ALT OVERSHOOT WHEN XING RESTR NOT MADE. RATE OF DSCNT REQUIRED APCHING 7000 FPM 5 NM N OF FLW; CA.

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RETURNING TO BUR ON AN EMPTY LEG; WE RECEIVED A CLRNC FROM ZOA TO DSND FROM FL410 TO FL240; 5 MI N OF THE FELLOWS VOR. I PROMPTLY ENTERED THE NEW RESTR INTO THE FMS VNAV GUIDANCE PAGE AND WAS STUNNED TO SEE THE INITIAL DSCNT RATE REQUIRED WAS OVER 6200 FPM! I THOUGHT I HAD TO HAVE ENTERED THE DATA INCORRECTLY AND DID IT AGAIN WITH THE SAME RESULT. I THEN ASKED THE CAPT (PNF) IF HE COULD VERIFY MY INPUTS AS I COULDN'T BELIEVE THE RESULT. TOGETHER; WE ENTERED THE DATA A THIRD TIME AND THE RATE WAS NOW APCHING 7000 FPM. AT THIS TIME; ZOA CAME BACK ON THE RADIO AND ASKED IF WE WOULD MAKE THE RESTR BECAUSE IT WAS FOR TFC. I SHOUTED 'NO WAY' TO THE CAPT; BUT HE REPLIED AFFIRMATIVELY TO CTR. HE THEN TOLD ME TO JUST USE THE SPD BRAKES AS WE DID NOT HAVE ANY PAX ON BOARD. I THEN PROCEEDED TO MAKE A MAX EFFORT DSCNT AND HAD THE VSI PEGGED OUT AT OVER 6000 FPM. ON THIS ACFT; THE VSI IS ALSO THE TCASII DISPLAY AND I NOTICED WE HAD AN RA FAIL ANNUNCIATION. THIS WAS DUE TO THE HIGH RATE OF DSCNT. FINALLY; I APCHED FL240 AND TRIED TO LEVEL OFF; BUT WAS UNABLE TO DO SO AND ACTUALLY DSNDED TO MAYBE FL235. ADDITIONALLY; I THINK I DID NOT REACH ASSIGNED ALT UNTIL WELL INSIDE THE 5 MI RESTR. I FEEL WE SHOULD NOT HAVE ACCEPTED THE DSCNT CLRNC IN THE FIRST PLACE; OR AT A MINIMUM; RPTED WE WOULD BE UNABLE TO MAKE IT ONCE IT BECAME APPARENT THE RATE OF DSCNT WOULD BE TOO HIGH. I DON'T THINK ATC SHOULD HAVE GIVEN THE CLRNC EITHER; AS IT WAS UNSAFE TO MAKE SUCH A HIGH RATE OF DSCNT SO THAT YOUR TCASII SYS BECOMES USELESS.