Technical data

13773-001
20-50
Page 2 30 Nov 2000
Note: Widely spaced multiple groups shall mean those in which fasteners are from four
to six inches apart.
(3) General Installation Procedures
CAUTION: Screws in closely spaced geometric pattern which secure hydraulic or air seals,
hold hydraulic pressure, or are used in critical areas should use the double-twist
method of lockwiring. Lockwiring shall not be used to secure fasteners or fittings
which are spaced more than six inches apart, unless tie points are provided on
adjacent parts to shorten the span of safety wire to less than six inches. When
safety wiring closely spaced multiple groups, the number of units that can be
safety wired by a 24-inch length of wire shall be the maximum number in a series.
Note: Safety wire 0.20 inch (0.5mm) in diameter shall have 10 to 13 twists per one inch
(25.4 mm).
Safety wire 0.032 inch (0.8mm) in diameter shall have 6 to 12 twists per one inch
(25.4 mm).
(a) Ensure fasteners to be safetied are correctly tightened and, where specified, torqued.
(b) Start and finish twisting the safety wire within 0.109 inch (3 mm) of the wire locking hole in
either part (when using the double wire method).
Note: Safety wire between the parts must be tight. The safety wire at the head of
the part must not be capable of being pulled over its head by using finger
tension. The end of the safety-tie (pigtail) must contain a minimum of five
twists, but not to exceed 0.703 inch (18 mm) in length. Twist slightly more
wire than needed for the pigtail.
(c) Cut pigtails square to prevent snagging.
Note: Pigtails should be made without sharp bends to prevent fractures and to
prevent them from touching other components. Use new wire for each
application, never re-use old wire. Parts should be safety wired so that the
wire is placed in tension (pulled on) if a part attempts to loosen.
(4) Required Installations of Safety Wire
(a) Bolts and other fasteners securing critical parts that affect airplane safety and operation.
Note: In blind-tapped hole applications of bolts or castellated nuts on studs, lock-
wiring is installed in the same manner as described for bolt heads. Hollow
head bolts are safetied in the same manner as regular bolts.
(b) Drain plugs and cocks may be safetied to a bolt, nut, or other part having a free tie hole.
(c) External snap rings may be locked if necessary using general locking principles as illus-
trated.
Note: Internal snap rings should not be safety wired.
(d) When locking is required on electrical connectors which use threaded coupling rings, or on
plugs which employ screws or rings to fasten individual parts of which plug together, they
shall be safety wired with 0.020” diameter wire in accordance with locking principles as
described and illustrated.