you are correct,. I forgot for a moment that the airport is removed unless it is the current active waypoint. I guess the answer, especially with changes to basic operation being made,  is to always check that the box is doing what you think you asked it to do.  The Pilot Guide tell you to do that too.

But my other comment stands - if you load VTF,  you are specifically telling the system not to use an IAF so you can't really expect it to start using a PT you told it to disregard. 

Edited by midlifeflyer
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There is a way in my 430 to load a whole approach for vectors to final, and then activate a particular leg once you are getting to the final approach course.  I don’t have a GTN, so you might check the GTN manual on this.  So you load the whole approach, and let’s say just for the sake of example that it has a straight in IAF, and then a couple of IAF’s further out that are NoPT and on a “T.” You are geing vectored onto the final approach course inside the straight-in IAF and outside the FAF.  You are cleared to intercept the final approach course.  You would go in to FPL (Flight Plan), pick the FAF, highlight it, and then hit Direct-Direct-Enter.  Two “Directs” gets you an “Activate Leg” screen and ENT then activates that leg, the IAF to FAF leg.  A magenta line should appear for that leg, and I don’t really recall, but I think it extends out some distance beyond the first point of the leg, in this instance the IAF. You can then intercept that leg and the rest of the approach will sequence normally.  I don’t use this very much, maybe once a year, so you might try it in clear air (VFR) to make sure it works, esp. in a different GPS.  This works for any leg in a flight plan, including any leg in an approach.

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On 7/7/2018 at 11:35 AM, DXB said:

I do appreciate the lively discussion among more experienced folks, and I think there's little doubt I need more practice and training as a brand new IFR pilot  ;).

My experience over the weekend illustrates some of the points made above. I tried loading an IAF for an RNAV approach that requires a procedure turn in a hold because I wanted to ask to fly the full approach later for practice.  Though I didn't "activate" the approach,  just loading it changed my course guidance to the IAF as opposed to the direct leg to the airport I had been assigned.  Loading VTF instead took care of this issue, and as noted by someone above, it retained the IAF because in this case it was on the final approach course.  I was later sent direct to that IAF and cleared for the approach, so I hit direct to that fix.  Unfortunately that gave me course guidance for a 150 degree hairpin turn  at that fix rather than the procedure turn in the hold I needed -  I thought the box would be smart enough to know I needed the procedure turn, but it wasn't.  Flying the hold without the magenta line was no biggie, but it certainly taught me that I haven't figured out the box yet.

When I got a new panel installed with all new toys and gadgets in my 252, this is what worked for me. Take a pilot friend along. Ideally they are Instrument rated, but its not required, but not a CFI... (:ph34r: I don't want to have to pay for the time). Go out and find an uncontrolled field with an instrument approach on a VFR day.

I flew the approach over and over again (VFR and not talking to ATC, just local traffic on the unicom), until I learned the box, buttons, autopilot, etc. As far as anyone was concerned, we were just out for a scenic flight and there wasn't anyone else in the pattern. It was the best way for me to try all the different combinations and learn what worked, what didn't, and what the results were for different actions.

Have fun.

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11 hours ago, jlunseth said:

There is a way in my 430 to load a whole approach for vectors to final, and then activate a particular leg once you are getting to the final approach course.  I don’t have a GTN, so you might check the GTN manual on this.  So you load the whole approach, and let’s say just for the sake of example that it has a straight in IAF, and then a couple of IAF’s further out that are NoPT and on a “T.” You are geing vectored onto the final approach course inside the straight-in IAF and outside the FAF.  You are cleared to intercept the final approach course.  You would go in to FPL (Flight Plan), pick the FAF, highlight it, and then hit Direct-Direct-Enter.  Two “Directs” gets you an “Activate Leg” screen and ENT then activates that leg, the IAF to FAF leg.  A magenta line should appear for that leg, and I don’t really recall, but I think it extends out some distance beyond the first point of the leg, in this instance the IAF. You can then intercept that leg and the rest of the approach will sequence normally.  I don’t use this very much, maybe once a year, so you might try it in clear air (VFR) to make sure it works, esp. in a different GPS.  This works for any leg in a flight plan, including any leg in an approach.

That functionality will work pretty much the same in the 430/530, the GTN, and the G1000, as well as the Avidyne IFR. In the Garmin, some say they prefer doing it with the Menu key instead of Direct Direct. 

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