ACR EXECUTES GAR DUE TO TCASII RA REF TFC ON APCH PATH.

Narrative

AFTER RECEIVING LNDG CLRNC FROM MIA TWR FOR RWY 9R; WE WERE ADVISED THAT A HELI WAS ORBITING BELOW 500 FT IN THE AREA OF RWY 9R APCH PATH. WE WERE UNABLE TO ACQUIRE THIS TFC VISUALLY BUT RECEIVED SEVERAL TCASII TA'S. THE TARGET WAS INDICATING SLIGHTLY R OF OUR ACFT AND AT 300 FT. AT APPROX 500 FT AGL WE RECEIVED A TCASII RA CLB ADVISORY AND SINCE NEITHER OF US COULD SEE THE TFC; THE CAPT ELECTED TO GAR. THE TFC NOW APPEARED DIRECTLY IN FRONT OF US ON OUR HSI'S. DURING THE SUBSEQUENT GAR WE WERE GIVEN HDG AND INSTRUCTED TO CLB TO 3000 FT AND CONTACT DEP CTL. DURING THE GAR; PROBABLY DUE IN PART TO THE VERY HIGH WORKLOAD OF CONFIGN CHANGES; PWR ADJUSTMENTS; FREQ CHANGES AND HDG CHANGES; THE CAPT (PF) ALTHOUGH ACKNOWLEDGING THE ASSIGNED ALT AS WE APCHED 3000 FT WAS UNABLE TO LEVEL OUR ACFT IMMEDIATELY AND WE REACHED 3300 FT BEFORE RECOVERY WAS MADE TO 3000 FT. THE GAR SHOULD HAVE BEEN UNNECESSARY AS ALLOWING A HELI TO ORBIT ON THE FINAL APCH PATH AT 300 FT AGL; TO A HIGH DENSITY ACR RWY; SEEMS TO BE ASKING FOR TROUBLE.