ACR X AND Y TCASII RA HAD LTSS DUE TO ATC EQUIP PROB LOSS OF COM DUE TO PWR FAILURE.

Narrative

ON JUN/SUN/94; I WAS THE CAPT ON ACR X ENRTE FROM PIT TO LGA. WE CONTACTED NY APCH (LGA) AND WERE CLRED TO 4000 FT DIRECT TO LGA VOR. WE DID NOT RECEIVE ANOTHER XMISSION FROM APCH. ABOUT 5 MI S OF LGA (MASPETH TANKS) WE ATTEMPTED SEVERAL CONTACTS WITH APCH WITHOUT SUCCESS. THE FO ATTEMPTED TO CONTACT TWR WITH NO SUCCESS. I TRIED A ZNY FREQ WITHOUT SUCCESS. UNBEKNOWNST TO US; LGA APCH AND TWR HAD A COMPLETE PWR FAILURE WITH NO COM ABILITY WITH ANY OF THE ACFT UNDER THEIR CTL. FOR SOME REASON; THEIR BACKUP SYS DID NOT WORK EITHER. OVERHEAD LGA; I GLANCED DOWN AT OUR TCASII PRIOR TO INITIATING A HOLDING ENTRY TURN. I NOTICED AN ACFT Y ON TCASII AT 8 MI AND 12 O'CLOCK AT OUR ALT. I TURNED 10 TO 20 DEGS R. WHEN HE WAS 5 MI; 11 O'CLOCK WE BOTH HAD A VISUAL CONTACT ON THIS ACFT. THE TCASII THEN COMMANDED AN RA CLB. I CLBED TO 4800 FT WITH VISUAL CONTACT. WE THEN FOLLOWED THE OTHER ACFT INBOUND TO LGA. THE FO FINALLY MADE RADIO CONTACT WITH LGA GND CTL; THE FIRST FREQ ABLE TO OPERATE AT LGA. THE REST OF THE APCH AND LNDG WERE NORMAL. THE FAILURE OF RADIO COM AT LGA AND THE LACK OF AN EFFECTIVE BACKUP SYS PUT THE LIVES OF HUNDREDS OF PEOPLE IN JEOPARDY. SUPPLEMENTAL INFO FROM ACN 275487: INBOUND TO LGA ON EXTOL ARR (044 DEG RADIAL INBOUND) AT 4000 FT MSL. AT 10- 12 PLUS MI FROM LGA; I ATTEMPTED TO CONTACT LGA APCH FOR LOWER ALT. AFTER SEVERAL ATTEMPTS I WENT TO #2 RADIO. THERE WAS NO ANSWER. I THEN SWITCHED TO LGA TWR FREQ. THERE WAS NO ANSWER FROM LGA TWR. AT 5 TO 6 MI WE GOT A TCASII RA TO 'DSND.' WE INITIATED A DSCNT WITH VISUAL CONTACT ON THE CONFLICTING TFC. I INSTRUCTED THE FLYING FO TO MAKE A L DSNDING TURN INTO THE DOWNWIND FOR RWY 22. I ESTABLISHED CONTACT WITH LGA GND AS WE WERE IN THE L DSNDING TURN. HE CLRED US TO LAND. WE COULD SEE ANOTHER B-737 ON FINAL; SO I TOLD LGA WE WOULD FOLLOW THE B-737 FOR LNDG. WE MADE A NORMAL LNDG ON RWY 22.