HSI not lining up

[Reaper33]

Hello,

 

I've noticed when taking off from Batumi airfield rwy 31, if I want to set my HSI to match the runway heading, it's off by a degree. I have to set the HSI course to 300 to match when I'm pointing straight down the runway. Is this due to the magnetic variation not being set? How do I change this in the A-10? Thanks.

[roadrabbit]

Hello,

 

I've noticed when taking off from Batumi airfield rwy 31, if I want to set my HSI to match the runway heading, it's off by a degree. I have to set the HSI course to 300 to match when I'm pointing straight down the runway. Is this due to the magnetic variation not being set? How do I change this in the A-10? Thanks.

 

Only by a degree? :smilewink:

This, apparently, is a bug within DCS World according to others wiser than me. However, this does reflect what happens in the real world - magnetic variation shifts continuously up from 0 degs per year to +/- 2 to 3 degs per year. This means that a 'given' runway magnetic direction (or 'course' <N America> or 'track' <UK and elsewhere>) can change annually. The runway direction is given corrected to the nearest 10 degs.

 

It is usual to change a runway's official magnetic direction only when the 'rounding' takes it to a different nominal 10 deg mark. Thus a runway with a direction of 274 degs M is called Runway 27, one with a direction of 276 degs M is called Runway 28. Note that Runway 28 can therefore have a real magnetic direction of any where from 275 to 284 degs M.

 

Of course some countries do not change as often as perhaps they should, so the difference between the real runway direction and the published runway direction can sometimes be greater. :cry:

 

To find out the real runway direction the easiest way is to line up for take-off on the runway as accurately as possible (on centre line with nose pointing at middle of runway as far away from the aircraft as possible). Then note your magnetic heading and set it on the 'course' pointer of the HSI. Read off the numbers at top right for the real magnetic direction. :D

Edited August 4, 2013 by roadrabbit
Added question mark

[Reaper33]

Thanks for the info. I'm used to seeing runways at 145 azimuth as rwy 14. But to be off by 1 degree it's not right. Especially when trying to line up for an ILS at a different airfield where you can't just line up on the runway to find the true azimuth.

 

If it's a bug, then that's pretty annoying :x

[Johnpilot]

It is not a bug, but actual reality as stated. Runway headings are not absolute as roadrabbit said as runway 27 is not necessarily 270 exactly. ILS signals are directional and are set to to be the exactly "down" the runway. Assuming there is no Localizer offset which I have seen one of in my old training days in the civ world.

 

You will find the same thing with the TACAN as it is not always exactly on the middle of the runway.

 

John

[Reaper33]

Thanks Johnpilot. After a bit of digging around I found the aerodrome charts and it shows Batumi's azimuth there as 299 degrees. At least I have somewhere to look this up now!

 

Many thanks.

[IdleBoards]

DCS doesn't simulate changing magnetic variation. While it does indeed vary from one end of the map to the other, at any given point it is static.

 

The fact that some runways in the game world are aligned correctly with respect to magnetic north, while others have an orientation equal to double magvar (or inverse magvar) is indeed a bug in DCS.