Look through a Piper Cherokee service manual from the 1970s, and you'll note that the manufacturer gets pretty specific about certain things, such as requiring spark plugs to be torqued into the cylinders at between 360 and 420 inch-pounds, and fuel primer jets to be tightened at 60 inch-pounds. Forces necessary to ensure holding power are frequently specified by manufacturers, but when they're not, mechanics are required to exercise sound judgment based on skill and experience. As pilots, this is just one more area in which we have to trust that our mechanics aren't going to let us down. The chances of a pilot being able to detect an improperly torqued part even in what seems to be a thorough pre-flight inspection are pretty slim. If installed properly, the spark plugs, fuel primer jets and numerous other parts on which your life depends will stay put despite the vibration, heat, cold and stresses that are part of everyday flying. When things aren't secured as they're supposed to be, it sometimes becomes the NTSB's business.
展开▼
