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Insulations,” dated 8 June 1983, was used for this program. Previous testing has shown that
significant wire abrasion can be achieved within 500 hours using this method.
Selection of the wire types took into consideration the differences that fillers can have in the
PTFE construction by taking types that vary in filler content, and in the construction differences
of extrusions versus tape-wrapped products. The PTFE insulated wire may behave differently
than the PI/PTFE due to the rigidity of the polyimide underneath the PTFE wrap. Also, to test
the theory that conductor differences could play a part in the interaction of wire types, two alloy
constructions were tested. Three-way combinations were not expected to have more degradation
than a two-wire interaction.
The specific wire types tested are shown in table B-3.
TABLE B-3. WIRE TYPES, SPECIFICATION OR COMMERCIAL EQUIVALENT
Wire Code Wire Type Part Number
1 PVC/glass/nylon MIL-W-5086/2-22-9
2 PI BMS13-51T08C01G22-50
3 XPI, alloy Spec 88A
4 XLETFE BMS13-48T08C01G22
5 XLETFE, alloy MIL-W-22759/42-24-9
6 PTFE, extruded MIL-W-22759/9-22-9
7 PTFE, extruded mineral-filled MIL-W-22759/8-22-9
8 PTFE, tape wrap Not included in program
9 PTFE/glass MIL-W-22759/1-22-9
10 PI/PTFE BMS13-60T19C01G22
11 PI/PTFE, alloy BMS13-60T04C1G22
B.4. TEST PROCEDURES AND DATA COLLECTION.
4.1 Group I.
A total of 48 wire combinations were tested in group I, which consisted of bundles that were
uncontaminated, and were subjected to 500 hours of vibration conditioning. The unshaded boxes
shown in table B-4 were the combinations selected for group I of the program.
B-4
TABLE B-4. GROUP I TEST WIRE COMBINATIONS
Wire
Type 1 2 3 4 5 6 7 8 9 10 11
1
2
3
4
5
6
7
8
9
10
11
The shaded areas are duplicate or very implausible wire combinations that were not tested. Nonmineral-
filled PTFE insulated wire is not normally approved for use in open wire harnesses;
however, it was included in this study to baseline the PTFE with the mineral filler. Nylon can
crack off the insulation, leaving behind glass braided PVC insulated wire. (Other wire types
incorporate the use of glass braid in the outer layer of larger gauge sizes for mechanical
protection.) It is anticipated that wire in this condition will be replaced at the same time that the
new wire is added, eliminating the need to have a glass braid vibration test. Nylon, which cracks
off the wire, can cause foreign object damage in the wire bundles that may accelerate the
degradation. Fluids, metal shavings, and other debris may also accelerate the degradation of the
wire. Coaxial cables generally have FEP, PTFE, or XLETFE insulations that would behave
similarly to the wires listed in this test program; however, rubber types are not incorporated in
this test program. Therefore, twisted pairs were tested in a limited fashion, since it is possible
that these constructions would increase the stress placed on adjacent wire. The ultimate
degradation mechanism for the two wire types, however, would be identical.
B.4.1.1 Assembly of Bundles.
Similar to the NAC TR-2333 testing, wire bundles consisted of 20 wires of the same or two
different types of insulation. Each bundle consisted of 12 single wires and 4 twisted pairs that
were cut to approximately 36 inches in length. For bundles containing two wire types, half of
the singles and twisted pairs were of each wire type. The wires were installed so that each wire
type would have single wires and twisted pairs located in the outer and inner portions of the
bundles. Annealed copper type constructions were 22 gauge, whereas alloy type conductors
were 24 or 22 gauge, indicative of the actual sizes used in the aircraft. One end of each wire was
terminated with an electrical contact and installed in a connector. The unterminated end of each
wire was dipped in RTV to prevent dielectric withstand voltage or insulation resistance failures
from adjacent exposed conductors rather than wear from the vibration testing. Tiedown straps
and lacing string were alternately used on the bundles to contain the wires, and MS21919
cushion clamps were used to secure the bundles to the vibration fixtures. The clamps mounted
on the vibrated center plates were 11 inches apart. The lacing string and the tiedown strap
B-5
installed on the bundle between those clamps were approximately 3 inches from the clamps. The
lacing string and tiedown strap installed between the clamps on the stationary plates and the
vibrating center plate were spaced at approximately 3-inch intervals. A bend was put into the
nonterminated end of each bundle, and it was secured with cushion clamps to a stationary plate
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