Propeller retorque procedure ?

I was surprised when my Bellville washer kits came from Catto with instructions to periodically retorque. I was naively expecting the Bellville washers to eliminate the periodic retorque.

After reading the archives about Belleville Washers, the term ?retorque? comes into question. Static friction is at play both tightening AND untightening. So how does one say ? the torque WAS correct? ? It seems to me the only correct process is to just loosen the bolt, assure proper ?lightly lubricated threads? and reinstall the bolt with continuous movement to the proper torque..
So educate me. How does one confirm? the torque was OK? without starting over ?

Typically the retorque requirement for a propeller is because it is made of a dimensionally unstable material (wood). It will seasonally change in dimension because of temp./humidity changes, etc. If it shrinks, there will obviously be a loss in bolt tension preload and even with nordlock washers simply retorquing should bring it back up to spec. Some have argued over the years that the bolts should be loosened every time the torque is checked because if the prop has dimensionally expanded, the preload on the bolts is likely higher than desired, so that should be corrected. There is enough tolerance allowance above the standard spec for the bolts that this isn't necessary. In fact it can be counter productive because if there is a major seasonal change in the humidity back in the opposite direction, being just a little tight will allow it to go back to normal on its own, but if you lower the preload, it will then be shifting to under torqued.

How critical doing a retorque procedure is depends on many factors but one of the biggest is what the weather environment is like that the airplane primarily operates in.
Back when I and other friends were flying RV's with wood props (far more common 25-30 years ago), we did a torque check at every oil change.

I have seen (and even heard in flight) what happens when a prob starts to lose its friction preload between the prop extension and crush plate. It is scary.


I think a Catto prop has wood core fiberglass composite construction? If so it will likely need to be treated somewhat the same is a purely wood prop.