Aircraft transmission systems carters are usually made with precipitation-strengthened aluminium alloys. These pieces are subjected to long-term (>1000h) in-service ageing at temperatures between 150-200°C, close to the initial precipitation ageing temperatures. The effect of this ageing on the nano-precipitates is both challenging to explore (given the duration and potential temperature range) and to model since multiple mechanisms are at play. The aim of this proposal which is part of the PhD project of Thomas Perrin (with SAFRAN Transmission Systems) is to use space-resolved SAXS-WAXS on multiple samples aged for long durations (up to 5000h) in a gradient furnace, so that we can acquire all kinetics at all temperatures. This would represent an unprecedented corpus of data which would enable to distinguish between the possible mechanisms (in particular, the potential phase transitions that would be detected by WAXS) and which would serve as a training set for the alloy design model.