EWIS terminology does real work in a maintenance organisation. A work card that says “inspect” when it means “detailed inspection” invites a lighter job than the maintenance programme intended. A finding written up as “contamination” when the AMC’s definition would not catch it produces an argument with the customer instead of a rectification. And an engineering order that borrows a term from the manufacturer’s manual while the audit trail runs back to an EASA AMC leaves a gap someone will find.

This glossary reproduces the definitions from Section 6 of AMC 20-22 — the EWIS training programme in AMC-20, Annex to ED Decision 2022/001/R — quoted accurately, each with a short note on where it bites in the hangar or the planning office. These are the regulator’s own definitions, and they are what your syllabus, your findings and your work cards should be measured against.

One deliberate choice: we have grouped these logically rather than alphabetising them — inspection types together, contamination and housekeeping terms together, damage mechanisms together, significant-item terms together. Alphabetical order separates GVI from DET and puts swarf next to nothing it relates to. Grouped, the vocabulary teaches itself. If you want the AMC’s own order, it is alphabetical in Section 6.

A note on the practical commentary throughout: the quoted definitions are the AMC’s. The observations about how they play out on the floor are Raven’s own operational view, and are marked as such.

The system itself

Electrical Wiring Interconnection System (EWIS)

The AMC’s definition is a cross-reference: “See CS 25.1701.”

That brevity is significant. The AMC does not restate the scope; it points at the certification specification, where EWIS is defined by what it includes — wires, connectors, terminations, splices, shields, clamps, and the supporting hardware — and by a set of exclusions. In our experience the most common scoping error in a Part-145 procedure is treating EWIS as “the wiring” and forgetting that the definition reaches the clamps, brackets and ties that hold it, which is precisely where installation errors and chafing originate. If your procedure defines EWIS in its own words, check those words against CS 25.1701 rather than against habit.

Lightning/High Intensity Radiated Field (L/HIRF) protection

“The protection of aeroplane electrical systems and structure from induced voltages or currents by means of shielded wires, raceways, bonding jumpers, connectors, composite fairings with conductive mesh, static dischargers, and the inherent conductivity of the structure; may include aeroplane specific devices, e.g., RF Gaskets.”

Read the list of means, not just the purpose. Each item is something a maintainer can defeat without touching a wire: a bonding jumper left off, a raceway lid mis-seated, an RF gasket reused when it should have been renewed, a fairing with damaged conductive mesh signed off as cosmetic. The definition is effectively a list of things that look like hardware and function as protection.

Inspection types

These four define the language of the maintenance programme. Getting them right in a work card is the difference between the inspection the designer specified and the inspection you actually performed.

General Visual Inspection (GVI)

“A visual examination of an interior or exterior area, installation, or assembly to detect obvious damage, failure or irregularity. This level of inspection is made from within touching distance unless otherwise specified. A mirror may be necessary to enhance visual access to all exposed surfaces in the inspection area. This level of inspection is made under normally available lighting conditions such as daylight, hangar lighting, flashlight or droplight and may require removal or opening of access panels or doors. Stands, ladders or platforms may be required to gain proximity to the area being checked.”

The load-bearing phrases are “obvious”, “within touching distance” and “normally available lighting”. A GVI performed from the floor of the hangar on a bundle three metres up is not a GVI. The definition also tells you that stands and access panel removal are inside the task, not extras to be negotiated — which has direct consequences for how planning allocates time and equipment.

Detailed Inspection (DET)

“An intensive examination of a specific item, installation, or assembly to detect damage, failure or irregularity. Available lighting is normally supplemented with a direct source of good lighting at an intensity deemed appropriate. Inspection aids such as mirrors, magnifying lenses or other means may be necessary. Surface cleaning and elaborate access procedures may be required.”

Note what changes from GVI: “obvious” disappears, lighting must be supplemented, aids may be necessary, and cleaning enters the picture. The word “intensive” is doing real work. Our operational view: if the certifying staff member could have completed the task without setting up additional light, it probably was not a DET, and that is a question worth asking during in-process monitoring rather than after an escape.

Zonal Inspection

“A collective term comprising selected GVI and visual checks that are applied to each zone, defined by access and area, to check system and powerplant installations and structure for security and general condition.”

Zonal is a container, not a level. It bundles GVIs and visual checks by area. The planning-office consequence is that a zonal task’s rigour comes from the GVIs inside it — so “covered by the zonal” is not automatically an answer to “was the wiring inspected to the required level?”

Stand-alone General Visual Inspection (GVI)

“A GVI which is not performed as part of a zonal inspection. Even in cases where the interval coincides with the zonal inspection, the stand-alone GVI shall remain an independent step within the work card.”

This is the definition most often violated by well-intentioned work-card optimisation. Note the “shall”: when the intervals coincide, the temptation is to merge the two steps and save a signature. The AMC forecloses it. If you are rationalising a check package, this definition is the one to put in front of whoever is proposing the merge.

Contamination and housekeeping

Section 7 of the AMC explains why these terms exist at all: “Over the years there have been a number of in-flight smoke and fire events where contamination sustained and caused the fire to spread. Regulators and Accident Investigators have conducted aircraft inspections and found wiring contaminated with items such as dust, dirt, metal shavings, lavatory waste water, coffee, soft drinks, and napkins. In some cases, dust has been found completely covering wire bundles and the surrounding area.” The definitions below are built around fire propagation, not tidiness.

Contamination

“For the purposes of this AMC, wiring contamination refers to either of the following: — The presence of a foreign material that is likely to cause degradation of wiring. — The presence of a foreign material that is capable of sustaining combustion after removal of ignition source.”

Two independent limbs, joined by “either”. A finding qualifies if the material degrades the wiring or if it sustains combustion — it does not need to do both. In our experience this is the single most misapplied definition in EWIS findings: dust that will not corrode anything still meets the second limb, and dismissing it as housekeeping is a technical error, not a judgement call.

Combustible

“For the purposes of this AMC, the term combustible refers to the ability of any solid, liquid or gaseous material to cause a fire to be sustained after removal of the ignition source. The term is used in place of inflammable/flammable. It should not be interpreted as identifying material that will burn when subjected to a continuous source of heat as occurs when a fire develops.”

The final sentence is the one to read twice. “Combustible” here is a narrow, technical test — will the fire continue once the ignition source is gone — and explicitly not the broad “will burn if you hold a flame to it”. Almost everything burns under a continuous heat source; that is not what this term captures. When you write a finding, the question is self-sustaining combustion.

Swarf

“A term used to describe the metal particles, generated from drilling and machining operations. Such particles may accumulate on and between wires within a wire bundle.”

Note the source: your own work generates it. Swarf is not something that arrives on the aircraft; it is created by drilling during a mod or repair and then migrates. The second sentence — “on and between wires within a wire bundle” — is the reason a post-task clean-up that only sweeps surfaces is inadequate. This definition, more than any other, is an argument for the sequencing rules in your engineering orders: protect or remove the bundle before you drill, not after.

Damage mechanisms and failure

Arc tracking

“A phenomenon in which a conductive carbon path is formed across an insulating surface. This carbon path provides a short circuit path through which current can flow. Normally, a result of electrical arcing. Also referred to as ‘Carbon Arc Tracking’, ‘Wet Arc Tracking’, or ‘Dry Arc Tracking’.”

The mechanism to internalise is that the insulation itself becomes the conductor. That is why arc tracking damage can extend well beyond the original fault point and why an apparently local burn mark warrants tracing the bundle rather than cutting out the visible damage. The three alternative names matter for documentation searches — a manufacturer’s manual or a service bulletin may use any of them.

Needling

“The puncturing of a wire’s insulation to make contact with the core to test the continuity and presence of voltage in the wire segment.”

Included in the AMC’s glossary because it is a troubleshooting technique that creates the conditions for later failure: a breach in the insulation, invisible once the probe is withdrawn, that admits moisture and provides a start point for arc tracking. Raven’s view: the practical control is not just training staff not to needle, but making sure your troubleshooting procedures and test equipment do not quietly require it.

Functional Failure

“Failure of an item to perform its intended function within specified limits.”

Short, and broader than it looks. “Within specified limits” means degraded performance counts — an item still working, but outside limits, has functionally failed. This is the hinge between a defect report and a maintenance-programme consequence, and it is worth stating in training that “it still works” is not a disposition.

Significant items

These two come from maintenance programme development and appear in EWIS training because wiring interacts with both.

Maintenance Significant Item (MSI)

“Items identified by the manufacturer whose failure: — could affect safety (on ground or in flight). — is undetectable during operations. — could have significant operational impact. — could have significant economic impact.”

Two things to note. First, MSIs are “identified by the manufacturer” — this is not a designation your organisation assigns. Second, the criteria include operational and economic impact, not only safety, which is why the MSI list is longer than intuition suggests and why deferring work on an MSI deserves more scrutiny than deferring work generally.

Structural Significant Item (SSI)

“Any detail, element or assembly that contributes significantly to carrying flight, ground, pressure, or control loads and whose failure could affect the structural integrity necessary for the safety of the aeroplane.”

The EWIS relevance is proximity and access. Wiring runs through and is clamped to structure that is significant, and the AMC’s Section 7 warning applies directly: “a person performing an inspection of an electrical power centre or avionics compartment may inadvertently cause damage to wiring in an adjacent area.” The inverse is equally true — work on wiring in an SSI area brings structural consequences into scope.

Using the AMC’s EWIS terminology in your documentation

Three closing points from an audit perspective, all Raven’s own view.

• Quote, do not paraphrase, in procedures. If your MOE or your training material restates these definitions in house language, you have created a second standard that will eventually drift from the first. Quote the AMC and cite it.
• Match the term to the level of the task. The inspection definitions above are graded. A work card that says “check wiring” has told the mechanic nothing about lighting, distance, aids or cleaning — all of which the AMC’s own terms specify.
• Map the AMC’s references onto current regulation. AMC 20-22’s own reference list predates the regulations now in force — its definition of “Maintenance”, for instance, points at a regulation that has since been superseded by Regulation (EU) No 1321/2014. Practitioners should map its terms onto the current framework rather than citing the older instruments, and any internal document that copied those references across should be reviewed.

Where this vocabulary is taught

These terms are not a preamble to EWIS training — they are inside it. The AMC’s syllabus block C is Inspection (items 13 to 16) and block D is Housekeeping (items 17 to 22), which is where the inspection types and the contamination definitions live. Raven’s EWIS courses map each Waypoint one-to-one to a single AMC 20-22 syllabus line item, grouped into Lessons A to G matching the AMC’s own blocks, so a term is taught where the AMC places it and the traceability from syllabus to delivery is direct.

For staff directly involved in EWIS maintenance and inspection, the Appendix A programme is covered in EWIS Target Groups 1 and 2. For engineering and planning staff working on in-service aeroplanes, see EWIS Target Group 3 and EWIS Target Groups 4 and 5.

For the wider regulatory picture, start with our pillar guide to EASA EWIS training. To work out who in your organisation needs which programme, read Which EWIS target group am I? and Is EWIS training mandatory? And once a programme is running, EWIS refresher training: the two-year cycle explained covers what the AMC says about keeping it current.