Definition
Service Bulletins are the manufacturer's primary mechanism for communicating in-service technical information to operators. The format is standardized within each manufacturer's documentation system but generally includes the bulletin number, the affected models and serial numbers, the reason for issuance, the recommended action, the compliance time, and the approved technical data for accomplishing the work. SBs are categorized by the issuing manufacturer with terminology such as "Mandatory," "Recommended," "Optional," "Alert," or numerical priority codes — the categorization reflects the manufacturer's safety judgement, not the regulator's.
The critical distinction between an SB and an Airworthiness Directive is legal force. An AD, issued by the FAA under 14 CFR §39 or by EASA under the Basic Regulation Article 76 and Part 21.A.3B, is mandatory for compliance — failure to comply makes the aircraft non-airworthy and the operator non-compliant. An SB, issued by the manufacturer, is a recommendation — even an SB labelled "Mandatory" by the manufacturer is not legally mandatory unless the regulator subsequently issues an AD that incorporates the SB or makes it a precondition for continued airworthiness.
In practice, most SBs become effectively mandatory through several routes. The competent authority may issue an AD that mandates SB compliance within a specified compliance time. The operator's Approved Maintenance Programme may incorporate the SB as a scheduled task, in which case the operator's commitment to the AMP makes the SB mandatory under §121.367 / §135.411 / EASA M.A.302. The operator's continuing-airworthiness assessment may conclude that the SB addresses a safety issue significant enough that compliance is part of the operator's safety responsibility under §91.403 or M.A.301. An aircraft with an outstanding manufacturer-Mandatory SB and no AD compliance can fly legally — but it generally cannot pass a thorough pre-purchase inspection or insurance audit without the operator demonstrating a deliberate non-compliance decision documented in the maintenance records.
SBs may be issued in revision sequences. SB 24-1234, SB 24-1234R1, SB 24-1234R2 represent successive revisions of the same underlying service bulletin, typically as the manufacturer learns more about the in-service issue. Operators must track which revision they have complied with, because an AD may eventually mandate the latest revision and prior compliance may not satisfy the AD.
Why It Matters for Flight Schools
For CAMOs and maintenance organizations, SB management is a continuous review function. Every manufacturer publishes SBs on a continuing basis — sometimes through formal subscription services, sometimes through fleet bulletins, sometimes through type-club channels — and the operator's continuing-airworthiness team has to evaluate every SB against the operator's specific aircraft and operating profile. Decisions to comply, to defer, or to decline must be documented with reasoning, because an inspector reviewing maintenance records years later will ask why an applicable SB was not actioned.
The operational risk pattern is the SB that becomes an AD. A manufacturer issues an SB recommending a structural inspection. The operator decides to defer compliance pending more service experience. Eighteen months later the regulator issues an AD mandating the SB inspection within 30 days. The operator now has 30 days to inspect a fleet of 12 aircraft, against a regulatory deadline, against the maintenance organization's available capacity. Operators with mature SB-tracking discipline saw the AD coming and had inspections planned; operators without it scramble.
How Aviatize Handles This
Aviatize's maintenance control module tracks service bulletins per aircraft and per engine/component as a structured catalogue — SB number, issuing manufacturer, applicability (model, serial range, condition), compliance status (complied, in progress, deferred with reason, declined with reason), and the revision tracked. When an AD subsequently incorporates an SB the operator has already complied with, the platform links the AD to the prior SB compliance evidence, satisfying the AD record-keeping requirement without re-inspection.
For SB-to-AD escalation, Aviatize tracks regulator activity feeds and flags SBs that have moved into AD status. When an AD with a tight compliance window references an SB that the operator has already deferred, the platform shows the affected fleet, the prior deferral decision, the new AD compliance window, and the maintenance capacity required — turning a regulatory surprise into a planned project. The CAMO postholder gets the visibility the regulator audits for, and the maintenance department gets the lead time it needs to plan the work without disrupting commercial operations.