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How to use GMC?


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IIRC it is for when your in different zones around the globe. You can set your latitude and hemisphere. But how it works and how to use it are horses of a different colour:)

 

We need a manual:music_whistling:

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The GMK-1A as fiited to the Belsim Mi-8 is a pure gyromagnetik compass system, while the GMK-1AE also has a Astro compass mode (celestial navigation using triangulation of the Sun position).

 

The GMK-1A as fitted to the Belsim Mi-8 does not use the panel for the Astro compass and probably is set up like this description from the FCOM:

 

WARNING

The Mi-17 aircraft in use by TSMO

may feature the GMK-1AE Astro

Compass control panel, without the

kit having been installed. The celestial

navigation feature will be nonfunctional,

while the Directional

Gyro and Magnetic Compass modes

of this system will be operative. Domestic

field modifications to foreign

instrumentation, communications,

and navigation systems on these aircraft

are not standardized, avionics

systems interface and functionality is

not assured.

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The GMK-1 system finds and compensates for magnetic north by latitude and displays this information on the compasses at the top of the pilot and copilot stations. It also sends this information to the autopilot heading system and the doppler navigation system. If you don't turn on the breaker on the right triangular panel, for example, then you can't use the heading hold autopilot.

 

This information is a continuation from the above from fjacobsen, from the US Army TM 1-1520-Mi-17-10 , which if you search for this PDF online, is the closest thing to an actual manual we are going to get. Looking at the Russian manual available, it only seems to mention it a few times but doesn't explain it. (I'm sure it's a work in progress, just like the English version.) There's also a very good manual that used to be in the docs directory for the Mi-8, but disappeared along with the partial Russian manual around 1.2.6. (Mi-17-1V-Flight-Manual.pdf)

 

gmk1.jpggmk2.jpg

 

Still, the information regarding the 3K switch usage is somewhat ambiguous, though in this segment (courtesy of the Kazan Mi-17-1V manual) suggests it can be used to check the responses from the autopilot system before takeoff:

 

gmk3.jpg

 

I suspect the mentioned cumulative error for the compass isn't modeled. There was a different navigational system for the Ka-50 in which you could correct for cumulative gyroscopic navigational drift by flying over a map location or looking at a spot on the terrain via the Shkval to correct for the drift, but that [drift] never got modeled, though you could still use that feature. If I have time, I'd like to see what happens if you turned off the GMK system or kept the gyro cutoff switch on the left triangular panel off.


Edited by Strekaya
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The fs9/fsx freeware Project Tupolev Tu-154 has a similar (if not the same) instrument. It's functional as I recall. Haven't flown the 154 for a few years.

 

There's a comprehensive English manual included in the package if anyone is interested to download...

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  • 2 weeks later...
The fs9/fsx freeware Project Tupolev Tu-154 has a similar (if not the same) instrument. It's functional as I recall. Haven't flown the 154 for a few years.

 

There's a comprehensive English manual included in the package if anyone is interested to download...

 

Although the basic concept of the Mi-8 GMK-1 and the Tu-154´s TKS-P2 gyroscopical navigation system is the same, the latter one is far more complex and capable.

Therefore, I would NOT recommend documentation from the Tu-154 project to be used as a reference for operational procedures for the Mi-8´s GMK-1.

 

However, the general idea behind great-circle navigation and the differences of a gyrocompass vs. magnetic compass can also be found in this documentation and are worth reading, if one is interested in that.

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