AASSEP-12 witness (breaking) wire for aircraft emergency controls

What it is

AASSEP-12, the Allied Aircraft Servicing and Standard Equipment Publication on witness (breaking) wire, is NATO's agreed specification for a wire used to temporarily lock aircraft emergency controls and equipment: break the wire, and it is immediately visible that the control has been operated or the equipment opened. It is covered by STANAG 3752, the NATO agreement by which participating nations commit to using it, rather than a separate technical layer on top of it. Edition A, version 1 was promulgated in May 2024.

The wire agreement, and figures this page does not reproduce

The publication's own aim (clause 1.2) is to standardize the material, dimensions and mechanical requirements of witness (breaking) wire when it is used for this kind of temporary locking. The agreement itself (clause 1.3) leaves the wire's material optional, fixes a maximum breaking load and a minimum diameter for the hole the wire passes through, and sets an approach to colour identification: an unprotected clear copper wire needs no distinguishing colour, but a colour coating required by national regulation must contrast recognisably with the locking material. This page does not print the specific breaking load or hole diameter the clause sets; reproducing a NATO publication's own technical text is a licence condition, and the current clause is the authoritative source for anyone sourcing or fitting the wire.

An equivalent civil standard, and four national reservations

Clause 1.3(e) allows ISO 244:1979, "Aircraft – Sealing wire", to be used in place of the STANAG's own specification. Four participating nations go further and have recorded specific reservations against the base agreement: Bulgaria excludes Su-25K/UBK aircraft entirely, and Canada, Norway and Slovakia each reserve the right to fit wire prescribed by the aircraft's original equipment manufacturer where it does not conform to the STANAG, with Norway's reservation extended to aircraft purchased in future. Whichever specification is actually fitted, that choice has to match what the relevant nation has ratified or reserved.

A separate security clause

Independently of the wire agreement, AASSEP-12 carries a general security clause headed "Defence Against Terrorism": aircraft equipment and materiel must be labelled, processed and stored so as to prevent access and tampering by unauthorized personnel, such equipment is inspected and certified before it is used or applied, and servicing and maintenance of aircraft is restricted to authorized personnel. The document does not explain why a wire specification also carries this clause; the two requirements simply sit together in the same short document.

Who it addresses, and how it binds

AASSEP-12 speaks to the practice of servicing and maintaining aircraft rather than naming a manufacturer or a national authority directly; its security clause states that this work "shall be performed ONLY by authorized personnel". It binds through national agreement: participating nations record their commitment to use it in STANAG 3752, and the publication itself is effective upon receipt once that agreement is in place. For a supplier or a maintenance organisation, it reaches them the way an Allied Publication normally does, through a national requirement or a contract that names it, not because the document exists on its own.

How it is checked

AASSEP-12 names no certification, audit or accreditation scheme, and no body is described as assessing an organisation's compliance with it. Where the document uses the word "certified", it describes a check on a piece of equipment before use, not on an organisation: relevant equipment is inspected and certified for operational integrity and reliability before it is used. There is no accredited certification body, government surveillance arrangement, or notified-body assessment described anywhere in the text.

How you get it

AASSEP-12 is published by the NATO Standardization Office and, like every NATO standardization document, carries no charge. The Standardization Document Database is the authoritative source, and a national standardization authority can also supply a copy. We credit NATO for the catalogue and neither sell nor host a copy ourselves.