What happened
On April 15, 2005, an Airbus A320-231, registration I-LINH, was cruising at FL300 near the Sorrento VOR when the flight crew experienced a loud impact followed by an extensive crack in the right cockpit windshield. Following the event, the crew donned oxygen masks and initiated a rapid descent. After approximately two minutes, the crew confirmed that cabin pressurization remained stable, reduced the rate of descent, and diverted to Naples Capodichino Airport. During the approach, an "ANTI-ICE R WINDSHIELD" advisory briefly appeared on the ECAM. The aircraft landed without further incident.
The investigation
The ANSV investigation initially considered a birdstrike, but ground inspections and chemical-biological analysis of the area near the damage ruled out any biological remains, making a birdstrike highly improbable at that altitude. The investigation focused on the structural integrity of the multi-layer windshield.
An examination conducted with the manufacturer revealed that the damage was confined to the non-structural outer glass layer; the two internal structural layers responsible for aerodynamic and pressurization loads remained intact. The investigation identified a "burn-out" defect in the electro-conductive heating layer located between the outer glass and the PVB resin interlayer. This defect caused localized overheating, which led to the fracture of the outer glass. Further analysis determined that the heating layer defect was caused by moisture accumulation, which had infiltrated the assembly due to the erosion of the windshield seal.
Findings
- The primary cause of the outer glass fracture was localized overheating.
- The overheating was triggered by a defect in the heating element.
- Moisture infiltration through an eroded windshield seal was the root cause of the heating element failure.
- The windshield had accumulated approximately 21,600 service hours, a high value for the component.