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前面一篇文章中，提到了3号风挡划痕的标准：
驾驶舱3号风挡的划痕和掉块放行标准
后面也就几个问题咨询了厂家，SR：4-5236858347。
虽然在AMM TASK 56-11-00-200-803，Inspect the Flight Compartment Windows的Flight Deck Windows Damage Description部分给出了缺陷的定义：
Scratch: The linear removal or displacement of material from the surface of a pane.
风挡表面材料被线性去除。
Chips: The removal of material from the surface of a glass or acrylic pane, usually from the impact with a hard object. The descriptions that follow are a list of different types of chips.
材料从玻璃或丙烯酸风挡表面被去除，通常是由于受到硬物的冲击。
但是有时我们还是很难区分这两种缺陷。为此咨询了下厂家：
Q1.Damage in Ref/B/ have an obvious width,so we consider it chips.But Ref/C/ is difficult to distinguish whether they are chips or scratches.How to distinguish scratch and chips?
A1. Provided that the reported damages are not cracks, Boeing considers the damages shown in Ref /B/ attachment as chips due to their width. Damages shown in Ref /C/ attachment are considered as scratches, except damage #2 which is considered as combination of a scratch and a chip. However, Boeing can speculate only since the photos are not clean and focused.
Please note that cracks can develop at the base of scratches and then propagate through the entire pane. It will lead to the window pane fracture. Boeing considers the reported damages are common to the inner structural pane that carries spanssure loads. Therefore, it is highly recommended to repair the subject No. 3 acrylic windows in order to remove the scratches and/or chips per AMM TASK 56-11-21-300-801. Otherwise, Boeing recommends to schedule these windows for replacement at the nearest opportunity.
注1：厂家刚开始的回复是下面的，认为是有裂纹，我们回复确定没有裂纹才给出上面的回复的。
Please note that Boeing considers damages shown on Ref /B/ and /C/ pictures as cracks in stretched acrylic. According to Ref /A/ AMM, there is no limit for this type of cracks applicable to No. 3 window. Therefore, the windows shown on Ref /B/ and /C/ pictures are to be replaced.
As for scratches and chips identification, please see AMM Figure 609/56-11-00-990-815 for glass pane chips. Chips in acrylic will have similar shapes. For both glass and acrylic panes chips are actual removal of material, usually caused by a FOD impact. While scratches are thin, mostly long lines without obvious evidence of material removal. Please see Ref /E/ attachment that provides picture of typical scratches.
▲Ref E:picture of typical scratches（这种毋庸置疑，谁都知道啊）
注2：这些照片都是从NRC附件里的，缺陷描述都是scratch，所以都没有给出宽度，只有长度和深度数据。可以看出，厂家其实也是根据损伤的宽度来区分scratch与chips的。当然这些风挡都已经换掉了，本文只是讨论放行标准，并不是维护标准，咱们平时风挡的维护标准都是很高的。
深度小于0.005 in. (0.127 mm)的划痕
前面的文章中，有留言提到了：
其实这很好理解，就当这个表格最下方省略了深度为0的一行。要不然给出0.0005英寸的标准干啥用呢？
索性也问了一下：
Q2.a：If the scratch depth is less than 0.005 in. (0.127 mm), should we use the data for 0.005 in. (0.127 mm) scratch depth or ignore the scratch？
A2.a：If scratches have depths less than 0.005 inches, they can be left in as-is condition provided there is no other damage to the window exceeding the AMM limits and pilot's vision is not impaired.
感觉明显不对啊。于是又补了一下：
Q2：Refer to A2.a. of Ref /B/ message, why does table 601 give the length limit corresponding to 0.005 in. (0.127 mm) scratch depth? When will the data for the 0.005 in.(0.127 mm) scratch depth be used?
A2. "Table 601/56-11-00-993-801 Acrylic Scratch Depths" is to be interspanted as following: if scratches have depths less than 0.005 inches, the limits for scratches of 0.005 inch depth are to be applied.
划痕的总长度计算
这个答案是我万万没有想到的。
假设，现在3号风挡外表面有深度小于0.010 in. (0.254mm)的划痕总长度210mm，单条划痕也是小于76.2mm的，符合放行标准。外表面再新增加一条划痕，长度是20mm：
如果这么理解的话，新划痕深度更深了，反而不超标。这明显是不符合逻辑的。所以，我认为，在应用表中深度对应的标准计算总长度时，应该额外加上所有超过此深度的划痕的总长度。
Q2.b：Currently there is a total length of 210mm scratches with less than 0.010 in. (0.254mm) depth on outer Pane. If a new scratch with a length of 20mm is found: if the depth of the new scratch is less than 0.010 in. (0.254 mm), the total length is 230mm, greater than 9.0 in. (228.6 mm), according to the data for 0.010 in. (0.254 mm) depth scratch, it is not allowed; If the depth of the new scratch is between 0.010 in. (0.254 mm) and 0.020 in. (0.508 mm), according to the data for 0.020 in. (0.508 mm) depth scratch, the scratches is allowed. This is obviously inconsistent with logic.
Therefore, we consider that the scratch length of all larger depth table values needs to be added when calculating the total length for one table value depth. For example, to calculated total length for 0.010 in. (0.254mm) depth, we must add all scratch length of depth more than 0.010 in. (0.254mm).
A2.b.In case of multiple scratches with depths within different depth ranges, the limit for the maximum scratch depth is to be applied for the maximum cumulative length of all scratches. That is to say, if there are few scratches of 0.010 in. (0.254mm) depth or less, but a new scratch is found and its depth is between 0.010 in. (0.254 mm) and 0.020 in. (0.508 mm), the maximum cumulative length for all scratches is to be 5.0 in. (127.0 mm) according to the data for 0.020 in. (0.508 mm) depth scratch.
又补充问了一下：
Q3：For example, outer pane with these scratches: Depth 0.008 in.*Length 2.6 in.,Depth 0.008 in.*Length 2.8 in.,Depth 0.015 in.*Length 0.5 in.Refer to A2.b., is that means the maximum cumulative length for all scratches is 5.9 in. to use the data for 0.020 in. depth scratch and exceed the AMM limits?
A3. Yes, CEA's understanding is correct. However, the window could be polished per AMM TASK 56-11-21-300-801, if necessary, to reduce the depth of the scratches to a table depth value and use the applicable data for inspection.
现在假设，3号风挡外表面有三条裂纹：
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深0.008 in.*长2.6in.
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深0.008 in.*长 2.8in.
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深0.015 in.*长 0.5 in.
以我们一般人的思维，两条0.008英寸深度的划痕应用0.010英寸深度对应的标准，不超标；一条深度0.015英寸深度的划痕应用0.020英寸深度对应的标准，也不超标。
但是，实际上，计算划痕累计总长度时，要累计所有深度划痕的总长度，而不仅仅是应用此深度标准的划痕累计总长度。
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