B777 ACFT DSNDING WAS GIVEN A LATE HOLDING CLRNC (20 SECONDS TO HOLD); PNF WENT HEAD DOWN TO PROGRAM FMC WHILE PF THOUGHT ALT CLRNC WAS TO 10000 FT THOUGH THE ALERT WINDOW HAD 11000 SET. PF CAPT DSNDED 500 FT BELOW ASSIGNED.

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ON DSCNT (JASEN 2 ARR) IAD; LESS THAN 3 MI FROM DRUZZ INTXN; WE WERE ISSUED HOLDING CLRNC AT DRUZZ. PF WAS HAND FLYING THE B777; DSNDING TO 11000 FT AT 250 KTS. PNF READ BACK HOLD CLRNC AND IMMEDIATELY STARTS TO PUT THE HOLD IN THE FMC. PF THOUGHT HOLD CLRNC WAS DRUZZ AT 10000 FT. ALT WINDOW WAS STILL AT 11000 FT (WITH LESS THAN 20 SECONDS TO THE INTXN). AFTER HOLD WAS ISSUED; PNF HEAD DOWN TO PROGRAM RADIOS; FMC ETC. I DIDN'T NOTICE DSCNT BELOW 11000 FT UNTIL ALT WARNING HORN ACTIVATED. PF ASKED IF HOLD CLRNC WAS 10000 FT. PNF REPLIED; 'I THINK IT'S 11000 FT.' IMMEDIATELY INQUIRED WITH ATC AND ACKNOWLEDGED 11000 FT.' DSNDED TO 10500 FT AND CLBED BACK TO 11000 FT WHILE ENTERING HOLD UPON LEVEL OFF; RETURNED TO AUTOPLT AND EVERYTHING WAS A-OK. THE ISSUANCE OF A CLRNC 20 SECONDS BEFORE A HOLDING FIX AT 250 KTS IN DSCNT IS VERY POOR CTLING. THIS SHOULDN'T HAPPEN. A VECTOR BACK TO THE HOLD FIX WOULD HAVE BEEN APPROPRIATE. PNF SHOULD HAVE POSSIBLY ASKED FOR A VECTOR OR HDG AND STAYED HEADS UP. UPON RECEIVING HOLD PF POSSIBLY RETURNED TO AUTOPLT OP.