AD/CFM56/33 - Inspection of Fan Blades with 25 Degree Mid-span Shrouds

This Airworthiness Directive (AD/CFM56/33, 10/2014) requires inspection and, where necessary, removal and replacement of certain fan blades fitted to CFM International CFM56-3 turbofan engines when those blades have 25 degree mid-span shrouds. The AD applies to CFM56-3 engines, all serial numbers, only when fitted with specific fan blade part numbers listed in the Applicability section: P/N 9527M99P08, 9527M99P09, 9527M99P10, P/N 9527M99P11, P/N 1285M39P01, or fan blade pairs P/N 335-088-901-0, 335-088-902-0, 335-088-903-0, and 335-088-904-0 (Applicability). It excludes installation of these blades on the CFM56-3C engine model (Note 2). The AD makes the inspection mandatory and sets a repeat interval for subsequent inspections.

Mechanically, the AD does three things. First, it mandates an inspection in accordance with paragraphs 3.A (on-wing) or 3.B (in-shop) of CFM Service Bulletin CFM56-3/3B/3C 72-1067, original issue (Requirements 1). Second, it requires removal and replacement of any blade where damage is found, following the accomplishment instructions of the same Service Bulletin (Requirement 2). Third, it prohibits installation of the listed blades on any CFM56-3 engine model unless those blades have been previously inspected in accordance with paragraph 3 of the accomplishment instructions of that Service Bulletin (Requirement 3). The AD accepts inspections already completed within the previous 3,000 flight cycles (FC) before the AD effective date as satisfying Requirement 1 (Note 3). Compliance timing is explicit: if the inspection has not been done it must be completed before further flight; otherwise inspections must be repeated at intervals not exceeding 3,000 FC from the last inspection (Compliance (a)). If damage is found, replacement must occur before further flight (Compliance (b)). The AD became effective 9 May 2014 and is signed by the Delegate of the Civil Aviation Safety Authority (Delegate signature block).

The AD cites a reported multiple fan blade failure event and associated wear at the contact location with fan blade dampers as the immediate technical rationale for the mandatory inspections (Background). The stated safety objective is to reduce the risk of multiple fan blade failure and consequential uncontained rotor failure by enforcing the inspection and remedial regime defined by the CFM service bulletin (Background). The AD also refers to EASA AD 2009-0036 (Note 5), signalling that it addresses the same unsafe condition described in that EASA document.

The AD is organised around a small set of interlocking concepts: applicability, mandated inspection procedures drawn from a manufacturer service bulletin, corrective action on discovery of damage, installation controls, compliance intervals, and cross-reference to prior EASA action.

Applicability. The AD targets CFM56-3 turbofan engines "when equipped with fan blades with 25 degree mid-span shrouds" and then lists specific part numbers that identify the affected hardware (Applicability). The language "all serial numbers" widens the scope to every airframe/engine serial if fitted with the listed blades. The AD also contains two clarifying notes in the Applicability block: Note 1 observes these engines are known to be fitted to, but not limited to, Boeing 737 series aeroplanes; Note 2 states that "The installation of fan blades with 25 degree mid-span shrouds is not allowed on the CFM56-3C engine model." Those notes delimit where the listed hardware is known to appear and where installation is prohibited.

Inspection standard and source document. The AD does not itself set technical inspection steps. Instead it mandates inspections "in accordance with paragraphs 3.A (On-wing) or 3.B (In-shop) of CFM Service Bulletin (SB) CFM56-3/3B/3C 72-1067 original issue" (Requirements 1). That means the AD adopts the manufacturer service bulletin’s inspection methodology, including on-wing and in-shop procedures, as the regulatory standard. The AD explicitly permits use of later approved revisions of that SB for compliance (Note 4), which allows conformity to updated manufacturer procedures where those revisions have regulatory approval.

Remedial action. If damage is found during inspection, Requirement 2 instructs removal and replacement "as instructed in the accomplishment instructions of CFM SB CFM56-3/3B/3C 72-1067 original issue." The AD therefore delegates the detailed repair/replace criteria and replacement method to the Service Bulletin.

Installation control. Requirement 3 imposes a pre-installation inspection gate: do not install the identified fan blades on any CFM56-3 engine model "unless they have been previously inspected in accordance with paragraph 3 of the accomplishment instructions of CFM SB" (Requirements 3). In practice this requires proof that any listed blade intended for installation has passed the SB inspection regime.

Compliance interval and timing. The AD sets a before-further-flight obligation for initial inspections where not previously done, and repeat inspections "at intervals not exceeding 3,000 FC from the last inspection" when the initial inspection has been done (Compliance (a)). Replacement after damage is found must be completed "before further flight" (Compliance (b)). The AD also makes Requirement 3 effective "after the effective date of this AD" (Compliance (c)).

Operators. The primary operational burden falls on aircraft operators and maintenance organisations that operate aeroplanes equipped with CFM56-3 engines fitted with the listed fan blade part numbers. The Applicability makes the scope specific: CFM56-3 engines, all serial numbers, when equipped with fan blades having 25 degree mid-span shrouds and the listed P/Ns. Note 1 signals that this configuration is known to be fitted to Boeing 737 series aeroplanes, so operators of Boeing 737 types should prioritise checking fleet configuration records.

Maintenance organisations and line stations. The AD mandates inspections "on-wing" or "in-shop" in accordance with specified paragraphs of the CFM service bulletin (Requirements 1). That affects maintenance planning and resource allocation at both line maintenance and shop levels: trained personnel, inspection tools, and potential in-shop capacity if in-shop inspection or blade replacement is required.

Aircraft owners, lessors and supply chains. Owners and lessors who are responsible under contractual arrangements for airworthiness must ensure inspections and remedial actions are performed before further flight where required, and that any blades intended for installation have the requisite inspection history (Requirement 3). Spare parts warehouses and part sellers that handle the listed P/Ns must ensure blades are documented as inspected before supplying them for installation onto CFM56-3 engines.

Engine manufacturers and field engineers. CFM International’s service bulletin is the technical standard the AD imports. CFM’s field support will likely be involved in interpreting the SB paragraphs 3.A/3.B, in determining acceptable later revisions (Note 4), and in providing replacement blades or guidance when damage is found. The AD’s reference to the SB means the manufacturer’s technicians, documentation and approved revision process are directly implicated.

Regulator. The Civil Aviation Safety Authority, through its delegate signature, is the issuing body. The AD reflects CASA’s regulatory decision to adopt the inspection and installation controls domestically. The AD itself does not spell out enforcement measures or penalties, but its issuance is an exercise of CASA’s airworthiness oversight function (Delegate signature block; Effective date).

Suppliers of blades. Firms that manufacture, distribute or stock the specific P/Ns listed will be affected by Requirement 3: they must ensure that blades supplied for installation are either already inspected per paragraph 3 of the SB or are not installed until inspected. This creates a chain-of-custody and record-keeping obligation for suppliers, even though the AD does not specify record-keeping mechanics.

Key duties under the AD are specific, time-mounted and traceable to the AD’s Requirements and Compliance paragraphs.

Duty to inspect. Requirement 1 places a duty on the operator or maintenance organisation to "Perform an inspection of fan blades ... in accordance with paragraphs 3.A (On-wing) or 3.B (In-shop) of CFM Service Bulletin ... 72-1067 original issue." If the inspection has not already been completed, Compliance (a) requires it "before further flight." If an inspection has been completed, the duty is to repeat it "at intervals not exceeding 3,000 FC from the last inspection" (Compliance (a)). The AD accepts inspections done in accordance with the SB original issue within the 3,000 FC window preceding the AD effective date as satisfying the initial duty (Requirements, Note 3).

Duty to remediate. Requirement 2 creates a mandatory corrective duty: "If any damage is found, remove and replace the blades as instructed in the accomplishment instructions of CFM SB ... 72-1067 original issue." Compliance (b) requires this remedial action to be taken "before further flight." The AD therefore imposes a zero-tolerance approach to flying with damaged blades as defined by the SB’s damage criteria.

Duty on installation. Requirement 3 creates a prospective duty: "Do not install on any CFM56-3 engine model fan blades [listed P/Ns] unless they have been previously inspected in accordance with paragraph 3 of the accomplishment instructions of CFM SB ... 72-1067 original issue." Compliance (c) makes this an immediate prohibition after the effective date. Note 2 further prohibits installation of such blades on the CFM56-3C model entirely. The installation prohibition therefore functions as a gate for parts supply, inventory control and airworthiness release.

Duty to use approved revisions. Note 4 states "The use of later approved revisions of CFM SB CFM56-3/3B/3C 72-1067 original issue is acceptable for compliance with the requirements of this AD." This creates a duty to use only those later revisions that have regulatory approval for compliance. It implicitly requires operators to confirm whether a later SB revision is "approved" for AD compliance.

Rights and practical options. The AD gives operators a practical option as to where the inspection is carried out: on-wing under paragraph 3.A or in-shop under paragraph 3.B of the SB. It also recognises past compliance where an SB inspection was completed within 3,000 FC prior to the AD effective date. The acceptance of later approved SB revisions allows operators to adopt updated inspection methods when they have been approved, rather than being rigidly bound to the original issue SB if a later revision is more practical or clearer.

The text of the AD itself does not specify criminal, civil or administrative penalties or set out an explicit enforcement regime. The document is an airworthiness directive issued by the Civil Aviation Safety Authority, signed by a CASA delegate, and framed in mandatory terms: actions "must be taken" and inspections or remedial actions are required "before further flight" or at specified intervals (Requirements; Compliance). The AD therefore sets out mandatory regulatory obligations, but it does not include penalty clauses or provide procedural details about enforcement in the text supplied.

Consequences implicit in the AD. The AD’s mandatory language and the prescription of actions and timing are regulatory instruments used by the aviation regulator to manage safety risk. Compliance obligations are time-critical and relate directly to airworthiness and flight safety. Where such ADs are issued, non-compliance typically carries regulatory exposure under the broader aviation safety framework administered by the regulator. The AD, however, contains no express statement in the provided text on the nature of enforcement steps the regulator will take in cases of non-compliance, or on fines, grounding orders, or certificate suspensions.

Regulatory provenance. The document is signed by "Mike Higgins, Delegate of the Civil Aviation Safety Authority" and is dated 30 April 2014, with an effective date of 9 May 2014. That indicates it is an instrument issued by CASA. The AD’s enforceability would arise from CASA’s statutory powers and regulatory framework, but those powers and any associated penalty mechanisms are not set out in this AD document. The AD does not cite the enabling statutory provision for CASA’s power to issue airworthiness directives in this text.

Operational enforcement mechanics not specified. The AD specifies actions, timing and acceptable source documents for inspection and remediation. It does not, within the supplied text, provide processes for approval of deviations, methods for reporting compliance to CASA, nor administrative procedures for prosecuting non-compliance. It does allow for the use of "later approved revisions" of the referenced service bulletin (Note 4), which indicates there is a mechanism for approving later revisions for compliance, but the AD does not describe how that approval is obtained or recorded.

Interaction with EASA AD. The AD refers to EASA AD 2009-0036 as addressing the same unsafe condition (Note 5). That cross-reference does not itself create enforcement action, but it may be relevant to inspectors or international operators who have already taken action under the EASA AD. The AD recognises inspections performed under the service bulletin within 3,000 FC before the AD effective date as satisfying Requirement 1; this narrows the window for potential enforcement actions related to past inspections, but the AD does not state how proof of such past inspections must be produced.

Direct cross-reference to EASA. The AD explicitly states it "addresses the same unsafe condition as EASA AD 2009-0036" (Background; Note 5). That is the only cross-jurisdictional or external AD reference in the text. The AD therefore sits in a regulatory family addressing the same technical failure mode, and operators who have acted under EASA AD 2009-0036 or the referenced CFM service bulletin may have compliance steps that overlap or have been completed prior to this CASA AD.

Adoption of manufacturer service bulletin as standard. Rather than reproducing technical inspection steps, the AD mandates compliance with paragraphs 3.A and 3.B of CFM Service Bulletin CFM56-3/3B/3C 72-1067 original issue and accepts later approved revisions (Requirements; Note 4). This creates a normative link to the manufacturer’s documentation and any approval processes that pertain to those service bulletin revisions. Any legal or regulatory framework governing the approval of service bulletin revisions will therefore be relevant to compliance, even though those frameworks are not described in the AD.

Installation prohibition for a specific engine model. Note 2 states the installation of the 25 degree mid-span shrouded blades is "not allowed on the CFM56-3C engine model." This is an explicit regulatory prohibition that interacts with type-certification, engine configuration control and installation approval regimes. Operators of CFM56-3C engines must therefore ensure procurement and maintenance practices are consistent with that prohibition.

Temporal interaction with prior inspections. Note 3 provides a temporal carve-out: "Inspections completed in accordance with CFM SB ... original issue, within the last 3,000 Flight Cycles (FC) before the effective date of this AD satisfies Requirement 1 of this AD." That interacts with record-keeping and retrospective compliance obligations: if an operator can demonstrate an inspection meeting those criteria, the operator is not required to re-inspect immediately but is subject to the stated repetition interval thereafter. That interaction depends on the operator’s ability to produce records that align with the SB standard and the AD timing.

Regulatory approval process for service bulletin revisions. The AD’s acceptance of "later approved revisions" of the SB for compliance creates an interaction with any statutory or administrative processes under which such revisions are approved. The AD does not describe the approval authority or process, so operators must locate the approval channel (for example, CASA approvals or other authorised regulatory recognitions) to rely on later revisions for compliance.

The supplied document contains minimal amendment history. The AD is identified as AD/CFM56/33, issue 10/2014, and it became effective on 9 May 2014 (header and Compliance). The signature block is dated 30 April 2014 and signed by "Mike Higgins, Delegate of the Civil Aviation Safety Authority."

The AD explicitly refers to an earlier regulatory instrument by another authority, EASA AD 2009-0036 dated 20 February 2009, as addressing the same unsafe condition (Background; Note 5). The AD does not include any internal amendments or supersessions in the supplied text. There is no list of prior Australian ADs that it replaces, nor is there a later amendment to this AD recorded in the text provided.

The AD allows the use of "later approved revisions" of CFM SB CFM56-3/3B/3C 72-1067 original issue for compliance (Note 4). That language anticipates that the referenced service bulletin may be revised, and that such revisions may be approved for AD compliance. The AD itself does not record any such approvals or list specific later revision numbers; rather it preserves the right to accept approved later revisions as compliant methods. Any amendment history relating to the service bulletin or to subsequent AD revisions would need to be sought from CASA records, CFM International communications, or a consolidated AD register, none of which are included in this document.

No further amendment entries, revision notes, withdrawal notices, or supersessions are present in the supplied text. The document appears to be a standalone AD with an effective date and an express cross-reference to an earlier EASA AD, but without an appended record of subsequent changes.

Users seeking to determine whether this AD has been amended, superseded, or withdrawn after its effective date must consult CASA’s published AD register or other official channels, because such post-issue actions are not recorded in the AD text provided here.

The supplied AD text does not contain any litigation history, citations to court decisions, appeals, or references to legal proceedings associated with AD/CFM56/33. The document confines itself to the technical applicability, mandated actions, timing for compliance, relevant notes and the safety background explaining why the AD was issued.

The Background cites a reported multiple fan blade failure event as the factual trigger for regulatory action, but the AD does not reference any litigation arising from that event or from its issuance. There are no references to disputes about the AD, challenges to CASA’s decision, or judicial interpretations of the AD’s requirements within the document.

Given the absence of litigation material in the supplied text, there is no source-grounded litigation history to report. Any legal challenges, enforcement actions, or court rulings relating to this AD, the underlying incident, or associated maintenance practice would need to be located in external legal or regulatory records. The AD itself provides no record of such proceedings.

This AD contains several practical and legal traps that operators, maintainers, parts suppliers and lessors must note, each of which derives directly from the language of the AD.

1. Applicability hinges on part numbers and the phrase "when equipped with fan blades with 25 degree mid-span shrouds." That means not every CFM56-3 engine is affected; only those specifically fitted with the listed P/Ns are in scope (Applicability). Failure to verify part numbers or the presence of 25 degree mid-span shrouds in records can lead to incorrect assumptions of compliance or non-compliance.

2. Past inspections may exempt immediate action, but only if they meet precise conditions. The AD states "Inspections completed in accordance with CFM SB ... original issue, within the last 3,000 Flight Cycles (FC) before the effective date of this AD satisfies Requirement 1 of this AD" (Requirements, Note 3). Operators must therefore be able to demonstrate that the inspection was: a) performed using the SB original issue method, and b) occurred within 3,000 FC prior to the AD effective date (9 May 2014). Inspections using other documents, slightly different methods, or outside the 3,000 FC window are not accepted by this clause.

3. The AD accepts "later approved revisions" of the service bulletin for compliance (Note 4), but approval status matters. Not all later revisions are automatically acceptable; they must be "approved" for AD compliance. The AD does not specify who approves revisions or how approval is recorded. Operators must confirm the approval status through appropriate channels before relying on a later SB revision.

4. Installation prohibition nuance. Requirement 3 prohibits installation of the listed blades on any CFM56-3 engine model "unless they have been previously inspected in accordance with paragraph 3 of the accomplishment instructions of CFM SB ..." (Requirements 3). Yet Note 2 separately states that installation of blades with 25 degree mid-span shrouds "is not allowed on the CFM56-3C engine model." Two points follow: for the 3C model, installation is flatly disallowed; for other CFM56-3 models, installation is permitted only if prior inspection is documented. Operators and parts suppliers must therefore treat the 3C model as an absolute prohibition, not a conditional installation subject to inspection.

5. Timing pressure: "before further flight." For initial inspections where not previously complied with, Compliance (a) requires the inspection "before further flight." For any damage found, Compliance (b) requires removal/replacement "before further flight." That phrase imposes immediate operational constraints and may require grounding an aircraft for inspection or replacement until the action is done. There is no explicitly stated grace period in the AD.

This section sets out a practical, source-grounded compliance checklist directly derived from the AD’s Requirements and Compliance paragraphs. It does not invent additional obligations beyond those stated.

1. Identify affected engines and parts. Review maintenance records, parts tags and physical inspections to ascertain whether any CFM56-3 engines in your fleet are fitted with fan blades having 25 degree mid-span shrouds and the listed part numbers: P/N 9527M99P08, 9527M99P09, 9527M99P10, P/N 9527M99P11, P/N 1285M39P01, or fan blade pairs P/N 335-088-901-0, 335-088-902-0, 335-088-903-0, and 335-088-904-0 (Applicability).

2. Check for previous compliant inspections. Determine whether an inspection in accordance with CFM SB CFM56-3/3B/3C 72-1067 original issue was completed within the 3,000 FC window prior to 9 May 2014. If such an inspection exists and the records show it followed the SB original issue method, Requirement 1 is satisfied until the next interval (Requirements; Note 3).

3. Schedule immediate inspection if required. If no qualifying inspection exists, perform the inspection "before further flight" (Compliance (a)). Use the SB paragraphs identified by the AD: paragraph 3.A for on-wing inspections or paragraph 3.B for in-shop inspections (Requirements 1). Obtain the CFM SB 72-1067 original issue (or a later revision if that revision is approved for compliance per Note 4) and follow the precise inspection methods and acceptance criteria set out in paragraph 3.

4. If damage is found, remediate before flight. If the inspection reveals any damage as defined by the SB, remove and replace the affected blade(s) "as instructed in the accomplishment instructions of CFM SB CFM56-3/3B/3C 72-1067 original issue" and do so "before further flight" (Requirements 2; Compliance (b)). Ensure replacement blades are of approved part numbers and have the required inspection provenance before installation.

5. Do not install listed blades without prior inspection. For any blade of the listed P/Ns intended for installation on a CFM56-3 engine model, ensure it has been previously inspected in accordance with paragraph 3 of the SB accomplishment instructions before installation. For the CFM56-3C model, do not install these blades at all (Requirements 3; Note 2; Compliance (c)).

6. Use approved SB revisions where available. If relying on a later revision of SB 72-1067, verify that the revision is "approved" for AD compliance (Note 4). Operators should obtain evidence of approval , for example from CASA, an authorised representative, or an approved maintenance organisation , before relying on a later revision to satisfy the AD.