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and dielectric withstand voltage testing. The bundles remained on the fixtures for the visual
examination and dry electrical testing. After this testing was completed, the bundles were
removed from the 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.
B-8
B.4.2.3 Specific Tests.
Prior to the vibration conditioning, the bundles were subjected to dry insulation resistance and
dielectric withstand voltage testing. No failures were noted. Following the environmental
conditioning, the same tests were performed as in group I.
a. Visual Inspection. After 100 and 250 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 and 250 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 250 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-9
B.4.3 Group III—Crush Test.
Fourteen-inch lengths of untested wires were subjected to a crush test at room temperature to
determine which wire insulations were more susceptible to damage. The test method was a
variation to the standard dynamic cut through test, with the difference being that two
perpendicular wires are compressed against each other instead of a blade being pressed on a
wire. The same 24 wire combinations that were evaluated in group II were subjected to the crush
test. For each combination of wires tested, eight crushes were performed at approximately 1/2-
inch intervals. Half of the crushes were performed with an 80-pound load applied and half with
a 120-pound load. The wires were then evaluated for damage.
B-10
APPENDIX C—TEST DATA
TABLE C-1. GROUP I VISUAL OBSERVATIONS ON MOUNTED BUNDLES
On Bundle Number*
Condition Observed
After 100 hrs
Vibration
After 250 hrs
Vibration
After 500 hrs
Vibration
Twisted pairs separating
from bundle
Strap rubbing on center
plate
2-12, 14, 18, 22, 23,
28, 31, 37-39, 41, 45-
47
2-12, 14, 16, 18, 20,
22, 23, 26, 28, 30,
31, 35, 37-39, 41,
45-47
1, 2, 8-10, 14, 18,
22, 28, 30, 31, 35,
37-40, 45, 47
Wire rubbing on plate 1, 2, 4-6, 8, 10, 12,
14, 16-18, 20, 22, 25,
27-33, 35-40, 42-47
1, 2, 4-6, 8, 10, 12-
15, 17-22, 24, 25,
27-33, 35-47
1, 2, 4-6, 8, 10-12,
14, 17-20, 22, 24,
25, 27-33, 35-37, 39-
48
White residue from clamp
or wire insulation
1, 13, 25, 36, 37, 48 1, 5, 8, 12, 13, 15,
18, 20, 22, 24, 25,
27, 29, 32, 36, 37,
39, 48
Bundle slipping in clamp 11-13, 23-25, 29, 35,
36, 47, 48
1, 2, 4, 5, 11-13, 17,
20, 23-25, 29, 30,
33, 35, 36, 47, 48
All
Lacing string cutting into
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