16PR4559_rev_D_Harness_Fab_Braided_Metal_Shielding.pdf

GENERAL DYNAMICS

Fort Worth Division Code Indent: 81755

16PR4559

REV. D

29 JANUARY 1991

F-16 AIRPLANES: ENGINEERING INSTRUCTIONS

FOR FABRICATING WIRING HARNESS BRAIDED

METAL SHIELDING

This document contains Technical Data considered to be a resource under l-402b.3 of DoD Regulation Number 5400.7’-R and is not a Ilrecordl! required to be released under the Freedom of Information Act.

GENERAL DYNAMICS

Fort Worth Division Code Indent: 81755

16PR4559

REV. D

29 JANUARY 1991

F-16 AIRPLANES: ENGINEERING INSTRUCTIONS

FOR FABRICATING WIRING HARNESS BRAIDED METAL SHIELDING

Prepared by:

Systems Interface Components Design

Approved:

fl. (f . Z)M’w- M. E. Duncan Engineering Chief Systems Interface Components Design

L2!(Q6!4$$JL-$

R. O. Roberts Manager Electrical Systems

16PR4559

REV. D

l.. . /

1.0

2.0

2.1

2.2

3.0

3.1

SCOPE

This report describes the F-16 Airplane engineering requirements for the fabrication of braided metal shielding on electrical wiring harnesses. Wiring harness jacket fabrication requirements are described in report 16PR106. The additional requirements for incorporating braided shielding are described herein.

APPLICABLE DOCUMENTS

GD/FW enqineerinq drawinqs and instructions.

H16DW - - - Series, Wiring Harness Drawings

16PR106 Engineering Instructions for Fabricating Wiring Harness Braided Jackets

16PR145 Engineering Instructions for Electrical and Electronic Harness Fabrication

GD/FW additional harness components.

P5440, Wire, Electrical, Copper, Tinned, Annealed

P5372, Tape, Electrical, Teflon

REQUIREMENTS

Harness fabrication Drier to metal braidinq. The harness wire bundle fabrication, forming, spot taping and termination shall proceed as described in 16PR106 paragraph 3.3.1 and 16PR145. In special cases where convoluted tubing or some other component must be added over the braided harness, one or more connectors and associated hardware may be installed later.

After fabrication, the entire harness shall be tightly wrapped with P5372 tape with an overlap of approximately 50%. The tape shall cover all of the wire bundle that will be in contact with the metal braid.

Prior to metal braiding, install those parts necessary for the proper sequence of operations. Identification sleeves, wire terminations, cable shield terminations, connectors and associated hardware, tubular wire braid sleeving, braided plastic sleeves, shrink tubing, and harness identification should be assembled as necessary. If any connectors are to be installed after metal braiding, the installed contacts and associated wires shall be protected by tape or tubing during the metal braiding operation.

3.2 Metal braidinq.

3.2.1 Braid requirements. The braid shall be woven on the

harness so that the minimum coverage is 90%. Opt imum braid angle is 32 degrees. The braid should be push-back (18 degrees to 40 degrees) where possible. For some harness segment diameters this will not be practical. The best combination of braiding wire ends (number of parallel wires on a spool) and braiding machine size (number of carriers or spools) should be selected for the diameter of harness segment being braided. GRAPH I is a general guide for spool ends, machine carriers, and harness segment diameters.

3.2.2 Braidinq wire. Tin coated copper wire per P5440 is to

be used for wiring harness shield braiding. spools of 33 gage wire with 4, 8 or 12 ends (parallel wires) per spool are used as required for the best braid configuration.

3.2.3 Amlication of metal wire braid to the wirin~ harness.

3.2.3.1 Braidinq harness branches.

Metal braid the harness branches (break-outs) first.

Start with a pigtail and braid over the harness branch to the main trunk and over the main harness trunk for a distance of 1 to 2 inches. Terminate in a pigtail and clip the pigtail to a length of approximately 1,/2 inch.

Bend the pigtail down over the metal braid. If necessary, tape the pigtail down over the metal braid but do not tape over more than 1/2 inch pigtail length.

Apply metal braiding to the other harness branches in the same manner. Any harness branches that are not to be metal braided should have metal braid applied over the last 2 inches of the branch to the main trunk and on the main trunk in the normal manner. Cut the pigtails to 1/2 inch length at both ends and fold over on the braid. Secure if necessary.

3.2.3.2 Braidinq the main harness trunk. After all the harness branches have been metal braided, the main harness trunk should be metal braided. Start with a pigtail at one end and braid over the main trunk. Locations of the braid starting and ending points are described in Paragraph 3.2.3.4.

3.2.3.3 Harness chanqes. Wiring harness design changes may

require removal of some or all of the metal shield braid to permit wire additions or rerouting. Where applicable, re-braiding shall follow the procedures previously described.

In some instances significantly faster and less expensive methods of re-braiding production harnesses are indicated. It will be acceptable in these cases for harness branches to over-braid the main harness trunk and for braid junctions to be formed on straight runs. In each case the overbraiding shall overlap the underbraid by 1 to 2 inches of metal to metal contact and a short pigtail shall be formed at the ends of the overbraid.

3.2.3.4 Metal braidinq at electrical connectors. Sufficient

metal braid must be applied to permit metal braid plus any shield wire that may be contained within cables in the bundle to extend into the connector grounding or retaining ring. From date-of-release of this document on ~ metal braid should maintain adequate, full 360 degrees coverage, around the connector EMI backshell.

All stops and starts shall have a back-braid with a metal-to-metal overlap of 1 to 2 inches. There are two methods of applying metal braid at electrical connectors:

(1)

REV. D

Use of C1OOO86-XX expandable metal sleevinq. This sleeving must be slid over the bundle prior to connector installation and harness braiding. The large end of the tapered sleeve should be locked into the compression ring of the backshell per 16PR145, Section 8, then stretched until snug around the bundle. The goal is to provide the maximum push-back achievable. Harness braid shall be back-braided over the expandable metal sleeve with a metal-to-metal overlap of 1 to 2 inches.

(2) Use of metal braidinq with push-back anqle.

Length of push-back braiding should be established to allow insertion and removal of wire terminations without permanent deformation of the braid. This braiding can be done:

(a) Braiding may be done either with or without connectors installed. If braiding is done prior to connector installation, apply metal braid close to the wire and cable ends creating sufficie-nt excess braid to permit termination when connector is added. Start and finish with a pigtail as applicable.

Remove the pigtail at the connector end. If braiding is done after connector installation, start with a pigtail and metal braid over the connector starting near the mating face (providing sufficient braid length for subsequent termination in the EMI backshell) . Where the metal braiding ends at a connector, overbraid the connector and terminate in a pigtail in the same manner as braiding starting at a connector. Remove the pigtail at the connector end.

(b) Braiding may be done either as a continuation of the harness braid or a different braiding machine may be used either before or after harness braiding. If braiding is done on a different braiding machine from harness braid, back-braid over the connector wire braid with a metal-to-metal braid overlap of 1 to 2 inches.

An alternative method to achieve a push-back angle is to braid over a split tube placed around the harness, then remove the split tube and stretch braiding to install in the EMI backshell.

3.2.3.5 Shieldinq braid criteria. The finished braid on the

harness should be free of loops or unbraided areas.

The braid may be moved slightly along the harness length to obtain a more uniform appearance.

The shield coverage should be 90% minimum. This can be calculated from braid measurements as specified in specification MIL-C-27500 paragraph 4.5.5. The recommended method is to gage the spacing between parallel wire groups. The perpendicular distance between wire groups (gap between parallel groups) is measured in terms of individual braid wire widths per Table I.

Table I - Braid Criteria for 90% Minimum Coverage

Space Between Wire Groups Number / Max. in of Ends Avera~e Non-Uniform Sections

4 ,// 2 wires max. 2-1/2 wires max.

8“ less than 4 wires 5 wires max.

.1;2 less than 6 wires 7-1/2 wires max.

3.2.4 , Harness fabrication after metal braidinq.

After all metal shield braiding of the harness is complete and

/ the metal braid is properly positioned, the entire / wiring harness metal braid shall be wrapped with tape i i’ up to the location of the C8844 sleeving securing position on the harness or at the end of the metalf braid on ends not using a connector. The P5372 tape shall be tightly wrapped with some overlap but not more than 50%.

The wiring harness shall then be braided with thread inI accordance with 16PR106. The shield connections at all harness ends, the C8844 expandable sleeving, and other hardware and identification shall be installed to complete the harness fabrication in accordance with

16PR145.