A320 TRIES TO MAKE AN ILS APCH INTO SNA WITHOUT AN AWARENESS THAT THE GS IS INOP. FLC NOTICE ALT DISCREPANCY OVER OM AND FLY VISUAL APCH TO LNDG.

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OUTSIDE OF THE OM FOR RWY 19R AT SNA; WE WERE GIVEN A VECTOR; ALT; AND 'CLRED ILS APCH' AT SNA. WE INTERCEPTED THE COURSE; AND SHORTLY AFTER ACQUIRED THE GLIDE PATH. COMPANY REQUIRES US TO CHK GS XING ALT AT THE OM; AND I PERCEIVED US TO BE LOW BY ABOUT 250 FT. BY THIS TIME I COULD SEE THE GND; BUT NOT THE ARPT; AND I COULD SEE THERE WAS NO RWY WHERE WE WERE POINTED. I SAID; 'THIS DOESN'T LOOK RIGHT' AND PNF AGREED. I TURNED OFF THE AUTOPLT AND LEVELED AT 1600 FT OR SO. WE WERE ABOVE LOC MINIMUMS AT THIS POINT AND HAD A BRIEF DISCUSSION OF OUR 'FALSE GS.' I ACQUIRED THE RWY VISUALLY; AND MADE AN UNEVENTFUL LNDG. AFTER THE PARKING CHK I LISTENED TO ATIS AND HEARD FOR THE FIRST TIME; 'SANTA ANA GS INOP.' AT OUR COMPANY; PNF LISTENS TO ATIS AND WRITES IT DOWN. PF (ME) NORMALLY DOES NOT LISTEN TO THE ACTUAL BROADCAST. PNF ADMITTED HE MUST HAVE MISSED THE NOTAM WHICH CAME AT THE END OF THE ATIS MESSAGE AFTER A BRIEF PAUSE. EITHER HE DIDN'T HEAR THE ENTIRE MESSAGE; OR THE NOTAM WAS CUT OFF BY OUR SQUELCH. LESSONS LEARNED: 1) OBVIOUSLY; PNF SHOULD HAVE CAUGHT THE NOTAM IN THE ATIS. IT WAS MENTIONED NOWHERE ELSE; NOT IN OUR PAPERWORK; NOT BY TWR; AND NOT BY APCH; IF THEY EVEN KNEW ABOUT IT. 2) IT IS POSSIBLE TO HAVE A MALFUNCTIONING GLIDE PATH WITH NO INDICATION WHATSOEVER. ON OUR INSTS; THE GLIDE PATH DISPLAYED NORMALLY; IDENTED NORMALLY; AND THERE WERE NO FLAGS. 3) THE ALT CHK AT THE OM IS VERY IMPORTANT; BUT NOWHERE IN OUR PROCS IS THERE A TOLERANCE. I HAVE FLOWN ILS'S THAT WERE OPERATING FINE; BUT THE ALT AT OM WAS OFF BY HUNDREDS OF FT. IN THE FUTURE; AS PF; I THINK I WILL LISTEN TO ATIS AS A DOUBLECHK. HOWEVER; I THINK SOMETHING AS IMPORTANT AS INOP GS SHOULD BE KNOWN BY APCH; AND IF PLANES ARE SEEN 500 FT LOW AT FAF; SOMETHING SHOULD BE SAID. ALSO; IF GS IS MALFUNCTIONING; IT SHOULD BE TURNED OFF SO ACFT SYS DISPLAY OFF FLAGS. LASTLY; IT WOULD BE NICE IF THE AIRBUS 320 RADIO HAD A SQUELCH KNOB THAT COULD BE ADJUSTED OR TURNED OFF IF WE SUSPECT THE SQUELCH IS CUTTING OFF PART OF THE MESSAGE. SUPPLEMENTAL INFO FROM ACN 372220: ADOPT A STANDARD CLRNC PHRASEOLOGY FOR AN APCH CLRNC TO AN APCH THAT IS OPERATING IN A DEGRADED MODE. SOMETHING LIKE 'CLRED FOR THE ILS RWY 19R; GS OUT.' THIS WOULD PROVIDE AN ADDITIONAL COM TO A COCKPIT CREW THAT THE APCH THEY ARE ABOUT TO COMMENCE IS DEGRADED. TURN OFF THE GS XMITTER IF IT IS KNOW TO BE UNRELIABLE.