Roy Smith wrote:

In article , wrote:
Special instrument approach procedures may be for a location that
doesn't have a public IAP or it may be at a location that does have a
public IAP. An example is KRNO where the special ILS lowers the
minimums by several hundred feet.

What lets a special approach get lower minimums? The nav signals are the
same, the runway is the same, the terrain is the same, so what's different
about this one operator with the special approach that lets them get lower
mins?

In the case of Reno and Missoula ILS IAPs, the operators have the performance
capability to climb at greater than 200 feet per mile in the missed approach
segment. Most light aircraft can't do what's required at mountain airports
like those.

As to your comment about nav signals, etc, being the same, that is in the
process of undergoing a very big change with RNP and performanced-based
concepts. Other parts of the world are ahead of us on this one. Thus far,
the aircraft with both the equipment and the nav performance proof to do this
is the Boeing 737-NG series. They have minimums at some mountain airports
(Canada being a notable example) of 250 and 3/4 where you might find minimums
of 1,500 and 3.

Alaska Airlines has straight-in minimums of 250 and 3/4 at Palm Springs where
your minimums are circling only 2000 and 5.