I do think it is important that the instructors in the industry present as near a unified view as possible on this point because, although 'learned discussion' has its place, it confuses the hell out of the students if they think that even the instructors do not agree whether a great circle is a straight line or not.
We will only achieve that by getting all instructors to say only the things which are true. The statement that “all rhumb lines are curves” is untrue. As explained in my previous post some are curves and some (meridians, and parallels of latitude) are not.
Telling half truths will cause even more confusion. We may for example tell them the following:
1. All parallels of latitude are rhumb lines.
2. All rhumb lines spiral towards the Equator.
Any student with half a brain will then confuse him/her self to hell trying to understand how the parallels of latitude spiral towards the poles.
Whilst I take your point that some people may have an 'intuitive vision' that rhumb lines are straight lines
I did not say that. What I actually said was:
But it has the disadvantage that it shows parallels of latitude as curved lines, which is contrary to most people’s intuitive vision.
And
It shows the parallels of latitude as straight lines, which complies with most people’s intuitive vision.
When people are asked to visualize the globe with the meridians and parallels of latitude, many, probably most, will see the side view with straight horizontal lines representing the parallels of latitude. For these people sketching rhumb lines as straight lines will be easiest. Some people will of course it from a slightly higher angle, with both the meridians and the parallels of latitude represented by curves. Those people may find it easier to sketch rhumb lines as curves. Each student should use the method which works best for him/her.
The proper way to look at it, though, has to be from directly above.
I think that only God (and possibly a very few astronauts now and then) look at the Earth from directly above. There is no universally accepted proper or improper way to view it. The “most proper way to look at it” is whatever way each individual finds to be the intuitive one for them.