GTN VNAV and visual approach tips

[iamtheari]

I’m wondering how the rest of you use these features, especially together. I have a specific use case that came up today and I’d like to find a way to automate it (my computer programming background specifies to automate every task you have to do twice).

Say you’re direct to an airport and set the VNAV so you’ll be at pattern altitude 3 miles before the airport. The GTN creates a temporary waypoint at destination minus 3. So far, so good. Now, Tower says to make straight in for a runway about 30 degrees off your track and report a 5-mile final. The visual approach feature of the GTN sets up a 3-mile final. Also, if you’re on autopilot, activating the visual approach or a leg on it will first throw the CDI off to the side and turn the plane to intercept it. The work-around I’m using is to turn on heading mode on the autopilot to ballpark a 5-mile final.

The better way to do this would appear to be to create an along-track fix on the final approach course from the GTN visual approach, 5 miles out, and then go direct to that fix to sequence the approach. But that isn’t allowed. Selecting the V3NM fix doesn’t offer an Along Track button and selecting the runway fix offers Along Track but limits it to the range of -1 to -3.

Is there a way to create an along-track waypoint outside of the 3-mile fix from the visual approach, on the final approach course?

 

[Hang 4]

I'd load a RNAV approach for the same runway and there's likely a fix that is roughly right for your need. If you have an iPad or a MFD that shows an extended centerline and the 3 mile visual fix, you could also just eyeball it.

 

[RussR]

I get what you're trying to accomplish, and it would be nice to be able to head right to that point. Can't you change the length of the visual final in the GTN? It's been a little while since I tried and I can't remember. Maybe in settings somewhere.

But realize that a tower's "report 5 mile final" call isn't usually meant to be performed to a high level of precision. The primary purpose of that call is really to serve as a reminder to the tower controller of your position so that you can be cleared to land. So if you just put the heading bug to intercept a little outside of the 3nm visual approach, that's going to be just fine in almost all cases.

 

[eman1200]

are you VFR?

my happy hour buzz is preventing me from making any sense of this situation. Hang4 summed it up, there’s prob a fix roughly 5 miles , fly to it.

 

[midlifeflyer]

Sorry, I've seen the feature but haven't used it*. I love the tech of modern avionics but in this, I'm in the "that's a lot of extra work for what a solo student pilot...oops.. 'learner' is expected to do visually" camp.

*actually, I tried out the Dynon version in a light sport. Thought it was cute but pretty silly. Yes, there is a very good reason to accurately intercept the final approach course at unfamiliar, busy, or multiple runway airport but there are multiple ways to do that.

 

[Palmpilot]

When you set the GTN to fly direct to the airport, will it display your distance to the airport? If so, you could just eyeball it while watching that distance readout, and make adjustments as needed.

 

[iamtheari]

I get what you're trying to accomplish, and it would be nice to be able to head right to that point. Can't you change the length of the visual final in the GTN? It's been a little while since I tried and I can't remember. Maybe in settings somewhere.

But realize that a tower's "report 5 mile final" call isn't usually meant to be performed to a high level of precision. The primary purpose of that call is really to serve as a reminder to the tower controller of your position so that you can be cleared to land. So if you just put the heading bug to intercept a little outside of the 3nm visual approach, that's going to be just fine in almost all cases.

I’ll have to look in the settings to see if there is a setting for the visual approach guidance leg length. It’s definitely not something I can’t fly without the autopilot following the magenta line for me. But the GTN has two features at play (VNAV and guidance for visual approaches) and I want to master the use of those features, the same as I do with every other tool in the toolbox. Because if all you have is a hammer that you don’t know how to use, everything looks like a nail that you’re going to miss and smash your thumb.

 

[midlifeflyer]

I’ll have to look in the settings to see if there is a setting for the visual approach guidance leg length. It’s definitely not something I can’t fly without the autopilot following the magenta line for me. But the GTN has two features at play (VNAV and guidance for visual approaches) and I want to master the use of those features, the same as I do with every other tool in the toolbox. Because if all you have is a hammer that you don’t know how to use, everything looks like a nail that you’re going to miss and smash your thumb.

I compliment you but there are tools in every box many people never use. In some cases, they've never been exposed to it. In other cases, they decide it's not important enough to add to their bag of tricks. Personally, I love VNAV because, especially when coupled, it's so cool. Don't feel the same way about visual approaches. I'd rather know how to remove a HILPT when told to expect straight in and put it back when ATC later instructs me to hold there.

 

[iamtheari]

I compliment you but there are tools in every box many people never use. In some cases, they've never been exposed to it. In other cases, they decide it's not important enough to add to their bag of tricks. Personally, I love VNAV because, especially when coupled, it's so cool. Don't feel the same way about visual approaches. I'd rather know how to remove a HILPT when told to expect straight in and put it back when ATC later instructs me to hold there.

You are, of course, right. But do you know how cool it is to set up a VNAV to the 3-mile final altitude that the GTN calculated and have the autopilot sequence you onto the visual glide path?

There are just oodles of features in these boxes. I’m aware that I will not find all of them useful and that I might not even find all of the features to begin with. But I’m going to do my best to understand what they all do. Learning is only bad when it carries the opportunity cost of other learning.

 

[midlifeflyer]

You are, of course, right. But do you know how cool it is to set up a VNAV to the 3-mile final altitude that the GTN calculated and have the autopilot sequence you onto the visual glide path?

Dunno. Do I?

A did this flight in a airplane also, with a friend as safety pilot. He thought it was amazing.

 

[emes]

I’d just use a convenient waypoint from a real approach or create one if not. Make it at least 5 miles away, appropriate altitude and then activate the visual approach once you’ve made your calls.