Narrative:

About 10 mi north of the sbv VOR, I commented to the first officer, that the ATC center appeared to be 'late' in issuing us a descent clearance. He then requested a lower altitude, as I had then requested, anticipating a clearance to cross the aldan intersection at 10000' and 250 KTS, as depicted on the sbv sbv 2 arrival to rdu. The ATC controller then issued the clearance to cross 'aldan' at 10000'. I then told the controller that we would be unable to make the restriction. He then instructed us to 'do the best you can.' I leveled at 10000', 3 mi beyond the aldan intersection (south), at cruise airspeed, and then began reducing to 250 KTS, although no speed restriction was issued. After being changed over to rdu approach, I confirmed with rdu approach that we had informed center of being unable to accept the crossing restriction. Rdu approach said that they were aware of the situation. There appeared to be no problem, as we leveled within 3 mi, and coordinated with ATC...however, I understand that the phrase 'do the best you can' does not replace the clearance issued by ATC. I clearly declined the clearance, as we were unable to comply. Yet the controller came back with a 'do the best you can', answer, which still left me wondering if I had violated a previous clearance, which I had definitely declined, previously. Solution: have ATC controllers aware of this 'pitfall', and restate a clearance, eg, 'roger, reclred to descend 10000', expedite your descent please.' northwest, there is no 'guess work'. Otherwise, ATC coordination with us very nicely.

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Original NASA ASRS Text

Title: ACR UNABLE TO ACCEPT CLRNC TO MEET CROSSING RESTRICTION.

Narrative: ABOUT 10 MI N OF THE SBV VOR, I COMMENTED TO THE F/O, THAT THE ATC CTR APPEARED TO BE 'LATE' IN ISSUING US A DSNT CLRNC. HE THEN REQUESTED A LOWER ALT, AS I HAD THEN REQUESTED, ANTICIPATING A CLRNC TO CROSS THE ALDAN INTXN AT 10000' AND 250 KTS, AS DEPICTED ON THE SBV SBV 2 ARR TO RDU. THE ATC CTLR THEN ISSUED THE CLRNC TO CROSS 'ALDAN' AT 10000'. I THEN TOLD THE CTLR THAT WE WOULD BE UNABLE TO MAKE THE RESTRICTION. HE THEN INSTRUCTED US TO 'DO THE BEST YOU CAN.' I LEVELED AT 10000', 3 MI BEYOND THE ALDAN INTXN (S), AT CRUISE AIRSPD, AND THEN BEGAN REDUCING TO 250 KTS, ALTHOUGH NO SPD RESTRICTION WAS ISSUED. AFTER BEING CHANGED OVER TO RDU APCH, I CONFIRMED WITH RDU APCH THAT WE HAD INFORMED CTR OF BEING UNABLE TO ACCEPT THE XING RESTRICTION. RDU APCH SAID THAT THEY WERE AWARE OF THE SITUATION. THERE APPEARED TO BE NO PROB, AS WE LEVELED WITHIN 3 MI, AND COORDINATED WITH ATC...HOWEVER, I UNDERSTAND THAT THE PHRASE 'DO THE BEST YOU CAN' DOES NOT REPLACE THE CLRNC ISSUED BY ATC. I CLRLY DECLINED THE CLRNC, AS WE WERE UNABLE TO COMPLY. YET THE CTLR CAME BACK WITH A 'DO THE BEST YOU CAN', ANSWER, WHICH STILL LEFT ME WONDERING IF I HAD VIOLATED A PREVIOUS CLRNC, WHICH I HAD DEFINITELY DECLINED, PREVIOUSLY. SOLUTION: HAVE ATC CTLRS AWARE OF THIS 'PITFALL', AND RESTATE A CLRNC, EG, 'ROGER, RECLRED TO DSND 10000', EXPEDITE YOUR DSNT PLEASE.' NW, THERE IS NO 'GUESS WORK'. OTHERWISE, ATC COORD WITH US VERY NICELY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.