Today I've prepared flight plan for route FABL-FBMN. I've set EVEN flight level because magnetic heading is 353, true heading is 343 (as LNM shows for direct connection - orthodrome).
When I clicked button "Adjust flight level ..." it changed flight level to ODD.

I've checked other similar direction - for flight/route FABL-FZSA (magnetic heading 358, true heading 357) it always corrects/adjusts  flight level to ODD, but IMHO it should be EVEN level because it's Westbounded flight (E/W hemispherical rules).

 

Question to Alex - is it any "hidden" factor in algorithm during hemispherical rule calculation under LNM (magnetic variation or so on ...) I don't know about?

Regards,
Piotr

 

[edit]

There is no more question - I've found the correct answer.
I was sure that direct route FABL-FBMN displayed at map view shows magnetic heading FABL->FBMN taken into hemispherical rules calculation, but I was wrong because 353 heading I saw is ending  magnetic heading.
When I've checked the same distance under external Great Circle Mapper tool and then in LNM  under "Measure distance tool" it shows magnetic heading as starting at 006  (initial magnetic course) and changing to 353 (magnetic end course) and now everything is clear for me🙂 (I hope I don't waste your time yet) why this is Eastbound route (initial magnetic course - of course).

BTW - maybe it would be a good idea change displaying current displayed magnetic course to initial magnetic heading (the same that is taken to hemispherical rules calculations) at map view?
 

Edited March 16, 20215 yr by ppgas

Can't add anything to your conclusions. All correct. This is a corner case which is hard to resolve.

I could add initial magnetic heading as an additional option for display. Have to see.

The Great Circle plays a role too which results even in different departure and arrival true course.

Alex

 

13 minutes ago, albar965 said:

I could add initial magnetic heading as an additional option for display. Have to see.

 

It would be great Alex 😄

 

Regards,
Piotr