wrote:
On Thu, 06 Jan 2005 11:52:39 -0500, Ron Natalie
wrote:


The OBS has no meaning to a CDI when using a localizer.
It's left or right of the localizer beam where "left and right" is defined
as looking inward on the front course. It's only when the pilot's left and
right is reversed (as they are looking inward on the back course) that things
are "reversed."



This is not true. The OBS ring has no effect on the needle, but it
certainly has meaning.

If the OBS ring is set to the inbound (only) localizer course, it can
be interpreted exactly as the equivalent VOR course.

You can make the same interpretations no matter what the OBS is set to.
It is necessary and sufficient to know what the inbound course is.

The only time the selector is useful is on a HSI.