AD/RB211/36 - High Pressure Turbine Cooling Air Holes

The AD formalises several interlocking technical and procedural concepts drawn from the Rolls-Royce service communications it incorporates. First, the inspection method: an Eddy Current Inspection, the AD requires the ECI as defined in Section 3 of Rolls-Royce NMSB 72-AE969 or later EASA approved revision (Requirement 1). That ties the mandated technique and acceptance criteria to a named Rolls-Royce NMSB and to the EASA approval framework, rather than specifying generic NDT parameters in the AD text itself.

Second, applicability: the AD lists a range of RB211 model designations and states the engines are "installed on, but not limited to, Boeing 747, Boeing 767 and Lockheed L-1011 aircraft" (Applicability). The phrase "installed on, but not limited to" indicates the AD applies to the specified engine models irrespective of airframe model, and that the listed aircraft are examples rather than an exhaustive list.

Third, timing and triggers: the AD defines a cycles-based threshold (greater than 2,750 cycles since new) as the trigger for immediate inspection obligations. It then uses shop-visit events as the practical inspection opportunity. Two alternative timing rules are provided: inspect at the next shop visit where HP turbine blades are removed; or if the rotor is in a shop visit with blades removed and not yet reinstalled into the Combustor Outer Case, the disc must be inspected before fitment to the aeroplane (Compliance schedule a and b). After the initial inspection, the AD requires ECI at every subsequent shop visit where HP turbine blades are removed (Compliance 2).

Fourth, equivalence of prior inspection: the AD allows a previously completed ECI carried out per Rolls-Royce TSD594-J Overhaul Process Manual Task 70-00-00-200-223, done at a disc life above 2,750 cycles since new and which meets the AD criteria, to satisfy the inspection requirement (Compliance note). This creates a narrow route to compliance without re-inspection where operators can demonstrate the prior inspection meets the AD’s substantive requirements.

Fifth, risk narrative: the background states that cracks were found in disc rims, traced to scores in cooling air holes introduced during manufacture or overhaul, and that undetected cracking could lead to uncontained disc failure (Background). The AD therefore links the inspection mandate to a specific identified failure mode and a described origin of the defect.

Finally, document hierarchy and approvals: the AD requires use of the NMSB or later EASA approved revision, and explicitly references EASA AD 2006-0180. That sets up an implementation chain where the mandated inspection procedure is controlled by the Rolls-Royce NMSB content and any EASA approvals, rather than being expanded on within the AD text.

The AD is addressed to operators and maintainers of Rolls-Royce RB211 engines in the listed model series. The applicability clause explicitly names multiple RB211 model designations and notes the engines are installed on, but not limited to, Boeing 747, Boeing 767 and Lockheed L-1011 aircraft (Applicability). Practically, that means:

• Aircraft operators who register, operate, or maintain aeroplanes with the listed RB211 engine models must ensure these engines are inspected in accordance with the AD requirements. The AD ties inspection timing to shop visits where HP turbine blades are removed, so operators scheduling engine shop visits and overhauls are the primary actors responsible for implementation (Compliance schedule).

• Maintenance organisations and overhaul shops performing blade removal, rotor disassembly, or HP turbine work must perform the ECI per the Rolls-Royce NMSB Section 3 when required. The AD conditions are triggered by maintenance events (blade removal, shop visit) and by accumulated cycles since new, so maintenance providers are the point of execution.

• Rolls-Royce as the engine manufacturer is involved indirectly through the NMSB and the Overhaul Process Manual referenced. The AD uses Rolls-Royce documents (NMSB 72-AE969 and TSD594-J) to specify inspection technique and to validate previous inspections. That allocates procedural authority to Rolls-Royce documents and any EASA approvals they obtain.

• Regulators and certificating authorities, represented here by the Civil Aviation Safety Authority which issued the AD, are decision-makers with enforcement authority implied by the AD being issued and effective (signature and effective date). The AD also references EASA AD 2006-0180, which indicates coordination or harmonisation across airworthiness authorities.

• Vendors who manufacture or overhaul HPT discs may be implicated. The background states the scores may have been introduced during new part manufacture or overhaul, which identifies both manufacturing and overhaul processes as potential origins of the defect. This affects parties responsible for the physical integrity of new parts and for their overhaul quality control.

The AD’s language places the inspection obligation on the owner/operator/maintainer at shop visits and uses cycles-since-new as a criterion. Therefore the actors who keep records of cycles since new, who decide on shop visit timing, and who perform blade removal are effectively required to ensure compliance.

Duties

• Carry out an Eddy Current Inspection (ECI) on specified HP turbine discs: The primary duty is to perform an ECI as defined in Section 3 of Rolls-Royce NMSB 72-AE969 or later EASA approved revision on the HP turbine discs identified in Sections 1.A.(3) and 1.A.(4) of that NMSB (Requirement 1). That duty is technical and prescriptive in that it points to a named inspection procedure.

• Repeat inspections: The AD requires the inspection to be repeated as detailed in Requirement 1, and explicitly requires ECI at every subsequent shop visit where HP turbine blades have been removed from the HP turbine disc (Requirement 2). This obliges ongoing, event-driven inspection at future maintenance intervals.

• Schedule-based compliance: Operators must observe the cycles threshold and timing rules. If cycles since new are greater than 2,750 on the effective date, the disc must be inspected at the next shop visit when blades are removed, or if currently in shop and blades already removed, inspected before reinstallation (Compliance schedule a and b). Those rules impose duties that interact with record-keeping of cycles since new and with maintenance scheduling.

• Use EASA-approved revisions: The prescribed inspection procedure is subject to EASA approval if a later revision of the NMSB is used (Requirement 1). That requires operators to confirm the revision they apply has EASA approval.

• Record equivalence: Where a disc previously passed inspection under Rolls-Royce TSD594-J Overhaul Process Manual Task 70-00-00-200-223 above 2,750 cycles since new and meets the AD criteria, that previous inspection satisfies Requirement 1 (Compliance note). The duty to establish equivalence rests with the operator/maintainer to demonstrate that earlier inspection meets the AD’s requirements.

Rights and practical entitlements

• Use of prior compliant inspections: Operators may rely on an earlier inspection performed under the specified TSD594-J task as satisfying the AD, where the inspection meets the criteria and was performed above the cycles threshold. That reduces duplication for operators who had a qualifying earlier inspection.

• Reliance on approved documents: The AD delegates the technical detail to Rolls-Royce NMSB 72-AE969 and recognises later EASA approved revisions. This gives operators the right to follow the current EASA approved NMSB revision rather than being tied to the exact words of the AD, provided EASA approval is obtained for revisions.

• Timing flexibility within constrained rules: The AD sets a "whichever is the soonest" formulation for the immediate compliance trigger, which affords operators a narrow scheduling choice: inspect at the next appropriate shop visit, or, in the case of an engine already in a shop visit with blades removed, inspect before fitment. That provides project-level discretion while imposing a firm cut-off.

No explicit appeal or waiver mechanism is provided in the AD text itself. There is also no explicit allocation of cost responsibility between manufacturers, overhaul organisations, and operators in the AD text. The duties are prescriptive about inspection technique and timing, and the rights are limited to the two practical reliefs noted: recognition of earlier qualifying inspections and the ability to use later EASA approved NMSB revisions.

The AD text itself does not specify civil or criminal penalties, fines, or enforcement procedures. It records the issuing authority and effective date: James Coyne, Delegate of the Civil Aviation Safety Authority, 21 July 2006, and the AD becomes effective on 31 August 2006 (signature and effective date). The instrument sets mandatory technical requirements and timing, but it contains no explicit enforcement or penalty provisions within the text provided.

From the structure of the AD, enforcement is effected by the AD’s status as a mandatory airworthiness directive issued by the Civil Aviation Safety Authority; the text identifies the AD, prescribes actions, and sets compliance triggers and timing. The AD also cross-references EASA AD 2006-0180 and requires use of EASA approved revisions of the Rolls-Royce NMSB, linking the AD to established airworthiness oversight mechanisms and approvals.

Because the AD does not itself set out enforcement mechanisms or sanctions, readers must look to the broader regulatory framework and enforcement authorities referenced implicitly by the AD for the consequences of non-compliance. The AD text provides the technical and timing obligations that a regulator could enforce, but does not articulate the enforcement tools, penalties, or procedural steps that would follow non-compliance. The AD similarly does not specify any certification, reporting, or return-to-service documentation beyond the inspection and timing requirements stated.

Operators and maintenance organisations therefore need to treat the AD as a mandatory obligation and ensure their records demonstrate compliance per the AD text. The AD also accepts prior inspections performed per Rolls-Royce TSD594-J under specified conditions as satisfying Requirement 1, which is a compliance pathway to document and retain. The absence of penalties in the AD text should not be read as absence of enforcement risk; the issuing authority and the fact of a mandatory AD imply regulatory oversight, but the instrument as provided does not enumerate the enforcement process or sanctions.

The AD explicitly incorporates and references external airworthiness documents and an EASA airworthiness directive. It requires the ECI "as defined in Section 3., Accomplishment instructions of Rolls-Royce NMSB 72-AE969 or later EASA approved revision" (Requirement 1). That means the AD’s technical obligations are implemented by following a manufacturer-issued service communication whose later revisions are admissible only if EASA has approved them. The AD therefore creates a document hierarchy in which the NMSB and any EASA approvals become operationally significant.

The AD also refers to EASA AD 2006-0180 dated 26 June 2006 (Note). That cross-reference indicates the AD is coordinated with or follows a related EASA directive. The practical effect is that compliance might require attention to both the CASA AD and the EASA AD, and to the approved content of the Rolls-Royce NMSB as accepted by EASA. Operators and maintainers must reconcile the CASA AD with the EASA AD and the Rolls-Royce NMSB and ensure they apply the version of the NMSB that has EASA approval.

In addition, the AD accepts as compliant a previous inspection performed according to Rolls-Royce TSD594-J Overhaul Process Manual Task 70-00-00-200-223 under specified conditions (Compliance note). That creates an interaction between the AD and the manufacturer’s overhaul process manual. Where a previous overhaul manual inspection exists and meets the AD’s criteria, the AD requirement is satisfied; the AD therefore treats the overhaul manual task as potentially authoritative for compliance purposes.

The AD does not itself reference or modify specific statutes, regulations, or penalties. It is an instrument that sets mandatory maintenance and inspection requirements and delegates the technical detail to manufacturer and EASA-approved documents. The AD’s practical interactions are therefore with:

• Manufacturer documentation (Rolls-Royce NMSB 72-AE969 and TSD594-J), which provide the substantive inspection procedures and acceptance criteria that the AD mandates or recognises.

• EASA approvals, because later revisions of the NMSB are accepted only if EASA approves them, and because the AD expressly refers to an EASA AD. That ties the AD to European airworthiness oversight in addition to the issuing authority.

• Maintenance scheduling and record-keeping frameworks, because the AD conditions its triggers on "cycles since new" and on shop visits where blades are removed. That interfaces with operators’ logbooks and maintenance management systems.

The AD text does not specify how conflicts between the AD, the NMSB, and EASA AD would be resolved should any arise. It does, however, indicate that EASA-approved revisions of the NMSB are acceptable, which implies that the most current EASA-approved NMSB content governs the technical method to be used in meeting the AD.

The AD as provided contains internal notes about document revision acceptance, but does not itself list prior amendments to the AD text. Key temporal markers and references in the document are:

• The AD identification: AD/RB211/36, dated 9/2006 (document header).

• Reference to EASA AD 2006-0180 dated 26 June 2006 (Note under Requirement 1).

• Effective date of the AD: becomes effective on 31 August 2006 (Compliance).

• Issuance date and signature: James Coyne, Delegate of the Civil Aviation Safety Authority, dated 21 July 2006 (signature block).

The AD allows the use of "later EASA approved revision" of Rolls-Royce NMSB 72-AE969 when performing the ECI (Requirement 1). That provision creates an avenue for operational amendment in that the operative technical procedure may be updated by later NMSB revisions once those revisions receive EASA approval. The AD therefore leaves open the possibility that the mandated inspection procedure may be updated over time through manufacturer revisions that have EASA approval, without the AD text itself needing amendment for each procedural update.

The AD also accepts prior inspections performed in accordance with Rolls-Royce TSD594-J Overhaul Process Manual Task 70-00-00-200-223, where those inspections were performed above 2,750 cycles since new and meet the AD criteria, as satisfying Requirement 1 (Compliance note). This recognition functions as an accommodation for prior compliant activity rather than as an amendment to the AD. The AD contains no explicit amendment record beyond these references and the dates provided.

The document does not state any subsequent modifications, revocations, supersessions, or clarifying amendments within the provided text. Any actual historical amendments, replacements, or extensions of the AD would need to be sought in the issuing authority’s subsequent publications or in updated AD lists, but such material is not included in the text provided.

The AD text contains no references to litigation, appeals, judicial decisions, or administrative reviews concerning this AD. There are no cases, stay orders, injunctions, or dispute records mentioned in the document. The only legal authorities explicitly named in the AD are the Civil Aviation Safety Authority as the issuer and EASA as the approving authority for later revisions of the Rolls-Royce NMSB. The AD does not reference any adjudicated disputes or precedent cases.

Because the instrument itself is an administrative safety directive focused on technical inspection requirements, the document does not document any enforcement actions or legal proceedings within its text. If parties affected by the AD later pursued litigation or administrative review, those proceedings would not be reflected in this AD text. The AD as provided is therefore silent on litigation history.

The AD contains several precise formulations and cross-references that can create practical pitfalls if operators or maintainers do not read the wording carefully.

• Broad applicability phrasing: The applicability clause lists specific RB211 models and then adds "installed on, but not limited to, Boeing 747, Boeing 767 and Lockheed L-1011 aircraft." That wording means the AD is not confined to those airframes, so operators must consider engines of the model list regardless of airframe type. Failure to interpret that breadth could leave engines uninspected.

• Cycles threshold and timing interplay: The immediate compliance trigger is a combination of cycles-since-new and maintenance events. The AD uses "greater than 2750 cycles on the effective date" as the numerical threshold, linked to shop visit events (Compliance schedule a and b). Operators need accurate cycles records. A common mistake would be to apply the inspection only when cycles exceed 2,750 during future operation, rather than checking the cycles-on-hand as of the effective date and scheduling inspection at the next appropriate shop visit.

• "Whichever is the soonest" language: The AD directs compliance "By whichever is the soonest of the following conditions" and then gives two alternatives. This formulation can be misapplied if maintenance planners attempt to delay inspection past the next shop visit. The AD mandates inspection at the next occasion where blades are removed, unless the engine is already in that state in which case inspection must precede fitment.

• Delegation of technical detail to NMSB: The ECI procedure and acceptance criteria are not detailed in the AD; they are contained in Section 3 of Rolls-Royce NMSB 72-AE969, or in a later EASA approved revision. Operators must obtain and apply the correct NMSB section, and must confirm EASA approval for later revisions. Using an unapproved or vendor-only revision may not satisfy the AD.

• Acceptance of prior inspections is narrowly framed: The AD accepts prior inspections under Rolls-Royce TSD594-J Overhaul Process Manual Task 70-00-00-200-223 as satisfying the AD only if the inspection occurred at a disc life above 2,750 cycles since new and meets the criteria detailed in Requirement 1. Operators cannot assume any prior inspection qualifies; they must verify that the prior inspection was exactly per the referenced task and that its conditions match the AD’s criteria.

• Defect origin and liability implications: The background notes scores may have been introduced during new part manufacture or during overhaul (Background). That identifies both manufacturers and overhaul shops as potential origins of the defect. Parties assessing cost allocation or liability should note the AD does not allocate responsibility, but it does identify multiple possible origins of the damage.

• EASA approval dependency: The AD permits use of "later EASA approved revision" of the NMSB. Where operators rely on a newer NMSB revision, they must ensure EASA approval has been granted. Using a later revision without EASA approval is not authorised by the AD wording.

• Absence of enforcement detail in the AD: The text does not set out penalties, reporting obligations, or the mechanism for confirming compliance beyond the inspection requirements. Operators should not interpret that absence as reducing enforcement risk; rather, they should ensure that inspection records are complete and available to their regulator.

• Document identification granularity: The AD refers to "HP turbine discs identified in Sections 1.A.(3) and 1.A.(4) of Rolls-Royce NMSB 72-AE969." Practically, implementers must obtain the exact NMSB and locate those sections to determine the precise disc serials or part numbers covered. Failure to retrieve and read those NMSB sections could lead to both over- and under-inclusion of components subject to inspection.

Compliance with the AD requires a combination of document control, record verification, scheduling, and execution of the specified ECI procedure. The following step-by-step checklist aligns with the AD text and the AD’s cross-references.

1. Identify affected engines and discs

   • Determine whether any engines hosted by your aeroplanes are listed RB211 models in the AD Applicability. Treat the listed aircraft models as examples rather than exhaustive limits; check all airframes with the listed engine models (Applicability).
   • Obtain Rolls-Royce NMSB 72-AE969 and locate Sections 1.A.(3) and 1.A.(4) to identify the specific HP turbine discs the NMSB targets. The AD requires that the ECI be applied to the discs identified in those sections (Requirement 1).

2. Confirm cycle counts and shop visit status

   • For each affected disc, determine "cycles since new" as of the AD effective date (31 August 2006). If cycles since new are greater than 2,750 on that effective date, the AD triggers immediate inspection at the next applicable shop visit per paragraph a of the Compliance schedule.
   • If an affected HP turbine rotor is already undergoing a shop visit on the effective date, and the HP turbine blades have been removed and the rotor has not yet been reinstalled into the Combustor Outer Case, then the disc must be inspected before fitment back to the aeroplane (Compliance schedule b).

3. Obtain the correct inspection procedure and approvals

   • Acquire Rolls-Royce NMSB 72-AE969 and proceed to Section 3, Accomplishment instructions, which defines the ECI procedure. The AD mandates the ECI "as defined" in that section (Requirement 1).
   • If you intend to use a later revision of NMSB 72-AE969, confirm EASA approval for that revision, because the AD specifies "or later EASA approved revision" (Requirement 1). Do not rely on an unapproved NMSB revision for compliance.

4. Execute the Eddy Current Inspection

   • Perform the ECI in accordance with the defined steps and acceptance criteria in Section 3 of the NMSB. Ensure inspection equipment, calibration, probe types, scanning patterns, and acceptance criteria match the NMSB requirements.
   • If the disc meets acceptance criteria, document the inspection results in maintenance records. If cracking or scores are found that exceed acceptance criteria, follow the remedial actions specified in the NMSB and applicable maintenance procedures.

5. Recognise prior compliant inspections where applicable

   • If a disc previously passed an ECI per Rolls-Royce TSD594-J Overhaul Process Manual Task 70-00-00-200-223, and that inspection was performed at a disc life above 2,750 cycles since new and meets the criteria detailed in Requirement 1, the AD states that this prior inspection satisfies Requirement 1 (Compliance note). Retain documentation of that prior inspection to evidence compliance.

6. Schedule repeat inspections

   • The AD requires ECI at every subsequent shop visit where HP turbine blades are removed from the disc (Requirement 2). Amend maintenance plans and workscopes to ensure that every blade removal event triggers the ECI procedure.

7. Maintain records and traceability

   • Record the NMSB revision and EASA approval used to perform the inspection, date of inspection, inspector identity, inspection results, and any corrective actions taken. Retain the disc life (cycles since new) records that demonstrate when the AD’s threshold applied.
   • If relying on a prior TSD594-J inspection for compliance, preserve the original inspection report and demonstrate it meets the AD criteria.

8. Coordinate with manufacturer and regulator as needed

   • Where inspection results reveal scores or cracks, follow the Rolls-Royce NMSB remediation instructions and report to any relevant regulatory or manufacturer points of contact as required by your internal procedures. The AD notes the cracks may originate in manufacture or overhaul, so consider notifying the manufacturer or overhaul provider in appropriate cases (Background).
   • If there is any uncertainty about whether a specific inspection procedure or NMSB revision is EASA-approved, verify EASA approval status before relying on that revision to satisfy the AD.

9. Operational clearance

   • Do not reinstall the HP turbine disc into the Combustor Outer Case and do not return the engine to service without completing the ECI as required when the AD’s conditions are met. This is explicit where the AD requires inspection before fitment when the rotor is already in a shop visit with blades removed (Compliance schedule b).

10. Audit and compliance assurance

• Incorporate AD compliance verification into maintenance audits and quality assurance checks. Because the AD contains no penalties within the text, compliance evidence is the primary way to demonstrate to authorities that the mandated inspection obligations have been met.

By following the NMSB Section 3 ECI procedure, the cycles and shop-visit scheduling rules, the repeat inspection requirement, and the documentation paths for prior inspections per TSD594-J, operators and maintainers can create an auditable trail that aligns with the AD’s explicit requirements (Requirement 1; Compliance schedule; Compliance note; Requirement 2; Background).