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question about heading indicator setting when flying in NAV mode

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I learned that when you're flying in NAV mode (on the autopilot), following the flight plan on the GPS, you adjust your heading marker on the heading indicator to match the heading of the flight, so when you have to switch back from NAV to HDG setting on the autopilot, you stick to the current heading

However, I often notice that the heading I read on the GPS and the heading I read on the heading indicator can differ by 5 or even by 10 degrees. For example, the heading on the GPS reads 145, while the heading on the heading indicator reads 152.

 

Which reading do I follow here? Do I set my heading marker to match the GPS, at 145, even though the marker is not centered at the 12 o'clock position on the heading indicator? Or do I match the heading marker to the 12 o'clock position on the heading indicator, at heading 152, while the heading of my flight plan is 145?

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Try turning down range of ND to probably 5 or 10. and you will see they will exactly match.

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Funny, I'm having the same problem.  Usually the DG is ok when sitting on the runway but as soon as I take to flight, it starts wandering off and the differance between the DG and the FSX default GPS can be as much as 12 degrees.  I flew a number of aircraft to make sure it wasn't just 1 plane and they all did it.  I also tried flights where I cancelled the weather just in case winds aloft where throwing the DG out and it still did it.  It gets pretty frustrating when your coming in for a landing and ATC is giving you headings to the airport and your having to guess which heading to set on the autopilot to get the correct heading stated by ATC.  :(  Any help would be much apprecitated.  :)

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This is due to the DG procession. When flying you must constantly cross check it with the magnetic compass in straight and level and correct it by using the dial on the DG if there is just drift. To fix this in FSX or FS9 you can press the D button on the keyboard or just turn the dial. In some complex planes this dial is on the co-pilots DG.

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The GPS will give you two compass numbers;  The track for the calculated course, and the track that your actually "tracking"...

 

With any winds aloft, rarely will either match your heading..

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Like the previous poster suggested, there is a difference between a track, which you read in the GPS in your example, and a heading, which includes a wind correction in order to maintain track. 

 

Ex. If your track should be 360, and there is a tong wind from the east, you will have to take a heading of greater than 360 in order for the wind to not blow you off your desired track. How much depends on your TAS and the wind direction and strength.

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Thanks for the information guys.  I will pay more attention to what my DG and compass are doing during the flight.  I fly the Ifly 737's and I've noticed that when I set the autopliot to.... say.... 055, the MFD reads 057 after the turn has been completed by the autopilot.  Would this be the same problem?  Thanks for your input.  There seems to be a lot of things I don't know about FSX. :blink:

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There five terms to consider:

 

Course: The line across the ground that you want/plan to be following

 

Track: The line across the ground that you are following

 

Heading: The direction that the aircraft nose is pointing

 

Bearing: A line from you, to a point, refrenced by a compass

 

Relative Bearing: Same as bearing, but treats your current heading as 0/360

 

 

And of course there is 'declination'.. the difference between True North and Magnetic North... it varies by geographic location..

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Thanks for the information guys.  I will pay more attention to what my DG and compass are doing during the flight.  I fly the Ifly 737's and I've noticed that when I set the autopliot to.... say.... 055, the MFD reads 057 after the turn has been completed by the autopilot.  Would this be the same problem?  Thanks for your input.  There seems to be a lot of things I don't know about FSX. :blink:

The 737 doesn't have gyro driven instruments so ithe heading that is indicated on the displays is always the correct magnetic heading.

 

On the 737 the white line indicates your track line, and the little triangle is your heading. If you look at the top of your compass rose you will see the letters trk mag. Meaning: magnetic track.

 

So in your example, there was probably some wind from the west, which meant that a heading of 055 (indicated by the little triangle) resulted in a track of 057.

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Thanks again!  I guess navagation is not one of my strong points and it looks like I don't fully understand what the instruments are telling me.  Thanks to you guys, I have a better idea of what's going on now.  ^_^

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What I read looks to me like its about the difference between instrument calibration, or function, but that's not what I mean. I recently build a new computer and didn't see the problem for a while, but yesterday I had a clear example. I'd like to show a picture, but after over an hour of trying to get a URL or a link pasted, I'm giving up...

 

The DTK of the GPS reads: 106

The TRK of the GPS reads: 109

The ADF/VOR gauge reads a direction of: 107

The needle of the ADF/VOR gauge points straight up at: 107

The VOR needle on my HDI reads: 108

 

And I think those are the deviations people are talking about, but my problem is in the following:

 

The number I had to dial into the HDG of the autopilot to follow the coarse above, and therefor the heading of the HDI is: 137!

 

Al my gauges and GPS point, give or take a couple of degrees, to the same direction, only on the HDI the VOR needle is deviating to the left by 30 degrees and I have to track a HDG on the HDI of about 30 degrees more then all other parameters show, to stay on coarse. If I dial in the same heading as the other gauges are reading, ATC corrects me and by the end of the flight the deviation increased to about 35 degrees even.

 

Is this normal behavior? If so, how do I deal with it and if not, how do I fix it?

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I'm not sure what you are talking about here, but it depends on the airplane you are flying.

 

It sounds like you are now talking about a gyro driven heading indicator. 

 

You need to reset those about every 15 mins and align them with your compass, because they have many errors, which I will not explain, but they cause the HI to deviate more and more over time. 

 

In FSX you can push the "d" button to quickly reset the heading indicator.

 

Hope this helps.

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Thanks Outofphaze, I'll have a look at it.

This example came up in the Carenado B1900D, which is a new one for me, but it happened to me before with other aircrafts, can remember this fast which ones it were.

It seems strange to me, though, that with everything I read about simflying, and all the videos lessons I watched, this is the first time I hear about a gyro driven heading indicator. So it can well be that there's the problem, indeed. I'll see if I can find some information about it and hope this will help. :)

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Look for a utility file in the library called 'magdec' and add it as a scenery, keeping it always at the highest scenery level. The 30 degrees of heading error is most likely caused by one of your addon sceneries. It is a common problem. There are fixes in the library.

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