In article tJV6f.11984$gF4.4699@trnddc07,
"Russ MacDonald" wrote:

One of my students asked me a question the other day that I have been unable
to answer.

Many instrument approaches are labeled with a letter following the primary
name and the letter indicates that the final approach course is not lined up
(beyond 30 degrees) with any runway, and that a circling approach is
required. For example: VOR-A.

That said, what is the difference between VOR-A, VOR-B, VOR-C, etc? Does
the letter have any additional significance? Why, at some airports is there
a VOR-B or VOR-C but no VOR-A? Is it because there used to be a VOR-A and
it was decommissioned?

There is no significance other than the order the approaches were first
published. They start at A for the first circling approach at an airport,
and work their way through the alphabet. Some airports have a bunch of
them; LGA has an LDA-A, VOR/DME-E, VOR-F, VOR-DME/G, and VOR-DME/H.
Presumably at some time there were B, C, and D approaches which have since
been revoked.

BTW, it's not just mis-alignment between the FAC and the runway. An
approach will also not get straight-in minimums if the descent profile is
too steep (IIRC, 400 ft/nm). Compare and contrast, for example, the VOR-A
and the VOR/DME-24 at POU. Exactly the same FAC, but the DME approach gets
you a couple hundred feet lower at the FAF, so it qualifies for straight-in.