Challenger landing gear, harness handling know-how

Effectivity: Challenger 600/601/604/605/650 aircraft  

ATA: 32 - Landing Gear, Harness Handling 

By: Victor Silva (CSE) 

Bombardier Technical Services would like to remind all maintenance personnel to handle the main landing gear (MLG) harnesses with care. Installation must follow the recommendations provided in the aircraft maintenance manual (AMM) associated tasks, as well as the original equipment manufacturer component maintenance manual (CMM), to ensure correct service loops and avoid improper routing. 

Some operators and approved MRO facilities/Safran Landing System Inc., have reported an increase in the number of MLG harnesses with protective covers, sleeves or braiding either kinked, missing or damaged. Some of these discrepancies on the MLG harness have caused anti-skid faults and/or WOW faults, often intermittent, due to induced internal wire damage, which often misled troubleshooting actions. 

To raise awareness, Safran has released Service Letter No. SL6XX-32-002 Notice to Operators and R&O Centers: Harness Handling, currently available on our Customer Portal under Vendor SIL Notices.  

This type of MLG harness damage is not directly related to normal operation of the aircraft and the most probable cause may be handling during maintenance actions, accidental damage or improper harness routing during installation, causing stress points, twisting or kinks during gear operation and/or chafing. Pay close attention to the harness sections on the gear upper pivot points between the uppermost MLG strut clamps and the first airframe fairlead clamp, as well as the trailing arm area.   

Please advise maintenance personnel that proper routing and service loop lengths as instructed in the AMM and CMM are essential to reduce the risk of gear harness damage to ensure harness longevity during operation. Additionally, if troubleshooting intermittent anti-skid faults or WOW faults, follow the associated SmartFix recommendations and remember to closely inspect the MLG harnesses for signs of the above-mentioned types of damage (examples pictured below).