MD11 CREW CONTINUED AN UNSTABILIZED APCH IN IMC AT ATL. ATCT LCL CTLR ISSUED A GAR.

Narrative

RADAR VECTORS TO INTERCEPT ATL LOC ILS RWY 8L. DUE TO OTHER ARR ACFT; ATL APCH CTL CLRED US TO MAINTAIN 4000 FT; 170 KTS UNTIL ESTABLISHED FOR ILS RWY 8L. RESULTED IN INTERCEPTING ILS ABOVE GS 2 MI FROM OM. LATE RECOGNIZING THIS. CROSSED CATTA OM APPROX 800 FT HIGH. ATTEMPTED TO DSND TO GS AT 1500-2000 FPM ON GS AT APPROX 1000 FT; THEN LOST GS SIGNAL. NOTE: BOTH PRECEDING AND FOLLOWING ACFT RPTED ERRATIC GS SIGNALS FOR RWY 8L. CONTINUED STABLE DSCNT TO RWY 8L; BUT WITH INTERMITTENT LOC/GS SIGNAL; CROSSED RWY 15 APPROX 300 FT (WX 300 FT OVCST 1 1/2 MI VISIBILITY) PLANNING A MISSED APCH WHEN TWR ISSUED A GAR. 2 FACTORS; HIGH IN CLOSE VECTORS BY ATC DUE TO SEQUENCING TFC CAUSED ACFT TO JOIN LOC ABOVE GS AND NOT RECOGNIZED IMMEDIATELY BY CREW. ONCE RECOGNIZED; CREW INCREASED DSCNT AT OM TO RE-ESTABLISH GS; BUT MALFUNCTIONING ILS GAVE CONFUSING COCKPIT SIGNALS THAT NEVER ALLOWED ACFT TO RE-ESTABLISH PROPER POS. RESULTED IN WELL ABOVE AT MINIMUMS AND GAR. RECOMMEND: CREW SHOULD HAVE EXECUTED MISSED APCH SOONER IN IMC WHEN HIGH AT OM AND FIRST SIGN OF ERRATIC ILS SIGNAL. ATC: BETTER VECTORS. TWR: RPT INTERMITTENT ILS PER PIREP.