"Jim Carter" wrote in message
news:000801c6ba26$9bd59ff0$4001a8c0@omnibook6100.. .
Could this be a case of NA meaning one thing for CAT IIIc and
something else for other purposes?

No. In addition to the inherent implausibility of such an inconsistency, Sam
has pointed out that FAR 97.3n explicitly defines NA to mean "not
authorized" with regard to IAPs.

How could an approach be authorized if the visibility requirement is "not
authorized"?

I don't follow. If "NA" appears in the IIIC line, it means a IIIC approach
is not authorized.

Couldn't it be unlisted because there are no DA or RVR limitations to
list?

No, then it would be an unpublished approach wouldn't it?

Not necessarily. The IIIC approach is published by virtue of the approach
plate that is labeled "CAT III". By definition, CAT III comprises IIIA,
IIIB, and IIIC. There's a section of the plate that lists visibility
limitations for the subcategories; the omission of IIIC from that section
means that there is no visibility limitation for IIIC.

The EWS plate lists all three approach minima.

Assuming that's a typo for EWR (I find no EWS), the plate for ILS 4R CAT III
does not list minima for IIIC; rather, it says the IIIC approach is not
authorized (NA). http://www.naco.faa.gov/d-tpp/0608/00285I4RC3.PDF

--Gary