Old DC-9 generator relay finally let go after 30 years

Had a generator relay fail on an old DC-9 last month at a hangar in Tulsa. The part had been in service since 1994 and just quit without warning during a run-up test. I ended up having to track down a NOS relay from a parts supplier in Arizona to get it swapped in two days. Anyone else run into old parts that just decide to die with zero signs beforehand?

3 comments

3 Comments

wells.evan3h ago

Yeah, I gotta push back a little on this one. Parts don't just "decide to die" out of nowhere. That relay had 30 years of heat cycles, vibration, and electrical load on it. If you'd traced its history, you'd probably find it was already showing signs of stress on a maintenance log or a past inspection that got overlooked. The real issue is that we stopped making these parts decades ago, so when something like that goes, people panic instead of planning ahead. I think most of us have been burned by a part that seemed fine until it wasn't, but that's on us for not having a spare on the shelf or budgeting for its age.

henryr4534m ago

Read somewhere corrosion is the real killer on those old relays, not just age.

margaretc423h agoMost Upvoted

I read a piece in Aviation Maintenance Magazine last year that said most generator relay failures actually come from internal corrosion building up over decades, not sudden electrical overloads. So it was probably cooking itself slowly the whole time.