Page 36 - Aeronca 7A Interactive Service Manual
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SAFETYING
GENERAL
The word “safetying” is a shop term universally used in the aircraft industry. Briefly, safetying is defined as
“Securing by various means any nut or bolt on the aircraft so that vibration will not cause it to loosen during
operation.”
METHODS
Three basic methods are used in safetying: safety wire, cotter pins, and self-locking nuts or retainer
washers and pal nuts.
Wire, either soft brass or steel is used on cylinder studs, control cable turnbuckles and engine accessory
attaching bolts.
Cotter pins are used on airplane and engine controls, landing gear and tail wheel assemblies or any other
point where a turning or actuating movement takes place.
Self-locking nuts or washers are used only on fairing attachments, or other non-moving components of
the airplane.
Self-locking nuts are secured with fibre inserts at the inside top of the nut. This lock nut should be replaced
any time it is removed from the bolt.
Three types of lock washers – external spider, internal spider, and split types – are used at points on non-
moving parts.
Pal or speed nuts include designs which force the nut thread against the bolt or screw thread when
tightened. These nuts should never be used over again and should be replaced with new when removed.
CAUTION: In the event any safetying should be replaced on the aircraft, it should be
inspected by a licensed aircraft or engine mechanic. Substitution of any one of the three
methods described above, one for another is not permissible.
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