Applicable configuration

An applicable configuration describes what an asset may carry: its locations, and the parts allowed at each of them. It is a definition reference, not a fleet state — it never says what is fitted to a given unit, only what is permitted to be.

That distinction governs everything else. An applicable configuration is written once for a model; the applied configuration lives on each individual unit and changes with every removal.

Employment points

An employment point is a functional location: “fan module”, “nose radar”, “avionics bay 2”. They form a free hierarchy — a point may contain others, as deep as the breakdown requires.

Two natures coexist in the same configuration, and the screen keeps them apart:

They live together because an aircraft has only one breakdown, but they answer different questions — and a stores station gets neither CSN nor ISN: it is not a catalogue figure.

The “Stores station” nature is only offered when the configuration carries stores: its target belongs to a family whose category is checked “Carries stores”. On a part configuration — an engine, an avionics bay — the field does not show and the server refuses any station. On a configuration that carries stores, the “Point the stations” link opens their plan.

How a location is identified: ATA, CSN, ISN

Three codes, three different questions. This is the point that costs the most to confuse.

The CSN designates a location, not a part

The CSN is fixed. It designates the illustration figure and the item in the catalogue — the place, therefore. It does not change when the part occupying it changes.

Our field holds only what follows the ATA, because the ATA is already entered just above. The screen recomposes the full key: chapter-section-subject + precision, that is 73-11-02-A1010.

The ISN designates a variant, not the figure

This is the most common mistake: the ISN is not the figure number — that is the CSN. The ISN is the rank of the item within the figure, and it is what lets two variants coexist at the same location:

• 00A — the original starter, reference PN-OLD-123;
• 010 — its interchangeable evolution, reference PN-NEW-987.

Same CSN, two ISNs. Without this mechanism you would have to invent a second location for a part that occupies the first — and the traceability of the evolution would be lost.

Two items on the same figure therefore cannot share a rank: the screen refuses.

Compatible parts

Under each employment point, the list of parts allowed at that location. One of them is marked primary: the nominal one, the one expected. The others are interchangeable alternatives.

A part is only offered if it is installable — a consumable or an ingredient does not appear in the list.

This section saves immediately. Adding, removing or editing a compatible part writes to the database on click, without waiting for the “Save” at the bottom of the window. That button only covers the employment point’s own record (ATA, CSN, label, parameters).

Entering an ISN

1. Open the employment point (pencil in the tree).
2. Scroll to Compatible PNs.
3. Click the rank in the left-hand column — it becomes editable in place.
4. Type the value — 010, 00A — then press Enter. Esc cancels.

Notes are edited the same way, and “primary” toggles with a click on the pill. No window opens: typing three characters does not warrant one.

The field is optional: it only matters if you work from an illustrated parts catalogue. A purely maintenance-oriented breakdown can do without it entirely.

The interchangeability code (ICY)

When two variants follow one another at the same location — same CSN, two ISNs — the Interchangeability (ICY) column states how each relates to the other. It is the S2000M illustrated-catalogue code, which the standard splits in two:

• Prev. (PIY) — the relationship with the preceding variant;
• Next (SIY) — the relationship with the succeeding variant.

The two lists are not the same, and the screen only offers the codes valid in each direction: a code accepted here would be refused — or misread — by a partner.

The code is informative. It neither allows nor blocks any installation: fitment conditions do that. Nor is it derived from “Primary”.

Interchangeability on the part record is a different thing: a global rule, “A replaced by B”, valid everywhere. The ICY code only holds at this location, in this configuration.

Correcting the part on a row

The ⇄ button replaces the reference without losing the rank, the notes or the conditions.

It only exists to correct a data-entry mistake. If the part evolves into an interchangeable reference, do not use it: add a second row with a new ISN and keep the first one. Replacing in place would erase the fact that another part occupied that location — exactly what the CSN/ISN pair exists to preserve.

Fitment conditions

A part may be allowed only under condition — a specific amendment, a version, a state. Each compatibility carries its condition expression and the regime that applies when it is not satisfied: blocking (fitting is refused) or warning (acknowledgeable).

The choice is declared per compatibility, because it is a definition commitment: not all restrictions carry the same weight.

Exchanging the location-oriented catalogue (S2000M)

This configuration’s location-oriented catalogue is exported, or compared with a manufacturer’s (S2000M locipd), in the Export / compare workshop of the Interoperability section — not from this record: file exchanges do not mix with business screens.

Versions and effective date

An applicable configuration carries a version number and an effective date. You do not rewrite a configuration in service: you publish a new version. What was fitted was fitted under a given definition, and that definition must stay readable years later.

What the applicable configuration makes possible

• Breaking down a unit — fitting a module to an employment point, with the compatibility check and counter propagation.
• 2D station pointing — see the Station pointing screen.
• Data exchange — the CSN/ISN pair is the common key with the illustrated parts catalogues of the S-Series standards. It is what lets a part received from a partner be matched to the location it occupies in your own data, see Data exchange.