Aircraft electrical parts are the hardware that terminates, joins, protects, supports, and grounds aircraft wiring. That covers ring terminals, splices, connectors and contacts, heat-shrink tubing, cable ties, grommet edging, terminal blocks, and bonding jumpers. The FAA's AC 43.13-1B, Chapter 11, sets out acceptable practices for each of these [1].

WHAT'S IN STOCK

OneMonroe's electronics components cover most of the wiring hardware in this guide, including:

- MS25036 ring terminals
- M81824/1 splices
- D38999, MS3106, and MS3116 connectors, plus M39029 contacts and MS3181 covers
- M23053/5 heat-shrink tubing
- MS3367 cable ties and MS21266 grommet edging
- M81714 junction (terminal) blocks
- MS25226 and M83519 parts, switches, and other electrical products
- MS25083 and M83413 bonding jumpers

RING TERMINALS

MS25036 terminals are insulated, copper ring-tongue crimp terminals. Boeing's distributor listings describe them as closed-barrel, nylon-insulated, 300 V terminals sized by wire gauge and stud size [2]. Shop ring terminals.

What the FAA says about terminals:

- Pre-insulated crimp-type ring-tongue terminals are preferred [1].
- Select by current rating, wire size and insulation diameter, conductor and insulation compatibility, stud size, and environment [1].
- Match the terminal's stud hole to the stud diameter [1].
- No more than four terminal lugs, or three lugs and a bus bar, on any one stud [1].
- Don't put spacers or washers between terminal tongues [1].
- Copper solderless crimp terminals should conform to MIL-T-7928 [1].

SPLICES

M81824/1 splices are insulated, environment-resistant, permanent crimp splices for copper wire, qualified under SAE AS81824 [3].

AC 43.13-1B's splicing rules [1]:

- Keep splices to a minimum, and avoid them in areas of extreme vibration.
- Self-insulated splice connectors are preferred.
- Environmentally sealed splices are a reliable option in SWAMP (severe wind and moisture) areas.
- No more than one splice in any wire segment between two connectors or disconnect points, with a few listed exceptions.
- Stagger splices in a bundle so the bundle doesn't grow.
- Don't splice within 12 inches of a termination device, except in the cases the AC lists.

CRIMP TOOLS

Terminals and splices are only as reliable as the crimp. The FAA says terminal lugs and splices must be installed with a high-quality ratchet-type crimping tool, preferably calibrated [1]. Inspect the tool so its full-cycle ratchet can't be released mid-crimp, and use go/no-go gages before crimping [1]. A crimp that's too deep or too shallow can cut strands or fail to hold the wire [1].

CONNECTORS AND CONTACTS

OneMonroe's mil-spec and commercial connectors include D38999 and MS3106/MS3116 styles. M39029 crimp contacts fit connectors such as MIL-DTL-38999 Series III, according to Glenair's AS39029 contact catalog [4].

AC 43.13-1B connector guidance [1]:

- Use environment-resistant connectors where they'll be exposed to fluids, vibration, heat, mechanical shock, or corrosion.
- Replace a connector with one of the same basic type and design.
- Use the proper insertion or extraction tool on crimp-type connectors.
- Fill every contact cavity with a wired or unwired contact. Unwired contacts get a sealing plug.
- Make sure connectors are fully mated and that coupling nuts are safetied where the maintenance manual requires.
- Cover unused plugs and receptacles to keep out dust and moisture. Receptacles get dust caps; plugs can get a dust cap or polyolefin shrink sleeving.
- Mount connectors so moisture drains out of them when unmated.

HEAT-SHRINK TUBING

M23053/5 is a mil-spec, crosslinked polyolefin heat-shrink tubing, formerly MIL-I-23053/5 [5]. AC 43.13-1B recommends polyolefin sleeving where resistance to solvents and synthetic hydraulic fluids is needed [1]. Browse heat-shrink tubing.

Where the FAA calls for shrink sleeving:

- Over noninsulated splices, using dual-wall shrink sleeving of a suitable material [1].
- Over terminals that aren't pre-insulated, secured so it can't slip [1].
- As printed wire-identification sleeves, shrunk with the manufacturer's recommended heating tool [1].

One limit: insulating tubing protects wire from chafing and fluids, but the FAA prohibits using it to support wire in place of stand-offs [1].

CABLE TIES, CLAMPS, AND GROMMETS

MS3367 ties: AC 43.13-1B Table 11-22 lists MS3367 miniature, intermediate, standard, and heavy straps by bundle diameter, installed with MS90387 tools at set tension [1].

Limits on plastic straps: The AC says straps may be used where temperatures don't exceed 120°C, but not in SWAMP areas such as wheel wells, in high-vibration areas where failure could let wiring chafe or foul linkages, or where they're exposed to UV unless UV-resistant [1].

Clamps: Support wire bundles with MS21919 clamps at intervals not exceeding 24 inches. Clamps should fit snugly without pinching [1]. Ties between clamps don't replace adequate clamping [1].

Grommets: MS21266 grommet edging is a molded nylon 6/6 strip for protecting wire at hole edges [6]. The FAA says to use protective grommets wherever wires can't be clamped to keep at least 3/8 inch clearance from structure at penetrations [1].

TERMINAL BLOCKS

The FAA's inspection items for terminal blocks [1]:

- Blocks are securely mounted with adequate electrical clearance or insulation strips.
- Connections and nuts on unused studs are tight.
- No more than four terminal connections per stud unless specifically authorized.
- Cracked terminal strips and stripped studs are replaced.

BONDING JUMPERS

Bonding jumpers provide a low-resistance electrical path between parts and structure. AC 43.13-1B guidance [1]:

- Keep jumpers as short as practical. Each connection should not exceed 0.003 ohm.
- Remove paint and anodizing at the contact area. On aluminum, apply a conductive chemical treatment such as Alodine within 24 hours.
- Don't use self-tapping screws for bonding. Use standard threaded screws or bolts.
- Aluminum alloy jumpers are recommended for most cases. Use copper jumpers to bond stainless steel, cadmium-plated steel, copper, brass, or bronze.
- Don't let jumpers interfere with movable controls.

For washer types and materials, see our overview of aircraft washers.

FAQ

Q: How many terminals can go on one stud?
A: No more than four terminal lugs, or three lugs and a bus bar, per AC 43.13-1B [1].

Q: Can I use nylon cable ties anywhere on an aircraft?
A: No. The FAA limits plastic straps to areas at or below 120°C and bars them from SWAMP areas, high-vibration areas where failure could cause damage, and UV exposure unless UV-resistant [1].

Q: How far apart should wire bundle clamps be?
A: No more than 24 inches apart [1].

Q: What resistance should a bonding jumper connection have?
A: No more than 0.003 ohm per connection [1].

Q: What should I do with empty connector contact cavities?
A: Fill them with unwired contacts and sealing plugs, per AC 43.13-1B [1].

Shop: Electronics Components | Ring Terminals | Connectors | Heat Shrink Tubing | Bonding Jumpers

Related Guides: Aircraft Washers | Aircraft Screws

This guide is part of the Monroe Aerospace Guides library. Browse the full library, or contact our team to source a hard-to-find electrical part.

References

[1] FAA, AC 43.13-1B, Chapter 11, Aircraft Electrical Systems: https://www.faasafety.gov/files/events/SO/SO35/2020/SO35100907/AC_43.13_Chapter_11_Electrical.pdf
[2] Boeing Distribution, TE MS25036-107 PIDG Ring Tongue Terminal: https://shop.boeing.com/cpd/bdi_ms25036-107=3c
[3] NAVAIR, Supplemental Information Sheet for QPL 81824 (SAE AS81824 splices): https://www.navair.navy.mil/qpl/sites/g/files/jejdrs526/files/document/%5Bfilename%5D/QPL-81824-11-SIS.pdf
[4] Glenair, SAE-AS39029 Crimp Contacts: https://www.glenair.com/as39029-qpl-and-glenair-commercial-high-performance-connector-contacts/sae-as39029-crimp-contacts/
[5] Electro Insulation, M23053/5 Polyolefin Heat Shrink Tubing: https://www.electroinsulation.com/mil-spec/m23053-5.html
[6] Essentra Components, MS21266 Grommet Strips: https://www.essentracomponents.com/en-us/s/cable-grommets/grommet-strips/serrated-strip