Use plain washers under lockwashers to prevent damage to material surface.
Use aluminum alloy washers under bolt heads or nuts on aluminum alloy or magnesium structures where
corrosion is a factor.
Use the AN961 brass nonstructural washer in electrical components and instrument mounting where
nonmagnetic properties are required.
AN part number. The AN washer code designation indicates type of washer, material, inside and outside
diameter and thickness. Specific details and dimensions can only be definitely determined by referring to the particular
b. Lockwashers. Use lockwashers, MS35338 (split type) or MS35335, MS35336, MS35790 (internal, external, or
countersunk teeth type), as shown in figures 2-30 and 2-31, with plain nuts when self-locking or castellated-type nuts are
not applicable. Lockwashers may be used to prevent loosening of threaded fasteners in airframe construction under the
Figure 2-28. Airframe Plain Nut
Lockwashers are not to be used on primary structures, secondary
structures, superstructures, or accessories where failure might result in
damage or danger to aircraft or personnel.
Do not use lockwashers on soft metal, such as aluminum or magnesium, without a plain washer
underneath to prevent damage to soft metal surface. Lockwashers shall not be used where their failure
would permit leakage, or on exposed surfaces subject to airflow. Neither shall they be installed in places
where they will be subjected to corrosion conditions, nor in places where they must be removed frequently.
Damage to components may otherwise result.
Do not reuse tabwashers Damage to components may otherwise result.
Figure 2-29. Plain Washer
Figure 2-30. Split Lockwasher