Narrative:

Window heat filament sagged to the middle of the first officer's windscreen and began to glow and burn. Turned off heat and window cracked in multiple places within seconds. Descended and slowed. Ran the checklist. Declared an emergency and diverted to ZZZ. Cabin advisory to flight attendants. Landed safely.

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Original NASA ASRS Text

Title: A B737-300 IN CRUISE AT FL330 DECLARED AN EMER AND DIVERTED DUE TO FO'S WINDSHIELD SENSOR GLOWED, SAGGED, THEN WINDOW CRACKED.

Narrative: WINDOW HEAT FILAMENT SAGGED TO THE MIDDLE OF THE FO'S WINDSCREEN AND BEGAN TO GLOW AND BURN. TURNED OFF HEAT AND WINDOW CRACKED IN MULTIPLE PLACES WITHIN SECONDS. DSNDED AND SLOWED. RAN THE CHKLIST. DECLARED AN EMER AND DIVERTED TO ZZZ. CABIN ADVISORY TO FLT ATTENDANTS. LANDED SAFELY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.