NTSB Identification: CEN11IA649
Scheduled 14 CFR Part 129: Foreign operation of AIR CANADA
Incident occurred Saturday, September 17, 2011 in Chicago, IL
Probable Cause Approval Date: 11/07/2012
Aircraft: Airbus Industrie A320-211, registration: C-FGYL
Injuries: 140 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

The first officer's (FO) windshield cracked during cruise flight. The crack subsequently progressed into multiple multidirectional cracks that obscured the FO’s view through the window. The flight crew was unable to determine the severity of the cracks and diverted without further incident. A postincident examination of the windshield revealed an area of arcing located along the electrical bus bar at the lower edge of the windshield, near the forward corner. This location coincided with the area in which the power and sensing element wires were routed around the structural glass plies. The area of arcing was surrounded by a cloudy and degraded interlayer, which was consistent with the presence of moisture. A section of the moisture seal was worn and appeared to have been repaired, resulting in moisture ingress. The moisture degraded the interlayer and electrical system resulting in a discontinuity that led to electrical arcing and failure of the heating system causing the windshield cracking. The latest windshield revisions, with part numbers NP-165331-1/-2, are available and include enhancements that reduce the potential for moisture ingress and its subsequent effects on the electrical system.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

The infiltration of moisture into the windshield heating layer that induced arcing in the heating system that subsequently cracked the windshield.

Full narrative available

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