I finally saw the inspection data on our APU oil samples

We pulled the quarterly oil analysis reports from the last 3 years on the 757 fleet, and I was shocked to see that the copper levels in APU 4 were 3 times higher than any other unit. Our maintenance manager said it's been flying like that for 18 months without any issues. Is that normal for the APS3200 or did we just get lucky?

2 comments

2 Comments

alex_hall9124d ago

Copper 4 on the APS3200 is actually a known issue. I worked a line in 2018 where our fleet had two APUs with copper numbers that high and they both ran for another year before we finally swapped them. One of them even passed a borescope check at 2,000 hours past the recommended interval. The engineers told us the copper usually comes from the oil cooler core, not the bearings, so it doesn't always mean immediate failure. Your maintenance manager might be right that it's fine for now, but I'd still want to see the iron and nickel trends to be sure.

julia_jones7224d ago

Hold on, two thousand hours past the recommended interval? That's wild, I wouldn't have trusted that borescope for a second.