Compass heading wrong?

[IonicRipper]

Just got back in the MI-8 after a long time away from it and noticed after a few missions that the compass heading is wrong by about 5 to 10 degrees? Am I forgetting something?

[Cibit]

How are you determining that the compass is wrong?

There is a subtraction of 6 degrees from any map reading you get because of the flat map IIRC at least from the very beginning of DCS world this has been the case:)

[drPhibes]

The magnetic declination (the difference between magnetic and geographic north) is approximately 6° in the Caucasus area, and around 11° in Nevada.

[Whisper]

I'm trying to get confirmation on this : all instruments on Mi8 are using magnetic North as north? And F10 map is using geographic north for azimuth indication? Is that it or am I mistaken somewhere?

Which means we need to substract 6° (in caucasus) from F10 map reading to enter either azimuth on "HSI" (yes, that's not the correct term :) UGR-4UK, there you go) or on the Doppler nav system, that's it?

Edited October 22, 2016 by Whisper

[lmp]

I'm trying to get confirmation on this : all instruments on Mi8 are using magnetic North as north? And F10 map is using geographic north for azimuth indication? Is that it or am I mistaken somewhere?

Which means we need to substract 6° (in caucasus) from F10 map reading to enter either azimuth on "HSI" (yes, that's not the correct term :) UGR-4UK, there you go) or on the Doppler nav system, that's it?

 

The whiskey compass on the canopy frame is magnetic of course. As for the GMK-1, it starts in MK (magnetic compass) mode, but as far as I understand you can switch it to GPK (gyrocompass mode) and manually set the magnetic variation using the ZK switch.

[Whisper]

Well, there is apparently a fixed 6° deviation set up when you start up the chopper :

[EDIT : wrong info following!!]

If, once GMK1 is up & running, on a chopper on ground aligned to 0° geographic (ie aligned north on ME & F10 map), you switch from GPK to MK (which performs an automatic gyro alignment to detected magnetic north, from what the doc say), your UGR-4UK will indicate a heading of 354° after a few seconds, which should be the heading of geographic north relative to magetic north, in caucasus.

Switching back to GPK doesn't put back the heading to 0, meaning you need to correct geo north manually with the ZK switch

 

So that means that initially, on an untouched Mi8, UGR-4UK indicates geographic north.

[/EDIT]

 

EDIT : Further testing proves the above wrong! HSI indicates 354° heading on startup no matter what, I was just not waiting long enough for proper alignment! It's not me switching to MK which made the heading go 254°, but the end of alignment process!

So the whole chopper is aligned on magnetic north! Including GMK1, in MK or GPK mode, and the UGR-4UK gives heading relative to magnetic north.

As said above, to use geographic north, copilot must switch to GPK mode and correct the heading using the SK switch.

 

 

What about doppler nav systems? Do they use corrected GMK input (ie, heading relative to geographic north) or "MK", uncorrected GMK input (ie, relative to magnetic north)?

 

EDIT 2 : preliminary tests seems to tell the Doppler Nav systems use corrected GMK input when GMK1 is in GPK position.

Edited October 24, 2016 by Whisper

[Rogue Trooper]

Generally, until the manual comes out, I will stick with measuring line of flight on the F10 map and subtracting 6 degs for caucases and 12 odd degs for Nevada.

 

Gets me within visual range and safely within unguided rocket launch range every time... now if only I can work out the altitude, temperature variation for rocket release in Nevada... the heat and altitude are killing my rockets range.

[Whisper]

Currently my startup checklist includes the realignment of GMK1 to geographic north and it works everytime.

1) proceed with startup

2) get your current geographic heading (F2 or F10 map view)

3) switch to GPK mode, assert your heading on UGR-4UK is actually not your geographic heading

4) click on SK switch until heading is aligned with your geographic heading

5) go on your merry way, you'll have accurate heading on your UGR-4UK and your Doppler Nav.