Understanding the flight direction degree for great circle and rhumb line
 

http://i.stack.imgur.com/sQMbG.png


So I am trying to understand the image above. If you fly in the Northern Hemisphere going west. The image said it's 150 degree if you fly Great Circle while 270 degree flying rhumb line.

If you think about this on a map, how is it possible to be 150 degree? Shouldn't the degree be between north(360) and west(270) as you fly west? I'm so confused. Please help. Thanks in advance.

Whoever has drawn the diagram has put the great circle arrows on in the wrong direction. This shows great circles and rhumb lines on a mercator chart, which is the only chart considered for ATPLs where they look different, on all other charts the great circle approximates or is a straight line. Its better to get your head around great circles and rhumb lines either on the earth or on one of the other charts first.

Heres is my memory aid:

- Rhumb Line (constant heading)

- Great Circle (heading is changing constantly - traveling westbound (NH) HDG/track decreases, traveling eastbound (NH) HDG/track increases - opposite in SH = Southern Hemisphere) this is where the convergency formula comes into the game (general navigation)

HDGs given in green color are correct for an EASTBOUND flight.
They messed up the arrows

And rum comes from Jamaica, so it's always to the Equator

The tip of the penis points to the pole... Never get it wrong again!

Thanks guys, I think I figure out what is going on. The direction of the great circle path can go east or west. It is measure against the meridians in the diagram.

Correct - it goes directly East or West at the Vertex (an important point for many questions).