Found a use for vectors to final

David Megginson

David Megginson

Pattern Altitude
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When I was shooting practice approaches at CYOW this afternoon, Tower vectored me to an intercept about 15 nm from the runway. There was no published leg of the RNAV LPV approach that I could intercept that far out, so I did some quick taps on my GTN 650 and changed from the original transition waypoint to Vectors to Final.

Normally, I follow the standard advice never to use VTF and instead just to choose the most likely transition (then activate legs as needed). This is the first time in the four years since I bought my GTN that I actually needed VTF.
 
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David Megginson said:
When I was shooting practice approaches at CYOW this afternoon, Tower vectored me to an intercept about 15 nm from the runway. There was no published leg of the RNAV LPVMapproach that I could intercept that far out, so I did some quick taps on my GTN 650 and changed from the original transition waypoint to Vectors to Final.

Normally, I follow the standard advice never to use VTF and instead just to choose the most likely transition (then activate legs as needed). This is the first time in the four years since I bought my GTN that I actually needed VTF.
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Which Approach. They gots like 16 RNAV Approaches there.
 
David Megginson said:
When I was shooting practice approaches at CYOW this afternoon, Tower vectored me to an intercept about 15 nm from the runway. There was no published leg of the RNAV LPVMapproach that I could intercept that far out, so I did some quick taps on my GTN 650 and changed from the original transition waypoint to Vectors to Final.

Normally, I follow the standard advice never to use VTF and instead just to choose the most likely transition (then activate legs as needed). This is the first time in the four years since I bought my GTN that I actually needed VTF.
Click to expand...

Why do you say it is standard advice never to use VTF? Vectors to final is the default in most places with radar unless you want to fly a specific transition, in which case you have to ask for it.
 
David Megginson said:
When I was shooting practice approaches at CYOW this afternoon, Tower vectored me to an intercept about 15 nm from the runway. There was no published leg of the RNAV LPVMapproach that I could intercept that far out, so I did some quick taps on my GTN 650 and changed from the original transition waypoint to Vectors to Final.

Normally, I follow the standard advice never to use VTF and instead just to choose the most likely transition (then activate legs as needed). This is the first time in the four years since I bought my GTN that I actually needed VTF.
Click to expand...
I think people go a bit overboard with "no VTF." The reason is that many GPS navigators apps well as some advanced FMS systems, remove the fixes before the FAC. But while that is an excellent reason not to load VTF initially, and while many would argue that the better course of action in your example would be to activate the TEXEN - VODUL leg, there is nothing wrong with VTF.
 
TommyG said:
What do you mean don’t use VTF? If you’re being vectored absolutely use VTF.
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The AIM recommends against it because of the removal of prior fixes in many systems. ATC deciding to send you to a fix after beginning vectors requires reloading the approach.

Edit. Consider this approach. You are inbound from the southeast. ATC tells you to expect vectors to final so you load it that way. Then they change their mind and say, "proceed direct VOLAG." Not that big a deal to reload (in most GA GPS units) but much easier to load VOLAG to begin with and activate the leg to the FAF or VTF later.
 
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midlifeflyer said:
The AIM recommends against it because if the removal of prior fixes in many systems. ATC deciding to send you to a fix after beginning vectors requires reloading the approach.
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There is learning from books, and learning from experience. The AIM is good as a reference to learning, but in the real world what it suggests isn’t always practical.
 
midlifeflyer said:
… while many would argue that the better course of action in your example would be to activate the TEXEN - VODUL leg, there is nothing wrong with VTF.
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Thanks! I realise now that I need to go back and confirm what would have happened if I activated TEXEN–VODUL when I was still a few miles south of TEXEN. I'd assumed it would send me direct TEXEN rather than intercepting an extension of the leg, but perhaps that's not true.
 
TommyG said:
Yes load the full approach when you are still enroute. But once you see how you are being brought in, switch to VTF. The OP says he advised to never use VTF.
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We agree. I mentioned that in an earlier post.

Funny. I stopped loading VTF initially long before the AIM recommended it. It was my first flight -as safety pilot for a friend- in a G1000. "Expect VTF." Load VTF. "Proceed direct THSFX." "Oops!"
 
TommyG said:
Yes load the full approach when you are still enroute. But once you see how you are being brought in, switch to VTF. The OP says he advised to never use VTF.
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In this case, I'd been flying south towards WATTO all set up when ATC told me to hold current heading. As I flew in south, I fully believed they'd clear me direct TEXEN until the last moment, when they told me to intercept. I switched to VTF in a few seconds, but the needle was already moving towards the centre of the CDI by the time I had it changed over.

It was a perfectly normal instruction for an ILS, but it felt strange for RNAV.
 
David Megginson said:
Thanks! I realise now that I need to go back and confirm what would have happened if I activated TEXEN–VODUL when I was still a few miles south of TEXEN. I'd assumed it would send me direct TEXEN rather than intercepting an extension of the leg, but perhaps that's not true.
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It's funky. In the units I looked at, you wouldn't see a magenta extension beyond TEXEN, but the CDI and autopilot (when switching from HDG to NAV or APR) intercept the course.
 
midlifeflyer said:
It's funky. In the units I looked at, you wouldn't see a magenta extension beyond TEXEN, but the CDI and autopilot (when switching from HDG to NAV or APR) intercept the course.
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So it's a bit like OBS mode before you hit the first waypoint of the leg. I'll confirm in the GTN trainer, but that will make two new things I learned today.

In Canada, we have to fly an IPC every two years (basically a full IFR flight test). I'm planning mine next month, and it will be only the second since I added RNAV capability to the plane, so the more edge cases I experience before then, the better.
 
midlifeflyer said:
Funny. I stopped loading VTF initially long before the AIM recommended it. It was my first flight -as safety pilot for a friend- in a G1000. "Expect VTF." Load VTF. "Proceed direct THSFX." "Oops!"
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That was exactly my experience the very first time I ever went up with a safety pilot. I've been VTF-shy ever since.
 
asicer said:
That was exactly my experience the very first time I ever went up with a safety pilot. I've been VTF-shy ever since.
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Yes, this has happened a few times for me. But I don't think it warrants foregoing VTF altogether. It isn't a big deal to reload the approach from that fix. You could also say, no give me the vectors you promised.
 
David Megginson said:
So it's a bit like OBS mode before you hit the first waypoint of the leg. I'll confirm in the GTN trainer, but that will make two new things I learned today.

In Canada, we have to fly an IPC every two years (basically a full IFR flight test). I'm planning mine next month, and it will be only the second since I added RNAV capability to the plane, so the more edge cases I experience before then, the better.
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We are a bit looser here, but I can tell you that the better part of the IPCs and recurrent instrument training I give is about the equipment. I have a short list of tasks. I'm not sure they are really edge cases, but they are tasks - real things that happen - which I have found many pilots don't know how to do. VTF is not specifically on the list and I don't try to convince a pilot on my philosophy about it, but it comes up. For example, if, playing ATC I tell the pilot to expect vectors to final and they load VTF, I'm going to change my mind to ensure they know what to do. As long as they handle it properly, I don't really care what technique they use.
 
asicer said:
That was exactly my experience the very first time I ever went up with a safety pilot. I've been VTF-shy ever since.
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Back in my pre-RNAV IFR days, I was never shy about asking ATC for a temporary heading vector when they gave me a complex revised clearance that required unfolding charts and looking up frequencies and airway radials.

I don't think that would be unreasonable to ask for in the RNAV age, either, if anything catches you by surprise and you need a minute or two to push some buttons and cycle through screens.
 
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I'm newly minted IR and i guess I don't get the VTF shyness. It's like 4 button pushes in the 530 and takes 3 seconds to reload the approach.
 
sarangan said:
Yes, this has happened a few times for me. But I don't think it warrants foregoing VTF altogether. It isn't a big deal to reload the approach from that fix. You could also say, no give me the vectors you promised.
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I said I was VTF-shy. I didn't say I was completely opposed to it.
 
midlifeflyer said:
It's funky. In the units I looked at, you wouldn't see a magenta extension beyond TEXEN, but the CDI and autopilot (when switching from HDG to NAV or APR) intercept the course.
Click to expand...

David Megginson said:
So it's a bit like OBS mode before you hit the first waypoint of the leg. I'll confirm in the GTN trainer, but that will make two new things I learned today.
Click to expand...
And confirmed in the Garmin PC trainer. Exactly as @midlifeflyer described, when I activated the TEXEN-VODUL leg before TEXEN, the GTN did not draw an extended magenta line south of TEXEN, but it acted as if it were there, and intercepted an extension of the leg rather than taking me straight to TEXEN. This is not documented in the "Activate Leg" section of the GTN user manual, so I guess it just has to get passed on from pilot to pilot by word of mouth.

So next time this happens, instead of reloading the approach with a VTF transition, I could just activate the first leg of the final approach course and it would have the same effect. Thanks for the info.
 
David Megginson said:
And confirmed in the Garmin PC trainer. Exactly as @midlifeflyer described, when I activated the TEXEN-VODUL leg before TEXEN, the GTN did not draw an extended magenta line south of TEXEN, but it acted as if it were there, and intercepted an extension of the leg rather than taking me straight to TEXEN. This is not documented in the "Activate Leg" section of the GTN user manual, so I guess it just has to get passed on from pilot to pilot by word of mouth.

So next time this happens, instead of reloading the approach with a VTF transition, I could just activate the first leg of the final approach course and it would have the same effect. Thanks for the info.
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I can't say I was all that surprised when I first saw it. It was a scenario I was curious about and was just wondering what it would do. Thinking about it, it kind of makes sense. When you activate a leg, you are telling the system you don't need anything before it, so no magenta line until the leg you are activating and no sequencing through the prior waypoints, although they are there in case you need them. OTOH, you are also telling the system that the active course the course of the activated leg. So the CDI is using it and o still have primary NAV.

The potential advantage of VTF in this situation with a GTN (or other unit which does not remove waypoints from the flight plan in that mode), is the magenta line itself. Since it extends back from the FAF to infinity (at least in a practical sense), the display can be helpful for additional situational awareness.
 
midlifeflyer said:
I think people go a bit overboard with "no VTF." The reason is that many GPS navigators apps well as some advanced FMS systems, remove the fixes before the FAC. But while that is an excellent reason not to load VTF initially, and while many would argue that the better course of action in your example would be to activate the TEXEN - VODUL leg, there is nothing wrong with VTF.
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I couldn't have said it any better. Never using VTF is just as short-sighted as always using VTF. It's a good tool in the right situation, and a potential trap in others. The trick is to know which is which.

- Martin
 
midlifeflyer said:
People take a good recommendation for initial loading with a logical IAF and end up applying it to the VTF universe.
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Exactly. Also worth noting that newer GPS navigators like the GTN don't remove all the waypoints on the final approach course before the FAWP/FAF when you choose VTF, so the problems aren't as big as with the GNS (for which the advice was originally developed).
 
midlifeflyer said:
I can't say I was all that surprised when I first saw it. It was a scenario I was curious about and was just wondering what it would do. Thinking about it, it kind of makes sense. When you activate a leg, you are telling the system you don't need anything before it, so no magenta line until the leg you are activating and no sequencing through the prior waypoints, although they are there in case you need them. OTOH, you are also telling the system that the active course the course of the activated leg. So the CDI is using it and o still have primary NAV.

The potential advantage of VTF in this situation with a GTN (or other unit which does not remove waypoints from the flight plan in that mode), is the magenta line itself. Since it extends back from the FAF to infinity (at least in a practical sense), the display can be helpful for additional situational awareness.
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It would improve the user experience if they drew, say, a dotted magenta line for the extension. The Rule of Least Surprise applies to avionics interface design even more than most other user interfaces.
 
David Megginson said:
So it's a bit like OBS mode before you hit the first waypoint of the leg. I'll confirm in the GTN trainer, but that will make two new things I learned today.

In Canada, we have to fly an IPC every two years (basically a full IFR flight test). I'm planning mine next month, and it will be only the second since I added RNAV capability to the plane, so the more edge cases I experience before then, the better.
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The CDI course is set to the course 320 degrees for TEXEN to VODUL when you activate the leg. but the Map shows the leg in magenta and not the extended course beyond TEXEN, even though it is the lateral guidance provided on the CDI.
 
Interesting discussion. My cfii and I have done nothing but vectors to final. Load the airport into the flight plan as destination. When you get close check the weather and winds, tell ATC what approach you’d like, and they vector you to it. Brief approach and load into GTN.

How would you pre load the initial fix for an approach before you even knew what approach you want given the winds, which you can only pick up when you arrive?
 
WDD said:
How would you pre load the initial fix for an approach before you even knew what approach you want given the winds, which you can only pick up when you arrive?
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Except at the larger airports served by the air carriers, I will request the approach and how I wish to join it, after I listen to the ATIS/ASOS. Usually I will get the response that I can expect it and then load the approach using the IAF of my request. I don't activate the approach until either cleared for the approach or to a fix on the procedure.
 
WDD said:
Interesting discussion. My cfii and I have done nothing but vectors to final. Load the airport into the flight plan as destination. When you get close check the weather and winds, tell ATC what approach you’d like, and they vector you to it. Brief approach and load into GTN.

How would you pre load the initial fix for an approach before you even knew what approach you want given the winds, which you can only pick up when you arrive?
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If you don't know the winds yet, then it will be hard to know which approach to preload at all (unless your destination airport has only one).

Once you know which approach is in use, you normally preload it using the most-suitable transition for the direction you're arriving from, unless ATC has suggested otherwise. For example, with this approach (CYMW RNAV 21) I'd anticipate the DASUD transition if I were arriving from roughly between SW to NW, GADIV if I were arriving from between N and NE, or GOVOS if I were arriving from between E and S (no need to memorize any rules; you can just eyeball it—the goal is to avoid any turn >90°).

CYMW_RNAV_GNSS_RWY_21.png


For smaller airports where you know the approach, you can ask Centre to clear you direct to the appropriate transition waypoint from 100 nm or more away, assuming there's no complex airspace between you and it. For bigger airports and/or airports inside a terminal area, they'll tell you what approach and transition to expect when you switch from Centre to Terminal/Approach (typically about 30 nm away).

Note that this is all for RNAV approaches. If your CFII and you are practicing radio-based approaches (especially LOC or ILS), then VTF will often make sense (note that it becomes advisory-only after the FAF).
 
WDD said:
…..How would you pre load the initial fix for an approach before you even knew what approach you want given the winds, which you can only pick up when you arrive?
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So you can only get winds when you arrive? Too bad we don’t have a way to get this stuff before the flight……
 
David Megginson said:
Exactly. Also worth noting that newer GPS navigators like the GTN don't remove all the waypoints on the final approach course before the FAWP/FAF when you choose VTF, so the problems aren't as big as with the GNS (for which the advice was originally developed).
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That's true but I think there is still value. Take your CMYW approach. Not knowing ATC preferences there, inbound from the northeast, there are three practical choices. Direct GOVAS, Direct GADIV, and vectors to intercept the FAC before ILEPO. One choice gives the whole thing, and I would ordinarily choose GOVAS even though I would ask for GADIV (I'm assuming at nontowered field, Canada ATC, like their US counterparts, ask us what we want and will agree absent a traffic conflict).

But I think the real benefit of selecting a logical IAF is the briefing. It forces us to look at the Plan View which gives us the big picture of where we are, where we are going, and how we will get there.
 
I can indeed look at the metars and tafs before I leave/file. But it might change the time you get there. In any event - what I’m doing now is not preloading an approach. I’m being tought to do that on the fly after I get the ATTIS. And ATC vectors me to intercept.

How often does one end up having to change to another approach vs what you had preloaded?
 
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WDD said:
Interesting discussion. My cfii and I have done nothing but vectors to final. Load the airport into the flight plan as destination. When you get close check the weather and winds, tell ATC what approach you’d like, and they vector you to it. Brief approach and load into GTN.
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Must be pretty early in your training.

How would you pre load the initial fix for an approach before you even knew what approach you want given the winds, which you can only pick up when you arrive?
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To add and maybe collect the answers.
  • Preflight briefing.
  • Enroute FIS-B or XM weather.
  • ATIS for towered airports - they advertise the winds and approach in use (although you can ask for another-there is no CFII in the other seat insisting you do this approach and no other).
  • AWOS at nontowered airports before ATC asks, "what approach do you want?" (ditto to the comment on ATIS)
My approach is typically briefed and loaded before speaking with the final approach controller at my destination. When it's a short flight, it's briefed on the ground before I leave.
 
WDD said:
I can indeed look at the metars and tafs before I leave/file. But it might change the time you get there. In any event - what I’m doing now is not preloading an approach. I’m being thought to do that on the fly after I get the ATTIS.

How often does one end up having to change to another approach vs what you had preloaded?
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Let me ask you. On a 1-3 hour flight, does not matter whether IFR or VFR, training or whatever, how often has the wind direction at your destination changed enough to use a different runway?

It happened to me twice in 30 years.

First time was on my instrument checkride. It was a real one, not a DPE-induced one. The Class C (ARSA in those days) had a runway change. So they put me in a hold (yeah, I had a real hold on my checkride) and told me to expect a different approach.

The second was a few years ago at RDU, a Class C airport with multiple runways. In that case, loading late would not have helped. I was already receiving vectors to one when I was instructed to switch to the other. That's probably the most common approach change scenario.

Keep in mind the the training environment is very artificial. It's approach-intensive rather than trip-intensive. On a real trip you have a lot of low workload periods. Even if all you have are radios to pick up ATIS or AWOS, you are generally going to have the weather long before you speak with the final approach controller and plenty of time to brief the approach. You'll usually be sitting there trying to think of something to do! :D
 
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