That time a worn pin on a D-sub connector grounded a whole fleet for three days

I got called out to a regional hangar near Tulsa about 6 months ago because three of their King Airs kept throwing nav light faults. The shop guys had already swapped bulbs, tested breakers, the whole nine yards. I started digging into the first plane and found the D-sub connector on the wing harness had a single pin that was almost flat from vibration wear. It was making intermittent contact but the real kicker was that it was grounding out against the shell every time the flaps moved. I checked the other two birds and they had the same exact wear pattern on the same pin. Turned out the whole batch of connectors came from a bad supplier run three years prior. We ended up replacing all 20 connectors across those planes and the squawk went away for good. Has anyone else run into batch defects like that where it's the same pin failing on multiple airframes?

2 comments

2 Comments

lily_stone766d ago

Hang on, do you REALLY think a bad batch of connectors was the root cause here? I have to push back a little because Ive seen this exact thing happen and it wasnt the connectors at all. It was the harness routing putting too much stress on that specific pin location. The vibration wear you described is a classic sign of a mechanical issue, not a manufacturing defect. If those pins are all failing in the same spot on multiple planes, Id look at how the harness is secured or if theres some interference happening when the flaps move. Replacing all those connectors might have fixed it for now, but Im betting the real problem is still there waiting to come back.

wesleybutler6d ago

Hang on, you're almost right but I think you got the mechanical part backwards a little. The vibration wear you're seeing is actually more common when a connector itself is bad from the factory, because a loose pin can move around inside the housing and that motion causes the wear. If it was strictly a harness routing problem, you'd see the damage on the wire outside the connector first, not down inside where the pin sits. I've had this exact fight before with a fleet of work trucks where we kept chasing bad connectors only to find out the harness was fine but the pins were slightly undersized from the manufacturer. It's worth double checking the pin diameter with a micrometer before you reroute the whole harness.