Vent: The time I spent three days chasing a ghost signal on a Citation X

Last month, we had a Citation X in the hangar with a weird, intermittent 'COM 2 FAIL' message that would pop up for maybe two seconds during climb, then clear. No logs, no hard faults. My boss said 'just run the BITE test and sign it off,' but it didn't feel right. I spent the first day checking all the usual suspects, the antenna couplers, the tray connections, everything was tight. On day two, I started looking at the coax runs behind the main panel. I found it, a tiny, almost invisible nick in the shielding on a RG-400 cable where it rubbed against a zip tie bracket. It was only making contact under specific vibration and flex. Fixed it with a new section and proper clamps. It's just so frustrating when the book says one thing, but the plane is telling you another. Anyone else had a gremlin that only showed up under flight conditions?

3 comments

3 Comments

grant.zara1mo ago

That zip tie bracket was the real ghost all along.

jamesm381mo ago

Remember how the bracket always seemed to come loose right after you finished a ride? I bet road vibration was slowly working it off, not some gremlin. That plastic gets brittle from sun and heat cycles too, so it was probably cracking where you couldn't see it.

susan1301mo ago

Ever think about how much cabin pressure change during climb could be stressing those old wire bundles? I had a King Air where a cracked solder joint on a nav light would only open up above 15,000 feet. The cold and pressure change would pull it apart just enough. It's like what grant.zara said about the bracket being the ghost, sometimes the fix is right but the root cause is the environment making a small problem act big. You chasing that vibration fault is the same idea, the plane has to be in the exact right spot for the problem to show itself.