机组反应在10100米/8psi压差机组报告左3风挡外层，疑似出现四处裂纹痕迹，机组向管制申请降高度值6300米后再次检查疑似裂纹消失不见。经咨询波音，飞机处于结冰区不加温构型风挡外层可能出现冰晶，由于三号风挡使用丙烯酸树脂材料，世界机队范围内极少（very few）收到客户报告出现冰晶情况，本机风挡前缘风蚀尺寸波音认为允许损伤且不构成影响。
SR:4-4834790930
After reviewing the photos provided in Ref /A/, Boeing agrees with Hainan Airlines assessment that it is highly probable that the suspected damages are ice crystals forming on the outside surface of outer pane since the L3 acrylic window is unheated.
Boeing received very few reports of ice crystals forming from other operators due to L3 acrylic
unheated window configuration.
