Had a DME alt fail during a run-up in Denver last Tuesday

I was doing a quick run-up on a King Air and the alternator just dropped offline. No warning, no flicker, just a red light. Turned out the brush block was worn down to almost nothing after only 600 hours since last overhaul. Swapped it with a spare I had in the truck and it came right back. Anyone else seen these DME alts wear out way faster than the OEM ones?

3 comments

3 Comments

quinn16112d ago

You ever check the brush block part number against what DME originally shipped with the unit? I saw a batch a couple years back where they switched suppliers for the brush material and it started wearing out at like 500 hours instead of the usual 1500. Had to pull the logs and find the old spec to get the right replacement. Might be worth verifying your spare part number too, just to be safe.

the_alice13d ago

Oh man, that's like the fifth brush failure I've heard about on DME units in the last year. It's almost like they're using a different compound or something that just gives up way too fast. Makes you wonder if the cost savings upfront is worth the headache of having to replace them twice as often. I've noticed the same trend with a lot of aftermarket parts in different industries too, not just aviation. Everyone wants to save a buck now but ends up paying more later in labor and downtime.

david70312d ago

Back in the 90s I worked at a shop that rebuilt starters and alternators for heavy trucks. We had a similar problem with a batch of brushes from a new supplier that would crumble apart right around 600 hours. The company that bought them saved about 30 cents per brush but ended up paying for it when every single unit came back under warranty a few months later. It's a shame because the original brush material was fine, but someone in purchasing got a bonus for cutting costs and nobody checked the long term results.

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