Firmware update vs factory recalibration for a Collins Pro Line 21 issue on a King Air

I had a pitot static readout glitch last week on a 2006 King Air and went with the firmware flash instead of the full bench recalibration, and now I'm second guessing if the 0.5 knot offset I'm seeing is normal or a sign I made the wrong call, anyone run into this before?

3 comments

3 Comments

alice_hart27d ago

Half a knot on a King Air pitot static is barely a rounding error honestly. I've seen guys chase tenths of a knot for months and then realize it was just the digital readout being finicky at low airspeeds. Collins firmware updates are known to shift baseline offsets a little after a flash, it's not the same as a bench recalibration where they physically zero the transducer. Unless you're flying into minimums with that offset showing on the PFD I'd say you're probably fine. Check it against the GPS groundspeed next time you're in smooth air at a steady speed, if it holds within 2 knots across the range you're good. Sending it to the shop for a full recal is expensive and takes weeks, and for half a knot you might just end up with the same offset from a different transducer anyway.

the_stella27d ago

Yeah, that part about chasing tenths for months really hits home. I spent a solid two weeks once going back and forth with avionics over a 0.3 knot discrepancy on a 206. Turned out the static port had a tiny piece of tape residue left from a paint job. All that time and nobody thought to just wipe it off. And you're spot on about the GPS groundspeed check. I do that every time now before I even touch the pitot system. Half a knot is noise in my book too, especially when you figure the instruments are bouncing around anyway in any real turbulence. If it flies straight and the numbers aren't screaming at you, why waste the cash on a bench job that might not even fix it? Have you ever had a transducer come back from the shop with the exact same offset you sent it in for?

brian32818d ago

Question whether it's really that serious. Half a knot on a King Air is basically a rounding error in my book, and @the_stella is right that chasing tenths usually ends up being some weird static port tape or a bad ground, not the actual transducer. Unless you're shooting an approach to minimums with that error staring you in the face, I'd just fly it and check the GPS groundspeed a couple times, you'll probably forget about it by next week.

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