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737NG飞机副翼PCU杆端有个蓝色封圈露出
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几年前遇到几次同样的疑问,问了波音。隔的时间久了,今天又有同事提出疑问,再次拿出来分享。

01

背景



工作者检查发现副翼PCU杆端有一个蓝色封圈挤出迹象,打压操作测试检查PCU无渗漏。工作者有两个疑问。第一,此封圈露出来是否正常。第二,此封圈损坏的放行标准。


刮环挤出

02

答疑解惑


查询AMM无相关说明,查阅CMM27-09-23,这个封圈是一个刮环,不是液压密封圈。


抽查几架飞机,部分飞机由于污染刮环变黑,可能大家不会太留意。部分飞机刮环蓝色很明显,往往大家会觉得异常。当然也确实有些刮环扭曲,在问波音之前将PCU换掉了,后来抽查的飞机刮环均没发现损伤。


刮环受污染颜色变黑


干净的刮环颜色

咨询波音,回复内容大致如下。如果刮环损伤,波音技术上不反对( NTO)继续使用 PCU ,前提是PCU外部渗漏每个作动循环不超过 1 滴。并要求每个航后检查 PCU 泄漏情况,在100个飞行循环内尽快更换刮环。波音确认刮环的作用是在活塞杆接触内部液压密封圈前清洁活塞杆。刮环的变形或损坏不会直接导致液压渗漏,因为刮环实际上不是液压密封件。但是,刮环的变形或损坏可能会使污染物进入并损坏活塞杆密封圈,这种情况可能导致液压通过密封圈和刮环向外渗漏。

 

03

维护建议


日常检查如发现刮环露出,建议近距离检查刮环有无损坏。


如刮环损坏或变形,按AMM29-00-00,检查测试PCU渗漏情况,并尽量更换PCU。


SR原文如下。

SUBJECT: Questions on The Piston Rod Scrapper of The Aileron PCU


DESCRIPTION:

=====================

The piston rod scrapper(PN:S33865-5H5) on the aileron PCUs of the datum airplanes were found exposed.One of the srappers was damaged, please see the attachments. No leakage was found on the PCU.


DESIRED ACTION:

======================

Q1. Should the PCU continue to service if the Scrapper come out from the flange end or damage but no leakage was found?


RESPONSE:


Boeing has reviewed the message and has NTO (No Technical Objection) to continue service with the condition of the scraper seal on the aileron PCU rod end provided that the external leakage limit of the Aileron when it moves does not exceed 1 drop per each cycle. Inspect the PCU for the leaking condition at every over-night stop and replace the seal as soon as practical but not to exceed 100 FC. Boeing confirms the purpose of the scraper ring is to clean the surface of the piston rod before it contacts the piston rod seals which are further inside the actuator assembly. Distortion or damage of the scraper ring will not directly result in hydraulic leakage since the scraper ring is not actually a hydraulic seal. However, deformation or damage to the scraper ring could allow contaminates to pass and cause damage to the piston rod seals. This condition could result in hydraulic leakage past the rod seals and scraper ring.


Please be advised that a Boeing No Technical Objection should not be construed as an indication of regulatory agency approval and will need to be coordinated with your local authorities regarding a formal regulatory agency approval. Obtaining the flight approval from the local regulatory agency for the subject airplane with the above data is the sole responsibility of the operator.


This NTO does not represent or imply formal Boeing approval or certification. The operator retains the final responsibility to ensure that the proposed technical, operational and/or procedural change will function as intended without introducing other problems and to coordinate with the appropriate regulatory agency (or agencies) to obtain all necessary approvals if required. No Technical Objections are defined in Boeing Service Letter 767-SL-00-018-H. It is the responsibility of the operator to review the Service Letter to ensure conformity to those conditions and to understand the limitations detailed within.


Furthermore, we have an ongoing investigation to determine the best solution moving forward for this design. br/>


Thank you,





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