ACR MLG CREW MISSED A XING RESTR.

Narrative

I WAS FLYING MY FIRST LEG ON IOE AFTER SIMULATOR TRANSITION TRAINING. THE CAPT WAS FLYING THE ACFT; AND I WAS DOING THE PNF DUTIES. WE WERE FLYING THE WESTMINSTER 2 ARR TO BALTIMORE. WE HAD BEEN CLRED TO CROSS LIZIO INTXN AT FL250. ABOUT 5 NM W OF LIZIO; WE WERE CLRED TO CROSS LIZIO AT FL250 AND TO CROSS MUMSY INTXN. AT 15000 FT WE HAD ALREADY ENTERED LIZIO AT 250 KTS AND 15000 FT IN THE NAV COMPUTERS. E OF LIZIO INTXN IN OUR DSCNT ENRTE TO MUMSY I WAS ABLE TO COPY THE BWI ATIS; AND FINISH PROGRAMMING THE NAV COMPUTERS. IN ENTERING THE DATA INTO THE DATABASE; WE WERE UNAWARE THAT THE 15000 FT CONSTRAINT AT MUMSY WAS DELETED. THEREFORE; THE ACFT HAD REVERTED TO A 1000 FPM RATE OF DSCNT. WE REALIZED THE ERROR AS WE WERE XING OVER MUMSY AT ABOUT 18000 FT. AT THIS POINT WE ALSO HAD A RADIO CHANGE FROM ZDC TO DULLES APCH. UPON NOTICING OUR MISTAKE THE CAPT IMMEDIATELY INCREASED OUR RATE OF DSCNT DOWN TO OUR NOW CLRED ALT OF 11000 FT. HE ALSO QUERIED THE CTLR ABOUT OUR ALT CLRNC AND IF OUR PRESENT ALT WAS 'OK' FOR OUR POS. DULLES APCH DID NOT REPLY. AFTER A BRIEF HESITATION; APCH CTL CONTINUED NORMAL ATC XMISSION. SHORTLY; THEREAFTER WE SWITCHED TO BWI APCH AND LANDED WITHOUT INCIDENT. NEITHER ZDC OR DULLES APCH MENTIONED OR ASKED ABOUT OUR DEV AT MUMSY;WE ASSUMED NO CONFLICT HAD EXISTED. CONTRIBUTING FACTORS: 1) ATIS INFO WHICH IS UNREADABLE UNTIL WITHIN 100 NM. PARTICULARLY; WITH MODERN; STATE OF THE ART 'GLASS' ACFT THAT REQUIRE DATA TO BE LOADED INTO THE DATABASE FOR NAV. 2) NAV COMPUTER SOFTWARE ALLOWS PLT ENTERED CONSTRAINTS TO BE DROPPED OUT AFTER CHANGING OR MODIFYING AREA ARRS; APCHS; RWYS; ETC. 3) THE VARIABLES ASSOCIATED WITH INSTRUCTING IN A DYNAMIC ENVIRONMENT. SUPPLEMENTAL INFO FROM ACN 279032: THE ATIS IS NOT READABLE UNTIL APPROX 100-130 W OF THE ARPT. I NEGLECTED TO ENSURE THAT 15000 FT AT MUMSY WAS RE-ENTERED; (SINCE IT AUTOMATICALLY DROPPED OUT AFTER THE ILS APCH WAS ENTERED). THE BWI ATIS IS ALSO DISTRACTING IN THAT AT 'NORMAL' RANGES AT LEAST 2 OTHER ATIS' ARE HEARD ON THE FREQ RATHER THAN BWI. THERE IS A POTENTIAL FOR THE CREW TO COPY INCORRECT INFO OR AT LEAST BE FRUSTRATED WHILE WAITING TO HEAR BWI INFO.