Compass deviation

[TacitBlue]

Now that I am learning about real world flight planning I have to wonder about compass deviation. In the real world, almost all compasses have errors, and don't always point to magnetic north, hence the compass card. I've never seen a compass card in an FS aircraft, so I was wondering if all FS compasses are perfect, and never deviate or, if there is deviation, where would I find the information about it?

[Woodlouse2002]

I should say they were all perfect and without deviation. Purely because it would be difficult to set up the compass to deviate according to the aircraft, as it would in reality, and secondly I don't believe the magnetic north pole moves in FS either meaning there is no variation.

[Brett_Henderson]

Once you've shown an instructor that you understand compass variation.. you can pretty much forget about true north when it comes to flying. Everything is magnetic north. Runways, VORs, the DG that you set by a compass, headings you'll be given by ATC (obviously) are all magnetic.

From what I've seen so far, the variation is pretty accurate in the sim. And as long as the M$ puts a new one out every couple of years.. we won't have to worry that the poles might have shifted a bit.

As for deviation.. yeah.. it'd be tough to simulate. The sim does a WONDERFUL job replicating compass turns (acceleration and banking errors). .. but trying to simulate the unique magnetic problems from airframes and avionics/electronics might not be worth the effort ?

[TacitBlue]

As I suspected.

You're right about magnetic variation though. I've done a few sim flights only using a sectional chart, plotter, and E6b. On the first one, I totally forgot about mag variation and went way off course (actually on course, but true, not magnetic), on the others I was pretty close.

[beaky]

I agree that FS seems to show some variation, but definitley no deviation due to aircraft peculiarities. Never paid much attention to the compass card corrections in real aircraft: the deviation is usually so minor that it would hardly make much difference in VFR flight.

[Brett_Henderson]

Compass cards seem like something left over from the pre gyro days ( a long time ago ) and until the FAA acts UNgovernment like and changes the regs.. they'll be around and if nothing else.. something for insurance companies to harp on. I suppose, if you're flying dead level .. can take the time to settle on one of the eight major headings.. read the compass.. read the card .. do the math and THEN set your gyro, they "kinda" make sense. That all assumes of course your "finger-thumb" twisting is accurate and you've got a brand new gyro that won't start drifting within seconds ... EVEN if you're someone who likes to fly by the compass and are REALLY good at calculating compass-turn roll-outs.. Do you think you're gonna be any better, +/- than the compass itself is (according to the card)?

I can't remember the last time I read a compass card.. even in actual IMC.

Now.. if you're flying nasty IMC and your gyro fails and you've lost contact with ATC for radar vectors.. AND you've lost your NAVS and can't track a VOR radial.. MAYBE that extra few degrees will matter.. But would they ?..  If all those things had gone wrong and you have no visual references.. you wouldn't have ANY idea what "exact" heading to fly in the first place  :P

[Marlin]

I read this yesterday and was waiting to see the differant responces that there were going to be.

For the sake of FS9, yes there are deviations depending on what aircraft you choose to fly.

But that wasn't the question, sooo how do you tell? When you fly you should have a map, then the map will tell you what the declination is.

To the best I can tell, it is 12 1/2 degrees here at a semi local airport. Taos NM



I think this is what you are talking about.

Now as to the adjustment every fifteen minutes goes, I have no idea what the general rule is. I know for sure the course has a lot to do with it. For example traveling E to W it will change faster that it you were traveling N to S.

Is this what you are talking about?

Sorry about the poor quality picture, it's dark and I didn't set up the tripod. The crease is just about right on the true north line.

[Brett_Henderson]

Marlin..

On that "chart" you'll find several, broken, magenta lines that will give you the variation. They have a number with a letter (  12E,  6W  for examples ). If you've got a plotter.. you can also got to a VOR rose and measure it.. literally ( like I think you did here )..

For the purpose of plotting an exact course using a chart.. variation is VERY important. Deviation.. on the other hand, is not so important.

I don't believe FS9 allows for deviation. I haven't noticed any..  and for there to be any.. the compass gauge would have to be customized to each model.. OR.. the gauge would have to read some specific "error code" from the model, air or aircraft.cfg file.. and I'm pretty sure it does not. I KNOW there's nothing in the cfg file, as I've written and edited quite a few. I've made a few models too and I'd bet that the program (FSDS or GMAX) doesn't generate a compass error reference.. Maybe the air file has something nested in it, but I really doubt it.

[Woodlouse2002]

You cannot tell deviation with a map. Variation yes but a map does not have it's north calibrated to an individual aircraft. And when you consider that the deviation in every single aircraft is different then you realise how unlikely it is to be in FS. In the golden age of sail it was said that the helmsman shouldn't carry his knife incase the blade caused the compass to deviate. Which goes to show the size of the factors of deviation.