Supplementary Maintenance Directive (DES)

A DES (“Directive d’Entretien Supplémentaire”) is an airworthiness document issued by the operator itself — not by the manufacturer (SB) or an authority (AD) — to impose a maintenance requirement that supplements the maintenance programme: a reinforced inspection decided in-house, a fleet-specific technical directive, a directive picking up a manufacturer recommendation not covered by a formal SB… It is the same airworthiness document pivot as SB / AD / MOD (same applicability rules, same due dates, same airworthiness verdict): the DES reuses that whole toolset instead of introducing a parallel system.

Who uses it: maintenance engineering (drafting, applicability, due dates), planning (work-order generation, compliance tracking) and — as soon as a DES is flagged “equivalent to an AD” — the technician signing the CRS, since it can then block return to service exactly like an airworthiness directive.

Dedicated screen

Maintenance › Supplementary Maintenance Directives

lists only DES-kind documents (SB/AD/MOD stay on the generic Airworthiness documents screen). The table adds two DES-specific columns:

Column	Content
Sub-type	The sub-type chosen from the catalogue (e.g. `DA — Applicability Directive`)
Equivalent to AD	Checked if the DES carries the same weight as an airworthiness directive

A “All sub-types…” multi-select filter isolates DES of one or more sub-types. The “+ New DES” button opens the generic form directly with kind = DES pre-selected.

Creating a DES

Creation goes through the generic airworthiness document form (the same screen used for an SB, an AD or a MOD): Reference, Revision, Title, Issuer, Compliance, issue/effective dates, Mandatory… As soon as the chosen type is DES, an extra block appears:

DES-specific fields

Sub-type
Picked from a configurable catalogue — see Administration › DES sub-types. Classifies DES by nature (e.g. Applicability Directive, Specific Technical Directive, One-time Directive…) and feeds the dedicated screen’s filter.
Equivalent to AD (equivalentToAd)
“Equivalent to an airworthiness directive (AD)” checkbox. A checked DES weighs as a mandatory obligation in the airworthiness verdict, even if the Mandatory field itself is not checked.
Technical level
Required qualification level to carry out the work: Piste (ramp), NTI1, NTI2 or NTI3. Informative field — it does not restrict who can close the work order, it documents the expected skill level.
Application deadline
Cut-off date beyond which the DES must be applied. Distinct from the due conditions (recurrence/meter) — it is a one-time ceiling date, typically used for a one-time DES.
External URL
Informative link to the source document (internal PDF, external referential…). Never queried automatically by the system — air-gapped constraint: the link is shown as-is, to be opened manually.

The context / the directive text itself is written in the document header’s Notes field (long markdown text, with an Edit/Preview toggle) — the same primitive used by other airworthiness documents. Hierarchical sections remain available if the DES needs to be broken down into numbered checkpoints.

Sub-types (admin catalogue)

Administration › DES sub-types manages the per-instance referential: code (stable identifier, immutable after creation), label, optional description, sort order and active/inactive. A deactivated sub-type stays visible on existing DES but disappears from the creation picker.

Targeting the affected fleet (applicability)

A DES uses the same applicability rules as other airworthiness documents — see

Airworthiness documents for the full list of selectors. In practice for a DES:

By fleet variant: aircraft type (family / variant / version) — the most common way to target a DES applying to a whole homogeneous fleet.
By individual: a specific aircraft (registration/MSN), or a specific component identified by its part number (PN), its PN + exact serial number, or a serial number range.
Include and Exclude rules accumulate, and an aircraft rule can be conditioned on the modification state of another document (e.g. “DES applicable only to non-embodied MOD-XXX aircraft”).

The Calculate button in the “Affected fleet” panel resolves these rules in real time against the fleet in stock or in service.

Setting a due date

Like an SB or an AD, a one-time DES targets a single action; a recurring or mixed DES carries one or several due conditions (calendar, meter, absolute deadline or event), arbitrated by the trigger policy (first threshold reached / all thresholds reached). A recurring condition can also carry conditional periodicity rules (“after triggering document Y is applied → new period”). See the full detail in

Airworthiness documents — the due-date mechanics are strictly identical. The DES-specific application deadline adds to these conditions: it caps the date beyond which the action is due, independently of the trigger policy.

Per-individual derogations

A DES uses the same per-individual derogations panel as other airworthiness documents — see

Airworthiness documents for the detail of the seven available dispositions (not applicable, application mandatory/optional, surveillance, service article, flight prohibited, destroyed). In practice for a DES: a specific aircraft exempted from a fleet-wide DES, or a specific unit declared flight-prohibited/destroyed without waiting for a new revision that would reformulate applicability for the whole fleet.

Impact on the airworthiness verdict

The airworthiness verdict (fit / not fit for return to service, signing the CRS) treats a DES exactly like other documents, with one extra rule:

An obligation is blocking when the document is mandatory OR equivalentToAd (Equivalent to AD), is open or in progress, and is either overdue or has no due window at all.

In practice:

A DES flagged “Equivalent to AD” behaves like an airworthiness directive even if the Mandatory field is not checked: overdue or without a due window, it renders the aircraft not fit for service just like an AD.
A DES that is neither mandatory nor “equivalent to AD” remains a plain recommendation: it shows up in compliance tracking but never blocks the CRS.
A DES flagged Mandatory (the classic checkbox, independently of “Equivalent to AD”) follows the same rule as any other mandatory document.
A per-individual derogation overrides these general rules for the targeted aircraft or unit: Flight prohibited hard-blocks, Not applicable/Destroyed withdraws the document for that individual, Application optional makes its tracking non-blocking, and Surveillance/Service article leave the verdict unchanged but display an Attention badge on the aircraft sheet.

Applying via a work order

From a to-do row of the DES (on the aircraft sheet, on the dedicated DES screen, or on the Compliance dashboard), the Generate work order button creates the work order that will carry out the DES — the same mechanics as for an SB/AD/MOD: the document’s sections become the WO checklist, the WO is filed under the aircraft’s airworthiness work package (NAV-<registration>), and the compliance settles automatically on WO completion (date, actor, WO as evidence). For a recurring DES, the next due date is recomputed from that compliance date.

Issuing a new revision

A new revision of a DES (e.g. rev. B fixing a technical point) follows the standard airworthiness document cycle: the “New revision” button on the document sheet creates a full copy — sections, applicability, due dates, sub-type, “Equivalent to AD”, technical level — under the new revision, sets the Supersedes link to the original, and starts as Draft. On activation, the previous revision switches to Superseded and its compliance records become void; its targets reappear as “to do” against the new revision. As with other documents, changing due dates on an Active DES that already has compliance records requires going through a new revision rather than editing in place.

Effect-driven links

A link between two documents (or between a document and a maintenance task) is no longer a mere documentary label — it is a mechanism. When the source document becomes compliant on an individual (an aircraft or a specific item), the system acts automatically on the target — for that same individual, never across the whole fleet. The goal: eliminate double work and planning oversights.

The action fires when a compliance record flips to Compliant (manual entry, settlement by a WO, or a cascading effect from another link). It applies to the compliant individual: making DES A compliant on aircraft F-ABCD acts on the target for F-ABCD only.

The link editor on the document sheet lets you pick the target (another document or a program task, via the usual searchable picker) and the effect — each effect is shown with a “what it does” label. A document displays both its outgoing and incoming links (symmetric ones, and those where it is the target).

Available effects

Effect	What it does when the source document becomes compliant on the individual
Triggers	Opens the target’s compliance (“to do”) on the individual.
Satisfies	Marks the target compliant on the individual (method of compliance “satisfied by…”).
Equivalent	Symmetric: complying with one closes the other on the individual.
Cancels / voids	Removes the target on the individual (not applicable), no work required.
Excludes / incompatible	Symmetric: the two cannot coexist — complying with one removes the other (not applicable).
Requires (prerequisite)	Blocks the source document’s compliance until the target is compliant on the individual (forceable).
Co-managed / batch	Co-planning: the target rides in the same due-date batch (grouped display).
Amends recurrence	On a task: reshapes its periodicity for the individual (new interval or one-off deferral).
References	No effect — purely documentary link (the former “related”).

Links to a maintenance task

A link can target a program task (PRE task sheet). The effect resolves down to the occurrence of that task in the individual’s plan (PEA) — aircraft and item alike:

Satisfies settles the task’s current occurrence (an already-completed work order is created, and the next due date re-arms itself).
Triggers forces the task immediately due for the individual; Cancels / Excludes suspends the task for the individual; Amends recurrence redefines its interval (recurring) or defers its next due date (one-off).

These effects apply live on the individual’s schedule, with the precedence DES override > amendment override > base periodicity. If the individual does not follow the linked task (no plan assigned, or the task is absent from the plan), the effect is a no-op, but traced.

Prerequisites (“requires”) and traceability

The Requires effect changes nothing: it is a guard. It refuses to make the source document compliant until the required document is itself compliant on the individual. An authorised user can force it through, provided they enter a justification — the override is timestamped and traced.

Every state changed by an effect is attributable: the record carries its originating link and a generated method of compliance (“satisfied by the source document’s reference”), and the operation is logged in the audit trail. You can tell why a compliance opened, closed, or became void.

Migration caution: links created before this mechanic are classified as “references” (no retroactive effect). For an old link to act, you must assign it an effect explicitly. No past compliance is altered after the fact.