Originally Posted by Eddie P
Hi guys, I’m looking for opinions and techniques.
One of my torque paint stripes on a Jam Nut was partially missing. Sure enough, the jam but on the outer left elevator backed off a few degrees after the last flight. I tightened it up before flight. And admittedly, it was an awkward fit for the wrench I was using.
The torque strip is primarily a QA marking to indicate that it was torqued to final torque during initial installation, but it does nothing to keep it backing off. It is also NOT
for determining if the nut or bolt is loose (although it might do that function). The torque paint can wear off or chip off at some point
. It is not that durable. As mentioned Lok-tite is the way to go. It comes in different flavors. One is temporary (where nut or bolt comes out for maintenance) and one is permanent (self explanatory and you can still take the fastener out but just more difficult). You only need a drop on threads of Lok-Tite.
I would love to hear and see how you guys “keep your nuts in check” without buggering up the nuts or airframe with wrenches. Also, what torque and how do you measure it?
Nuts and bolts most likely to come loose are under the cowl... where there is vibration.
At condition inspection (every year, everytime your cowl comes off) you should check the securiity of all nuts, especially in engine bay and flight controls. Some times you can do it by inspection, depending on they type of nut (safety wired or Castellated). Jam nut locking is hit or miss. If suspect untorque and retorque. I much prefer the nut be drilled for safety wired if it's critical. If a fastener is suspect take the fastener out, inspect the structure, reinstall. If hardware is damaged replace it.
Fasteners don't cost much. Some nuts with nylon inserts can be reused but some will replace them everytime. Spruce Aircraft, Wicks, Van's Aircraft can be sources for hardware. If the finish is scratched replace it. That is for corrosion prevention. Steel bolts and aluminum don't go together. That is why steel bolts have a finish, platin, typically clad or passivated.
To keep hardware from being buggered up use PROPER TOOLS
... Box end wrenches, crow foot, high quality wrenches that fit the bolts with out slop.... Many consumer grade tools are for use on low quality hardware not high tolerance aircraft hardware....
Research the different nuts and locking devices (google). EAA Sport Pilot, Kit Plane magazines and Google are good places to look. Each type has it's advantage and best application. You will see MS or AN specs for hardware which stands for Mil Spec and the older Army-Navy Spec..... Spruce and Wicks catalogs are great for learning hardware.
TYPES OF NUTS:
Nuts with inserts (nylon).
Nuts with all metal clamping for high temperature applications
Castellated nuts used with drilled bolt and cotter pin.
Nut drilled for safety wires.
Jam Nuts (typically two back to back plain nuts)
Plain nuts used with LOCK washers (split, star, serrated)
What nut or washer to use? Good starting point is VAN's building manual and drawings. If you did not get the planes order an electronic one. They will specify the proper nut and washer as applicable.
#1 thing is to have PROPER TORQUE to start with
. Torque and stretching the bolt creates clamping and friction resists the fastener getting loose (as it is stretched). This is typical on engine bolts. HOWEVER don't over torque fasteners. There are standard torques for different sizes, know them. Get yourself a good torque wrench. I recommend more than one torque wrench. A smaller lower torque range dial gauge, and a higher range torque wrench for larger bolts and nuts. The larger ones come in CLICK type or beam type. You can develope a "good and tight" feel, but use a torque wrench when possible. I maintain a BMW motorcycle and EVERY screw, nut bolt has a torque. It is WAY too easy to over torque.