1. WIRE
The usual choice for aircraft wiring is MIL-W-22759/16 (often abbreviated as M22759/16). It’s a multi-strand tinned copper wire coated with Ethylene Tetrafluoroethylene (Tefzel) insulation. The basic part number is followed by two “dash numbers.” The first indicates wire gauge and the second, insulation color.
ColorCodes.png
There are a few additional color codes that are fairly uncommon in the wild: P = pink, T = tan, D = dark (i.e. D6 = dark blue), L = light (i.e. L6 = light blue). Striping is indicated by two color numbers: -90 would be white with black stripe. Twisted pairs are sometimes called out by separating the conductor colors with a forward slash: -95/96 would be a twisted pair composed of white with green stripe and white with blue stripe.
It’s perfectly acceptable to use one color – usually white – for everything, but if you do this be sure to do a good job labeling your wires, twisting the correct pairs and keeping the pinout matched from end to end in harnesses.
If buying wire in 100’ increments in standard colors, Skygeek has good prices.
For shorter lengths, or for custom color striping, ProWire USA is a great source. They have a 10’ minimum for standard colors and they make custom striped wire at very reasonable prices with a 100’ minimum.
Also be sure to check the Bargain Bin at American Wire & Cable (click “MIL-Spec Wire & Cable” in the menu on the left, then “M22759”).
2. D-SUB CONNECTOR BODIES
This is one item for which Aircraft Spruce is very competitive on price. They sell good quality AMP connector bodies cheaper than any place I’ve found. Common sizes hold 9, 15, 25, 37 or 50 pins. Your avionics installation manuals will describe the sizes you need. Pay attention to connector gender, which is determined by contact type, not connector body. The female connector uses sockets and the male uses pins, but the female connector fits inside the male.
D9M_D9F_Connectors.jpg
Top: male. Bottom: female.
Links to connector bodies at Aircraft Spruce:
SteinAir stocks similar connectors, including 50-pin and high density types, as well as contacts, backshells and cinch nuts.
Be careful not to buy high density connectors or contacts unless that’s really what you need.
3. D-SUB CONTACTS (PINS & SOCKETS)
As I mentioned in Part 1, I recommend using turned, not stamped-and-formed contacts. The turned parts are more expensive, but they’re much easier to use, and to get consistently good results with. A cheap, generic 4-way indent tool will crimp turned pins and sockets just fine. Finding a tool with good dies for stamped-and-formed contacts is a challenge at reasonable prices, and getting consistently good results with them takes skill and practice.
Turned pins for male connectors – P/N: M39029/64-369 or 205089-1
Turned sockets for female connectors – P/N: M39029/63-368 or 205090-1
Both are available from any electronics parts distributor, or from...
B&C Specialty Products (pins / sockets)
SteinAir (pins / sockets)
Aircraft Spruce (pins / sockets)
There’s also an eBay seller offering bags of 100 at very attractive prices (pins / sockets).
4. D-SUB BACKSHELLS
This is the plastic or metal case that holds the connector body and provides strain relief for the wires. You can spend a small fortune on fancy metal backshells, but I wouldn’t bother. The Dynon factory uses inexpensive plastic parts (Assmann WSW “A-FT” series). You’ll need one for each d-sub connector you install.
SteinAir sells similar parts at similarly low cost.
5. D-SUB CINCH NUTS
The Assmann WSW “A-FT” series backshells come with thumbscrews to hold the (usually female) connector in place. Those work great in cases where your harness will connect to an avionics box that has a (usually male) connector with cinch nuts already installed. However, if you need to make an extension harness with both male and female ends, you’ll need a pair of cinch nuts for the male end (in place of the thumbscrews), so that a female connector’s thumbscrews can clamp the connectors together.
You’ll need so few of these that there’s little point in shopping around. Aircraft Spruce sells them in a complete set, with washers and #4-40 hex nuts to install them on the connector body, for $1.35/set. If you prefer, SteinAir sells connector bodies with cinch nuts already installed.
Note that you may have to clip away part of the molded internals of the backshell to install a connector with cinch nuts attached.
6. HEATSHRINK TUBING
The good stuff is so cheap, there’s no reason to use anything else. I use Qualtek "Q5-3X" series, which has a 3:1 shrink ratio (meaning it shrinks to 1/3 of its original diameter) and is both adhesive-lined and flame retardant. Digi-Key carries it in several useful diameters, in 4’ lengths.
I find that the 0.354” inside diameter Q5-3X tubing is a good fit over expandable sleeve on a 9-wire Dynon SkyView network harness.
7. EXPANDABLE SLEEVING (OPTIONAL)
This stuff isn’t strictly necessary, but it makes for a professional looking harness. If you prefer not to use expandable sleeve, then wire bundles can be dressed with nylon cable ties or lacing cord. For expandable sleeve, I use Techflex Clean Cut FR. 1/4” diameter sleeve costs ~$0.53/ft in 100’ rolls. It will easily expand (like a Chinese finger puzzle) to cover wire bundles up to about double its nominal diameter, so I don’t bother with the larger, more expensive sizes. The main advantages in using expandable sleeve are that the harness remains more flexible than if it’s dressed with cable ties or lacing cord, and it’s less likely to get caught on something while it’s being fished through the aircraft.