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A guy at the hangar in Wichita said he never signs off a pitot heat check till he tests it twice, and now I'm second guessing my whole flow
Last month I was swapping a heated pitot on a King Air and a tech named Ray who's been at this shop near Wichita for 22 years watched me run the ground check. I hit it once, got the amp draw I wanted, and started closing up the panel. He stopped me and said he never signs one off till he runs it a second time cold, because a probe that heats fine warm can still open up once it's been cold soaked at altitude. I pushed back at first, figuring a good reading is a good reading, but he pulled two old log entries where a second check caught a bad element that passed the first time. Now I'm stuck in the middle. Doing it twice adds maybe ten minutes per plane, and on a busy day that stacks up fast, but if it catches one bad probe a year it pays for itself a hundred times over. The other side of me thinks if the manual only calls for one functional check, we shouldn't be inventing our own rules and slowing down the line. So where do you all land on repeating checks the book doesn't require? Do you do the second run, or is that just old shop lore?
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jake_hall8826d ago
Man, hold up, a good amp reading on the first hit doesn't actually prove what Ray was checking for. The element resistance changes with temp, so a probe that pulls the right amps on a warm day on the ramp can still have a weak spot that only shows up when it's cold soaked, which is why the second run has to be from a cold start to mean anything. If you're running it twice back to back while the probe is still hot from the first check, you're just testing the same condition twice and you won't catch the thing Ray's log entries caught. The manual calling for one functional check doesn't mean the check is bulletproof, it just means that's the least you have to do.
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