Routine Maintenance check turns expensive when the Tech did the job in a hurry. This is what happens when you don’t follow standard practices:
A twisted tube made from stainless steel no less. Three errors happened here in rapid succession, which lead to an expensive damaged part, and a grounded aircraft.
- First problem was that the B-nut was cross-threaded (thread damage visible on right side fitting), which is why you always start the nuts by hand for the first few threads.
- Second error was a lack of a back-up wrench. See the large hex on each of the three fittings? Back-up wrench goes there! To eliminate this kind of damage.
- Third error was over-torque. You can often get away with no back-up wrench (see item 2 above) if you torque to specifications. No torque wrench = blue-ball torque = damage like this.