Investigation of Black Soot-Induced Degradation of Environmental Control Systems (ECS) & Aircraft Avionics Failures

Efficient and effective cooling of aircraft avionics is required to achieve optimized performance, reliable & extended operation. Thus, rated temperature ranges for safe operation of avionics are ensured by employing Environmental Control System (ECS) in aircraft, which uses ram air in closed circuits to cool avionics Line Replaceable Units (LRUs). Heat is dissipated out into the closed-circuit ram air stream (sink) from the PCB cards (source) via forced convective heat exchange. During this process, heated components leave soot particles into the downstream which are subsequently condensed & accumulated in the ECS components (in the form of black soot). Being a good insulator of heat, it reduces efficiency of ECS system over the years by decreasing heat transfer rate. Whereas, inspections of ECS components (permanently closed hollow walls of avionics LRUs) are not a part of Scheduled Preventive Maintenance Programs (SPMPs) at field level in aviation industry. Therefore, the soot deposition goes unchecked until the LRUs are replaced as “condition-based item” which resultantly may cause degradation of performance of aircraft avionics, burning of PCBs due to overheating due to reduced efficiency of ECS because of black soot deposition phenomena. This research has investigated degradation of ECS system performance due to ageing & black carbon soot using empirical, experimental & CFD methods. It was found that black carbon soot deposition in ECS contributes 11% rise in operating temperature of avionics LRUs.