Why are many flight plans not straight lines?

[Sunspace]

@GusNSpot

Magnetic or true 90º?

They are two different directions.

Most non pilots or non long distance sailors do not make or understand the distinction in my experience.

Or non-Canadians.

There were places in Canada that are north of the North Magnetic Pole (NMP), but the NMP is on the move, and has now apparently exited the Canadian territorial claim.

[terentii]

@robert_columbia

Pay careful attention to a globe.

Flying from the Caribbean to England involves hugging the coast of North America all the way to Canada.

Flying from California to Japan involves hugging the coast of Alaska and far-eastern Russia.

And…???

[Richard_Pearse]

@Musicat

I would like to correct myself. The last line should read: Since your compass heading will change, you WILL cross the Equator. If you keep a constant 90º heading, you will not.

A constant 90º heading is not flying a great circle track though, and that is what the poster was talking about.

All lines of longitude are great circles. The only line of latitude that is a great circle is the equator (assuming we are referencing true north.) If you are flying a great circle track you will always cross the equator eventually, unless you are following the equator itself.

This is noticeable even on short legs of 100 NM or so. When flying north/south your heading doesn’t change, but when flying more easterly/westerly tracks the heading changes by a few degrees from waypoint to waypoint.

[Novelty_Bobble]

This is all weirdly fascinating.

I do know a bit about the great circle routes but have flown long distance and round the world on some routes that did cause a furrowed brow or two, the human mind isn’t that great at visualising these things sometimes, even when you know it must be true.

One long flight that I made was Queenstown New Zealand to LAX. Couldn’t remember how that looked so used the site already mentioned to plot it out.

http://www.gcmap.com/mapui?P=ZQN-LAX

Ha! does that qualify for the most boring and least visually/conceptually difficult long haul route ever? It sort of does exactly what your brain says it should. Where’s the fun in that?

[GusNSpot]

Well, it starts out really nice.

After that it would be movie / or nap time for sure.

Or maybe I would just try to spot ships & sail boats out in the ocean, anything to keep from going crazy…

[Colophon]

If you draw a line from LA to Johannesburg in Google Maps using the Distance Calculator (which uses great circles) then it definitely starts out slightly north of east. Try it.