A WINDOW BLEW OUT OF A PRESSURIZED LTT REQUIRING AN EMER DSCNT.

Narrative

WE WERE CLRED TO OUR FINAL CRUISING ALT OF FL200. AS WE NEARED THAT ALT; THERE WAS A LOUD BANG IN THE AFT OF THE ACFT. QUICKLY THERE WAS DEPRESSURIZATION OF THE CABIN. PAX RPTED A BROKEN PAX WINDOW AND THE DECISION WAS MADE TO QUICKLY DSND TO A LEVEL WHERE THE ACFT AND PAX WOULD BE SAFER. AS IN OUR TRAINING; WE DSNDED IN A 30 DEG BANK AND ABOUT 4000-5000 FPM AND ALERTED CTR WE NEEDED LOWER BECAUSE OF A BROKEN WINDOW AND DEPRESSURIZATION. FROM THE COCKPIT IT WAS NOT KNOWN HOW EXTENSIVE THE DAMAGE WAS; BUT WE MONITORED THE INSTS AND SAW NO OTHER IRREGULARITIES. ATC ASKED US OUR INTENTIONS AND WE ASKED TO RETURN TO OUR DEP ARPT. THE CTLR ASKED IF WE WERE IN AN EMER. THE OTHER PLT WAS HANDLING THE RADIO AND SAID 'NOT AT THIS TIME.' WE DEFINITELY TOOK EMER ACTION. THERE WAS LITTLE RADIO DISCUSSION DURING OUR INITIAL HANDLING OF THE SIT AND WE DID NOT FORMALLY DECLARE AN EMER. IN RETROSPECT; WE PROBABLY SHOULD HAVE SPECIFICALLY STATED MAYDAY. HOWEVER; AFTER THINGS WERE STABILIZED; WE WERE LIKELY NOT IN AN EMER SIT. CAUSE OF THE WINDOW FAILURE IS UNKNOWN.