Why some approaches are NA as alternates

What is the reason for an approach (or a whole airport) to be NA as
an alternate? Is there some attribute an approach has to have to be
worthy of being filed as an alternate?

The one that got me wondering was KAST (Astoria, OR) which is NA except
for the VOR Rwy 8 when it also has ILS/LOC and GPS approaches.

--
Ben Jackson

http://www.ben.com/

I don't have the AST plate, Ben, but I would imagine that the situation is
similar to that on the ILS approach to rwy 17 at Olympia, which is also NA
as an alternate although the other approaches at OLM are OK. ATC cannot
monitor the outer marker for the ILS when the tower is closed, so if it
failed in the middle of the night a pilot shooting the approach would have
no warning that the marker was out of service. The A/FD says that the NDB at
AST is unmonitored...don't know what that has to do with the GPS.

Bob Gardner

"Ben Jackson" wrote in message
news:xnS6b.385577$Ho3.57620@sccrnsc03...
What is the reason for an approach (or a whole airport) to be NA as
an alternate? Is there some attribute an approach has to have to be
worthy of being filed as an alternate?

The one that got me wondering was KAST (Astoria, OR) which is NA except
for the VOR Rwy 8 when it also has ILS/LOC and GPS approaches.

--
Ben Jackson

http://www.ben.com/

On Mon, 08 Sep 2003 03:38:19 GMT, "Bob Gardner"
wrote:

The A/FD says that the NDB at
AST is unmonitored...don't know what that has to do with the GPS.

A GPS approach is never available as an alternate.

A GPS approach is never available as an alternate.


That's not true. Your alternate airport needs to have an approach besides
GPS, but that doesn't prevent you from flying the GPS approach at the
alternate airport if the weather is good enough for the GPS approach
minimums.

On Mon, 08 Sep 2003 15:59:11 GMT, "Steve" wrote:

A GPS approach is never available as an alternate.


That's not true. Your alternate airport needs to have an approach besides
GPS, but that doesn't prevent you from flying the GPS approach at the
alternate airport if the weather is good enough for the GPS approach
minimums.


It doesn't prevent you from flying but it does prevent you from filing
it as an alternate (that's is why they are NA).