magnetic variation data

Hi all,

I was sitting on Senaki 09 the other night having a look at the airport charts by vJaBoG32. The heading of the runway was bang-on 90deg according to the HSI. But the chart said it should be more like 88deg. The magnetic variation stated in the chart was E6deg with a 2010 written in brackets underneath it, which I assume means "data from 2010". That got me thinking how current is the magnetic variation data in this sim? The MV value in the CDU was set to E6.2, which gave me 90deg. I had to set it to E6.8 to get the 88deg stated in the chart. Does that make sense? If i want a difference of two degrees I should have to change the MV by two degrees, right? Could it be that the difference in heading in the game and on the chart is due to the game data being more recent?

Looking in the Data files there appears to be 5 sets of Magvar data

1990,1995,2000,2005,2010

.....\DCS_World\DCS World\Data\MagVar

hmm,

thanks but that still leaves me wondering. How do I know which data is used when I'm sitting on my runway? Could be the chart uses recent 2010 data while the sim, for this particular section of the world, uses 1995 data.

An what about changing MV by a mere 0.6deg resulting in a 2deg heading difference? Or was it just me and my lazy eye?

The values depend on the type of vehicle you use. The runway headings for the charts were measured out (not calculated) with the A-10C sitting on the runways. There is a known bug with other types than the A-10C. If you use the KA50 or P51 you get different heading readouts. Example: Sochi RWY 24 reads 236 deg mag heading in the A-10C. The P51 and the KA50 show 240 deg mag heading.

Regards

Mike

Servus,

all these questions came to mind when I was sitting in an A10C on the runway in an "take-off from runway"-scenario. So with the MV mentioned on the charts I should get a reading of 88deg as they are on the charts, not the 90deg I got. Or is this just me counting peas? Do pilots care for +-2deg deviation?

Set the Magnetic Variation Switch on the HARS control panel to +15 and switch short to to HARS and then back to EGI. You will see your 88 deg mag. And yes, Pilots take care of 2 deg. It even makes a differenz to fly the downwind 2 deg off.

Regards

Mike

"Do pilots care for +-2deg deviation?"

Yes that is a significant value.

The values depend on the type of vehicle you use. The runway headings for the charts were measured out (not calculated) with the A-10C sitting on the runways. There is a known bug with other types than the A-10C. If you use the KA50 or P51 you get different heading readouts. Example: Sochi RWY 24 reads 236 deg mag heading in the A-10C. The P51 and the KA50 show 240 deg mag heading.

Regards

Mike

In Russian a/c the cockpit headings are True, not Magnetic. In the P-51, the compass shows Magnetic and the Gyro shows True. However to get an accurate magnetic reading on the P-51 compass, it must be in a level attitude. Sitting on the runway in a nose up attitude introduces a tilt error of a few degrees on the compass.

In Russian a/c the cockpit headings are True, not Magnetic. In the P-51, the compass shows Magnetic and the Gyro shows True. However to get an accurate magnetic reading on the P-51 compass, it must be in a level attitude. Sitting on the runway in a nose up attitude introduces a tilt error of a few degrees on the compass.

Ref Russian aircraft being in True , do you mean IRL or in the Sim ? Spurred on by this post I tested the MIG29S and SU27 over a known track (Beslan - Nachlik) and found both to be displaying Magnetic.

The track from Beslan to Nachlik was measured from a Real world ONC and also by calculation from AIP Airfield ref points and Google maps all headings where within 1 degree True and came up as 294Deg True.

Using the Ruler tool in the Mission Editor it shows 286Deg. Assuming 5 East variation that would imply the value displayed by the ruler tool is Magnetic.

(Though Mag real world value should be 289deg Mag)

I jumped in game at Beslan 0 wind. By my real world calcs I determined that the correct Mag heading to fly was from Beslan to Nachlik was 294T -5 = 289Deg Mag.

I flew this heading (289) in the both the SU27 and Mig29 and arrived 1Km to the East of Nachlik airfield. I then entered Mission Editor and set up 2 wypts the origin over Beslan airfield and the second over Nachlik airfield. In sim the displayed track between these wypts om the HSI was 287deg. By this I again deduce that its displaying Magnetic though there appears to be a 1-2 deg error. Though the In Game Magvar along this track might be computed at 6 East) Looking at a TPC Real world shows the closest isogonal at 5Min 30secs East Variation... so 6 degs E Var would be reasonable.

CONCLSUION

Ruler tool in ME displays Magnetic

Russian HSI/HUD steering cues and scales are Magnetic.

Possible 1-2 degree error/Tolerance in Magvar

Applaud your effort, but unfortuantely the map is deceptive and the implications incorrect. As I think you already know, the DCS map projection produces a coordinate error compared to reality, which increases as we move further away from the map origin, which is all the way in the center of the Crimea. To test your own experiment, try matching some track lines in the Crimea between identifiable landmarks, like shoreline points for example. I think you will find the ME ruler suddenly matching the headings on Google Earth. Try to do the same on the northwestern corner of our populated map, say between Anapa and something else, and you begin to see the error. By the time you get down to Beslan, well, you know the rest. :)

In regards to cockpit headings in Russian a/c, it applies to both DCS and reality.

You can check the magnetic variation on any point of interest on the map by placing a flyable A-10C there and and checking the CDU NAV>OPTIONS page. Assuming you have the module, obviously. It should generally be 6-8 degrees throughout the map. Also a good way to compare Russian vs. Western heading readings in the cockpit.

Ref Russian aircraft being in True , do you mean IRL or in the Sim ? Spurred on by this post I tested the MIG29S and SU27 over a known track (Beslan - Nachlik) and found both to be displaying Magnetic.

 

The track from Beslan to Nachlik was measured from a Real world ONC and also by calculation from AIP Airfield ref points and Google maps all headings where within 1 degree True and came up as 294Deg True.

 

Using the Ruler tool in the Mission Editor it shows 286Deg. Assuming 5 East variation that would imply the value displayed by the ruler tool is Magnetic.

(Though Mag real world value should be 289deg Mag)

 

I jumped in game at Beslan 0 wind. By my real world calcs I determined that the correct Mag heading to fly was from Beslan to Nachlik was 294T -5 = 289Deg Mag.

 

I flew this heading (289) in the both the SU27 and Mig29 and arrived 1Km to the East of Nachlik airfield. I then entered Mission Editor and set up 2 wypts the origin over Beslan airfield and the second over Nachlik airfield. In sim the displayed track between these wypts om the HSI was 287deg. By this I again deduce that its displaying Magnetic though there appears to be a 1-2 deg error. Though the In Game Magvar along this track might be computed at 6 East) Looking at a TPC Real world shows the closest isogonal at 5Min 30secs East Variation... so 6 degs E Var would be reasonable.

 

CONCLSUION

Ruler tool in ME displays Magnetic

Russian HSI/HUD steering cues and scales are Magnetic.

Possible 1-2 degree error/Tolerance in Magvar

I understand the map distortion thing, but I didn't realise it was based on the centre of Crimea..... Beslan-Nachlik was not a good place to test then. Off to test closer to Crimea :)

I understand the map distortion thing, but I didn't realise it was based on the centre of Crimea..... Beslan-Nachlik was not a good place to test then. Off to test closer to Crimea :)

You can test it in Beslan as well, if you simply believe me. :) Not that I blame you for wanting to see it for yourself!

With your suggested route starting directly over Beslan and flying directly toward Nalchik (I'm talking about the airports), in an Su-27 flying 286 as indicated on the ME will get you exactly there. In your original test you flew 289 and hence ended up a little east of the destination. Now if you try the same track in the A-10C, you will find it to be about 280.

Tried it Anapa to Kerch. Ok I am convinced that the FC3 aeroplanes are in TRUE.

Not so convinced about the Russian types IRL only using True though. Reading a couple of MIG29 manuals describes use of Magnetic heading and inputing variation as a part of the GYRO alignment procedure. This involving use of the MAG SLAVE button immediately below the HSI. Sure the internal calculations are all in True but can be displayed to the pilot as Mag or True as that is simply just bias the heading scales appropriately.... no different to a TRUE or MAGNETIC switch found in many western types.

Tried it Anapa to Kerch. Ok I am convinced that the FC3 aeroplanes are in TRUE.

Not so convinced about the Russian types IRL only using True though. Reading a couple of MIG29 manuals describes use of Magnetic heading and inputing variation as a part of the GYRO alignment procedure. This involving use of the MAG SLAVE button immediately below the HSI. Sure the internal calculations are all in True but can be displayed to the pilot as Mag or True as that is simply just bias the heading scales appropriately.... no different to a TRUE or MAGNETIC switch found in many western types.