Service Bulletin Evaluation: Benefits, Risk and the CAMO Decision

An AD decision and an SB decision answer different questions

An airworthiness directive (AD) mandates action. A service bulletin (SB) is not mandatory merely because it has been issued. The first job is to establish whether an applicable AD requires the bulletin’s action; only then can the reviewer decide whether there is a discretionary choice to make.

That distinction follows the definition in Part-21 and the continuing-airworthiness obligation:

The AD compliance guide covers applicability, controlling limits and completion evidence. Keep those requirements controlling when an AD calls up an SB action. Choosing “Do not apply” in an evaluation cannot override the AD.

For a non-mandatory action, use the Service bulletin evaluation to record the technical case, the safety review and the decision. The form connects Expected benefits with Tolerability if not applied: what the change would improve, and what happens if the organisation does not make it.

Who needs the assessment procedure?

The scope is complex motor-powered aircraft or aircraft used by licensed air carriers. Either condition brings the aircraft within point (b)(4). Do not turn that wording into a rule limited to complex aircraft operated by airlines, or into a universal requirement for every aircraft managed by a CAMO.

The associated acceptable means of compliance identifies the information to assess:

Start with the bulletin’s revision, affected aircraft and parts, and related ADs. Compare its effectivity with the actual configuration. A manufacturer’s recommendation and an AD obligation have different consequences; record the actual relationship rather than relying on a publication’s label.

Weigh the benefit and the risk of non-application

Expected benefits asks the reviewer to make the case for applying the bulletin explicit. The following are practical decision aids, not a scoring method prescribed by CAMO.A.315(b)(4):

• Safety: identify the hazard the action addresses, the supporting evidence and the expected reduction in risk.
• Reliability: examine recurring defects, removals or interruptions that the change may reduce, using the aircraft’s operating experience where available.
• Economic: compare parts and labour costs, man-hours, downtime and any continuing maintenance burden with the expected savings. State what the estimate includes.
• Operational: explain whether the change would affect availability, operating restrictions or the way the aircraft is used.

Record uncertainty and alternatives in the evaluation narrative. For example, applying a modification at the next planned maintenance input may have a different downtime cost from a dedicated input. That comparison still needs a separate assessment of the risk during the waiting period.

Tolerability if not applied covers both declining the SB and postponing it beyond its stated compliance limits. For a non-mandatory bulletin, assess the consequences of going beyond the bulletin’s recommendation. Where an AD requires the action, its mandatory limits still govern under M.A.303.

A category alone is not the assessment. Use the organisation’s risk criteria, identify the evidence, describe any controls and explain how their effectiveness will be checked. In the form’s practical conventions, Acceptable needs no further risk reduction, Tolerable needs specified controls and review, and Intolerable needs risk reduction before acceptance. Not assessed means no judgement has been made. These labels do not create permission to ignore an unresolved safety concern.

Why the form asks what it asks

Document identity and related publications make the evaluation reproducible. A reviewer needs to know which issue, revision and supporting information led to the recommendation. The related-AD check separates discretionary evaluation from the obligations in M.A.303 and the actions and compliance times identified by 21.A.3B(d).

Product, effectivity and publication recommendation define the aircraft or parts assessed. Explain exclusions and earlier embodiment in the narrative, with references to the evidence. A conclusion for one configuration should not silently become a decision for the whole fleet.

Benefits, maintenance impact and resources connect the reason for the bulletin to the proposed action. The expected-benefit choices prompt the safety, reliability, economic and operational comparison. The recurring-task check exposes work that may continue after embodiment. Use the narrative for downtime and alternatives alongside the cost and man-hour estimates; not every consideration needs a separate question.

Risk reference and tolerability connect the recommendation to the safety risk management process required by CAMO.A.315(b)(4) and CAMO.A.200(a)(3). The reference should lead to the assessment and its evidence. Where controls or further review are needed, record what they are, who will follow them up and what would change the decision.

Recommendation and grounds turn the analysis into a reviewable proposal: apply, schedule for a defined opportunity, decline, monitor or record non-applicability. Explain why the chosen course follows from the evidence. A practical review trigger might be a bulletin revision, an increase in related defects, a change of operation or new safety information. The rule does not prescribe those particular triggers; they make the organisation’s decision revisitable.

A fictional evaluation across CAMO, maintenance and operations

ExampleAir’s CAMO is assessing a non-mandatory equipment modification for MSN-EXAMPLE-014. No applicable AD requires the action in this fictional case. ExampleMRO supplies an estimate of 12 man-hours and one day of aircraft downtime. Operations provides evidence of recurring dispatch interruptions, and the CAMO checks the defect history and the proposed configuration change.

The evaluation records a likely reliability and operational benefit. Its economic case compares a dedicated maintenance input with embodiment during the next planned input. The safety manager examines the risk of waiting beyond the bulletin’s recommended date, including any controls and evidence needed during that period. If the evidence does not support the proposed tolerability judgement, the recommendation goes back for changes.

A decision to use the next planned input records why that timing is acceptable under the organisation’s criteria, what would trigger an earlier review and who owns the follow-up. An estimate that the modification will save money is useful evidence; it is not, by itself, the safety assessment.

Safety review, decision and close-out

The form separates three written follow-up sections. The safety manager reviews the risk assessment, tolerability, controls and review arrangements. The continuing airworthiness manager records the application decision and its grounds, checking any AD obligations before accepting postponement or non-application. Planning or technical records staff record the work arrangements, communications, record updates and any remaining monitoring.

In Avioverse, each section is assigned to a workspace member, who records Approve or Request changes with a comment, or Not required with a reason. Only workspace members can be assignees. A supplier or maintainer outside the workspace provides information through the organisation’s usual arrangements; a member records it in the evaluation. An internal Approve response records a decision, not authority permission to depart from a mandatory requirement.

Implementation has its own follow-through. CAMO.A.315(b)(1) requires the AMP, including any applicable reliability programme, to be developed and controlled. Points (b)(5)–(6) address arranging appropriate maintenance, ordering and supervising it, and coordinating the related decisions. Under M.A.302(h), the AMP is periodically reviewed and amended when necessary in light of operating experience and new or modified instructions.

If the SB changes recurring work, link the evaluation to the AMP change and amendment process. For embodiment, connect close-out to the work order and completion evidence described in maintenance, release to service and records. For a declined or monitored bulletin, close-out should leave the reason and any review trigger clear to the next person reading it.

Where to read it yourself

The assessment and risk-management provisions are CAMO.A.315(b)(4), its AMC1, and CAMO.A.200(a)(3); AMP review is M.A.302(h), and the AD obligation is M.A.303. These were checked against the 2025-09-02 revision of the EASA Easy Access Rules for Continuing Airworthiness. The AD definition and minimum contents are in 21.A.3B(a) and (d), checked against the 2025-11-27 revision of the Easy Access Rules for Initial Airworthiness and Environmental Protection. The benefit categories, form roles and example are practical ways to organise the work.