GPS Track or Compass?

TheGolfPilot

TheGolfPilot

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Golfpilot
When I am flying an airway, the gps track and the heading assigned for the airway are dead on but the compass is sometimes 5 degrees or a little more off. Recently I have been setting my HSI to match the GPS, not the compass and have noticed I have been getting a lot less corrections from ATC when it comes time to receive headings.
In training I was taught to line the HSI up with the compass. Is there something wrong with my new found way to fly straighter and find the right heading faster?
 
The HSI in the 172 I've been flying seems to precess a bit throughout the flight. I have to realign it several times in the course of a typical IFR flight. How often do you realign your HSI to your wet compass inflight?
 
I need to realign about once every 15-30 minutes. I was curious if others realign with their gps instead of compass. Seems like the gps is simply more accurate.
 
You've been setting your HSI to match what, exactly, on your GPS?
 
TheGolfPilot said:
When I am flying an airway, the gps track and the heading assigned for the airway are dead on but the compass is sometimes 5 degrees or a little more off. Recently I have been setting my HSI to match the GPS, not the compass and have noticed I have been getting a lot less corrections from ATC when it comes time to receive headings.
In training I was taught to line the HSI up with the compass. Is there something wrong with my new found way to fly straighter and find the right heading faster?
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1) Do you understand the difference between heading and track?

2) Which one is ATC telling you to fly?

3) Does your compass show your heading without applying any corrections?
 
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"turn left heading 150" I would be turning left to track 150. While the compass is showing a heading of 140. If I turn to compass heading (corrected for error) to 150, I almost always get "right 10 degrees" or "right 160".
When people fly with an Aspen or glass panel, there is no need for correction. what is the HSI on the glass panel getting its information from?

It really got me thinking when I was flying the SVFR corridor over LAX and my gps and vor heading are matched up but my compass isn't.

On a windy day the direction the nose is pointing vs track can be significantly different.

What I am saying is that I get less talk from the controller when my plane flies the heading they give me vs pointing my nose where the controller asks me to "heading" and making him correct for wind.
 
MauleSkinner said:
Does your compass show your heading without applying any corrections?
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OP, have you thought about this question? Does your compass have a correction card?

After the compass is sorted, does the wind ever blow where you live ?
 
TheGolfPilot said:
When people fly with an Aspen or glass panel, there is no need for correction. what is the HSI on the glass panel getting its information from?
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Glass panel HSIs get their info from a flux gate...which senses the earth's magnetic field, not airplane track.
 
JHW said:
OP, have you thought about this question? Does your compass have a correction card?

After the compass is sorted, does the wind ever blow where you live ?
Click to expand...

Ya, that article I posted answered my question. "heading" means two different things to the ATC controller. When receiving headings though, they want compass heading. "What is your heading to CCR vor?" means track and "Fly heading XXX" means compass heading.
 
TheGolfPilot said:
"turn left heading 150" I would be turning left to track 150. While the compass is showing a heading of 140. If I turn to compass heading (corrected for error) to 150, I almost always get "right 10 degrees" or "right 160".
When people fly with an Aspen or glass panel, there is no need for correction. what is the HSI on the glass panel getting its information from?

It really got me thinking when I was flying the SVFR corridor over LAX and my gps and vor heading are matched up but my compass isn't.

On a windy day the direction the nose is pointing vs track can be significantly different.

What I am saying is that I get less talk from the controller when my plane flies the heading they give me vs pointing my nose where the controller asks me to "heading" and making him correct for wind.
Click to expand...

I'm pretty sure "the letter of the law" is fly the magnetic HEADING. Controllers get a feel for what the wind is doing and pretty much know what headings to assign to get the course they want when vectoring. That being said I'll bet so many pilots "fly the course" when being vectored nowadays with GPS navigation being the rule rather than the exception that controllers are getting used it and pilots that are flying the assigned HEADINGS are getting more adjustments when being vectored.
The SFRA over LAX is based on the SMO 132 degree radial. If the winds are such that your holding heading to stay on that radial is 145, then that's the heading you should be flying. If it changes, it changes. You stay on the 132 radial
 
Often confusion over things like this is due to inability to define simple terms.

Make absolutely sure you can precisely define the terms compass heading, magnetic heading, variation, deviation, wind correction angle and magnetic course to start.

And which is displayed where in the cockpit and to which a controller is referring when he assigns a heading to fly.

This is all very basic student pilot material. I suggest starting with the appropriate chapter in the Pilot's Handbook of Aeronautical Knowledge, and if that's not sufficient, maybe booking an hour of ground with an instructor.
 
FastEddieB said:
Often confusion over things like this is due to inability to define simple terms.

Make absolutely sure you can precisely define the terms compass heading, magnetic heading, variation, deviation, wind correction angle and magnetic course to start.

And which is displayed where in the cockpit and to which a controller is referring when he assigns a heading to fly.

This is all very basic student pilot material. I suggest starting with the appropriate chapter in the Pilot's Handbook of Aeronautical Knowledge, and if that's not sufficient, maybe booking an hour of ground with an instructor.
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Well put.
 
FastEddieB said:
Often confusion over things like this is due to inability to define simple terms.

Make absolutely sure you can precisely define the terms compass heading, magnetic heading, variation, deviation, wind correction angle and magnetic course to start.

And which is displayed where in the cockpit and to which a controller is referring when he assigns a heading to fly.

This is all very basic student pilot material. I suggest starting with the appropriate chapter in the Pilot's Handbook of Aeronautical Knowledge, and if that's not sufficient, maybe booking an hour of ground with an instructor.
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:yes:
 
FastEddieB said:
Often confusion over things like this is due to inability to define simple terms.

Make absolutely sure you can precisely define the terms compass heading, magnetic heading, variation, deviation, wind correction angle and magnetic course to start.

And which is displayed where in the cockpit and to which a controller is referring when he assigns a heading to fly.

This is all very basic student pilot material. I suggest starting with the appropriate chapter in the Pilot's Handbook of Aeronautical Knowledge, and if that's not sufficient, maybe booking an hour of ground with an instructor.
Click to expand...

I think my confusion was formed by discovery. The track course that atc finally arrives at was identical to the original vector time and time again. I flew the track instead of the heading a few times and noticed I was receiving far less adjustments, thus, taking a lot less atc bandwidth.

When atc says fly heading xxx direct to XXX vor, they don't want you to fly that heading, they want to you fly that track. If you fly that heading and end up 15 miles off of the vor, using the excuse "they told me to fly heading xxx" isn't going to magically lift you out of the mountain you flew into.

Simple vocabulary isn't the issue. I know what the different meanings are but ATC uses "heading" to describe most of them. I understand a good controller will take into account wind and should assign accordingly, and I NOW understand that flying the less efficient magnetic compass, taking up frequency bandwidth, is more important to the system then just doing what the controller wants.
 
TheGolfPilot said:
When atc says fly heading xxx direct to XXX vor...
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That does not sound like normal ATC language.

What they usually say to me is more like "467SA, turn left heading 260, direct xxx when able". Or, "Fly heading 340, join V134 and proceed on course".


In both (all) cases, when they assign a heading, they absolutely, positively want you to fly that heading and not second-guess them with random "corrections" as you seem to have been doing. If you think an assigned heading is insufficient for the task at hand, advise ATC of that fact rather than "rolling your own", so to speak.

And, legally, you are kind of obliged to do "just what the controller wants". It's not really "pilot's discretion" unless so advised or under emergency authority.
 
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ATC assumes that everyone given a specific heading assignment is subject to the same wind drift, so don't try to second guess them by flying what you think the track should be vs. the heading they assign.

You will either be given a "fly heading of" or "fly direct to" but not both at the same time, unless they are giving you some sort of nav intercept, in which case it will be be something like "fly heading of 020, intercept SAC vortac 030 radial, then direct SAC vortac."
 
TheGolfPilot said:
When atc says fly heading xxx direct to XXX vor, they don't want you to fly that heading, they want to you fly that track. If you fly that heading and end up 15 miles off of the vor, using the excuse "they told me to fly heading xxx" isn't going to magically lift you out of the mountain you flew into.
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When a controller tells you to fly a heading, he means heading, not track.

Further, that heading should be magnetic heading, corrected for compass errors.

The only time a controller wants you to fly track is when he/she clears you direct to a fix or a facility [VOR or NDB].

It you have an authoritative cite to the contrary, please post it.
 
This all cleared up my questioning. Again, ATC corrections were consistently leading to the track= original heading. I flew track a few times and got 0 corrections. I'm just going to go back to flying compass headings with corrections because that is what they want. Thanks for the wrist slaps, the FAR reasoning is obvious, the practical reasoning I'm guessing isn't something discussed on this forum. I probably need to ask a controller.
 
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TheGolfPilot said:
This all cleared up my questioning. Again, ATC corrections were consistently leading to the track= original heading. I flew track a few times and got 0 corrections. I'm just going to go back to flying compass headings with corrections because that is what they want. Thanks for the wrist slaps, the FAR reasoning is obvious, the practical reasoning I'm guessing isn't something discussed on this forum. I probably need to ask a controller.
Click to expand...

Here are a couple of pages from the controllers' handbook:
 

Attachments

TheGolfPilot said:
This all cleared up my questioning. Again, ATC corrections were consistently leading to the track= original heading. I flew track a few times and got 0 corrections. I'm just going to go back to flying compass headings with corrections because that is what they want. Thanks for the wrist slaps, the FAR reasoning is obvious, the practical reasoning I'm guessing isn't something discussed on this forum. I probably need to ask a controller.
Click to expand...


Just because you did it wrong doesn't mean you can't learn to do it correctly.:nono:

You could start by learning what heading, track, course, deviation, variation, wind correction, compass correction, mean. Your explanations are hard to read due to your misconceptions.

A couple of hours of private pilot ground school would help.:yesnod:
 
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TheGolfPilot said:
This all cleared up my questioning. Again, ATC corrections were consistently leading to the track= original heading. I flew track a few times and got 0 corrections. I'm just going to go back to flying compass headings with corrections because that is what they want. Thanks for the wrist slaps, the FAR reasoning is obvious, the practical reasoning I'm guessing isn't something discussed on this forum. I probably need to ask a controller.
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There are a lot of ATC trainees around the Bay Area, including at CCR.

Don't discount an ATC FU. It happens.

I've gotten "Fly heading 360" during an SFO Class B transition, in unusually strong but very smooth northeast winds (the Aspen reported 45 knots at 3500!). That was followed shortly after by "I need you close to the 10 thresholds for departing traffic," as the ATC-calculated wind correction wasn't even close to enough.
 
MauleSkinner said:
Personally, I'd trust MacClellan about as far as I can throw him...
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Yep!

His concluding paragraph in that link:

I know the dual meanings of heading in conversations with controllers can be confusing, but I believe the dilemma can be resolved this way: When a con-troller tells you to fly a heading, he wants you to maintain the assigned compass heading. When he asks for your present heading, he wants com-pass heading. But when a controller asks you for the heading to some point along your route, he wants you to tell him the desired track from your present position to that point. Make sense? It does to me.
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Doesn't make sense to me, Mac. I need an authoritative site for the "dual meaning of heading." Otherwise, it seems it came out of your personal mystery manual.
 
I think when Knoxville departure asks, "Say on course heading to destination", it's simply that they want to know in what general direction Copperhill airport lies.

It's just a loose and imprecise usage of the word "heading".
 
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FastEddieB said:
I think when Knoville departure asks, "Say on course heading to destination", it's simply that they want the know in what general direction Copperhill airport lies.

It's just a loose and imprecise usage of the word "heading".
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Amen.

They want to know the heading you will initially fly to go to Copperhill. If that is your heading for track, or not, they could not care less.
 
aterpster said:
Amen.

They want to know the heading you will initially fly to go to Copperhill. If that is your heading for track, or not, they could not care less.
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That's the way I see it. I give them an initial approximation before turning (course plus roughly guessed correction), and sneak in the proper wind correction later on. I've never had a complaint.
 
TheGolfPilot said:
I think my confusion was formed by discovery. The track course that atc finally arrives at was identical to the original vector time and time again. I flew the track instead of the heading a few times and noticed I was receiving far less adjustments, thus, taking a lot less atc bandwidth.

When atc says fly heading xxx direct to XXX vor, they don't want you to fly that heading, they want to you fly that track. If you fly that heading and end up 15 miles off of the vor, using the excuse "they told me to fly heading xxx" isn't going to magically lift you out of the mountain you flew into.

Simple vocabulary isn't the issue. I know what the different meanings are but ATC uses "heading" to describe most of them. I understand a good controller will take into account wind and should assign accordingly, and I NOW understand that flying the less efficient magnetic compass, taking up frequency bandwidth, is more important to the system then just doing what the controller wants.
Click to expand...

I don't want to say there is a lot of misunderstanding in this post, but I don't know any other way to say it.

Heading is what you read off your Directional Gyro, or Heading Indicator. If your DG says 360, your nose is ointed at 360.

Track is the line you draw on the ground with your xxxxx foot long crayon pointed at the ground, connected to your airplane.

Radials are lines directly away from a fixed object. Flying a radial is not the same as your heading. It is more akin to track, but is leading to a central hub, not some arbitrary point in the sky.

When a pilot is assigned a heading, they fly the heading, not guessing where the controller is trying to vector you to and then inputting your own wind correction angle, and then have them wondering why the correct wind correction angle they gave you is making you off course of your intended ground track with their heading.

Vocabulary is important. Having the same definition of ground track, heading, and other stuff is important as well.

I don't know if it is abnormal, but I have never flown an aircraft with a non-slaved HSI. Maybe it is an old school thing, but all of mine have been slaved to a flux gate (not flux capacitor) in the rear of the airplane. They require no precession since the HSI is automatically updated in real time. A directional gyro on the other hand requires constant tuning and fixing and adjustments through a long flight.
 
TheGolfPilot said:
When I am flying an airway, the gps track and the heading assigned for the airway are dead on but the compass is sometimes 5 degrees or a little more off. Recently I have been setting my HSI to match the GPS, not the compass and have noticed I have been getting a lot less corrections from ATC when it comes time to receive headings.
In training I was taught to line the HSI up with the compass. Is there something wrong with my new found way to fly straighter and find the right heading faster?
Click to expand...

When was the last time you swung your compass and updated the correction card, or applied the correction to your HSI when reading the compass to set it?
 
Henning said:
When was the last time you swung your compass and updated the correction card, or applied the correction to your HSI when reading the compass to set it?
Click to expand...

I'll have to take a look. I do fly 4 different planes so "getting used" to what one compass to another just isn't going to happen. They all have compass cards and not slaved HSI's. The HSI's need fairly constant adjusting to keep the plane straight
 
TheGolfPilot said:
I'll have to take a look. I do fly 4 different planes so "getting used" to what one compass to another just isn't going to happen. They all have compass cards and not slaved HSI's. The HSI's need fairly constant adjusting to keep the plane straight
Click to expand...


How do you "adjust" a HSI?:confused:
 
TheGolfPilot said:
I'll have to take a look. I do fly 4 different planes so "getting used" to what one compass to another just isn't going to happen. They all have compass cards and not slaved HSI's. The HSI's need fairly constant adjusting to keep the plane straight
Click to expand...

Do you look at the compass and apply the correction on the card for that heading to the number before entering it on the HSI?

If you use the GPS heading you are entering the ground track compensated for wind most likely, this is compensating wind already.
 
Henning said:
Same as a DG if it's not slaved to a flux gate compass.
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Yep. The only thing that surprises me is that the OP has access to FOUR (4) planes with non-slaved HSIs. I didn't think they were that common, I think I've only seen one in any plane I was in a position to perhaps fly. Of course, if they're all owned by the same FBO, maybe it's not too surprising.
 
azure said:
Yep. The only thing that surprises me is that the OP has access to FOUR (4) planes with non-slaved HSIs. I didn't think they were that common, I think I've only seen one in any plane I was in a position to perhaps fly. Of course, if they're all owned by the same FBO, maybe it's not too surprising.
Click to expand...

It got you an HSI for $2500 instead of $12,500. I could see a flight school doing a fleet.
 
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