Correct Cargo Door Seal Installation for Safe Operation
Source: Airbus Safety First URL: https://safetyfirst.airbus.com/correct-cargo-door-seal-installation-for-safe-operation/ Published: 2024-07-10 Category: Maintenance, emergency descent, pressure, pressurisation, pressurization PDF: Original PDF
Incorrect installation of a cargo doors seal may lead to unsafe in-flight operations such as abnormal cabin or an pressurization ineffective cargo fire extinguishing system.
This article recalls the essential steps of the AMM for correct door cargo seal installation, including the required inspection after installation.
Check the latest version of this article on safetyfrst.airbus.com and on the Safety first app for iOS and Android devices.
CASE STUDY
Section titled “CASE STUDY”Event Description
Section titled “Event Description”An A319 aircraft was performing a non-revenue flight from its main base, following a maintenance check. There were two passengers and two flight crew members onboard. During climb, a CAB PR EXCESS CAB ALT ECAM warning triggered. The flight crew initiated an emergency descent and opted to perform an in-flight turn back. The aircraft safely landed without further incident.
Event Analysis
Section titled “Event Analysis”Cargo door seal found incorrectly installed
Section titled “Cargo door seal found incorrectly installed”During troubleshooting, the maintenance crew observed that the aft cargo door pressure seal was incorrectly installed.
Records showed that the cargo door seals were replaced during the maintenance check as per the mandatory Service Bulletin (SB) A320-52-1195.
The seal of the aft cargo door failed to inflate due to its incorrect installation causing an air leak, which caused the CAB PR EXCESS CAB ALT ECAM warning to trigger.
The aircraft safely returned to operation when the aft cargo door seal was reinstalled correctly and inspected.
CARGO DOOR SEAL
Section titled “CARGO DOOR SEAL”Cargo door seals are made of reinforced silicone rubber and are installed in the retainer around the door structure. They ensure air tightness around the cargo door to maintain aircraft pressurization.
Seal Design
Section titled “Seal Design”On Airbus aircraft, the airtightness of the cargo doors are ensured by inflatable seals. Inflatable cargo door seals have inflation holes located on their inner surface (the cargo facing side) of the seal, that allows the pressurized air from the cabin to enter the seal, which causes it to inflate as the altitude increases and this ensures the airtightness around the seal (fig.1).
(fig.1) Concept of an inflatable seal - typical view
Incorrect Installation Causing Air Leaks
Section titled “Incorrect Installation Causing Air Leaks”If the inflatable seal is installed incorrectly, and the inflation hole is in the wrong position, the pressurized air can compress the seal and create air leaks (fig.2).
(fig.2) Incorrect installation of the inflatable seal can create air leaks
Effects of incorrect installation
Section titled “Effects of incorrect installation”Two potential effects from incorrect seal installation include pressurization issues and the reduced effectiveness of the cargo fire extinguishing system. Air leaking around the cargo door seal can make it difficult to pressurize the aircraft, or it can potentially cause an in-flight depressurization event requiring an emergency descent. In the event of a cargo fire, the air leaking around the seal may allow the extinguishing agent to escape the cargo compartment and fail to extinguish the fire.
Increased Risk Exposure on A320 Family Aircraft
Section titled “Increased Risk Exposure on A320 Family Aircraft”Most of the reported cases of incorrect seal installation occurred on A320 family aircraft for two main reasons:
High number of cargo door seal replacements required by service bulletin
Section titled “High number of cargo door seal replacements required by service bulletin”The Airworthiness Directive (AD) 2021-0049 published by the EASA in March 2021 mandates the installation of a new seal via Service Bulletins (SB) before March 2029 on all in-service A320 family aircraft delivered before November 2019. SB A320 52-1195 (for CEO aircraft) and SB A320 52-1196 (for NEO aircraft) require replacement of the aircraft’s cargo doors seals, canceling the need for repetitive cleaning and greasing of the old seal requested by the AD pending its replacement. The new seal has improved airtightness and does not require regular greasing to improve its efficiency.
This mandatory replacement of the seals on A320 family aircraft significantly increases the risk exposure to incorrect installation of the seal. Replacement of a cargo door seal is normally only performed when it is damaged during operation.
Different seal characteristics
Section titled “Different seal characteristics”Another reason A320 family cargo doors may have reported incorrect installations is because the seals on A320 family aircraft have a symmetrical shape and they are more flexible when compared to the seals installed on other Airbus aircraft models. On the other aircraft types (A220, A300, A310, A330, A340, A350 and A380 aircraft), the seals have a higher rigidity and some have an asymmetrical shape, which can aid the operator to correctly install the seal.
ENSURING CORRECT CARGO DOOR SEAL INSTALLATION
Section titled “ENSURING CORRECT CARGO DOOR SEAL INSTALLATION”Even if A300, A310, A330, A340, A350, A380 and A220 aircraft are less prone to incorrect installation, maintenance personnel must carefully follow the AMM/MP/AMP instruction to ensure that the seals are installed correctly. This includes careful consideration of the warnings, cautions, procedure and illustrations.
Additional inspection and dual signature
Section titled “Additional inspection and dual signature”A recommendation as an additional safety barrier is to require an additional inspection and dual signature for the cargo door seal installation task.
Ensuring correct seal installation on A320 family
Section titled “Ensuring correct seal installation on A320 family”Introduction of a caution tag
Section titled “Introduction of a caution tag”To prevent incorrect seal installation, the seal manufacturer has introduced an instruction notice included with seal deliveries (fig.3). This notice highlights the need to pay particular attention to the correct orientation of the cargo door seal holes.
(fig.3) Instruction notice included with seal deliveries
Correct positioning of the seal
Section titled “Correct positioning of the seal”Maintenance personnel must ensure that the inflation holes are located on the inner side (the cargo facing side) of the door. In addition, the cargo door seals do not have inflation holes in their lower part and so the maintenance personnel must ensure that the side of the seal marked with “LOWER DOOR” is positioned closest to the door locking mechanism (fig.4).
(fig.4) Example of Correct positioning of an aft cargo door seal on an A320 family aircraft
Installation of pre-formed corners
Section titled “Installation of pre-formed corners”Maintenance personnel should install the four pre-formed corners first to ensure the seal is in the correct position and to prevent wrinkles. White alignment marks help to identify and correctly position the pre-formed corners (fig.5).
(fig.5) Installation of the pre-formed corners before the straight sides ensures correct installation of the seal along the door frame
Mandatory Visual inspection
Section titled “Mandatory Visual inspection”A careful inspection of the seal as per AMM is required to ensure correct seal installation. The maintenance personnel must inspect the entire circumference of the cargo door seal. They must ensure the seal is not twisted and check that the inflation holes are facing towards the inner side of the cargo door by gently bending the seal (fig.6).
(fig.6) Slightly bending the seal enables the maintenance personnel to check the inflation holes are facing towards the inner surface of the door, which is the cargo side
A320 Cargo Doors Seal Installation Video
Section titled “A320 Cargo Doors Seal Installation Video”Airbus developed an awareness video to illustrate these essential steps for correct cargo doors seal installation on the A320 family.
Video: A320 Family - Cargo door seal installation
Further information can be found in the AMM/AMP and on the AirbusWorld portal and in the following documents:
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OIT Ref.: 999.0040/23 - ATA 52 – CARGO DOORS SEALS INSTALLATION
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ISI Ref.: 00.00.00437 - A320 Family Systems Ageing global ISI
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Maintenance Briefng Notes (MBN): Forward & aft cargo door seal installation
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TFU Ref.: 52.30.00034 - A320 Fam CARGO COMPARTMENT DOORS SEAL ADAPTATION FOR HALON LEAKAGE IMPROVEMENT
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RIL Reference: SA52M20001620
Contributors : Markus ADLER
Section titled “Contributors : Markus ADLER”Metallic Structure Design Responsible
Design Office
Christophe DELMAS
Section titled “Christophe DELMAS”Aircraft Safety Enhancement Manager Specialist Design Office
Jean Philippe JACQ
Section titled “Jean Philippe JACQ”Safety & Maintenance Expert
Customer Support
Cyril MONTOYA
Section titled “Cyril MONTOYA”Product Safety Enhancement Manager
On Airbus aircraft, the airtightness around the cargo doors is ensured by an inflatable cargo door seal. The inflation holes must be correctly oriented towards the inner surface of the door, which is facing the cargo, to function correctly. Incorrect installation of the seal may lead to a failure to pressurize the aircraft, loss of aircraft cabin pressure inflight, or cause the cargo fire extinguishing system to be less effective in the event of a cargo fire.
The AMM/MP/AMP provides instructions, warnings and illustrations to ensure correct installation of the cargo door seal and reminders are now also attached to each replacement seal for A320 family aircraft.
Once the seal is installed, a visual inspection of the entire seal is required to ensure that the seal is not twisted and the inflation holes are oriented towards the inner side of the cargo doors. It is recommended to require an additional inspection and dual certification of a cargo door seal installation task as an additional safety barrier.
Customer Support
With Thanks to Cesar GARCIA CASTILLA Product Safety Enhancement, Damien PARISE Customer Support Structure Fuselage Engineer
Safety first, 2024. Safety first is published by Airbus S.A.S. 1, rond point Maurice Bellonte - 31707 Blagnac Cedex/France.
Editor: Yannick Malinge, SVP AViation Safety.
Editorial team: Guillaume Estragnat, Vanessa Sadi, Gwyneth Duggan, Javier Martinez Marina, Tim Roach.
Photos by Airbus.
来源：Airbus Safety First URL：https://safetyfirst.airbus.com/correct-cargo-door-seal-installation-for-safe-operation/ 发布日期：2024-07-10 类别：维护、紧急下降、压力、增压、货舱灭火系统 PDF：Original PDF
货舱门封严安装不正确可能导致不安全的飞行运行，例如客舱异常或货舱灭火系统失效。
本文回顾了 AMM 中正确安装货舱门封严的基本步骤，包括安装后所需的检查。
请访问 safetyfirst.airbus.com 及 iOS 和 Android 版 Safety First 应用查看本文最新版本。
一架 A319 飞机在完成维护检查后，执行从主基地起飞的非商业航班。机上载有两名乘客和两名飞行机组人员。在爬升阶段，触发了 CAB PR EXCESS CAB ALT ECAM 警告。飞行机组执行了紧急下降并选择空中返航。飞机安全着陆，未发生进一步事故。
发现货舱门封严安装不正确
Section titled “发现货舱门封严安装不正确”在排故期间，维护人员观察到后货舱门压力封严安装不正确。
记录显示，货舱门封严根据强制服务通告（SB）A320-52-1195 在维护检查期间进行了更换。
后货舱门封严因安装不正确而未能充气，导致漏气，进而触发了 CAB PR EXCESS CAB ALT ECAM 警告。
后货舱门封严重新正确安装并检查后，飞机安全恢复运行。
货舱门封严由加强型硅橡胶制成，安装在门框护圈中。其功能是确保货舱门周围的密封性，以维持飞机增压。
在空客飞机上，货舱门的密封性通过可充气封严来保证。可充气货舱门封严在内表面（朝向货舱的一侧）设有充气孔，允许来自客舱的增压空气进入封严，使其随着高度增加而膨胀，从而确保封严周围的密封性**（图1）**。
（图1） 可充气封严原理——典型视图
安装不正确导致漏气
Section titled “安装不正确导致漏气”如果可充气封严安装不正确，充气孔位置错误，增压空气可能会压缩封严并造成漏气**（图2）**。
（图2） 可充气封严安装不正确会产生漏气
安装不正确的影响
Section titled “安装不正确的影响”封严安装不正确可能导致两种潜在后果：增压问题和货舱灭火系统效能降低。货舱门封严周围的漏气可能导致飞机难以增压，甚至可能造成需要紧急下降的空中释压事件。若发生货舱火灾，封严周围的漏气可能使灭火剂从货舱泄漏，无法扑灭火焰。
A320 系列飞机风险敞口增加
Section titled “A320 系列飞机风险敞口增加”大多数报告的封严安装不正确事件发生在 A320 系列飞机上，主要有两个原因：
服务通告要求大量更换货舱门封严
Section titled “服务通告要求大量更换货舱门封严”EASA 于 2021 年 3 月发布的适航指令（AD）2021-0049 要求在 2029 年 3 月前，通过服务通告（SB）在所有 2019 年 11 月之前交付的在役 A320 系列飞机上安装新封严。SB A320 52-1195（用于 CEO 飞机）和 SB A320 52-1196（用于 NEO 飞机）要求更换飞机的货舱门封严，取消了在更换前 AD 要求的旧封严定期清洁和润滑。新封严具有更好的密封性能，无需定期润滑以提高其效能。
A320 系列飞机上封严的强制更换显著增加了封严安装不正确的风险敞口。货舱门封严的更换通常只在运行中损坏时才进行。
不同密封条的特性
Section titled “不同密封条的特性”A320系列货舱门可能出现密封条安装不正确情况的另一个原因是，A320系列飞机上的密封条具有对称形状，且与其他空客机型上安装的密封条相比更加柔软。在其他机型（A220、A300、A310、A330、A340、A350和A380飞机）上，密封条具有更高的刚性，部分还具有非对称形状，这有助于操作人员正确安装密封条。
确保货舱门密封条正确安装
Section titled “确保货舱门密封条正确安装”即使A300、A310、A330、A340、A350、A380和A220飞机不太容易出现安装错误，维护人员也必须仔细遵循AMM/MP/AMP中的说明，以确保密封条正确安装。这包括仔细注意警告、注意事项、程序和图示。
附加检查和双人签署
Section titled “附加检查和双人签署”作为附加安全屏障，建议要求对货舱门密封条安装工作进行附加检查和双人签署。
确保A320系列正确安装密封条
Section titled “确保A320系列正确安装密封条”引入注意事项标签
Section titled “引入注意事项标签”为防止密封条安装错误，密封条制造商在交付密封条时附带了一份说明通知**（图3）**。该通知强调需要特别注意货舱门密封条孔位的正确方向。
（图3） 密封条交付时附带的使用说明通知
密封条的正确位置
Section titled “密封条的正确位置”维护人员必须确保充气孔位于门的内侧（朝向货舱的一侧）。此外，货舱门密封条的下部没有充气孔，因此维护人员必须确保密封条上标注有**“LOWER DOOR”的一侧位于最靠近门锁机构的位置（图4）**。
（图4） A320系列飞机后货舱门密封条正确安装位置示例
预制角落的安装
Section titled “预制角落的安装”维护人员应首先安装四个预制角落，以确保密封条处于正确位置并防止起皱。白色对准标记有助于识别和正确定位预制角落**（图5）**。
（图5） 在安装直线部分之前先安装预制角落，可确保密封条沿门框正确安装
强制目视检查
Section titled “强制目视检查”需要按照AMM对密封条进行仔细检查，以确保密封条安装正确。维护人员必须检查货舱门密封条的整个周圈。他们必须确保密封条没有扭曲，并通过轻轻弯曲密封条来检查充气孔是否朝向货舱门的内侧**（图6）**。
（图6） 轻轻弯曲密封条使维护人员能够检查充气孔是否朝向门的内侧表面，即货舱侧
A320货舱门密封条安装视频
Section titled “A320货舱门密封条安装视频”空客制作了一段宣传视频，来说明A320系列货舱门密封条正确安装的关键步骤。
视频：A320系列 - 货舱门密封条安装
更多信息请参阅AMM/AMP和AirbusWorld门户，以及以下文件：
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OIT Ref.: 999.0040/23 - ATA 52 – 货舱门密封条安装
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ISI Ref.: 00.00.00437 - A320系列系统老化全球ISI
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维护简报说明（MBN）：前货舱门和后货舱门密封条安装
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TFU Ref.: 52.30.00034 - A320系列货舱门密封条卤代烷泄漏改进适配
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RIL参考：SA52M20001620
贡献者：Markus ADLER
Section titled “贡献者：Markus ADLER”金属结构设计负责人
设计办公室
Christophe DELMAS
Section titled “Christophe DELMAS”飞机安全增强经理专员
设计办公室
Jean Philippe JACQ
Section titled “Jean Philippe JACQ”安全与维护专家
客户支持
Cyril MONTOYA
Section titled “Cyril MONTOYA”产品安全增强经理
在空客飞机上，货舱门周围的气密性由可充气式货舱门封严提供保障。充气孔必须正确朝向门的内侧表面（即朝向货物的方向）才能正常发挥功能。封严安装不当可能导致飞机增压失效、飞行中飞机客舱失压，或在发生货舱火灾时导致货舱灭火系统的有效性降低。
AMM/MP/AMP 提供了确保货舱门封严正确安装的说明、警告和图解说明，A320 系列飞机的每件更换封严件现在也附带安装提示卡。
封严安装完成后，需要对整个封严进行目视检查，以确保封严未发生扭曲，且充气孔朝向货舱门的内侧。建议将货舱门封严安装工作增加一次额外检查和双人签署作为附加安全屏障。
客户支持
特别致谢：Cesar GARCIA CASTILLA 产品安全增强，Damien PARISE 客户支持结构机身工程师
Safety first，2024 年。Safety first 由空中客车公司（Airbus S.A.S.）出版，地址：1, rond point Maurice Bellonte - 31707 Blagnac Cedex/法国。
编辑：Yannick Malinge，航空安全高级副总裁。
编辑团队：Guillaume Estragnat、Vanessa Sadi、Gwyneth Duggan、Javier Martinez Marina、Tim Roach。
照片由空客提供。