SD-8 drive Coupler Failure

[Ironflight]

When I decided to go all-electric in the design of my -8's avionics and instrumentation, one of the factors that went into the decision was the availability of the SD-8 backup alternator from B&C. This clever piece of equipment is a permanent magnet alternator that mounts in the exact same place and manner as a standard dry vacuum pump. One interesting thing that I didn't realize until I got it was that the orange "case" spins with the engine, so you actually have this moving part under the cowling. Unusual, but not a problem once you get used to the idea.

The other day when I had the cowling off, I was feeling around at the components on the accessory case, and found that I was able to spin the SD-8 without the prop moving. That's bad - it means that the shear coupling (similar to the one in a vacuum pump) has gone. I didn't know that could even happen with this device! I wrote a note to B&D, and got a prompt reply saying that I would get a call from Bill, the owner. Sure enough, he called this afternoon and apologized for the problem.

It turns out (according to Bill) that they had a bad batch of shear couplings go through their system about three years ago - right about the time I bought mine we figure. He said it was a materials problem that they didn't catch until the units started to fail. At any rate, he told me he was sending me out a new, better designed coupling for no charge, even though I was well out of warranty (three years and 700 hours!), and that it is very easy to change. I agreed that this would be easier than me sending the alternator back for them to fix.

Anyway, Kudos to B&C for good customer service, and if you have an SD-8 that you bought about three years ago, you might check to see if it is free spinning on the engine....(I know mine was good a month ago when I did a test of the backup system, so it was a recent failure).

Paul

[vic syracuse]

Paul, I had 2 failures on the 10 before I got one that worked. It's actually a different color than the originals. The new one worked fine for 500+ hours and is still going, I assume. I also went all electric, and I routinely test the SD-8 in flight to make sure it is working. I ran the output of both it and the main alternator through the amp sensor.

Take care.

Vic