OPERROR OCCURRED WHEN A DA10 COULD NOT HOLD ALT AFTER LOSING AN ENG AND DSNDED THROUGH THE ALT OF THE ACR MD80. THE MD80 RECEIVED A TCASII RA AND BEGAN DSCNT. THE RPTR SAYS THE RADAR CTLR FROZE. THE RPTR TOOK ACTION TO STOP THE DSCNT AND TURNED THE ACFT AWAY FROM THE DA10.

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I WAS WORKING D76 AT ZJX WHEN A DA01 SAID HE HAD ENG PROB. (I AM A PLT; THE RADAR CTLR WAS NOT.) SO I ASKED PLT ON FREQ IF HE WAS DECLARING AN EMER; OR HAD TO SHUT IT DOWN. HE SAID NO; BUT HE WAITED TO CHANGE DEST TO TLH. I DECIDED TO DSND TO A LOWER ALT. RADAR CTLR THEN GAVE HIM FL350 AND DIRECT TLH WHICH TURNED HIM DIRECTLY OVER AN ACR MD80 NBOUND ON J81. ABOUT 5 MI E OF THE ACR; THE DA01 SAID HE HAD TO SHUT DOWN THE ENG AND HAD TO HAVE A LOWER ALT AND COULD NOT MAINTAIN ALT. AFTER BEING TOLD TO MAINTAIN FL350 HE CAME BACK AND SAID AGAIN HE COULD NOT MAINTAIN ALT NOW AT FL345. THE ACR INTERRUPTS AND SAYS HE HAS A TCASII ALERT AND HE IS DSNDING. BOTH TARGETS ARE ON A PERFECT MERGER COURSE. RADAR CTLR FROZE; SO I TOOK FREQ AND TOLD THE ACR NOT TO DSND AND TO TURN L TO 090 DEGS IMMEDIATELY; IF HE DSNDS IT WOULD PUT HIM WITH THE DA10 WHO HAD LOST AN ENG AND WAS DSNDING. THE 2 ACFT GOT EACH OTHER IN SIGHT AND MISSED IN VERY CLOSE PROX. TCASII ALMOST PUT THESE 2 ACFT TOGETHER! I ONLY REACTED TO WHAT AT THE TIME SEEMED TO BE THE BEST SOLUTION.