A CANADAIR CL65 IN DSCNT AT FL240 DECLARED AN EMER AND DIVERTED DUE TO #1 CAPTS WINDSHIELD FAILURE IMPAIRING VISION.

Narrative

CAPT'S FRONT WINDSHIELD SHALTERED WHILE DSNDING THROUGH FL240. PRIOR (TWO MINS) TO THIS EVENT THE WINDSHIELD'S INNER HEATING ELEMENT APPARENTLY SHORT CIRCUITED CREATING A BRILLIANT ORANGE 'SPARKING' GLOW. THE GLOW APPEARED IN THE L BOTTOM CORNER AND COVERED APPROX 1/3 OF THE WINDOW. THE CAPT IMMEDIATELY SWITCHED OFF THE L WINDSHIELD HEAT SWITCH UPON THE 'GLOWING' EVENT. THIS ACTION CEASED THE GLOWING. AFTER SWITCHING OFF THE WINDSHIELD HEAT; WE OBSERVED APPROX 2-3 6-8 INCH FRACTURES IN ONE OF THE WINDOW'S THREE LAYERS. FEARING A POSSIBLE FIRE HAZARD WE DECLARED AN EMER. WHILE DSNDING THROUGH FL240; APPROX 2 MINS AFTER THE GLOWING EVENT THE ENTIRE WINDSHIELD SHATTERED. THE WINDOW REMAINED INTACT AND THE ACFT HELD CABIN PRESSURE. WE DIVERTED TO KIND. THE FO HAD TO LND BECAUSE THE CA WAS UNABLE TO VIEW FORWARD THROUGH THE SHATTERED WINDSHIELD. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE SEQUENCE OF EVENTS STARTED WITH TWO SMALL PINPOINTS OF ARCING AT THE BUSBARS. THE RPTR SAID THE ARCING CONTINUED FOR ABOUT 10 MINS. THEN A ORANGE GLOW ACROSS ONE THIRD OF THE WINDOW AND THE HEAT WAS TURNED OFF. THE RPTR STATED WE THEN OBSERVED THE MIDDLE PANE CRACKED AND A FEW MINS LATER THE OUTER PANE SHATTERED IMPAIRING THE CAPTS VISION. THE RPTR CLAIMS WHEN TALKING TO MAINT ABOUT THE WINDOW INCIDENT IT WAS RPTED THEY REPLACE ONE WINDOW A WEEK ON AVERAGE. THE RPTR ALSO CLAIMS TALKING TO THE SAFETY REPRESENTATIVE THIS FAILURE RATE WAS VERIFIED AND THE PRIMARY CAUSE WAS UNKNOWN.