"Ron Garrison" wrote...

I disagree that the ability to navigate to a place once means you can do it
again. AIM 1-1-9.b clearly states that localizer goidance is only valid out
to 35 degrees each side of the course, and that the back course is
specifically not to be used for guidance unless a back course procedure
exists.

Assume a 90kt holding speed and an NDB colocated with the localizer antenna
to identify the fix. If there were a 20kt wind blowing across the holding
course and you did not correct for it in the hold, then 3 minutes later when
you begin the inbound segment of the hold you will have been blown about 1
mile to the left or right of where you want to be. At 1.5 miles from the
airport, that is just about 35 degrees off of the inbound course. Any
stronger wind, or unfavorable errors flying the pattern, and the localizer
may be giving incorrect guidance.

All your information after the second sentence is good. However, it does not
bear directly on your first statement.

Holding over an NDB is a standard, practiced procedure even without any backup
NAVAIDs. Hopefully, if you are holding in IMC over an NDB, you have at least
some idea of the wind, and can make an initial correction on your first outbound
leg. If you don't, you must make a larger correction on the inbound course, but
you can still navigate back to the NDB.

If you are using other NAVAIDs as backups or crosschecks, that does not mean you
ignore your primary NAVAID. Assume you are holding over that NDB collocated
with the LOC. If your planned inbound course in the hold is close to the LOC
front course, you can use the LOC as a valid crosscheck, and possibly use it to
fine-tune your inbound heading in the crosswind. However, if your inbound
course in the hole was NOT coincident with the LOC course, you simply would not
choose to use the LOC as a backup. Still, you can use the NDB -- your primary
NAVAID -- and get back to the NDB.

Flying good IFR in IMC in "ideal" conditions (no wind, no turbulence, no
vertigo, no emergencies) requires practice. Flying in less-than-ideal
conditions is more challenging, and takes more practice and experience. As you
build on your experience, you will discover what YOU can do in specific
situations.