ISO-56-18-24068
1号风挡和2号风挡中间层都是乙烯基夹层作为主要的承力结构层。3号风挡加温构型的也使用乙烯基夹层作为主要的承力结构层。波音曾经给我司的一个SR 3-4203663198回复中，提到过当风挡内层和外层均失效的情况下，取证实验要求仅靠中间层能在11.5PSI压差下支持长达6个小时以上。因而是非常重要的安全防护层。
For laminated glass 737 flight deck windows, the vinyl interlayer is designed to carry fail-safe pressure if the structural inner glass pane fractures during aircraft operation. These flight deck windows were subjected to certification test, with the inner and outer glass panes intentionally fractured under 11.5 psi pressure and then held for a total of 6 hours at that pressure. These tests are performed on new production windows. Because the vinyl interlayer is the fail-safe layer in these windows, the AMM has strict requirements for window replacement for certain types of vinyl cracks.
这一层的裂纹波音有严格的限制。但从手册，确实看不出真实的样子。
在这个FIX中，SilkAir提供了3号风挡裂纹的案例图片，非常难得，可以作为参考。
