Narrative:

On oct/xa/99, I was the PF (first officer) on flight from iad to phl. The captain was running the radios. He acknowledged a clearance from center to cross what I believe was 20 mi south of dqo at 9000 ft. He set 9000 ft in the altitude window and I confirmed it. We were at 12000 ft at the time with an airspeed of approximately 300 KIAS. I created a waypoint in the FMC to correspond to 20 NM south of dqo and shortly thereafter initiated my descent. As we neared 10000 ft, ATC called and inquired whether or not we were going to make the crossing restr. The captain and I verified our position and concurred that we saw no problem 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 flight continued to phl without further incident. At the time I had approximately 100 hours in type and, being relatively task saturated on the short duration, low altitude flight, it is possible that I misheard the clearance, but it seems unlikely because the captain also believed that he heard and acknowledged 20 mi rather than 25.

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Original NASA ASRS Text

Title: 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.

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.