Originally Posted by
Colibri49
n305fa
According to what I've researched on Google, there is a dedicated "epicyclic module chip detector" which you describe above as "not very efficient, small size, big epicyclic case radius" which is generally correct. What I myself saw when the conical housing and top of the gearbox got dismantled to remove the ring of magnets, was a lip right around the edge of the tray to which the magnets were attached.
There was a gap of 1 or 2 cm in this lip to allow oil draining down from the epicyclics to get "focused" into a narrow stream passing over the epi chip detector below the gap (engineers please correct me if I'm wrong), thereby increasing the chances of metal particles getting detected.
So if that lip with a gap is still part of the tray's design and now that the ring of magnets is no longer in place, even the slightest particle from the epicyclics and mast area would be detected at a very early stage and long before the risk of a catastrophic break-up might occur. I can't accept the idea of only one or two particles being detected by this improved system (without magnets) followed by a sudden break-up?
Hence my question for the 3rd time "Was there any history of the Norwegian EC225 gearbox making metal before the crash, because if not the likelihood of similarity with REDL is probably reduced?"
Colibri
Having seen a number of "open" 332 &225 gearboxes in my time I can say there is no channelling of oil to the epi chip detector. There is a ridge around the edge of the outer module separator plate with a small depression in it where the epi chip detector sits. It's shown in fig 11 of the REDL report. As described to me on a course at EC/AH the Epicyclic chip detector relies chips being flung into its influence by the epicyclic system and by oil draining past the detector not by oil channelling.
Since REDL the procedures for assessing any particles found in the MGB has changed significantly.