View Latest Blog Entries
Close
Categories
Testing & Assessment Certification Aging Wires & Systems Standard & Regulation Management Maintenance & Sustainment Conference & Report Research Protection & Prevention Arcing Miscellaneous
Popular Tags
Visual Inspection AS50881 MIL-HDBK MIL-HDBK-525 High Voltage FAR Electromagnetic Interference (EMI) FAR 25.1707 AS4373 Maintenance Wire System Arcing Damage
All Tags in Alphabetical Order
2021 25.1701 25.1703 abrasion AC 33.4-3 Accelerated Aging ADMT Aging Systems AIR6808 AIR7502 Aircraft Power System aircraft safety Aircraft Service Life Extension Program (SLEP) altitude arc damage Arc Damage Modeling Tool Arc Fault (AF) Arc Fault Circuit Breaker (AFCB) Arc Track Resistance Arcing Arcing Damage AS22759 AS22759/87 AS23053 AS4373 AS4373 Method 704 AS50881 AS5692 AS6019 AS83519 AS85049 AS85485 AS85485 Wire Standard ASTM D150 ASTM D2671 ASTM D8355 ASTM F2696 ASTM F2799 ASTM F3230 ASTM F3309 ATSRAC Attenuation Automated Wire Testing System (AWTS) Automotive backshell batteries Bent Pin Analysis Best of Lectromec Best Practice bonding Cable Cable Bend cable testing Carbon Nanotube (CNT) Certification Chafing Chemical Testing Circuit Breaker circuit design Circuit Protection Coaxial cable cold bend collision comparative analysis Compliance Component Selection Condition Based Maintenance Conductor conductors conduit Connector connector selection connectors contacts Corona Corrosion Corrosion Preventing Compound (CPC) Cracking D-sub data analysis data cables degradat Degradation Delamination Derating design safety development diagnostic Dielectric breakdown dielectric constant Dimensional Life disinfectant Distributed Power System DO-160 dry arc dynamic cut through E-CFR Electrical Aircraft Electrical Component Electrical Power Electrical Testing Electromagnetic Interference (EMI) Electromagnetic Vulnerability (EMV) EMC EMF EN2235 EN3197 EN3475 EN6059 End of Service Life End of Year Energy Storage engines Environmental Environmental Cycling environmental stress ethernet eVTOL EWIS certification EWIS Component EWIS Design EWIS Failure EWIS sustainment EWIS Thermal Management EZAP FAA FAA AC 25.27 FAA AC 25.981-1C FAA Meeting failure conditions Failure Database Failure Modes and Effects Analysis (FMEA) FAQs FAR FAR 25.1703 FAR 25.1707 FAR 25.1709 fault tree Fixturing Flammability fleet reliability Flex Testing fluid exposure Forced Hydrolysis fuel system fuel tank ignition Functional Hazard Assessment functional testing Fundamental Articles Future Tech galvanic corrosion Glycol Gold Gold plating Green Taxiing Grounding hand sanitizer handbook Harness Design Hazard Analysis health monitoring heat shrink heat shrink tubing high current high Frequency high speed data cable High Voltage HIRF History Hot Stamping Humidity Variation HV system ICAs IEC60172 IEEE Inspection installation installation safety Instructions for Continued Airworthiness insulating material insulating tape Insulation insulation breakdown insulation resistance insulation testing interchangeability IPC-D-620 ISO 17025 Certified Lab ISO 9000 J1673 Kapton Laser Marking life limit life limited parts Life prediction life projection Lightning liquid nitrogen lunar maintainability Maintenance Maintenance costs Mandrel mean free path measurement mechanical stress Mechanical Testing MECSIP MIL-C-38999 MIL-C-85485 MIL-DTL-17 MIL-DTL-23053E MIL-DTL-3885G MIL-DTL-38999 MIL-E-25499 MIL-HDBK MIL-HDBK-1646 MIL-HDBK-217 MIL-HDBK-454 MIL-HDBK-516 MIL-HDBK-522 MIL-HDBK-525 MIL-HDBK-683 MIL-STD-1353 MIL-STD-1560 MIL-STD-1798 MIL-STD-464 MIL-T-7928 MIL-T-81490 MIL-W-22759/87 MIL-W-5088 MIL–STD–5088 Military 5088 modeling moon MS3320 NASA NEMA27500 Nickel nickel plating No Fault Found OEM off gassing Outgassing Over current Overheating of Wire Harness Parallel Arcing part selection Partial Discharge partial discharge at altitude Performance physical hazard assessment Physical Testing polyimdie Polyimide-PTFE Power over Ethernet power system Power systems predictive maintenance Presentation Probability of Failure Product Quality PTFE pull through Radiation Red Plague Corrosion Reduction of Hazardous Substances (RoHS) regulations relays Reliability Research Resistance Revision C Rewiring Project Risk Assessment S&T Meeting SAE SAE Committee Sanitizing Fluids Secondary Harness Protection Separation Requirements Series Arcing Service Life Extension Severe Wind and Moisture-Prone (SWAMP) Severity of Failure shelf life Shield Shielding Shrinkage signal cable Silver silver plated wire silver-plating skin depth skin effect Small aircraft smoke Solid State Circuit Breaker Space Certified Wires Splice standards Storage stored energy supportability Sustainment System Voltage Temperature Rating Temperature Variation Test methods Test Pricing Testing testing standard Thermal Circuit Breaker Thermal Endurance Thermal Index Thermal Runaway Thermal Shock Thermal Testing tin Tin plated conductors tin plating tin solder tin whiskering tin whiskers top 5 Transient Troubleshooting TWA800 UAVs UL94 USAF validation verification video Visual Inspection voltage voltage differential Voltage Tolerance vw-1 wet arc white paper whitelisting Wire Ampacity Wire Bend Wire Certification Wire Comparison wire damage wire failure wire performance wire properties Wire System wire testing Wire Verification wiring components work unit code

Circular connectors have been a part of the aircraft industry for nearly 90 years. Clearly, because of this long history, many lessons have been learned on the construction and use of these connectors. But before anyone can really consider how to use the connector, there are basics that must be understood. This article reviews some of the basics of circular connectors and it should also be useful as a connector type reference sheet.

Connectors
Finding the right connector for your application is important. Testing can ensure you are getting quality products into your system.

The MIL-DTL-38999 standard has been around for many years (currently in revision M), and because of the need to support both existing platform and new technologies, the standard is fairly lengthy. Given the wide range of connectors type and configurations covered in the standard, one would expect the standard to be two or more documents.

At the start of the MIL-DTL-38999, there is an identification of four series classes for the connectors specified in the document. On first pass, these connector designations may appear to be the same, but there are slight differences. The key differences are highlighted and should help to clarify some of the confusion.

Series

Description

Series I

This series of connector is designed for use where a quick disconnect coupling system is required for blind mating or other mating problem areas. As part of the design, the coupling and contacts are designed to endure high-vibration environmental conditions and are suitable for severe wind and moisture problem (SWAMP) areas.

Series II

The Series II connector is designed for use in areas not subjected to high vibration or SWAMP conditions. These connectors have a smaller profile and weight less than Series I connectors. Use of these is ideal where space or weight is at a premium. Note that the Series II connectors are not scoop-proof.

Series III

Series III connectors are designed for high vibration, elevated temperatures, and SWAMP area use. The best performing plating systems to prevent corrosion from salt spray are found on Series III and IV connectors.

Series IV

The Series IV connectors are designed for use where a quick disconnect coupling system is required. The connectors are also rated for vibration and SWAMP areas.

A scoop proof connector is one where it is not possible to damage the contacts while separating a mated pair. The connector shell is designed to require retraction before radial movement is possible.

Plating, Temperature, and Corrosion

There are six finishes for MIL-DTL-38999 connectors, each with their own positives and drawbacks. As a starting point, it is important to know the operational temperature range. An important item to note from the following table is that not all platings are the same. For example, The Finish code ‘M’ of electroless or electrodeposited nickel has a salt spray requirement of 2000 hours, whereas the salt spray requirement for other electrodeposited nickel finishes can be as low as 48 hours.

Class Code or Finish Code

Series

Description (finish or surface treatment)

Shell material

Salt spray (hours)

Upper Temp

Electrically Conductive Shell-to-shell Conductivity (millivolts)

A

I & II

Cadmium over nickel, light gold

AL

48

150°C

Yes (2.5)

B

I & II

Cadmium over nickel, olive-drab

AL

96/500

175°C

Yes (2.5)

C

I & II

Anodic, black

AL

48/500

200°C

No (N/A)

D

I & II

Tin (see 3.3.1.3)

CRS

24

150°C

Yes (10)

E

I & II

Passivate

SST

48/500

200°C

Yes (50)

F

All

Electroless nickel

AL

48

200°C

Yes (1)

G

All

Electroless nickel

AL

48

200°C

Yes (1)

H

III & IV

Passivate

SST

500

200°C

Yes (10)

J

III & IV

Cadmium over nickel, olive-drab

C

2000

175°C

Yes (3)

K

III & IV

Passivate

SST

500

200°C

Yes (10)

L

III & IV

Electrodeposited nickel

SST

500

200°C

Yes (1)

M

III & IV

Electroless or electrodeposited nickel

C

2000

200°C

Yes (3)

N

All

Electrodeposited nickel

SST

48

200°C

Yes (1)

R

All

Electroless nickel

AL

96

200°C

Yes (1)

S

III & IV

Electrodeposited nickel

SST

48

200°C

Yes (1)

T

All

Nickel fluorocarbon polymer

AL

500

175°C

Yes (2.5)

U

All

Cadmium over nickel, light gold

AL

96

175°C

Yes (2.5)

W

III & IV

Cadmium over nickel, olive-drab

AL

500

175°C

Yes (2.5)

X

All

Cadmium over nickel, olive-drab

AL

1000

175°C

Yes (2.5)

Y

III & IV

Passivate

SST

500

200°C

Yes (10)

Z

All

Zinc nickel

AL

500

175°C

Yes (2.5)

  • Al – Aluminum
  • CRS – Corrosion Resistance Steel
  • SST- Stainless Steel
  • C – Composite

Unlike the salt spray requirement, the upper-temperature limit for these platings remains constant regardless of the shell material or the series type.

Up Next

In the next article, we will review each type of plating style and how it might be best used in aircraft systems. Also covered will be some of tests used to qualify and set benchmarks on connector performance. If you are looking for connector testing, Lectromec’s test listing covers a wide range of those necessary for comparison, qualification, and performance verification. We are here to help.

Michael Traskos

Michael Traskos

President, Lectromec

Michael has been involved in wire degradation and failure assessments for more than a decade. He has worked on dozens of projects assessing the reliability and qualification of EWIS components. In September 2014, Michael was appointed as an FAA DER with a delegated authority covering EWIS certification.