«DO160/ED14» - Jessica France

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1 Training Workshop «DO160/ED14» - Jessica France Pros and cons of hermetically sealed boxes for environmental qualification of electrical items Edouard ZUNDEL Systems Qualification Engineer for Mechanical and Climatic aspects 1

2 Why to be sealed? Protection vs. gas penetration (air, flammable vapour...) Protection vs. liquid contamination (water, fuel...) Protection vs. solid pollution(sand, dust, carbon dust...) Under which conditions? Pressure, temperature, severe environmental conditions... For which duration? 1 month, 25 years... Depending on the above considerations it may become very complex to design and maintain a box hermetically sealed 2 2

3 How to besealed? To select materials that will not become porous regarding gas or liquids taking into account in service degradation To seal the interfaces and assemblies thanks to Welding Wet assembly of fasteners, O ring seal... Hermetically sealed connectors All materials and processes used to seal the box shall be qualified regarding in service operation and duration Robust and reproducible processes need to be formalized Qualification tests may be necessary for non COTS products 3 3

4 How to demonstrate sealing performance? To conduct sealing tests on representative items following international normative documents (e.g. NF EN ) To define and realize some inspection and maintenance tasks in order to ensure the sealing along the in service life of the product Failures and/or damages that may occur during manufacturing or in service life may be necessary regarding fuel vapor ignition risk 4 4

5 How to demonstrate sealing performance? To conduct sealing tests on representative items following international normative documents (e.g. NF EN ) To define and realize some inspection and maintenance tasks in order to ensure the sealing along the in service life of the product Failures and/or damages that may occur during manufacturing or in service life may be necessary regarding fuel vapor ignition risk 5 5

6 Main advantages of a hermetically sealed box vs. DO 160 Automatic compliance with: Section 6 (Humidity) Section 10 (water proofness) Section 9 under certain conditions (refer to next slide) Better behavior for: Section 4 (Temperature, except for altitude test) Section 5 (Temperature variation) Sections 11 to 15 Sections 20 and 24 No significant impact for other sections 6 6

7 Zoom on section 9 (explosion proofness): Airworthiness authorities request to consider double failure conditions regarding fuel vapor ignition (3 layers of protection at aircraft level) Aircraft zone I (fuel vapor normally present, e.g. fuel vapor area): The equipment shall not be able to ignite fuel vapor under normal operation and considering any single or double failure (e.g. short circuit combined with a malfunction of the circuit breaker). Aircraft zone II (fuel vapor only present resulting from one failure): The equipment shall not be able to ignite fuel vapor under normal condition and considering any single failure (e.g. internal spark or overheating of an electrical component). Aircraft zone III (fuel vapor only present resulting from a double failure): The equipment shall not be able to ignite fuel vapor under normal operating. Aircraft zone IV (No fuel vapor): No requirement Sealed box can be considered as 1 layer of protection that must be damaged before to consider that fuel vapor may come into contact with internal electronic components. 7 7

8 Pros and cons summary of a sealed solution Phase Pros Cons Comments Design X Strong constraints in particular at connectors level and need to demonstrate sealing performance Maintenance X Strong constraints in particular to ensure the performance along the in service operations Qualification X Mainly enhance the behavior ofthe equipment vs. environmental threats Certification X May be mandatory due to fuel tank ignition prevention 8 8

«DO160/ED14» - Jessica France

Training Workshop «DO160/ED14» - Jessica France ABD 100 1.2 Specificities of Sustained Engine Imbalance Edouard ZUNDEL Systems Qualification Engineer for Mechanical and Climatic aspects 1 FBO : Fan Blade