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that was perpendicular to the vibrating center plate (see figures D-14 and D-15 in appendix D).
In the NAC TR-2333 test program, a bend was placed in both ends of the bundle, but for this
program, only one end contained a bend so that the impact of this configuration could be
compared to that of a straight bundle.
B.4.1.2 Environmental Conditioning and Electrical Testing.
The bundles were subjected to the vibration profile shown in figure B-1. This profile is similar
to the one that produced the insulation wear documented in NAC TR-2333. The vibration testing
was stopped after 100, 250, and 500 cumulative hours for visual inspection and dry insulation
resistance and dielectric withstand voltage testing. The bundles remained on the fixtures for the
visual examination and dry electrical testing. After this testing had been completed, the bundles
were removed from vibration fixtures and subjected to wet insulation resistance and dielectric
withstand voltage testing. The clamps, tiedown straps, and lacing string were then removed to
permit a more thorough visual inspection of the wires and surfaces of the support components
that were in contact with the wires.
FIGURE B-1. RANDOM VIBRATION PROFILE
B-6
B.4.1.3 Specific Tests.
Detailed descriptions of the tests performed during the execution of the group I test program
follow.
a. Visual Inspection. After 100, 250, and 500 hours of vibration, the wire bundles were
inspected while still mounted on the test fixtures. The inspections were designed to
document things such as damage to the wires and support components; rotation of the
heads of the tie wraps; 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.
b. Dry Electrical Testing. After 100, 250, and 500 hours of vibration conditioning, the
fixtures and wire bundles were removed from the vibration table and subjected to dry
electrical tests using a DITMCO test station. The parameters of the testing were as
follows:
• Insulation resistance:
500 Vdc, 1000 megohms pass/fail threshold, 1 second dwell
• Dielectric withstand voltage:
1000 Vac (500 Vac/second ramp), 1 mA leakage current, 1 second dwell
The unterminated end of each wire was dipped in RTV to prevent dielectric withstand
voltage or insulation resistance failures from adjacent exposed conductors.
c. Wet Electrical Testing. After being subjected to the 500 hours of vibration conditioning,
visual examination, and dry electrical testing, the bundles were removed from the test
fixtures and soaked for a minimum of 1 hour in a 5% sodium chloride water bath, then
subjected to wet electrical testing using the following parameters:
• Insulation resistance:
500 Vdc, 1000 megohms pass/fail threshold, 1 minute dwell time
• Dielectric withstand voltage:
1000 Vac (500 Vac/second ramp), 1 mA leakage current, 1 minute dwell time
d. Visual Inspection of Disassembled Bundles. Following the wet electrical testing, the
clamps, tiedown straps, and lacing string were removed, and the wires were separated to
allow for a more thorough inspection of the complete insulation surface. The inspections
were designed to document outer wire wear from the clamps, plate, straps, and lacing
string; inner bundle wire-to-wire wear; and wear on the clamps, straps; and lacing string.
B-7
B.4.2 Group II.
Twenty-four of the original forty-eight wire bundle types were selected to be contaminated with
fluid, and a similar set of twenty-four to be contaminated with metal shavings. The selected
combinations are shown by the unshaded cells in table B-5.
TABLE B-5. GROUP II TEST COMBINATIONS
Wire
Type 1 2 3 4 7 9 10 11
1
2
3
4
7
9
10
11
B.4.2.1 Assembly of Bundles.
The bundles were supported and clamped the same as in group I.
B.4.2.2 Environmental Conditioning.
The center sections of one set of the 24 wire combinations in table B-5 were soaked for 4 hours
in Skydrol 500B4 hydraulic fluid, which meets Standard SAE AS1241, “Fire Resistant
Phosphate Ester Hydraulic Fluid For Aircraft,” at a temperature of approximately 50°C, then
allowed to drip dry.
An equivalent set of wire bundles was contaminated with aluminum drill shavings by birdcaging
the center section of the bundles before installing the clamps, tiedown straps, and lacing
string to allow the shavings to become entrapped within the bundle.
The bundles were subjected to the same vibration profile as in group I. The vibration testing was
stopped after 100 and 250 cumulative hours for visual inspection and dry insulation resistance
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