EMB145 FLT CREW CANNOT MEET CLB GRADIENT FOR LGA 9 DEP; CONEY CLB. CAPT BELIEVES PERFORMANCE REQUIREMENTS ARE INCORRECT.

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WE WERE ASSIGNED THE CONEY CLB FROM LGA WITH VECTORS TO THE ELIOT INTXN. THE PROC CALLS FOR A R TURN AFTER DEP FROM RWY 13 TO A 180 DEG HDG TO INTERCEPT THE CRI 043 DEG RADIAL; WITH A REQUIREMENT TO CROSS THE LGA 2.5 DME AT OR ABOVE 1500 FT. BECAUSE OF CLB REQUIREMENT; MY FO AND I WENT OVER THE DEP PROC CAREFULLY AND WE AGREED THAT WE WOULD NEED TO MAINTAIN THE PROFILE VERY CLOSELY TO ENSURE THAT WE MET THE CLB RESTR. PER THE PERFORMANCE DATA; THE 13DP (FOR THE CONEY CLB) HAD AN 'ALT-TO' LIMIT OF 44237 LBS WITH NO WIND (ACCOUNTING FOR THE 1 KT HEADWIND COMPONENT -- THE WINDS WERE 210 DEGS AT 6 KTS; WOULD YIELD A SLIGHTLY HIGHER MAX TKOF WT OF 44295 LBS). THE TEMP WAS 26 DEGS PER THE ATIS. OUR RAMP WT WAS RECORDED AT 42073 LBS; AND OUR ESTIMATED TKOF WT WAS ABOUT 200 LBS LESS THAN THAT; AT 41873 LBS. WE DEPARTED LGA USING STANDARD PROCS; AND THE FO DID A SOLID ROTATION DIRECTLY TO THE V-BARS AND VERY ACCURATELY FLEW THE PROFILE AS WE TURNED TO 180 DEGS. WE CROSSED THE LGA 2.5 DME AT 1040 FT; WELL SHORT OF THE 1500 FT REQUIREMENT. WE CROSSED 1500 FT AT ROUGHLY 2.9 DME; IF MEMORY SERVES. AS WE HAD SPECIFICALLY BRIEFED THE DEP AND HAD MAINTAINED THE ACFT IN VERY EXACTING COMPLIANCE WITH OUR DEP PROCS; I BELIEVE THAT THE PERFORMANCE NUMBERS WHICH WOULD YIELD THIS CLB PERFORMANCE REQUIRED OF THE CONEY CLB ARE INACCURATE.