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I finally stopped chasing intermittent faults with the meter and started logging bus data first
Had a flap asymmetry CAS message on a Challenger 604 that would only show up about 1 in 10 flights, and I spent two full shifts last month chasing it with a Fluke before a guy on my crew told me to just pull the ARINC 429 bus data and look for bad words. Turned out the left flap position transmitter was dropping one label every few hundred frames, which a meter will never catch because the signal looks fine at the connector every time you probe it. I get why people resist it, the laptop and harness take 20 minutes to set up, but I found it in 40 minutes after that instead of swapping parts for a week. Curious if anyone here has a go-to setup for catching dropouts on 429 or 1553 buses, I'm still using an old ballard box and wondering what else is out there.
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jordan_hill13d ago
I ran into something kind of similar years back on a King Air with a flaky bleed air fault that only popped up when it was cold soaked overnight. Turned out to be a bad solder joint on a cannon plug that would only open up once things shrank down, and no amount of wiggling on a warm hangar floor would ever show it. Took a scope watching the line while we hit the connector with freeze spray to finally pin it down, so yeah, sometimes the fault only shows up under the exact conditions you can't recreate on the ramp.
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jana76913d ago
Man, @jordan_hill, I gotta push back on this one, because chasing a ghost fault with freeze spray and a scope can eat a whole crew's week and still leave you with nothing to sign off. Sometimes the smarter move is to just swap the whole connector and move on instead of proving which tiny joint failed.
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