FAA Aviation Mechanic General (AMG)Materials, Hardware and ProcessesEasy
A mechanic is torquing a bolt through an aluminum fitting and installs an AN960 flat washer under the nut before final torque. What is the primary purpose of this washer?
- ATo distribute the clamping load and prevent the rotating nut from damaging the aluminum surface
- BTo act as a self-locking device that prevents the nut from backing off
- CTo reduce the effective bolt diameter needed for the joint
- DTo increase the electrical bonding path across the joint
Show answer & explanationAnswer & explanation
Correct answer: A. To distribute the clamping load and prevent the rotating nut from damaging the aluminum surface
A plain flat washer spreads the bearing load over a larger area and protects the softer aluminum surface from being scored or dented as the nut is torqued, but it does not provide any locking function.
Why the other options are wrong
- B. Locking is provided by cotter pins, self-locking nuts, or safety wire, not plain washers.
- C. Washers do not change the required bolt diameter for a given load.
- D. Electrical bonding is a separate function achieved with bonding jumpers, not washers.
AN960 Flat Washer
A plain steel or aluminum washer placed under a bolt head or nut to distribute bearing load and protect the structure surface, and sometimes used for shimming grip length.
- Distributes clamping load over wider area
- Protects soft materials from nut/bolt rotation damage
- Can be used to adjust bolt grip length
- Does not provide anti-rotation locking by itself
Memory trick: "Washer wide, load divide."