A320系列飞机液压系统渗漏检查与预防
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A320系列飞机液压系统渗漏检查与预防液压系统油液渗漏问题一直是困扰机务维修工作的难题，维护中存在很多困难，是影响航班正常性的重要因素之一。
如何做好油液的预防检查和控制措施就是我们各个飞机保障部门所力求解决的一大课题。
本文结合空客关于液压渗漏的SIL,分析了航线常见渗漏模式，与大家分享交流。
一、A320系列飞机液压系统的特点：在A320系列这样的现代民用客机上，尽管与电气、电子系统相比，液压系统的科技含量不高，但由于其自身具备体积功率比小，技术成熟，工作可靠性高等一系列优点，使得液压系统仍然广泛使用在各系统甚至是一些关键系统中，为它们提供动力源。
涉及液压系统的章节有：24章（应急发电）；27章（飞控）；29章（液压）；32章（起落架）；52章（货舱门）；78章（反推）。
如下图所示同时液压系统部件（动力部件、控制部件、执行部件、辅助部件，接头及管路）分布范围广，包括有：3个起落架及起落架轮舱、液压/勤务舱、货舱地板及侧板下、后附件舱、各飞行操纵面内部、发动机短舱吊架。
这么大的分布范围导致部件和管路数量很多，管路纵横密布，检查起来十分困难。
二、液压系统渗漏形式和特点：由于液压系统是以液体作为工作媒介，所以自诞生之日起一直伴随着一个突出问题，就是“油液渗漏”。
随着飞机设计、制造水平的提高，现代民用航空器的液压油渗漏问题有所改善，但却无法根治。
对于A320系列飞机来说，渗漏形式可分为以下两大类：1、部件本体渗漏：包括有壳体裂纹，结合面渗漏，作动部件渗漏等，部件封圈损伤；2、管路渗漏：包括有硬管管壁损伤，软管断丝，接头力矩不当，接头损伤，底座封圈损伤等；下图是几种常见的渗漏点：部件自身封严性能下降和接头封圈失效在部件渗漏中占了绝大部分比重。
通常情况下部件渗漏多为渐变过程，渗漏程度逐渐恶化，如果在渗漏前期及时发现并予以处理，就可以阻断严重渗漏的发生。
管接头漏油一般是由接头松动或损伤所致，前期也能发现并做预防处理。
而管路失效多为突变过程（这里指的是管子爆裂），通常是由于设计制作的问题，或者是安装间隙导致，前期无明显渗漏，较难检查，预防难度比较大。
根据以上渗漏形式，空客在2009/10/28颁布了一份新的SIL29-063，里面涉及了A320系列飞机所有和渗漏有关的部件及处理建议。
三，航线常见的几种渗漏模式：1、软管漏油：航线维护中由于软管导致的漏油事件已经发生过多起了，包括了起落架收放作动筒软管，飞控系统软管等。
在空客的SIL29-063里面也提到了对于此类软管的维护提示，例如：(3). ATA 32☆MLG Lock Stay Actuator Hose: Some green hydraulic system loss occurrences due to MLG Lock Stay Actuator Hose rupture have been reported. The origin of the leak has been identified as corrosion pitting of the stainless steel braiding on the exposed portion close to one end fitting. This, in combination with the bending stresses at that point result in propagation by fatigue cracking through the individual wires. An improved hose has been defined and made available under modification 35082J2663 and service bulletin RefA320-32-1296. For more details please refer to TFU 32.11.12.008.☆MLG Door Actuator Hose: Some operators have reported leakage from the post-mod 32954 standard MLG door actuator hose. Mod 32954 introduced via SB 32-1260 installed a shorter hose (PN AE2463921G0097) to avoid breakage and subsequent leakage. The origin of the leak has been found to be a fatigue fracture of the braid at end fitting level. The leakage was generally reported on aircraft that had accumulated from 6000 to 7000FC. A hose with an integrated 90ºfitting at the airframe side should be proposed. This modification should be made available through SB A320-32-1371 in Q2 2010. For further information refer to TFU 32.31.35.003.在SIL的附件表格中也有相关文件的描述以MLG舱门作动筒软管为例，根据TFU的建议在发现软管断丝时最好就直接更换，这是航线检查要求，并且在飞机更换完之后累计到6000FC时最好更换新管，类似软时寿控制。
针对软管的维护建议在SIL里有如下方面(3). Flexible HosesFlexible hoses are installed in the hydraulic distribution system where some level of movement is required, imposing a high level of stress on the tube caused by pressure fluctuation and pulsation in the system. If not replaced, damage to a hose or to the wire braid of a hose that is assessed as minor during inspection could lead to the loss of the hydraulic system during the next flights.☆ A regular inspection of the hoses should be performed to identify chafing marks located on the hose surface, cuts or kinking or any kind of damage.☆Any dents, kinks or deformation may hide underlying damage and is cause for hose removal.☆Replace wire braided hose:If two or more wires in one plait or several wires in a concentrated area are broken,If braid is protected by a neoprene overlay or a chafe guard and wear or chafing into the steel braid has occurred.☆If there is wear after chafing:Measure the width of the wear (W) and the external diameter (D).If W x 100 / D x 3.14 > 10% replace the flexible hose.Refer to figure 284, AMM task 20-23-11-991-089.☆The same installation recommendations as referenced above for rigid pipes apply for flexible hoses. During hose installation make sure to apply counter-torque to avoid twisting or unintended repositioning of the hose leading to a change of its’ routing.对于此类软管，还有一点要注意的就是之前出现过的后附件舱内蓝系统方向舵供油管2101GM漏油。
这根管子近期出现过两次渗漏，每次都造成了比较严重的后果。
AIRBUS针对这根管子单独颁布了SIL29-087，其中提到的是针对2101GM件号为P/N:AE2463922G0221的管子（EATON-AEROQUIP）。
通过厂家的测试认为件号为P/N: A9053003D0221（TITEFLEX）的管子抗腐蚀性优于EATON的产品，发生渗漏的可能性小很多，所以建议运行商尽量更换TITEFLEX的产品，并对EATON的管子每20000FH检查。
对于航线维护来说，根据这个SIL，我们尽量在定件的时候要参考厂家的建议，避免渗漏重复发生。
2、管路，接头和底座封圈漏油：日常的航线维护检查，通常会发现一个区域的油液较多，但打压检查相应周围的部件又没有发现明显渗漏的地方，只是几个接头或者底座有点湿，这时处理起来容易模糊，并且有可能对后续处理产生影响。
这种渗漏有可能是底座封圈损伤，腐蚀，老化导致的，也有可能是管路接头渗漏导致的，或者是管路的砂眼导致。
对于封圈来说，SIL29-063里并没有详细的建议，主要是要求按照SIL-064对于底座封圈进行详细目视检查，是否有黑色沉积物，并要求按照AMM更换底座封圈。
这里特地建议尽量使用封圈安装专用工具，可以有效的保证封圈在安装的过程中避免损伤。
对于封圈的更换，AIRBUS在SIL中针对部分运营商的措施提出如下意见：☆Airbus does not recommend a large fleet campaign of hydraulic seal replacements. An A330 operator carried out a fleet seal replacement campaign and the results were not satisfactory.☆The fact is that a fleet replacement campaign on seals is a major disturbance on the hydraulic system, and could therefore introduce more issues rather than providing a real improvement. As general good practice, it is advised to pay particular attention at high-pressure manifolds and at ground service panels for seepage at the opportunity of the scheduled General Visual Inspections as per MPD tasks performed in the landing gear bay. Seepage on a manifold is usually a clear indication of a seal pre-damage calling for preventive rectification.对此建议我们可以结合SIL29-064，对于经常发生漏油的总管上的接头底座重点检查，C检时，在可能的情况下全部更换为新件。
