Middle Marker minimums

The LOC-D approach for SAN DIEGO/GILLESPIE FIELD (SEE) shows different
minimums for "GRIGG FM". There is an ident code shown for GRIGG, but
no frequency. Is the dot-dash-dot ident just the generic MM ident? I
can't find "GRIGG" listed as an airspace fix at airnav.com. Are the
higher minimums to be used for an approach in an aircraft without an
operating audible marker annunciation? What does "FM" stand for?
Airnav shows GRIGG as a Middle Marker. Thanks.

"S Herman" wrote in message
...
The LOC-D approach for SAN DIEGO/GILLESPIE FIELD (SEE) shows different
minimums for "GRIGG FM". There is an ident code shown for GRIGG, but
no frequency. Is the dot-dash-dot ident just the generic MM ident? I

yes

can't find "GRIGG" listed as an airspace fix at airnav.com. Are the
higher minimums to be used for an approach in an aircraft without an
operating audible marker annunciation? What does "FM" stand for?

FM=fan marker

Airnav shows GRIGG as a Middle Marker. Thanks.

FM stands for Fan Marker. The frequency is 75MHz, true for all such markers.
The ident is modulated on a 3000Hz tone.

"S Herman" wrote in message
...
The LOC-D approach for SAN DIEGO/GILLESPIE FIELD (SEE) shows different
minimums for "GRIGG FM". There is an ident code shown for GRIGG, but
no frequency. Is the dot-dash-dot ident just the generic MM ident? I
can't find "GRIGG" listed as an airspace fix at airnav.com. Are the
higher minimums to be used for an approach in an aircraft without an
operating audible marker annunciation? What does "FM" stand for?
Airnav shows GRIGG as a Middle Marker. Thanks.

No. Middle markers are just dot-dash. It sounds different.


Is the dot-dash-dot ident just the generic MM ident?

yes

The LOC-D approach for SAN DIEGO/GILLESPIE FIELD (SEE) shows different
minimums for "GRIGG FM".

Yup.

There is an ident code shown for GRIGG, but no frequency.

Frequency for all marker beacons is 75 kHz (or is it MHz - never can
remember) - in any case, you either have a marker beacon receiver (most
are built into audio panels these days), or you don't. If you do, it's
the right frequency.

Is the dot-dash-dot ident just the generic MM ident?

Nope.

I can't find "GRIGG" listed as an airspace fix at airnav.com. Are the
higher minimums to be used for an approach in an aircraft without an
operating audible marker annunciation?

Not sure audible annunciation is required if there is visual
annunciation, but I've never seen a marker beacon receiver that didn't
have audio (whereas a lot of the old ones didn't have visual). In any
case, the higher mins are for aircraft that can't identify GRIGG.

The interesting question is this - can an alternative method (like IFR
GPS) be used to identify GRIGG? In any sane world, the answer would be
yes. If GRIGG was a compass locator (meaning an NDB was collocated
with the marker beacon) the answer would be yes. As it is, it may
legally be no. I know that IFR GPS can substitute for ADF or DME on an
approach (other than an NDB approach with no overlay) but I've never
seen any guidance that indicates it can substitute for a marker beacon.

What does "FM" stand for?

Fan marker. They used to exist on low frequency airways, once upon a
time. They're no longer described in the AIM, as far as I can tell.

Michael

S Herman wrote:

The LOC-D approach for SAN DIEGO/GILLESPIE FIELD (SEE) shows different
minimums for "GRIGG FM". There is an ident code shown for GRIGG, but
no frequency. Is the dot-dash-dot ident just the generic MM ident? I
can't find "GRIGG" listed as an airspace fix at airnav.com. Are the
higher minimums to be used for an approach in an aircraft without an
operating audible marker annunciation? What does "FM" stand for?
Airnav shows GRIGG as a Middle Marker. Thanks.

Airnav is wrong. It is an "airway's" fan or "Z" marker, and it is used as
a stepdown fix on that approach. In addition to the dot-dash-dot aural
ID, it would light the white light on your MB panel.

The original scheme was set when L/F Range stations, NDBs and ILSes were
the IFR nav system.

The white light was for either the "Z" marker that marked the cone of
silence of a range station or the same marker was used along the leg of a
range station for either a procedure turn fix or stepdown fix. Later, the
white light was pressed into service for the IM for CAT II ILSes, and for
applications like this one at KSEE where no other fix is available.