A BA3201 IN CRUISE AT 17000 FT DECLARED AN EMER AND DIVERTED DUE TO THE CAPT'S WINDSHIELD OUTER PANE FAILURE WITH SPIDER WEB CRACKING.

Narrative

SHORTLY AFTER REACHING FILED ALT OF 17000 FT MSL; THE L OUTER WINDSHIELD FAILED (SPIDER WEB TYPE FRACTURE). THE CAPT IMMEDIATELY CALLED FOR A REDUCTION IN SPD TO 150 KTS AND A DSCNT TO 10000 FT MSL. THE FO WAS THE PF AND PROMPTLY PERFORMED BOTH COMMANDS. ATC WAS ADVISED AND THE DSCNT WAS APPROVED. THE 'WINDOW FAILURE' EMER DRILL WAS PERFORMED AND COMPLIED WITH. THE ACM WAS BRIEFED AND READIED TO ASSIST. THE CAPT ELECTED TO DIVERT TO THE CLOSEST SUITABLE ARPT. COMPANY WAS ADVISED OF THE SIT. ATC WAS NOTIFIED OF THE PLAN OF ACTION AND EMER WAS DECLARED. AFTER 'LNDG PERFORMANCES' WERE CHKED AND THE APCH BRIEFED; A SUCCESSFUL LNDG WAS ACCOMPLISHED. BURN MARKS WERE OBSERVED ON THE EDGES OF THE WINDSHIELD WHERE THE HEATING ELEMENTS ARE LOCATED. IT APPEARS THE WINDSHIELD HAD FATIGUED/PARTIALLY MELTED AFTER ABOUT 18 YRS IN SVC. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE OUTER PANE WAS THE FAILED PART OF THE WINDOW. THE RPTR SAID WHEN MAINT REMOVED THE FAILED WINDOW THE RPTR OBSERVED THE WINDOW ELECTRICAL CONNECTOR PLUGS WERE BURNED AND THE WINDOW HEATING ELEMENT INDICATED GRADUAL MELTING AND WAS DISCOLORED A BLACK AND GREEN COLOR. THE RPTR STATED NO WINDOW HEAT CIRCUIT BREAKERS WERE FOUND TRIPPED.