ISO 1966:2026

• Abstract:

  This document specifies the design requirements (and tests) for the crimping of insulated and non-insulated joints to general purpose electrical cables for aircraft, with conductors of copper, copper alloy, aluminium or aluminium alloy, in locations in which the stabilized conductor temperature does not exceed the values specified for the relevant type of cable, i.e. 105 °C, 190 °C or 260 °C. This document specifies the type of cable to use for the joints (see 4.1). The document also contains recommendations relating to the inspection of such connections and the tools used to perform the crimping operation. Because satisfactory crimping is dependent upon the maintenance and setting of tools, it also contains recommendations for tests to confirm their serviceability. NOTE Testing of crimped joints to assess their suitability for aircraft shows that certain environmental conditions, for example vibration, have no significant effect on the performance of the joints. Therefore, such tests are not provided in this document.

• Status: Published
• Publication Date: 09-Jul-2026
• ICS: 49.060 - Aerospace electric equipment and systems
• Technical Committee: ISO/TC 20/SC 1 - Aerospace electrical requirements
• Drafting Committee: ISO/TC 20/SC 1 - Aerospace electrical requirements
• Current Stage: 6060 - International Standard published
• Start Date: 10-Jul-2026
• Due Date: 21-Nov-2026
• Completion Date: 10-Jul-2026

• Revises: ISO 1966:1973 - Crimped joints for aircraft electrical cables
• Effective Date: 25-Nov-2023

Overview

ISO 1966: Crimped joints for aircraft electrical cables is an international standard developed by the International Organization for Standardization (ISO) under technical committee ISO/TC 20/SC 1 (Aerospace electrical requirements). The standard specifies the design requirements and test procedures for crimping insulated and non-insulated terminations on general purpose electrical cables used in aircraft systems. It applies to electrical cables with copper, copper alloy, aluminium, or aluminium alloy conductors, as long as the stabilized temperature at the conductor does not exceed specified limits of 105 °C, 190 °C, or 260 °C.

Ensuring the reliability and safety of crimped joints is critical in aerospace applications, where electrical failures can have serious consequences. ISO 1966 provides guidance not only for the proper design and testing of crimped joints but also for inspection and tool maintenance, helping manufacturers, engineers, and quality professionals meet stringent aviation requirements.

Key Topics

• Design Requirements: Specifications for the selection of crimp barrel, plating materials, and protective treatments to ensure corrosion resistance and electrical integrity. The standard emphasizes the importance of proper dimensions, material compatibility, and prevention of electrochemical corrosion, especially for aluminium terminations.
• Crimping Tools and Dies: Requirements for the design, identification, and maintenance of crimping tools and dies, including correct marking and compatibility for repeatable, high-quality results.
• Types of Tests: Detailed procedures for type testing, production control, and user control. Key tests include:
  • Voltage drop test
  • Tensile strength test
  • Climatic testing (including salt mist and rapid temperature change)
  • Load and temperature cycling
  • Current ageing and vibration tests
  • Fluid resistance, heat ageing, and insulation grip tests for insulated joints
• Inspection and Quality Control: Guidance for the routine visual and mechanical inspection of every crimped joint, including routine checks of tools and periodic destructive testing to confirm performance metrics.
• Documentation: Manufacturers must declare material specifications, protective treatments, suitable cable types, recommended tools, identification codes, and instructions for users.

Applications

ISO 1966 is essential for aerospace manufacturing and maintenance organizations. Key applications include:

• Aircraft Wiring Harness Assembly: Ensuring standardized, reliable crimped terminations for avionic systems, control circuits, lighting, and power distribution.
• Quality Assurance: Establishing robust production and inspection protocols to maintain compliance with international aviation safety standards.
• Maintenance and Repair Operations: Providing clear criteria for the inspection, rework, and replacement of crimped joints during aircraft servicing.
• Certification Support: Meeting the documentation and test evidence requirements of regulatory bodies and customers seeking compliance with international or national aerospace electrical standards.

The standard is applicable wherever solderless, crimped connections are required in environments subject to vibration, temperature fluctuation, and demanding reliability criteria found in aircraft electrical systems.

Related Standards

Organizations implementing ISO 1966 should consider these related documents to ensure comprehensive compliance across aerospace electrical connections:

• IEC 60352-2: Solderless connections - Crimped connections - General requirements, test methods, and practical guidance.
• IEC 60068-2-6: Environmental testing - Sinusoidal vibration testing.
• IEC 60068-2-11: Environmental testing - Salt mist testing.
• ISO 2635: Specifications for conductors used in general purpose aircraft electrical cables.

By harmonizing with these standards, manufacturers and operators can enhance reliability, compatibility, and safety across aircraft electrical installations.

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Keywords: ISO 1966, aircraft electrical cables, crimped joints, aerospace crimping standard, crimped termination testing, aviation electrical reliability, insulated cable terminations, aerospace quality assurance, electrical cable standards, crimping tools and dies.

International
Standard
ISO 1966
Second edition
Crimped joints for aircraft electrical
2026-07
cables
Raccordements sertis pour câbles électriques utilisés à bord des
aéronefs
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Design requirements . 2
4.1 General .2
4.2 Crimped joints . .3
4.3 Wires .3
4.4 Tools and dies .3
5 Dimension . 3
6 Strength and performance . 4
7 Marking . . 4
8 Tests . 4
9 Type tests . 4
9.1 Test conditions .4
9.2 Test sequence and specimens.4
9.3 Inspection .5
9.4 Voltage drop test .5
9.5 Climatic test .6
9.6 Load and temperature cycling tests .6
9.7 Cycling current ageing .6
9.8 Rapid change of temperature .6
9.9 Salt mist .7
9.10 Sinusoidal vibrations with passage of current .8
9.11 Tensile test .8
9.12 Insulation grip tests .8
9.13 Tensile tests on conductor crimp alone .8
9.14 Additional tests for insulated joints .8
9.14.1 Samples .8
9.14.2 Fluid resistance .9
9.14.3 Heat ageing .9
9.14.4 Low temperature crimping .9
9.14.5 Dielectric strength .9
9.14.6 Flammability .9
10 Production control tests . 10
10.1 Terminations and cable splices .10
10.2 Tools and dies .10
11 Users’ control tests . 10
11.1 Routine inspection of crimped joints .10
11.2 Quality control tests .10
Bibliography .13

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT),see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 20, Aircraft and space vehicles, Subcommittee
SC 1, Aerospace electrical requirements.
This second edition cancels and replaces the first edition (ISO 1966:1973), which has been technically
revised.
The main changes are as follows:
— addition of Clause 2;
— addition of requirements for different crimp barrel materials and coating materials (see 4.1);
— addition of subclause 4.3;
— addition of requirements for the overall dimensions of the crimped joints (see Clause 6);
— revision of requirements for type test (see Clause 9);
— revision of the tables for test current, voltage drop and tensile strength tensile (Table 2 and Table 3).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
This document serves as an essential reference standard for aerospace manufacturers, engineers and
quality control professionals to promote consistency and safety of aircraft electrical systems.

v
International Standard ISO 1966:2026(en)
Crimped joints for aircraft electrical cables
1 Scope
This document specifies the design requirements (and tests) for the crimping of insulated and non-insulated
joints to general purpose electrical cables for aircraft, with conductors of copper, copper alloy, aluminium
or aluminium alloy, in locations in which the stabilized conductor temperature does not exceed the values
specified for the relevant type of cable, i.e. 105 °C, 190 °C or 260 °C. This document specifies the type of cable
to use for the joints (see 4.1).
The document also contains recommendations relating to the inspection of such connections and the tools
used to perform the crimping operation. Because satisfactory crimping is dependent upon the maintenance
and setting of tools, it also contains recommendations for tests to confirm their serviceability.
NOTE Testing of crimped joints to assess their suitability for aircraft shows that certain environmental
conditions, for example vibration, have no significant effect on the performance of the joints. Therefore, such tests are
not provided in this document.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
IEC 60068-2-6:2022, Environmental testing — Part 2-6: Tests — Test Fc: Vibration (sinusoidal)
IEC 60068-2-11:2021, Tests - Test Ka: Salt mist
IEC 60352-2:2024, Solderless connections — Part 2: Crimped connections — General requirements, test methods
and practical guidance
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
termination
permanent connection formed by the end of an electrical cable conductor with a terminal end (3.2) or a pin
or socket contact (3.3)
3.2
terminal end
connecting device with barrel(s) accommodating an electrical cable conductor with or without additional
provision to accommodate and secure the insulation
3.3
pin or socket contact
contact used in a plug or socket (receptacle) with a barrel at one end to accommodate an electrical cable
conductor with or without additional provision to secure the insulation

3.4
cable splice
connecting device with barrel(s) each accommodating an electrical cable conductor(s) with or without
additional provision to accommodate and secure the insulation
3.5
crimped joint
permanent solderless assembly made by crimping a conductor of an electrical cable into a crimp contact,
terminal end, or splice
3.6
crimping
method of firmly attaching a terminal end (3.2) or cable splice (3.4) to a conductor by re-shaping the barrel
around the conductor to establish good electrical and mechanical contact
3.7
insulation grip
part of a terminal barrel or cable splice (3.4) barrel into which the insulation of the cable is placed and which,
by reforming, grips the insulation
3.8
crimping tool
manually operated or power-operated mechanical device for making a crimp or insulation grip (3.7)
3.9
positioner
locator, turret or other device permanently or removably attached to a crimping tool (3.8), serving correctly
to locate and control the position of the crimp on the barrel
4 Design requirements
4.1 General
The protective treatment and surface finish of the terminal end, pin or socket contact or cable splice should
be of such a quality that the joint conforms with the requirements of this document.
The crimp barrel shall be plated with tin, tin-alloy, silver, gold or palladium. Other plating materials, such as
nickel (unless used as under-plate) may be used provided their suitability has been proven.
The aluminium or aluminium alloy terminal should be plated with tin or nickel.
The electrochemical potential difference between all conducting surfaces in contact should not exceed
0,25 V.
The design of the terminal end, pin or socket contact or cable splice shall be such that adequate engagement
of the cable conductor in the completed joint can be readily established by inspection.
Terminations for aluminium conductors shall be designed to prevent corrosion. The use of antioxidant
compounds or hermetic sealing is recommended.
Any material used for pre- or post-insulation shall be non-corrosive, resistant to abrasion, fungus and aircraft
fluids and shall not support combustion. The insulation, and internal sleeve if any, shall remain firmly fixed
in its correct position before and after crimping. The insulation should be colour-coded in respect of its
conductor size or sizes in accordance with the relevant national standards.
The manufacturer shall make the following information available:
a) terminal end, pin or socket contact or cable splice material specification;
b) protective treatment;
c) size and type of cable for which each item is available;
d) appropriate crimping tool or die references and settings;
e) the identification code of crimp marking;
f) information on the preparation of cable ends before crimping;
g) maximum overall dimensions of the completed crimp;
h) instruction sheets for the proper use of the recommended crimping tool.
4.2 Crimped joints
The completed crimped joint should take the form of a conductor crimp and insulation grip effected in one
operation, using the die or dies stipulated by the tool manufacturer. All terminal ends or cable splices for
size 12 cables or smaller shall have an insulation grip unless equivalent insulation support is otherwise
provided.
4.3 Wires
Copper cables should conform with the requirements of ISO 2635 or other international standards.
Aluminium cables should conform with the requirements of relevant international standards.
4.4 Tools and dies
Tools shall be so designed that:
a) they will correctly locate and control the position of the crimp;
b) they will not release the termination during normal operation until the crimp has been correctly
formed;
c) they will not axially deform pin or socket contacts or increase the effective diameter along the length of
the crimped section by more than the amount specified in the connector specification;
d) during the formation of the conductor crimp, they will apply the appropriate mark, where required by
Clause 7, to indicate the die size or tool which has been used;
e) they will not adversely affect the external protective treatment or insulation during the crimping
operation;
f) they will not fracture the terminal
...