Bleed Leak Detection Loop installation

Effectivity: Global 7500 aircraft

ATA 36-22

When installing bleed Leak Detection Loops (LDL), also called sensing elements, there are several factors to consider that may affect the reliability of the bleed-air leak-detection system, such as the handling during removal and installation. Always ensure that the LDL does not get twisted or bent to less than the minimum bend radius of one (1) inch.

It’s important to inspect for dents, fractures, frayed or open outer insulation, abrasions or other damages. Also, please be aware of clearances, bends, maintenance practices and other precautions during installation.

The above information and more can be found in the Aircraft Maintenance Publication (AMP) BD700-A-J36-22-00-00AAA-913A-A Bleed-air leak-detection system general maintenance procedure.

However, in this task, there is an important step that may be omitted because it is not always common knowledge. Prior to connection of the LDL, the connectors need to be cleaned and injected with insulating compound using a syringe as shown in the illustration below (extracted from the AMP).

This change was initiated several years ago due to issues with Bombardier commercial aircraft where some aircraft experienced nuisance messages that were caused by humidity and contamination in the connectors.

Although the requirement to clean and apply compound is found in the above-mentioned general maintenance procedure, it is not referenced in every LDL installation task in the AMP. The affected AMP tasks will be amended accordingly with several other improvements and released in the coming months. In the meantime, it is always good practice to refer to the Aircraft Maintenance Publication (AMP) BD700-A-J36-22-00-00AAA-913A-A Bleed-air leak-detection system general maintenance procedure when removing and installing LDL.