Cable Guide: M27500 Specification - NEMA WC 27500 2012 Part Anatomy

The M27500 specification covers the requirements for special purpose and power cables. Commonly used in avionics, aerospace, military, and airframe applications, these constructions are offered in shielded and unshielded cables and are composed of specific conductor sizes, insulation types, number of conductors, shielding material and jacket compounds. Ranging from 1 to 15 conductors, the part number is a combination of digits and letters (not to exceed 16) which help identify the exact components of each cable.

While the mil-spec has been replaced with the NEMA WC 27500 cable specification, industry professionals still refer to the spec as M27500. This particular cable is one of the only products where you can determine the construction and components just by evaluating the part number.

So let’s begin to break down the M27500 cable. M27500-20RC2S06 is one example of a part number on this specification:

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Color Coding and Shield Coverage

Color Code

The identification method is designated by a single character that denotes the color coding, identification sequence, and the amount of shield coverage. Our example indicates a “-” color coding, which requires one white conductor and one white conductor with a blue stripe all shielded with 85 percent coverage.

Shield Coverage 85%	Shield Coverage 90%	MIL-DTL-27500 Terminology	Color Identification Method
-	C	Preferred method Table A-1	Colored Stripes on White Wire-Stripe Color per Table A-1
A	D	Optional Method A Table A-1	Solid Color Wires-Colors per Table A-1
B	E	Optional Method B Table A-3	Band Marking (wire number) per table A-4 on Solid Colors (by AWG) per Table A-3
F	H	Preferred Method Table A-2	Colored Stripes on White Wire-Stripe Color per Table A-2
G	J	Optional Method A Table A-2	Solid Color Wires per Table A-2
K	M	Optional Method C Table A-3	Number Marking on Solid Color Wires (by AWG) per Table A-3
L	N	Optional Method D	Number Marking on White Wires
P	R	Optional Method B Table A-4	Band Marks per Table A-4 on Colored Stripes (by AWG) per Table A-3
S	T	Optional Method B Table A-4	Band Marks per Table A-4 on White Wires
U	V	--	For Color Codes Specified by the Procuring Activity

Preferred Method - Colors are stripes on white insulation (wire #1 has no stripe).

Optional Method A - Colors are solid insulation color. Wires 11-15 have a lighter base color stripe.

1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
White	Blue	Orange	Green	Red	Black	Yellow	Violet	Gray	Brown	Blue/Blue	Orange/Orange	Green/Green	Red/Red	Black/Black

Base Wire Specification

Cable Designators (Basic Wire specifications)

A one or two letter symbol will be used to designate the specification, type, and class of the inner conductors. In the above part , the designator is “RC” meaning the cables inners are M22759/11.

Table A: Color Identification Method for Wire and Shield Coverage

Shield
Coverage
85%

Shield
Coverage
90%

MIL-DTL-27500
Terminology

Color
Identification
Method

-

C

Preferred method
Table A-1

Colored Stripes on White
Wire-Stripe Color per Table A-1

A

D

Optional Method A
Table A-1

Solid Color
Wires-Colors per Table A-1

B

E

Optional Method B
Table A-3

Band Marking (wire number)
per table A-4
on Solid Colors (by AWG) per Table A-3

F

H

Preferred Method Table A-2

Colored Stripes on White
Wire-Stripe Color per Table A-2

G

J

Optional Method A
Table A-2

Solid Color Wires
per Table A-2

K

M

Optional Method C
Table A-3

Number Marking on Solid Color Wires
(by AWG) per Table A-3

L

N

Optional Method D

Number Marking on White Wires

P

R

Optional Method B
Table A-4

Band Marks per Table A-4
on Colored Stripes (by AWG)
per Table A-3

S

T

Optional Method B
Table A-4

Band Marks
per Table A-4 on White Wires

U

V

--

For Color Codes Specified
by the Procuring Activity

Shield Type

Shield style and material

The shield style and material of the overall shields will be designated by a single letter. Above we have an “S” shield which signifies a round silver-coated copper shielding.

Shield Coverage		MIL-DTL-27500 Terminology	Color Identification Method
85%	90%	MIL-DTL-27500 Terminology	Color Identification Method
-	C	Preferred method Table A-1	Colored Stripes on White Wire-Stripe Color per Table A-1
A	D	Optional Method A Table A-1	Solid Color Wires-Colors per Table A-1
B	E	Optional Method B Table A-3	Band Marking (wire number) per table A-4 on Solid Colors (by AWG) per Table A-3
F	H	Preferred Method Table A-2	Colored Stripes on White Wire-Stripe Color per Table A-2
G	J	Optional Method A Table A-2	Solid Color Wires per Table A-2
K	M	Optional Method C Table A-3	Number Marking on Solid Color Wires (by AWG) per Table A-3
L	N	Optional Method D	Number Marking on White Wires
P	R	Optional Method B Table A-4	Band Marks per Table A-4 on Colored Stripes (by AWG) per Table A-3
S	T	Optional Method B Table A-4	Band Marks per Table A-4 on White Wires
U	V	--	For Color Codes Specified by the Procuring Activity

Outer Jacket Material

Jacket material and temperature rating

The type of jacket is determined by a two digit number at the end of the product call out. Depending on the call out, the cable can be a single or double jacket. Single jacketed cables only have an outer jacket, but when double jacketed there is a jacket between a double shield and a jacket covering the outer shield. Since our example states an “06” jacket, we would have a single extruded taped PTFE jacket.

Shield Coverage		MIL-DTL-27500 Terminology	Color Identification Method
85%	90%	MIL-DTL-27500 Terminology	Color Identification Method
-	C	Preferred method Table A-1	Colored Stripes on White Wire-Stripe Color per Table A-1
A	D	Optional Method A Table A-1	Solid Color Wires-Colors per Table A-1
B	E	Optional Method B Table A-3	Band Marking (wire number) per table A-4 on Solid Colors (by AWG) per Table A-3
F	H	Preferred Method Table A-2	Colored Stripes on White Wire-Stripe Color per Table A-2
G	J	Optional Method A Table A-2	Solid Color Wires per Table A-2
K	M	Optional Method C Table A-3	Number Marking on Solid Color Wires (by AWG) per Table A-3
L	N	Optional Method D	Number Marking on White Wires
P	R	Optional Method B Table A-4	Band Marks per Table A-4 on Colored Stripes (by AWG) per Table A-3
S	T	Optional Method B Table A-4	Band Marks per Table A-4 on White Wires
U	V	--	For Color Codes Specified by the Procuring Activity

Identifying the Specification – Every part number will begin with M27500 because this is the specification call out.

Color Code – The identification method is designated by a single character that denotes the color coding, identification sequence, and the amount of shield coverage. Our example indicates a “-” color coding, which requires one white conductor and one white conductor with a blue stripe all shielded with 85 percent coverage.

Conductor Size – The basic wire size of the inner conductors will be identified. In this particular part number, the cable is composed of 20 gauge inners.

Cable Designators (Basic Wire specifications) – A one or two letter symbol will be used to designate the specification, type, and class of the inner conductors. In the above part , the designator is “RC” meaning the cables inners are M22759/11.

Number of Conductors Per Cable-This number defines how many inner conductors the cable will include. Depending on your shield and gauge sizes, the cables will have 1 to 15 conductors. Our example part would be composed of two inner conductors of M22759/11.

Shield style and material - The shield style and material of the overall shields will be designated by a single letter. Above we have an “S” shield which signifies a round silver-coated copper shielding.

Jacket material and temperature rating- The type of jacket is determined by a two digit number at the end of the product call out. Depending on the call out, the cable can be a single or double jacket. Single jacketed cables only have an outer jacket, but when double jacketed there is a jacket between a double shield and a jacket covering the outer shield. Since our example states an “06” jacket, we would have a single extruded taped PTFE jacket.

Breaking down part numbers can help you gain knowledge and understanding about the products you are purchasing and using daily. WireMasters is here to make your job easier! By using our reference sheets, you can reassure yourself on selecting the appropriate cable that best fits your application. By evaluating the M27500 part, we can look at all the cables characteristics without visually seeing the product. Below is a downloadable PDF chart to help you break down the M27500 specification.

WIREMASTERS M27500 PDF CHARTS

M27500

M27500 Base Wire Specification

M27500 Color Codes

M27500 Shield and Jacket Material

WireMasters carries a variety of these cables in stock. We are also on the QPL, which allows us to build U00 cables in-house! You may use these charts and PDF’s as a reference, but also feel free to contact our experienced sales staff for help locating the correct products and solutions for your application. Holding large stock quantities of these cables, we can ship your cable out the door the same day you place your order. If we don’t have the cable you are looking for, we can create a custom cable and work with our manufacturing partners to have it built just for you!