在航线检查中,如果发现水平安定面与机身间的滑动封严损坏,按CDL放行需要拆除损坏的封严和与之相关的连接组件,耗时较长,基本上都会造成延误。
事件背景
某737-800飞机,机组绕机检查发现右侧水平安定面滑动封严有缺失:
使用高空车接近飞机,详细检查封严连接组件损坏情况,发现右水平安定面上部机身滑动封严连接端断裂。
CDL涉及M项工作预估耗时较长,换机执行导致延误。
查询2020年至今机队有多次此处封严损伤和更换记录。
从损伤情况来看,都是上部的封严损坏。封严件号:181A8025-1(左上)和181A8025-2(右上)
偶尔还会发现与滑动封严相连的导向摩擦片【65】损坏:
水平安定面与机身间的滑动封严,在水平安定面配平时会随着水平安定面一起移动。封严损坏,可以按CDL 55-10-01办理故障保留放行:
CDL需要拆下封严及相关的连接组件,M项耗时会比较长,短停必定会造成延误。
参考737NG-FTD-53-01002:Horizontal Stabilizer Sliding Seal
之前针对下部封严过早损坏问题,波音推出了SB 737-53-1252:FUSELAGE - Stabilizer Center Section Front Spar - Sliding Seal and Track Modification.
Based on testing data obtained, failures are attributed to excessive loads applied to the seals by one or more of the following conditions: - Track misalignment, binding, improper seal trimming, and/or other interference - Contamination from ice, Dynol, paint, etc. - Misalignment of pedestal attach points relative to the track center-line - Misalignment of the rub block In-service evaluation of possible corrective actions begun in 1999
根据测试的数据,损坏是由于以下一种或多种情况下施加到封严的过度负载导致的:
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Track misalignment 滑轨错位
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binding 粘结
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improper seal trimming 封严修整不当
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other interference - Contamination from ice, Dynol, paint, etc.其他干涉-冰、Dynol、油漆污染,等
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Misalignment of pedestal attach points relative to the track center-line底座连接点相对于轨道中心线的错位
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Misalignment of the rub block In-service 摩擦块在使用中的错位
SB 737-53-1252主要的改进是:在 seal plate和滑轨安装时增加了施加减少摩擦的涂层,滑轨具有更宽的通道,可容纳加厚的seal plate。
经过改进后,下部封严的损坏确实减少了不少,目前表现突出的是上部封严损坏。
参考ISE-55-17-15825,厦航反映了水平安定面上部滑动封严损坏较多的问题,但是由于缺少其他航空公司的支持,厂家并不打算对上部封严进行改进:
A re-design of the upper seal was not addressed due to the structure geometry and lack of damage reports.
The seals are subject to deterioration in service, simply due to wear and fatigue from sliding in their tracks when the horizontal stabilizer trim is adjusted. Here are some suggestions for minimizing seal damage and minimizing the operational impact of damaged seals
1. Increasing the frequency of seal track cleaning can help increase seal service life. Fleet Team Digest Article 737NG-FTD-53-01002 has some suggestions for lubricating the tracks as well. (Some operators have applied a lubrication to the tracks with favorable results. Lubrications used are Zip Chem D5460NS, MIL60326(mu), and Dow Corning Molykote G-Rapid Plus (no mil spec).)经常润滑和清洁封严滑轨可增加封严使用时间。
2. The airplane can be operated for a limited time with one or more seals missing, in accordance with the 737NG Configuration Deviation List (CDL) 55-10-01.
3. The sliding seals are perhaps best viewed as consumable items with limited service life. Boeing Spares maintains an adequate inventory. Precautionary replacement of intact seals after an appropriate interval of flight cycles, based on the operator’s own service experience, is also an option. 设定时限,定期更换封严。
维护提示
当前并没有针对水平安定面与机身间的滑动封严及其滑轨的专门检查和清洁润滑工作。
目前的CMP有对垂尾和水平安定面进行外部区域检查(一般目视),120天重复间隔:
提醒在日常维护时注意加强此区域的检查,尽量及早发现缺陷,避免对周围部件造成更多损伤。比如下图中左侧安定面上滑动封严防磨胶带漏出,剪掉避免造成更大损伤,后续再完成详细检查:
上部封严拆装可以参考AMM53-31-31-000/400-802:
如果除了封严,发现其他连接部件也有损伤,损伤标准可参见SRM 53-80-70 Allowable Damage 4:
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