Originally Posted by
sph33r
Good evening all, I was wondering, if you guys could share your knowledge... its a two pronged question, actually...
Which regulatory system? Don't know if this is what your looking for, but here’s the FAA side. However, without more details on the anchor nut/locknut swap I can only give a general reply.
a. how acceptable is it to swap out an anchor nut with a lock nut, and if so is his given anywhere as standard practice?
It is perfectly acceptable to substitute hardware under the FARs provided it follows several requirements. And it’s technically considered an alteration vs a standard practice. How easily the fastener can be swapped depends on if the original installation data is FAA approved or FAA acceptable data, and if the hardware swap is considered a major or minor alteration. Regardless how complicated the latter sounds, a majority of hardware substitutions are considered minor alterations with acceptable data.
The go-to reference that allows the substitution is FAR Part 43.13(a) linked below. It gives the path to pursue with emphasis on the underlined statement after the bolded “or”. That latter statement opens up a large source of guidance docs to include “standard practice docs, specifications docs, etc. But keep in mind which FAR the aircraft is maintained under may also tweak the hardware swap criteria as well.
(a) Each person performing maintenance, alteration, or preventive maintenance on an aircraft, engine, propeller, or appliance shall use the methods, techniques, and practices prescribed in the current manufacturer's maintenance manual or Instructions for Continued Airworthiness prepared by its manufacturer, or other methods, techniques, and practices acceptable to the Administrator, except as noted in §43.16. […]
Part 43.13(a)
A simple example. Aircraft comes with screws installed on a panel that gets removed on a regular basis. You want to replace the screws with bolts due to screw tip wear. You look up the specs for the screws and bolts to see if they are equal or if the bolts are stronger. You then determine if the hardware swap is a major or minor alteration which in this case is a minor. The mechanic swaps out the screws with bolts under a simple logbook entry.
b. how applicable are general standard practices to an aircraft when its own technical manual has its own standard practices?
It depends on what FAR the aircraft is maintained under and if the hardware substitution is defined as a minor or major alteration. But in general Part 43.13(a) allows you to use whatever FAA
acceptable reference you want. Without the specific examples it’s tough to give any better references.