GTN - Actual vs Desired Track and Heading

[WDD]

So, I'm overthinking things. My goal is get very familiar and have proficiency with using the GTN and Heading Indicator for IFR, especially on approaches.

Assume I've loaded and activated the LPV approach for runway 9. I'm flying a magnetic heading of due east / 90 degrees, but I'm 1/2 mile to the north on a parallel course. As I'm to the left of the proper course, the GTN will show the Magenta "target bar" to the right of my Magenta triangle.

The GTN should show my "Actual Track" to be 90 degrees. What will the GTN show as the "Desired Track"?

My course of action BTW would be to bracket 10 degrees right, and hold it until I get on the proper path, and then end the bracket and return to 90 degrees heading.

 

[RussR]

The DTK will be whatever the published course is (with possibly a slight difference for magnetic variation calculation differences). So in your case, DTK = 090.

If you maintain a track (not a heading) of 090, you will parallel the course exactly.

So in your case you turn 10 degrees to the right. Assuming that will intercept the course, then once you're on the course, you don't want to "return to 90 degrees heading", you want to fly the heading that will keep you on a track of 090. Assuming that the wind blew you off course the first time, you would maybe fly heading 095. If you return to a heading of 090, you will probably just get blown off course again.

 

[WDD]

Interesting. So when flying an ATC Vector, fly "heading" via Heading Indicator. When flying the LPV, ILS, etc., fly the "Desired Track" on the GTN when you get on the "Magenta Line" that is the course aligned with the runway.

 

[eman1200]

sigh

 

[WDD]

sigh

Sparse comment. Elaborate?

 

[Cricket1]

Your actual heading is irrelevant. Fly whatever heading you need to make the Track the same as the Desired Track. If you do that, you will stay on the magenta line, and get to whatever point you have set the magenta line to.

I set up the display on my GTN 650 so DTK is on the upper left, and TRK upper right. Easy peasy to see what you need to do.

 

[Hang 4]

For the sceanrio you are describing, it's just a lot simpler than how you are thinking about it. You have a horizontal deviation indication showing you left or right of the approach course. You just need to center the needle. Typically you are getting vectored in at about 30 degrees different from the approach heading. Fly to center the needles and turn inbound as you begin to get some deflection. I typically never look at the GTN when I'm on a vector to final.

If you are talking partial panel, then Track vs DTK can be helpful.

 

[luvflyin]

Sparse comment. Elaborate?

He doesn’t like any question that’s ever been asked before, to be asked again.

 

[eman1200]

He doesn’t like any question that’s ever been asked before, to be asked again.

nah, that's not exactly it. but just ignore me anyways, I should'a just kept my mouth shut.

 

[luvflyin]

nah, that's not exactly it. but just ignore me anyways, I should'a just kept my mouth shut.

Maybe I shoulda said asked and answered. I don’t agree with ya on this particular thang, but I love ya anyway. I’d never ignore you.

 

[RussR]

Interesting. So when flying an ATC Vector, fly "heading" via Heading Indicator. When flying the LPV, ILS, etc., fly the "Desired Track" on the GTN when you get on the "Magenta Line" that is the course aligned with the runway.

Even before GPSes existed, that's exactly the same thing we were trying to accomplish by determining the heading that would hold us on an ILS/VOR/NDB course. Now we just have the additional information that removes the guesswork.

 

[eman1200]

Maybe I shoulda said asked and answered. I don’t agree with ya on this particular thang, but I love ya anyway. I’d never ignore you.

 

[WDD]

Understand if it seems tedious if the same question get asked again. Given there are a continual supply of "new guys", the same questions will come up. Didn't see anything in the search - I usually find some good material that way.

So despite that this is a repeat question, I really do appreciate those who are smarter "repeating the answer" to another person. Kind of like how teachers have to "repeat" the same material each year to a new class.

 

[eman1200]

that's NOT why I sighed.........just fuhgedaboudit

 

[somorris]

Don't let it bother you, WDD. The people who complain the loudest probably asked the same question when they were learning!

 

[eman1200]

Don't let it bother you, WDD. The people who complain the loudest probably asked the same question when they were learning!

nope, sorry, I knew how to use an HSI before instrument training. and basic heading vs DTK stuff. but no worries.

 

[WDD]

Don't let it bother you, WDD. The people who complain the loudest probably asked the same question when they were learning!

Nah - not bothered. Just expressing a “thank you” to those that answer an old question from a new person.

 

[bflynn]

I always mix up DTK and bearing. The DTK is the course you should be flying, regardless of whether you are left or right of the course. The bearing will change if you are off course.

Example, RNAV 13 to KSLE. DTK and TRK are the same even though you’re significantly left of course.



In the GTN, go to the Default Nav screen. You can immediately see this. Again, desired track and track are the same. But the bearing will be changing as you get closer and you can easily see you’re 0.26 miles left of course.

 

[dmspilot]

Nah - not bothered. Just expressing a “thank you” to those that answer an old question from a new person.

I think he's peeved that you asked what Garmin means by DTK on your Garmin GTN, when you could have asked Garmin what Garmin means when Garmin uses DTK on Garmin devices by looking in the Garmin manual and it would have taken less time than it took to ask and wait for a response. And you might have learned something else in the process. And you might retain it longer or understand it better since you did the work to learn the information yourself.

It is slightly ambiguous terminology, because "desired" might imply a desire to fly in a way that will re-intercept your planned course if you get off-course. Maybe they should have called it PTK. Then you might say the P could stand for "parallel" too.

 

[bflynn]

I dunno. The desired track IS the course you want to fly. You also want to be on centerline when you do.

 

[eman1200]

I think he's peeved that you asked what Garmin means by DTK on your Garmin GTN, when you could have asked Garmin what Garmin means when Garmin uses DTK on Garmin devices by looking in the Garmin manual and it would have taken less time than it took to ask and wait for a response. And you might have learned something else in the process. And you might retain it longer or understand it better since you did the work to learn the information yourself....

THANK YOU.......sniff..........somebody understands me......

it's not one thread that's an issue, it's the over and over and over...... look something up for cryin out loud, you're a gawd dang pilot.

I know individually some of his questions may be asked (or not asked) by other people, but the repetitive nature should be added as a hazardous attitude......."I'm not going to ever help myself, I'm always going to ask someone else because I can't take the time to look it up".

but it's all good, like I said, just ignore me.

 

[asicer]

look something up for cryin out loud, you're a gawd dang pilot.

But my CFI taught me to...

 

[WDD]

It is slightly ambiguous terminology, because "desired" might imply a desire to fly in a way that will re-intercept your planned course if you get off-course. Maybe they should have called it PTK. Then you might say the P could stand for "parallel" too.

Was wondering if it would indeed give you a course to intercept in certain configurations - but it doesn't. That was the crux of the question.

 

[David Megginson]

Interesting. So when flying an ATC Vector, fly "heading" via Heading Indicator. When flying the LPV, ILS, etc., fly the "Desired Track" on the GTN when you get on the "Magenta Line" that is the course aligned with the runway.

Exactly. It's not confusing at all if you consider aviation before the introduction of RNAV.

When you were flying to or from a navaid, you could determine your track, but otherwise (without visual contact with the ground) you knew only your heading. To assign you a specific track, ATC would clear you for a VOR radial or an NDB bearing, often via a published airway.

Approaches were almost always built around navaids (NDB, VOR, or LOC), so you'd be on a specific track while flying them as well. But if ATC just needed to steer you somewhere arbitrary (not to/from a navaid), they had to give you a heading, because you couldn't easily determine your track.

(This still happens, BTW, since not all aircraft have IFR GPSs — I flew IFR this way exclusively until I installed my GTN 650 four years ago.)

 

[WDD]

Good points. On my last flight with CFII, he was directing focus on the HSI after I was established on the approach.

I’m of the opinion that on the approach you want to follow the track. Heading might or might not keep you on the needles. If I bracket onto the track, it will guide me better than the heading indicator.

 

[David Megginson]

Good points. On my last flight with CFII, he was directing focus on the HSI after I was established on the approach.

I’m of the opinion that on the approach you want to follow the track. Heading might or might not keep you on the needles. If I bracket onto the track, it will guide me better than the heading indicator.

It used to matter more because ADF needles would wobble and VOR would scallop, but it's still true that flying a heading is the smoothest way to fly. Basically, it's a hierarchy:

• Hold an attitude using the AI
• Glance at the HI frequently to see if your attitude is keeping you on your desired heading, and if not, adjust your target attitude as needed.
• Glance the CDI every (say) 5–10 seconds to see if your heading is keeping you on the approach course, and if not, adjust your target heading as needed.

You can pass an IFR flight test by chasing the CDI instead of holding a heading (I did that quite a few times with my IPCs before I improved my scan), but you'll be doing a gentle slalom through the air, always a few seconds behind the plane, and operating it like a driver instead of an aviator.

 

[WDD]

How is keeping the plane pointed using the GTN desired track going to weave you more than pointing the plane looking at the heading indicator?

 

[RussR]

Good points. On my last flight with CFII, he was directing focus on the HSI after I was established on the approach.

I’m of the opinion that on the approach you want to follow the track. Heading might or might not keep you on the needles. If I bracket onto the track, it will guide me better than the heading indicator.

The HSI is still important because, for one, it's right in front of you whereas the GPS is usually off to the side.

So you still fly a heading, you just fly the heading that gives you the ground track you need. I work the two in concert with each other. I first get the track right by using the GPS, and then put the heading bug (or just remember if not equipped) on whatever heading the airplane is pointed to at that moment. Then it's easier to use the heading bug since it's in my normal scan. As you descend on an approach the heading will change as the wind does, but that's why you include the GPS track in your scan as well and adjust that heading as necessary. Do this right, and you can fairly easily fly an approach with like 1/10 scale deflection.

 

[David Megginson]

How is keeping the plane pointed using the GTN desired track going to weave you more than pointing the plane looking at the heading indicator?

If you're trying to use the CDI as primary, you'll always be reacting to what happened a few seconds ago, drifting slightly left or right of track and the making corrections only after the CDI has had time to move and you've had time to perceive it. If you react quickly, the deviations will be tiny, but they'll still be happening.

Flying a heading lets you anticipate rather than always reacting, and also lets you ignore small temporary deviations in rough air by holding a constant, mean heading. You should need to change your heading rarely, only because you've decided to refine it, or you've descended into a new wind layer.

Chasing the needle, you'll be turning the yoke left and right continuously, and also probably inducing a bit of adverse yaw that will make your passengers sicker.

tl;dr — your instructor is right about this one.

 

[WDD]

Let me clarify. Not chasing the needle, and using the attitude indicator as the primary BTW. What I'm saying is to use the actual track as depicted in the GTN vs Heading from the Heading Indicator.

Say I want to be on the path for 31 LPV. I want to be on that path, and also on a track of 311 to stay on it. But I'm left of the path. I look at the GTN to bracket to 315 actual track and hold it steady. I move the magenta bar to where it sits on the magenta triangle; now on desired path. I then remove the bracket and get back to the GTN actual track of 311. Now I'm on the path and actual track that I need.

How is using the Actual Track on the GTN going to be causing more problems than using the Heading as depicted on the Heading Indicator?

If I had a wind from the right, I would look at the Heading Indicator and probably see that holding the 311 actual track requires a 315 heading. I guess I could follow the 315 heading, but the purpose of holding a heading while on approach is to hold a track, so why not just follow the GTN which gives the actual track that I need?

 

[Hang 4]

Because you are looking to the side at the GTN, vs intruments that are your primary scan and right in front of you. You also need to manage altitude. How will you do that if you are looking over at the GTN? You have an intrument right in front of you that gives you all the information you need with no numbers for both vertical and horizonatal. That might be why @eman1200 was sighing.. you are making it much more complicated than it needs to be.

 

[David Megginson]

Let me clarify. Not chasing the needle, and using the attitude indicator as the primary BTW. What I'm saying is to use the actual track as depicted in the GTN vs Heading from the Heading Indicator.

That's a good idea, but still use the heading indicator as primary — cross-checking the TRK display will save you a bit of bracketing to find the right heading, but then still follow that heading; don't chase a number (there's a reason glass panels use pseudo-analog displays for altitude, airspeed, etc rather than just showing the raw number).

 

[aterpster]

Interesting. So when flying an ATC Vector, fly "heading" via Heading Indicator. When flying the LPV, ILS, etc., fly the "Desired Track" on the GTN when you get on the "Magenta Line" that is the course aligned with the runway.

Radar vectors are always headings. Controllers compensate for any wind component.

 

[iamtheari]

You can make your flying a lot busier and more fatiguing than it needs to be by chasing the TRK vs. DTK readouts on your GPS. I'm guilty of it, especially in VMC, but usually the best technique is to fly a heading that keeps the CDI or HSI needle centered and make small heading adjustments to deal with trends in the needle. I like to set (and frequently update) the heading bug to the heading that's working for my desired track and then fly the heading bug most of the time.

By the way, you don't know how easy you have it flying with an HSI. Those things were invented for a reason. Be careful to practice your scan with a CFII or at least a safety pilot before going into IMC if you change to a plane that has a DG and CDI instead of an HSI. It'll feel like flying partial panel if all your instrument time has been with an HSI.

 

[David Megginson]

YBy the way, you don't know how easy you have it flying with an HSI. Those things were invented for a reason. Be careful to practice your scan with a CFII or at least a safety pilot before going into IMC if you change to a plane that has a DG and CDI instead of an HSI. It'll feel like flying partial panel if all your instrument time has been with an HSI.

That's a great point. Before the cheap-retrofit-glass age, a mechanical HSI was out of reach for many of us, at $15-20K + installation (not far below the then price of a used Piper PA-28-140). Now even a cheap-b*****d pilot can have an HSI on a G5 or GI-275 for a small number of AMUs (not the AV-30C, though, before anyone asks, because it's not certified to replace the CDI in IFR flight).

 

[jordane93]

You don’t need to be meticulously looking at your TRK vs DTK. It’s a good cross reference to use on an approach but I wouldn’t be over focusing on it.

 

[WDD]

Good points. I’ll practice in the sim of focusing on the heading indicator and not on the GTN track

 

[iamtheari]

Good points. I’ll practice in the sim of focusing on the heading indicator and not on the GTN track

If you want to make it easier, without actually covering up the GTN, practice flying VOR radials such as Victor airways and don't program any flight plan into the GTN at all (so it won't show a DTK). Maybe set the GTN displayed fields to not include the actual track while you're at it. Force yourself to fly the needles without the crutch of DTK and TRK being shown all the time.

 

[WDD]

Another thought - the GTN is more precise, more granular - but maybe too much. I might be over correcting chasing that granularity (314 vs 311), vs following the HSI.

 

[David Megginson]

If you want to make it easier, without actually covering up the GTN, practice flying VOR radials such as Victor airways and don't program any flight plan into the GTN at all (so it won't show a DTK). Maybe set the GTN displayed fields to not include the actual track while you're at it. Force yourself to fly the needles without the crutch of DTK and TRK being shown all the time.

It took me way too many years to learn that lesson.