"Jose" wrote in message
. com...
And all it takes is a slight crosswind for the 181 degree aircraft
to need to fly 177 to maintain course, and then 181 again.

True, but as long as the course is being maintained, the corresponding
altitude doesn't change (the hemisphere rule applies to course, not
heading).

I agree with your larger point that (even aside from climbs and descents)
the hemisphere rule doesn't prevent near-head-on flight in the vicinity of
180 or 360 degree courses. For that reason, when VFR, I prefer to avoid such
courses if feasible; instead, I plot a course that zig-zags about ten
degrees away from the borderline direction. If nothing else, traffic is a
bit more conspicuous when its orientation is oblique so that the fuselage
profile becomes visible.

--Gary