A B737-500 FLC EXCEEDS THE 250 KTS UNDER 10000 FT AND FAILS TO MAKE THE SPECIFIED XING ALT 25 MI S OF DQO; DE.

Narrative

ON OCT/XA/99; I WAS THE PF (FO) ON FLT FROM IAD TO PHL. THE CAPT WAS RUNNING THE RADIOS. HE ACKNOWLEDGED A CLRNC FROM CTR TO CROSS WHAT I BELIEVE WAS 20 MI S OF DQO AT 9000 FT. HE SET 9000 FT IN THE ALT WINDOW AND I CONFIRMED IT. WE WERE AT 12000 FT AT THE TIME WITH AN AIRSPD OF APPROX 300 KIAS. I CREATED A WAYPOINT IN THE FMC TO CORRESPOND TO 20 NM S OF DQO AND SHORTLY THEREAFTER INITIATED MY DSCNT. AS WE NEARED 10000 FT; ATC CALLED AND INQUIRED WHETHER OR NOT WE WERE GOING TO MAKE THE XING RESTR. THE CAPT AND I VERIFIED OUR POS AND CONCURRED THAT WE SAW NO PROB WITH IT AND SAID SO TO ATC. ATC SAID WE WERE SUPPOSED TO CROSS 25 MI FROM DQO AT 9000 FT. WE HAD UNDERSTOOD 20 MI. IN THE ENSUING CONFUSION; I THEN NOTICED WE WERE DOING 300 KIAS WHILE PASSING 9500 FT. I RETARDED THE THROTTLES TO IDLE AND DEPLOYED THE SPOILERS IN AN ATTEMPT TO SLOW TO 250 KIAS AS QUICKLY AS POSSIBLE. THE FLT CONTINUED TO PHL WITHOUT FURTHER INCIDENT. AT THE TIME I HAD APPROX 100 HRS IN TYPE AND; BEING RELATIVELY TASK SATURATED ON THE SHORT DURATION; LOW ALT FLT; IT IS POSSIBLE THAT I MISHEARD THE CLRNC; BUT IT SEEMS UNLIKELY BECAUSE THE CAPT ALSO BELIEVED THAT HE HEARD AND ACKNOWLEDGED 20 MI RATHER THAN 25.