ACR X TCASII TA RA HAD LTSS FROM ACFT DSNDING THROUGH OCCUPIED ALT. SYS ERROR. PLTDEV.

Narrative

WE DEPARTED CVG ON ASSIGNED HDG OF 090 DEGS AND SWITCHED TO ZID. CTR CLRED US TO FL230 AND ASSIGNED A HDG OF 110 DEGS. WE REQUESTED PERMISSION TO DEVIATE FOR WX AND CTR APPROVED. THE CTLR THEN SWITCHED US TO THE NEXT CTLR. NO ONE ANSWERED ON THIS FREQ SO WE RETURNED TO THE PREVIOUS CTLR. HE GAVE US A DIFFERENT FREQ TO TRY AND MAKE THE COMMENT THAT 'THEY ARE REALLY BUSY OVER THERE.' THIS WAS THE LAST TIME WE WERE ABLE TO COMMUNICATE WITH A CTLR UNTIL AFTER THE TCASII RA NOR DID WE GET ANY ALERT OR TA FROM ATC. ON THE NEW FREQ WE COULD TELL THAT THE CTLR WAS SWAMPED WITH RADIO XMISSIONS. WE MADE A NUMBER OF ATTEMPTS TO CHK IN. EVEN THE CTLR'S XMISSIONS TO OTHER ACFT WERE BLOCKED. WE HAD NOW ENCOUNTERED MODERATE ICING AND TURB AND WERE STILL TRYING TO DEVIATE FOR WX. OUR ATTN WAS DRAWN TO A TCASII TARGET AT 2:30 O'CLOCK POS AND 10 MI DSNDING FROM FL240. WE QUICKLY REALIZED THAT THIS TARGET WAS HDG TOWARDS US AND THROUGH OUR ALT. WE TURNED L TO INCREASE THE SEPARATION AND THEN RECEIVED A TCASII RA TO DSND. WE COMPLIED AND HAD DSNDED APPROX 400 FT WHEN THE RA COMMAND REVERSED TO CLB. THE ACFT THEN PASSED BEHIND US WITHOUT INCIDENT. THE OTHER ACFT DID NOT APPEAR TO ALTER ITS FLT PATH. WE WERE FINALLY ABLE TO CONTACT THE ATC CTLR WHO GAVE US NO INDICATION OF ANY PROB. WE ADVISED THE CTLR OF THE RA AND WERE TOLD THAT THEY KNEW ABOUT IT BUT WERE VERY BUSY BEFOREHAND. A SUBSEQUENT CTLR GAVE US A PHONE NUMBER TO CALL 'ABOUT THE RA.' A LATER PHONE CONVERSATION WITH THE CTR WE WERE TOLD THAT THIS WAS NOT JUST ABOUT AN RA AND HE ALLEGED THAT WE HAD DEVIATED FROM A CLRNC. A LACK OF COM WAS AT THE CORE OF THIS PROB. WE HAD NOT RECEIVED ANY FURTHER CLRNC POINT AFTER OUR DEV. WE ATTEMPTED TO ESTABLISH COMS SEVERAL TIMES. IF THE CTLR WAS NOT SO BUSY THIS WOULD NOT HAVE HAPPENED. THERE WERE TOO MANY ACFT FOR THE CTLR TO TALK TO AND WE NEVER RECEIVED ANY TFC WARNINGS.