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。
SUBJECT: Questions on The Piston Rod Scrapper of The Aileron PCU
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.
Q1. Should the PCU continue to service if the Scrapper come out from the flange end or damage but no leakage was found?
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/>