DOC AIRBUS | AMM A320FBackshell Lockwire Procedure [CFML]
TASK 70-70-00-910-807-A
Backshell Lockwire Procedure
(1) This section describes the standard practices for securing a connector, its backshell, and associate parts by the use of Lockwire.
(2) The lockwire is installed to prevent a part from becoming loose. The wire is installed to apply an opposing force so that a part will not disengage.
(3) The general note section on the engineering drawing should specify the type and size of the safety wire to be used. If no instructions exist, use safety wire per MS20995N20.
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment
B. Referenced Information
3. Job Set-up
Subtask 70-70-00-860-053-A
Subtask 70-70-00-910-053-A
[Rev.10 from 2021]
2026.04.01 12:54:29 UTC
Backshell Lockwire Procedure
WARNING:
USE PROTECTIVE GOGGLES AND GLOVES WHEN YOU REMOVE OR INSTALL LOCKWIRE. EACH TIME YOU CUT LOCKWIRE, REMOVE AND DISCARD IT IMMEDIATELY. LOOSE LOCKWIRE CAN CUT YOU OR MAKE YOU BLIND, AND/OR CAN CAUSE DAMAGE.
CAUTION:
YOU CAN USE SAFETY CABLE OR SAFETY WIRE TO SAFETY THE BOLTS. YOU MUST INSTALL THE SAFETY WIRE OR THE CABLE TIGHTLY. IF YOU DO NOT OBEY THIS PRECAUTION, DAMAGE TO THE PYLON CAN OCCUR.
1. Reason for the Job(1) This section describes the standard practices for securing a connector, its backshell, and associate parts by the use of Lockwire.
(2) The lockwire is installed to prevent a part from becoming loose. The wire is installed to apply an opposing force so that a part will not disengage.
(3) The general note section on the engineering drawing should specify the type and size of the safety wire to be used. If no instructions exist, use safety wire per MS20995N20.
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment
| REFERENCE | QTY | DESIGNATION |
|---|---|---|
| No specific | 1 | CUTTER - WIRE, TWISTER |
| No specific | 1 | PLIERS - TWISTING, SPECIAL |
| REFERENCE | DESIGNATION |
|---|---|
Safety Wiring Connectors and Strain Relief ClampsSubtask 70-70-00-860-053-A
A. Not Applicable
4. ProcedureSubtask 70-70-00-910-053-A
A. Standard Practices for Lockwire
(1) There are three areas of the connector that need safety wiring:
(a) If a not-self-locking coupling nut is used, the coupling nut must be safety wired to a fixed point.
(b) If a backshell is used that provides a saddle clamp for strain relief, the saddle clamp mounting screws must be safety wired.
(c) If a backshell is installed that has safety wiring provisions in the coupling nut, it must be safety wired.
(2) Any non-self-locking coupling nuts used in high vibration areas must be safety wired. This includes the power plant area, and the pylon area.
(4) On strain relief saddle clamps, where a drilled head screw is not provided, replace the existing screw with a drilled fillister head screw of the same strength rating.
(5) All safety wiring is to be of the double twist wire method.
(6) Safety wire must be installed so that if the item being safety wired becomes loose, it will apply a tightening pull on the attached point.
(7) Safety wiring twists must be uniform. There must be six to ten twists per inch.
(8) Excess wire must be cut square and bent back.
Subtask 70-70-00-910-054-A (1) There are three areas of the connector that need safety wiring:
(a) If a not-self-locking coupling nut is used, the coupling nut must be safety wired to a fixed point.
(b) If a backshell is used that provides a saddle clamp for strain relief, the saddle clamp mounting screws must be safety wired.
(c) If a backshell is installed that has safety wiring provisions in the coupling nut, it must be safety wired.
(2) Any non-self-locking coupling nuts used in high vibration areas must be safety wired. This includes the power plant area, and the pylon area.
NOTE: Safety wiring must installed in the direction that fastener or coupler tightening will be maintained.
(3) Where safety wiring is required on a series of two or more equipment mounting screws, the screws must be safety wired with one continuous length of wire. (4) On strain relief saddle clamps, where a drilled head screw is not provided, replace the existing screw with a drilled fillister head screw of the same strength rating.
(5) All safety wiring is to be of the double twist wire method.
(6) Safety wire must be installed so that if the item being safety wired becomes loose, it will apply a tightening pull on the attached point.
(7) Safety wiring twists must be uniform. There must be six to ten twists per inch.
(8) Excess wire must be cut square and bent back.
B. Safety Procedure
(a) Pull half the wire through the hole in the part being safety wired. Pull the right-hand wire end under the other wire end.
1 Use a PLIERS - TWISTING, SPECIAL.
(c) Continue to twist the wires until they reach the attaching point such that if the item being safety wired tends to loosen, it will exert a tightening pull on the anchor. The twisted portion must be within 0.125 in. (3.17 mm) of attach point.
(d) Separate the wires and put one wire through the hole in the attach point.
(e) Join the wires again and twist the wires clockwise 0.25 in. (6.35 mm) to 0.5 in. (12.70 mm) (two to five twists) beyond the attach point.
(f) Cutt off the excess wire with CUTTER - WIRE, TWISTER and bend the end back toward the attach point so that will not cause damage.
NOTE: Lockwire is not reusable: always use new lockwire.
(1) Safety wire the connector, adapter or backshell, as follow: (a) Pull half the wire through the hole in the part being safety wired. Pull the right-hand wire end under the other wire end.
NOTE: When PLIERS-SAFETY WIRE are used, grip the wire near the end so that damaged wire will subsequently be cut off.
(b) Twist the wires in a clockwise direction. Should the item being safety wired require counterclockwise tightening, the order of wire twisting would be reversed. Twist the wires tight enough to prevent loops. There shall be six to ten twists per inch. 1 Use a PLIERS - TWISTING, SPECIAL.
(c) Continue to twist the wires until they reach the attaching point such that if the item being safety wired tends to loosen, it will exert a tightening pull on the anchor. The twisted portion must be within 0.125 in. (3.17 mm) of attach point.
(d) Separate the wires and put one wire through the hole in the attach point.
(e) Join the wires again and twist the wires clockwise 0.25 in. (6.35 mm) to 0.5 in. (12.70 mm) (two to five twists) beyond the attach point.
(f) Cutt off the excess wire with CUTTER - WIRE, TWISTER and bend the end back toward the attach point so that will not cause damage.