A JETSTREAM 41 ON INITIAL CLB HEARD A LOUD NOISE AND DISCOVERED THE ACFT WAS NOT PRESSURIZING AND ON CHKING FOUND THE CAPT'S EMER EXIT WINDOW NOT CLOSED AND LOCKED.

Narrative

DURING INITIAL CLBOUT THE CAPT NOTICED A LOUD WIND NOISE LIKE THE CABIN WAS NOT FULLY PRESSURIZING. HE THEN LOOKED AT HIS EMER EXIT WINDOW AND NOTICED THAT IT WAS NOT PROPERLY SEALED. WE DECIDED TO LEVEL OFF AT 4000 FT TO KEEP THE ACFT FROM PRESSURIZING FURTHER. WE WERE CONCERNED THAT FURTHER PRESSURIZATION COULD CAUSE STRUCTURAL FAILURE OF THE WINDOW. WE REQUESTED TO LEVEL OFF AT 4000 FT. WE FLEW THE ENTIRE TRIP AT 4000 FT ENRTE TO JFK. WE COULD NOT RETURN TO BWI BECAUSE WE WERE WT RESTR DUE TO THE LOSS OF OUR ANTI-SKID SYS. THIS WOULD HAVE REQUIRED US TO DECLARE AN EMER AND WE DID NOT FEEL THAT THIS SIT REQUIRED SUCH AN ACTION. THIS SIT WAS CAUSED BY EITHER CONTRACT MAINT OR THE PREVIOUS CAPT REMOVING THE WINDOW FOR FRESH AIR. AFTER CLOSING THE WINDOW THEY DID NOT PROPERLY RE-SEAL THE WINDOW. WE CONSULTED THE EMER CHKLIST; BUT THERE WAS NO CORRECTIVE ACTION LISTED FOR OUR PROB. THERE WAS A CHKLIST FOR POSSIBLE WINDOW FAILURE THAT WARNED US OF FLYING GLASS PIECES AND POSSIBLE BODILY INJURY. THIS CONCERNED US; WHICH LED TO THE DECISION FOR THE 4000 FT ALT AND A CRUISE SPD OF BTWN 200-220 KTS. THERE WERE NO FURTHER COMPLICATIONS DURING OUR TRIP. AFTER LNDG WE HAD MAINT CHK THE WINDOW FOR ANY STRESS FRACTURES OR DAMAGE.