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Glass
10
PI/PTFE
11
PI/PTFE
Alloy
The rationale for selecting the combinations for group I included:
• Selecting a type that would give the most encompassing data when several wire types had
similar characteristics (e.g., wire with copper alloy conductor is stiffer than wire with
annealed copper conductor, and may lead to different results).
• Excluding specific wire combinations that would not be expected in an application. For
example, many of the older aircraft are wired using PVC/glass/nylon insulated wire and
are repaired using the same wire type, but it is not typically used for modifications. Also,
the use of PVC/glass/nylon in combination with polyimide, XPI, PTFE, or composite
(wrapped aromatic polyimide (PI) and PTFE) insulated wire is expected to be minimal.
• Selecting types with which aircraft are typically wired, including in specific applications
and during modifications or repairs. For example, a combination of PVC/glass/nylon
with the mineral-filled PTFE, which is often used as an abrasion-resistant wire
construction in many aircraft, was included. The combination of PTFE and PI/PTFE
composite insulated wire was excluded, since the abrasion resistance variety is more
common.
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Forty-eight wire bundles were also tested in group II, but since two contamination variables
(metal shavings and hydraulic fluid) were introduced, the number of different wire combinations
tested for each contamination type had to be reduced to the twenty-four unshaded combinations
shown in table 3.
TABLE 3. WIRE COMBINATIONS TESTED IN GROUP II
Wire
Type
1
PVC/
G/N
2
PI
3
XPI
Alloy
4
XLETFE
7
MFPTFE
9
PTFE/
Glass
10
PI/PTFE
11
PI/PTFE
Alloy
1
PVC/
G/N
2
PI
3
XPI
Alloy
4
XLETFE
7
MF-PTFE
9
PTFE/
Glass
10
PI/PTFE
11
PI/PTFE
Alloy
The rationale used in selecting the wire combinations for group II was similar to that used for
group I, but also included
• selecting the types most commonly used in aircraft applications.
• removing XLETFE insulated copper alloy conductor wire since the difference between
the alloy and annealed versions was evaluated in the first test group.
• deleting combinations with the PTFE/glass fiber braid type insulated wire, except for the
one mixed with XLETFE insulated wire.
• removing combinations with the PI/PTFE alloy conductor wire, except for the ones with
either XLETFE or the PI/PTFE annealed copper conductor type.
4.5 CRUSH TEST WIRE COMBINATIONS.
The group III crush test was performed on single wires of the same 24 combinations as shown in
table 3.
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5. DISCUSSION AND RESULTS.
Potential risks associated with simulation testing are common in most test situations. These risks
include (1) whether the testing realistically simulates the actual conditions seen in operation, (2)
whether there is control over as many variables as possible, and (3) the variability of test
measurements and observations. To mitigate these risks, previous research, test data, and
procedures were consulted prior to finalizing the test plan. For comparison, mixed wire bundles
were tested with baseline nonmixed wire bundles.
The primary scope of this program was to determine the impact of mixing different wire
insulation types within the same bundle in an aircraft. The test data generated in this program
included electrical measurements, wire-to-wire wear, wear from support components, wear from
contaminants, and resistance to crushing. Summaries and comparisons of the test data permitted
conclusions to be drawn as to the role the variables played in the interactions between the same
wire and different wire types (The data generated for this test program is compiled in
appendix C).
5.1 GROUP I TEST RESULTS.
5.1.1 Visual Observations on Mounted Bundles.
Upon completion of 100, 250, and 500 hours of vibration exposure, the wire bundles were
visually inspected while still mounted on the test fixtures. General observations after 100 hours
of vibration included rotation of the heads of the straps; twisted pairs separating from the
bundles; wear marks on the fixtures from wires, straps; and lacing string; and slippage of bundles
in the cushion clamps. After 250 hours of vibration, additional observations included the
presence of white residue from wire insulation or cushion clamp, lacing string cutting into the
insulation, and wearing of the black wire stripe marking. The same types of conditions were
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