That old timer's advice about coax routing saved my tail on a King Air

Back in March I was helping a senior guy, Larry, do a 24 month inspection on a King Air 200 down in Wichita. He told me to never zip tie the coax bundles tight to the frame rails because vibration will work the connectors loose, even if the torque checks are good. I figured he was just being old school, so I left a few bundles snug like I always did. Three weeks later that same plane came back with a bad VOR receiver and the pilot said the needle was jumping around on every approach. We yanked the rack and the connector on the right antenna line had backed off about a quarter turn, exactly where Larry warned me about. Now I go back and loosen every tie strap on any plane I touch, and I check the cable routing chart before I close up anything. Has anyone else seen intermittent comm issues from over-tight ties on turbine twins, or was this just a one-off? I'd like to know if the airframe makers ever addressed this in their later service bulletins.

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kim_hart719d ago

Larry's advice sounds like one of those hard earned lessons that never makes it into the manual until after a bunch of planes have issues. I've seen similar stuff on 421s where the autopilot would drop out on rough days, and it turned out to be the same kind of thing, just a loose connector from the harness bouncing against a support. Airframe makers did tighten up some of the later King Air bulletins about cable support spacing, but a lot of it still comes down to how the mechanic ties things off. Your mileage may vary, but I'd trust the old timer on this one. It costs nothing to give the bundles a little slack, and it beats pulling a rack twice.