MIL-DTL-13273C
3.6.1.2 Jacket physical properties after aging. After accelerated aging for a period of 96 hours in an
oxygen bomb at a pressure of 300, plus or minus 10 psi, and a temperature of 70°C ± 1°C, the tensile
strength of the jacket shall be not less than 1000 psi, and the elongation shall be not less than 100%.
3.7 Electrical cord construction. The jacketed electrical cord shall be helical in form with adjacent
turns contiguous to form a helical cord having a straight length of cord on each end tangent to the helical
coil. The finished electrical cord shall have a left-hand lay in its helical section. The finished electrical
cord shall have a smooth and uniform jacket. The helix shall have an overall diameter of not more than
.875 inch (22.23 mm) for the 2-conductor cords, and shall not exceed 1.125 inch (28.58 mm) for 3 and 4-
conductor cords. The length of the helical portions, and the length of the straight ends shall be as
specified on the detail drawings.
3.8 Electrical cord extensile and retractile characteristics. The electrical cord prior to meeting any
extensile and retractile requirements shall first be conditioned by extending the coiled portion of the cord
to five times its retracted length and allowing it to retract freely six times. After this conditioning, the
adjacent coils shall be contiguous when the cord is on a horizontal surface.
3.8.1 Stretching. The finished cords shall be capable of being extended to four times its retracted
length, 60,000 times, at a rate of not more than 40 cycles per minute. During any stretching cycle, the
resistance of any conductor shall not vary more than 5% and the maximum resistance of any conductor at
or corrected to 68°F. shall not exceed the maximum value at the start of the test by more than 10%. After
completion of the stretching test, the cordage shall return to within 20% of its original retracted length
within one hour.
3.8.2 Extended length.
3.8.2.1 Extended under load. The finished cord when suspended vertically shall be capable of
extension at room temperature to at least 2.5 times its retracted length under a load of eight ounces for 2-
conductor cord and ten ounces for 3 and 4-conductor cord.
3.8.2.2 Extended, no load. The finished cord when suspended vertically shall be capable of
extension at room temperature to 5 times its retracted length; if released immediately it shall return to
within 10% of its retracted length within five minutes.
3.8.3 Low temperature extension.
3.8.3.1 Low temperature extension (-40 ± 2°F). After conditioning by placing for not less than 20
hours in a compartment maintained at a temperature of minus 40 ± 2°F, a suitable coiled portion of the
cord shall permit extension to 4 times its retracted length without fracture of the jacket, conductor
insulation, or conductors. Upon release, and while still exposed to the conditioning temperature, the cord
shall retract to not more than 200% of its original length 30 seconds after being released on a horizontal
surface. Frictional restraint shall be relieved by tapping on the surface. Force to extend its retracted
length within 5 seconds shall not exceed 20 pounds. The actual values shall be recorded and forwarded
with preproduction sample test data.
3.8.3.2 Low temperature extension (-65 ± 2°F). After conditioning by placing for not less than 20
hours in a compartment maintained at a temperature of minus 65 ± 2°F, a suitable coiled portion of the
cord shall permit extension to 4 times its retracted length without fracture of the jacket, conductor
insulation, or conductors. Upon release, and while still exposed to the conditioning temperature, the cord
shall retract to not more than 200% of its original length 30 seconds after being released on a horizontal
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