What happened
On August 13, 2015, a Saab 340A was operating at flight level FL 150 when the crew observed a crack appearing in the left front windshield. Upon inspection, the crew determined that the fracture was confined to the external layer of the windshield and that the aircraft's pressure hull had not been compromised. Because the destination airport was in close proximity, the crew elected to continue the flight according to the original plan.
Following the landing, the aircraft was handed over to maintenance personnel for a detailed inspection. The technical examination confirmed that the damage was limited strictly to the outer, heated layer of the glass.
The investigation
The investigation focused on the structural integrity of the windshield and the nature of the fracture. It was established that the load-bearing acrylic layers, which are significantly thicker than the glass layer, remained undamaged and intact. The investigation also reviewed the maintenance protocols for the cockpit windows, noting that under the current Maintenance Program, these windows are not classified as "Hard Time" or "Life Limited Parts," meaning they are not subject to scheduled replacement, but rather periodic inspections for delamination.
Findings
- The crack was caused by the wear or electrical short-circuiting of the windshield heating element, a condition that frequently leads to fractures in the outer protective glass layer.
- The structural integrity of the cockpit was maintained as the internal acrylic layers remained uncompromated.