A pilot is using a polar stereographic chart whose grid is parallel to the zero meridian, with Grid North in the direction of the North geographic pole. In polar regions, the pilot stops navigation in free-gyro mode after leaving the 6 microteslas zone, and the grid heading controlled by information from the inertial navigation system (INS) is 045°. After switching to "magnetic mode", the compass heading is 220°. The INS position at this moment is 76°N 180°W. The magnetic variation on the chart is 10°E. The compass shift on this heading at this point in time is:

  

Answer:

 

Aircraft position is 76°N 180°W, GRID heading 045°G

 

G  = T ± Convergency, so we can rearrange, T = G ± Convergency

 

With the GRID aligned to the zero meridian, Convergency = Aircraft longitude = 180

 

So,  T = 045 ± 180 = 225°T or 135°T (draw the diagram to confirm)

 

True Heading 225°T, VARIATION 10E, so Magnetic Heading = 215°M

 

In the 6 microteslas zone the MAG compass is no good – you will be in DG (gyro) mode, when you leave the 6 microteslas zone, you switch back to MAG mode.

 

When you switch back to MAGNETIC MODE, the compass heading is 220°M, the compass will now align correctly to 215°M, in other words, -5°