TCASII RA COMMANDS ACFT TO CLB INTO STALL CONDITION.

Narrative

SHORTLY AFTER DEP FROM ORF; ENRTE EWR; ATC ISSUED A RAPID SERIES OF TURNS AND CLB CLRNCS; AND MODIFIED THE CLRNCS TO HIGHER ALT. AS OUR ACFT WAS CLBING (ON A BEST RATE THROUGH 8000 FT CLRNC) AT 7300 FT OUR TCASII SAID 'MONITOR VERT SPD.' OUR AIRSPD WAS 220 KTS; ONLY 10 KTS ABOVE THE CLEAN MANEUVERING MINIMUM SPD IN ORDER TO COMPLY WITH ATC'S REQUEST FOR 'BEST RATE.' THE TCASII WARNING AT 7500 FT (RA) WAS 'CLB; CLB;' TCASII CALLED FOR 2500-3000 FPM CLB RATE. THE CLOSURE RATE ON A TWIN CESSNA WAS VERY RAPID. CONSIDERING OUR REDUCED AIRSPD; AND CONSEQUENT INABILITY TO CLB RAPIDLY; I COUNTERMANDED THE TCASII RA AND ORDERED THE FO TO DSND. JUST AS HE GOT THE 800-1200 FPM CLB RATE STOPPED; I SAW THE APCHING ACFT; AND TOLD HIM HE COULD RESUME THE CLB AS THE APCHING ACFT WAS R TO L RAPIDLY. I EXERCISED CAPT'S EMER AUTH TO DEVIATE FROM AN ATC CLRNC (I STOPPED THE CLB FOR A FEW SECONDS; AS THE ACFT WAS TOO SLOW TO COMPLY WITH TCASII RA). IT HAD NOT OCCURRED TO ME BEFORE THAT TCASII COULD GIVE A WARNING RA THAT THE ACFT WAS NOT CAPABLE OF COMPLYING WITH. I RECOMMEND THAT SUCH RA'S AS THESE BE EVALUATED FOR SAFETY BEFORE COMPLIANCE. IT IS POSSIBLE TO STALL THE ACFT WHILE TRYING TO COMPLY WITH THE LIGHTS ON THE IVSI. THE TCASII RA IS GIVEN WITH SUCH AN IMPERATIVE COMMAND THAT I COULD EASILY SEE A SERIOUS ACCIDENT RESULTING FROM AN ILL CONSIDERED COMPLIANCE.