AD/B747/46 Amdt 7 - Forward Fuselage Pressure Shell

The Directive’s central technical objects are fuselage geometry coordinates, inspection types, flight-cycle triggers, group-based applicability, service-bulletin technical procedures, and terminating modification options. Each concept has an operational definition in the text.

• Geometry coordinates. Inspections are specified by Body Stations (BS) and stringer numbers (S). The persistent core area is BS 420 to 460 and S-8 to S-12 (Requirement 1 and many of the new requirements). Other BS/S ranges are listed across Requirements 2A-2E and the later tables (for example, BS 200-240 from S-13A to 14E, BS 320-520 from S-0 to 8, etc.). These coordinates determine the physical scope of inspections and which structural elements,frames, tear straps, lap splices, window surrounds and under‑deck door areas,are to be inspected (Requirements and Figures referred in the Service Bulletin).

• Groups and applicability. The AD divides affected aeroplanes into Groups 1-11, as defined by Boeing Service Bulletin 747-53A2265 Revision 9; Group membership maps to line numbers and discrete airplane variants (Applicability table). Different Groups have tailored exemptions and inspection thresholds (notes in Requirement 2 and the Compliance table). For example, Group 1 is exempt from the 7,000‑flights inspection and certain groups are exempt from inspections above particular stringers or BS ranges (Notes under Requirement 2).

• Inspection types. The AD prescribes multiple inspection methods: external detailed visual inspections; close detailed visual inspections of internal pressure-shell structure and floor-beam/fuselage-frame junctions; internal detailed inspections; surface HFEC and internal surface HFEC (New Requirements 5-9); and nondestructive testing per Boeing NDT Manual for lap splices (Requirement 4; Note 2). The AD cross-references Boeing Service Bulletin BSB 747‑53A2265 Revision 9 for accomplishment instructions and Boeing NDT Manual D6-7170 for specific NDT technique and figure references.

• Flight-cycle (flight limit) scheduling. The AD uses total flight cycles as the primary metric to trigger and time inspections: e.g. before exceeding 7,000, 8,000, 10,000, 13,000, 16,000, 19,000 and 20,000 flights in the staged Requirements 2A-2E and new requirements (Requirements 2A-2E; Compliance paragraphs). The AD also prescribes the repetition intervals for routine inspections (for example, Requirement 1: initially before 8,000 cycles then at intervals not to exceed 25 cycles; Requirement 2E: repeat 2E inspection at intervals not to exceed 3,000 flights until 20,000 flights, then at intervals not to exceed 2,000 flights).

• Termination by modification. A defined terminating action is available: modification in accordance with Boeing SB 747‑53‑2272 Revision 18 cancels Requirements 1 and 2 and Requirements 5-9 for modified areas only (Compliance table; Background). The termination is limited to modified areas, and the Service Bulletin must be approved by FAA AMOC for that effect.

• Return-to-service and Authority control. The Directive explicitly prohibits returning known‑cracked aircraft to service without prior approval of the Authority (Note 15). The Authority may grant certain limited exemptions, such as temporarily deferring a right‑hand internal inspection where failed structure was found on the left side, subject to conditions and a maximum deferment to 13,000 flights (Note 14).

These concepts interact: group assignment determines which BS/S grids apply; flight-cycle counts determine which staged inspections are required and when; inspection technique (visual versus HFEC versus NDT) determines resource needs, downtime and skills required; and terminating modification options constrain long‑term maintenance planning because they cancel inspections only for modified areas and require an FAA AMOC‑approved revision. The Directive therefore establishes both recurring operational duties and a capital modification path that replaces recurring inspections for modified zones.

This AD affects a narrow, identifiable population and a broader set of professional actors who perform, approve or enforce the work. The primary physical subjects are Boeing 747 aircraft, line positions 1-685 built prior to August 1987, grouped into Groups 1-11 as defined by Boeing Service Bulletin 747‑53A2265 Revision 9 (Applicability table). The affected operators are owners and leasers of these specific aircraft, and their airworthiness and maintenance organisations responsible for continuing airworthiness.

The secondary affected parties include:

• Maintenance organisations and licensed maintenance personnel, required to perform detailed, close and HFEC inspections in accordance with Boeing SB 747‑53A2265 Revision 9 and Boeing NDT Manual D6‑7170 (Requirements and Notes). HFEC requires specific NDT capability and trained technicians. Internal inspections may require access panels removal and possible partial disassembly.

• Line maintenance and records staff, who must track total flight cycles for each aircraft and ensure the inspections are scheduled and performed at the flight-cycle thresholds established by the AD (Compliance paragraphs, Note 16 on flight counting).

• Regulatory authority staff (Civil Aviation Safety Authority delegate and approvals functions), who administer approvals for returning aircraft to service with unrepaired cracks (Note 15), handle exemptions (Note 14), and approve terminating modifications via FAA AMOC‑approved Service Bulletin revisions (Compliance table, Background).

• Engineers and designers handling modifications, because compliance with Boeing SB 747‑53‑2272 Revision 18 (or later FAA AMOC‑approved revision) provides terminating action only for modified areas (Compliance table).

• Airlines’ operational planners, because inspections timed by flight cycles may necessitate grounded time or additional maintenance scheduling, and certain inspections have short repetitive intervals (Requirement 1 requires inspections thereafter at intervals not to exceed 25 flight cycles; New Requirement 8 requires repetitive inspections not to exceed 1,000 flight cycles unless replaced by other flight-limit inspections).

• Safety managers, because the AD explicitly links to risk of structural failure and cabin decompression in its background and requires immediate inspections where cracks are found forward of BS 520 (Requirement 3 and 4).

• Certificate holders who provide NDT services and HFEC capability, because the AD requires surface HFEC for certain groups and zones (New Requirements 7-9).

Notably, the instrument excludes certain peripheral components from inspection: crew escape hatches, crew doors, and main entry doors are expressly excluded from the inspection requirements of this AD (Note 3). The AD also cancels previous AD/B747/324 and consolidates its requirements (Note 1 and Background), so parties that previously relied on AD/B747/324 must now follow this AD. Finally, aircraft on which modification per Boeing SB 747‑53‑2272 Rev 18 has been performed are affected only to the extent of unmodified areas; the modification cancels the listed inspections for modified areas only (Compliance).

Duties imposed by the Directive are procedural, technical, and temporal. Rights are limited administrative discretions granted by the Authority and limited mechanical options specified in the AD.

Key statutory duties and their source references in the AD:

• Perform external detailed visual inspection for cracked skin or loose/missing fasteners between BS 420-460 and S‑8-S‑12 on both left and right sides, and accomplish corrective actions in accordance with Boeing SB 747‑53A2265 Revision 9 (Requirement 1). Compliance timing: before accumulation of 8,000 total flight cycles or within 10 flight cycles after receipt of the Directive, whichever later; then repeat at intervals not to exceed 25 flight cycles (Compliance paragraph 1).

• Conduct close detailed visual inspection of the interior structure of the pressure shell, floor beam/fuselage frame junctions, plus external detailed visual inspection at fuselage frame fasteners at specified BS/S locations and at specified total-flight thresholds: 7,000, 10,000, 13,000, 16,000 and 19,000 flights (Requirements 2 and 2A-2E). Each sub‑paragraphed requirement lists exact BS and S ranges to be inspected before exceeding the specified flight limit.

• When frame cracks are found, conduct additional internal and external close visual inspections one frame bay and one stringer each side; extend to six stringer spacings each side where a frame crack exceeds half the cross section (Requirement 3).

• Inspect fuselage skin lap splices in vicinity of any frame or floor beam crack longer than 25mm for 500mm fore and aft in accordance with Boeing NDT Manual D6‑7170 Part 6 Subject 53‑30‑00 Figure 2 (Requirement 4).

• For Group‑based internal inspection requirements (New Requirements 5-9), perform internal detailed inspections and HFEC inspections of body frames and adjacent skin between BS 420-460 and S‑8-S‑12 at flight‑limit thresholds specified by group membership, and repeat at prescribed intervals. For Groups 7-11, surface HFEC is specifically required and repetitive internal HFEC/close detailed inspections are required at intervals not to exceed 1,000 flight cycles between flight‑limit inspections unless the longer flight‑limit inspection is performed (New Requirements 5-9 and associated Notes).

• Do not return aircraft known to have unrepaired cracks to service without prior approval of the Authority (Note 15).

• Record flight cycles excluding flights on which cabin pressure differential does not exceed 2.0 psi (Note 16). Thus operators must maintain accurate flight‑cycle accounting and apply the exclusion rule where applicable.

Rights and discretions granted within the AD:

• Termination option for recurring inspections in modified areas, by accomplishment of Boeing SB 747‑53‑2272 Revision 18 (or later FAA AMOC‑approved revision) (Compliance table; Background). This is a mechanical right to substitute a modification for recurring inspection burden, limited to the modified areas only.

• Deferment right for internal inspections behind the Flight Engineer’s panel on Groups 1-3 until 13,000 flights if no critical element on the corresponding left side is severed or has been replaced/repaired for fatigue damage; where deferred, external inspections at intervals not to exceed 1,000 flight cycles must be conducted per Boeing NDT Manual (Compliance notes).

• Authority discretion to grant a limited exemption from right‑side internal inspection in cases where failed structure is found on the left side, deferring the right side up to 1,500 flights but not beyond 13,000 total flights, if alternative methods clearly show no major cracking (Note 14). This is an authority‑managed risk mitigation pathway.

• Alternation of inspection methods is permitted, provided the corresponding repetitive inspection interval is not exceeded (Compliance paragraph 9). This allows operational flexibility provided intervals remain within the AD’s safety parameter.

The AD places procedural obligations on operators and maintenance organisations to follow the prescriptive inspection schedules, to carry out corrective actions per Boeing SB 747‑53A2265 Revision 9, to maintain flight‑cycle accounting with exclusions for low differential flights (Note 16), and to seek Authority approval if unrepaired cracks are present before returning to service (Note 15). Rights are primarily administrative flexibilities and a terminating modification path requiring an FAA AMOC‑approved service bulletin revision.

The text of AD/B747/46 Amendment 7 itself does not set out monetary penalties, criminal sanctions, or procedural enforcement mechanisms. Instead, the instrument operates as a regulatory direction issued by the Civil Aviation Safety Authority (CASA) delegate; compliance is mandatory for the affected aircraft and operators listed in the Applicability table and the compliance schedule (signature block by David Villiers, Delegate of CASA; Effective date). Where the AD speaks to enforcement‑related processes, it does so by imposing conditions that are subject to regulatory approval:

• The AD requires that “Aircraft known to have unrepaired cracks shall not be returned to service without the prior approval of the Authority” (Note 15). That gives CASA an explicit administrative control point to withhold return‑to‑service approvals until remedial actions are taken and documented.

• Note 14 indicates that the Authority may grant an exemption deferring a required inspection in limited circumstances, which implies CASA has discretion to authorise temporary relief subject to evidentiary demonstration that the corresponding element is not cracked.

• The AD references FAA AMOC approval as a condition for acceptance of Boeing SB 747‑53‑2272 Revision 18 as terminating action for modified areas. That cross‑jurisdictional reference places FAA AMOC approval as a gating condition for CASA to accept the terminating modification for the purposes of cancelling recurring inspections in those areas.

Because the AD is a regulatory direction from CASA, failure to comply would place operators outside the regulatory requirements governing the airworthiness of the aircraft. While this AD text does not list specific sanctions, CASA’s general enforcement powers and civil aviation legislation provide administrative and enforcement measures for non‑compliance with airworthiness directives. The AD itself limits the available reliefs and sets explicit conditions for return to service and for exemptions; those conditions must be satisfied and documented with the Authority.

Practically, enforcement points are: inspections must be done within the flight‑cycle windows specified (Compliance table and Requirements 2A-2E); corrective actions must follow Boeing SB 747‑53A2265 Revision 9; modifications per Boeing SB 747‑53‑2272 Rev 18 must be FAA AMOC‑approved to be accepted as terminating action for modified areas. The AD therefore sets compliance obligations that intersect with CASA’s approval and return‑to‑service authorities. The AD’s enforcement leverage is the Authority’s approval functions and the operational prohibition on returning cracked aircraft to service without prior approval (Note 15).

The Directive explicitly references and integrates other regulatory instruments, technical service bulletins and foreign authority directions. Those cross‑references determine how this AD operates alongside other safety law and technical standards.

• Interaction with prior ADs. The AD cancels AD/B747/324 and consolidates its requirements into AD/B747/46 (Note 1 and Background). It also replaces earlier FAA AD 91‑11‑01 with requirements reflecting FAA AD 2005‑08‑01 (Background). That means operators previously complying with AD/B747/324 or earlier FAA ADs must now comply with this consolidated AD, subject to the current requirements and thresholds.

• Interaction with FAA AD 2005‑08‑01. The AD incorporates the additional inspections and expanded inspection areas introduced by FAA AD 2005‑08‑01; the AD identifies the new FAA AD as the source of additional requirements and states that Boeing SB 747‑53A2265 Revision 9 contains detailed accomplishment instructions for those new requirements (Note 4; Background). This creates regulatory alignment with the FAA AD as a substantive source of inspection content and schedule.

• Interaction with Boeing service bulletins and NDT manuals. The AD delegates technical accomplishment instructions to Boeing Service Bulletin BSB 747‑53A2265 Revision 9 and to Boeing NDT Manual D6‑7170 Part 6 Subject 53‑30‑00 Figure 2 for lap splice inspection techniques (Requirements and Notes). Those service documents are technical standards referenced by the AD; operators must follow them for compliance.

• Termination via modification subject to FAA AMOC approval. The AD allows termination of recurring inspections for modified areas when modification is accomplished per Boeing SB 747‑53‑2272 Revision 18, but only when that service bulletin is approved by FAA AMOC (Compliance table; Background). This requires coordination between the operator, Boeing SB implementation, FAA AMOC approval and CASA acceptance. The FAA AMOC requirement is an inter-authority gate.

• Flight-cycle counting rules. The AD instructs that flights with cabin differential not exceeding 2.0 psi need not be counted for flight-cycle totals (Note 16). That interacts with operators’ recordkeeping and potentially with other regulatory obligations concerning flight logs and fatigue‑life accounting.

• Authority discretion and approvals. The AD gives the Authority (CASA) express discretion to approve return to service for aircraft with unrepaired cracks and to grant limited inspection deferments (Notes 14 and 15). Those permissions sit within regulatory administrative law processes and CASA’s established approvals mechanisms.

• Effect on maintenance approvals and licencing. The AD’s HFEC and NDT requirements implicate licenced NDT personnel and organisation approvals. Although the AD does not restate licensing law, its reference to specified NDT techniques requires that persons performing those techniques do so to the NDT manual standards and presumably within any applicable licencing or approval framework.

In short, the AD sits in a network of technical and regulatory instruments: it replaces specific earlier ADs; it imports technical methods from Boeing service documents and NDT manuals; it ties a terminating modification to FAA AMOC approval; and it imposes obligations that intersect with CASA’s approval powers. The AD does not itself amend primary aviation legislation; rather, it operates as a binding regulatory direction leveraging those other instruments and approval pathways.

The Directive has a recorded lineage and recent amendments that changed scope and mechanics. The document itself and its notes provide the following history.

• Origin. The Directive was originally raised on 4 February 1986 in response to multiple instances of severe cracking on the forward fuselage Section 41 (Background). At that time, its requirements exceeded Boeing Service Bulletin 747‑53A2265 Revision 8 and FAA AD 91‑11‑01 (Background).

• Consolidation and prior amendment (Amendment 6). A previous amendment (Amendment 6) restructured the AD by combining the requirements of the then‑current AD with AD/B747/324 and the new requirements from FAA AD 2005‑08‑01 (Background). The new FAA AD added extra inspections, expanded inspection areas and removed a one‑time deferral of an inspection; these changes were folded into AD/B747/46 through Amendment 6. The AD notes that Boeing SB 747‑53A2265 Revision 9 contains detailed accomplishment instructions for the requirements introduced at that amendment (Note 4).

• Amendment 7 (current text). Amendment 7 (this instrument) makes a correction to the provisions for terminating action that relate to modification in accordance with Boeing SB 747‑53‑2272 Revision 18. The Compliance table and Background state that compliance with Revision 18 or later revisions approved by FAA AMOC cancels the inspections per Requirements 1 and 2, together with Requirements 5 through Requirement 9 inclusive, for the modified areas only. Amendment 7’s effective date is 2 August 2007 (last Compliance note, Effective date).

• Supersessions/cancellations. The AD cancels AD/B747/324 as part of the consolidation, and it reflects that FAA AD 91‑11‑01 has been superseded by FAA AD 2005‑08‑01 (Notes and Background). The AD therefore represents the latest consolidated regulatory position as of Amendment 7.

• Technical references updated. Boeing SB 747‑53A2265 Revision 9 is the revision referenced for applicability grouping and detailed accomplishment instructions. The termination route references Boeing SB 747‑53‑2272 Revision 18 and any later revision approved by FAA AMOC.

The Directive’s amendment history shows an iterative response to inspection findings, alignment with FAA directives, and an attempt to provide a terminating modification path. The document explicitly records where prior ADs were folded into the current text and where new inspection requirements were adopted following FAA action.

The AD text supplies no litigation history, judicial decisions or references to court proceedings. There are no named cases in the document. The only legal/administrative authorities referenced are CASA (the issuing Authority), the FAA and the Boeing service documents (BSB 747‑53A2265 Rev 9; SB 747‑53‑2272 Rev 18), and FAA AMOC approval processes.

Because the AD is an administrative safety instrument, any enforcement or dispute would typically proceed through administrative review and aviation enforcement processes under aviation law; however, the Directive contains no record of litigation, appeals, or judicial interpretation within the text supplied. Readers should therefore treat this AD as a regulatory requirement without recorded litigation history in this document.

If judicial or tribunal proceedings regarding compliance, enforcement or interpretation of this AD exist, they are not referenced in this AD and are not part of the source material. The AD’s operational provisions about Authority approvals, exemptions and return‑to‑service are administrative mechanisms rather than litigated rules in the text provided.

The AD contains a number of detailed exceptions, deferrals, conditionalities and cross‑references that create operational pitfalls if overlooked. These are practical “gotchas” that operators, maintenance organisations and compliance professionals must watch for, and each one follows directly from the AD text.

• Group definitions are external to the AD. Applicability is “as defined by Boeing Service Bulletin 747‑53A2265, Revision 9.” Operators must therefore first determine correct Group membership by cross‑referencing the Service Bulletin; mis‑grouping an aeroplane will lead to incorrect inspection scheduling (Applicability table).

• Termination applies only to modified areas. Compliance with Boeing SB 747‑53‑2272 Revision 18 (and FAA AMOC approval) cancels Requirements 1 and 2 and Requirements 5-9 only for the modified areas. This is not a blanket cancellation. If an operator assumes that a single modification removes all inspection obligations, they may inadvertently fail to inspect unmodified areas (Compliance table; Background).

• Deferment conditions are conditional and limited. The internal inspection behind the Flight Engineer’s panel may be deferred until 13,000 flights for Groups 1-3 only where “no critical element of the pressure shell structure within the corresponding location on the left hand side is severed or otherwise locally ineffective, or has been previously replaced or repaired due to fatigue damage.” The AD specifies that where internal inspections have been deferred, external skin inspections must be conducted per Boeing NDT Manual at intervals not to exceed 1,000 flight cycles (Compliance paragraph on deferment; Note 13). Misapplication of the deferment or failure to carry the compensating external inspections is non‑compliant.

• Exemptions limited where failed structure is found. If failed structure has been found on the left-hand side, an exemption "may still be available" to defer close detailed internal inspection on the right side for 1,500 flights but not beyond 13,000 total flights, and only if it can be clearly shown by alternative methods that there is no major cracking of the corresponding right-side element (Note 14). This is an Authority discretion, not an automatic right; operators must compile and present alternative‑method evidence satisfactorily.

• Flight counting nuance. Flights with cabin pressure differential not exceeding 2.0 psi need not be counted (Note 16). Operators must therefore maintain flight records capable of distinguishing such flights to avoid miscounting and scheduling inspections too early or too late.

• Short repetitive intervals for some inspections. Requirement 1 prescribes repeat intervals not to exceed 25 flight cycles after the initial inspection; other inspections have repeat intervals as short as 750 flight cycles or 1,000 flight cycles depending on group and method (Compliance and new requirements). These short intervals impose operational scheduling pressure and may require frequent downtime.

• HFEC requirements and alternation. Groups 7-11 have HFEC inspection obligations (New Requirements 7-9). Operators may alternate inspection methods provided the repetitive interval is not exceeded; however alternating without proper equivalency and documentation risks failing to meet the AD’s specific method‑based obligations and the underlying FAA AD requirements (Compliance paragraph 9). HFEC capability and competence are essential.

• Scope excludes doors and hatches. Crew escape hatches, crew doors and main entry doors are excluded (Note 3). Failure to observe exclusions and wasting inspection resources on excluded components is an efficiency gotcha; conversely, assuming undocumented exclusions elsewhere is risky.

• Immediate inspection triggers for discovered cracks. Requirement 3 requires additional internal and external inspections one frame bay and one stringer each side of any frame crack, and Requirement 4 requires lap splice inspections where cracks exceed 25mm. Moreover, inspections per Requirement 3 and 4 must be done “before further flight” when cracks are found forward of BS 520 or when cracks longer than 25mm are discovered forward of BS 520 (Compliance paragraphs 3 and 4). That creates an immediate operational grounding and an Authority approval point if repairs remain undone (Note 15).

• Record of service bulletin revisions and approvals. The AD requires referencing and using specific revisions (e.g., BSB 747‑53A2265 Revision 9 and SB 747‑53‑2272 Revision 18) and FAA AMOC approval for terminating action. The requirement to use particular revisions creates a documentation and approvals tracking obligation; using the wrong revision or lacking an FAA AMOC approval undermines the terminating modification claim (Compliance; Background).

• Overlap of new and existing requirements. The AD warns that there may be overlap between existing requirements and the new FAA AD‑introduced requirements (Note 4). Operators must map out which inspections are duplicative and which are additive to avoid double‑counting work or missing an additive inspection.

Avoiding these gotchas requires cross‑referencing the specified Boeing Service Bulletin revision, documenting flight cycles with the 2.0 psi exclusion, ensuring NDT/HFEC capability and training, tracking terminated areas after modification, seeking Authority approvals where required, and preparing for immediate inspections and grounding where cracks are found forward of BS 520.

Compliance is a sequence of discrete steps grounded in the AD’s requirements, Boeing service bulletin accomplishment instructions, and recordkeeping and approval processes. Below is an actionable compliance checklist derived strictly from the AD text and its referenced notes.

1. Identify affected aeroplanes and groups

   • Determine whether the aeroplane is within line numbers 1-685 and built prior to August 1987 per the Applicability table.
   • Use Boeing Service Bulletin 747‑53A2265 Revision 9 to assign the aeroplane to one of Groups 1-11 (Applicability; note in table).

2. Establish current total flight‑cycle counts and applicable exemptions

   • Record total flight cycles for each aeroplane. Exclude flights on which cabin pressure differential does not exceed 2.0 psi from total flight‑cycle counts (Note 16).
   • Identify whether the aircraft has reached thresholds that trigger Requirements 2A-2E or the new requirements (e.g. 7,000; 8,000; 10,000; 13,000; 16,000; 19,000 flights).

3. Schedule and perform Requirement 1 initial and repeat inspections

   • For the external detailed visual inspection of BS 420-460 between S‑8 and S‑12 on both sides (Requirement 1), perform the initial inspection before accumulation of 8,000 total flight cycles or within 10 flight cycles after receipt of the Directive, whichever later.
   • Thereafter, perform the external inspection at intervals not to exceed 25 flight cycles (Compliance paragraph 1).
   • Accomplish corrective actions as specified by Boeing SB 747‑53A2265 Revision 9.

4. Schedule and perform staged internal and external inspections per Requirement 2 (2A-2E)

   • Consult the tables in Requirements 2A-2E to see which BS/S locations must be inspected before the relevant flight‑cycle threshold (7,000; 10,000; 13,000; 16,000; 19,000).
   • Perform close detailed internal inspections of the pressure shell structure (including floor beam/fuselage frame junctions) and external detailed inspections at fuselage frame fasteners as directed.
   • For Requirement 2E (before exceeding 19,000 flights), inspect all pressure shell structure from BS 140 to 520 and repeat at intervals not exceeding 3,000 flights until 20,000 flights; then inspect at 20,000 flights or within 2,000 flights since last inspected, whichever occurs later, and thereafter at intervals not to exceed 2,000 flights.

5. Conduct additional inspections when cracks are found

   • If any frame cracks are detected, conduct additional internal and external close detailed inspections one frame bay and one stringer each side of the crack; if the crack exceeds half the frame cross section, extend inspections to six stringer spacings each side (Requirement 3).
   • If any frame or floor beam crack longer than 25mm is found, inspect fuselage skin lap splices 500mm fore and aft in accordance with Boeing NDT Manual D6‑7170 (Requirement 4).
   • Complete these inspections before further flight where cracks are found forward of BS 520 (Compliance paragraphs 3 and 4).

6. Perform new internal/HFEC inspections as required by group and flight limits

   • For Groups 1-11, perform the internal detailed inspections and adjacent skin/tear strap inspections described in New Requirements 5 and 6 at the flight limits indicated (Notes 5-8 specify how certain flight-limit inspections may be considered acceptable for compliance with other requirements).
   • For Groups 7-11, perform surface HFEC inspections as specified in New Requirements 7-9, and repeat at intervals not to exceed 1,000 flight cycles between flight‑limit inspections unless the longer flight‑limit inspection is carried out.
   • Operators may alternate inspection methods provided repetitive intervals are not exceeded (Compliance paragraph 9).

7. Use specified technical procedures and document accomplishment

   • Follow the detailed accomplishment instructions in Boeing Service Bulletin BSB 747‑53A2265 Revision 9 for each mandated inspection (Requirement notes).
   • Use Boeing NDT Manual D6‑7170 Part 6 Subject 53‑30‑00 Figure 2 for lap splice inspections (Requirement 4, Note 2).
   • Keep inspection records that show dates, flight cycles at inspection, inspection method used, findings, corrective actions taken, and sign‑off by authorised personnel.

8. Implement terminating modification where desired and appropriate

   • If opting for terminating modification in particular areas, accomplish the modification in accordance with Boeing SB 747‑53‑2272 Revision 18 or later revisions approved by FAA AMOC. Ensure FAA AMOC approval is documented and accepted by the Authority because the AD ties termination to FAA AMOC approval (Compliance table; Background).
   • Understand that terminating modification cancels repetitive inspections only for the modified areas.

9. Manage deferments and exemptions with Authority involvement

   • If considering the deferment of internal inspections behind the Flight Engineer’s panel for Groups 1-3, confirm that corresponding left‑side structure has no failed or severed critical elements and that the external inspection compensatory regime (external inspections per Boeing NDT Manual at intervals ≤1,000 flights) is implemented (Compliance notes).
   • If failed structure is found on the left side and an operator seeks to defer right‑side internal inspection, prepare alternative‑method evidence for submission to the Authority to support a limited exemption of up to 1,500 flights but not beyond 13,000 total flights (Note 14).

10. Prepare for immediate actions when findings occur

    • If unrepaired cracks are found, do not return the aircraft to service without prior approval of the Authority (Note 15). Prepare repair plans and documentation for submission to the Authority before resumption of flights.

11. Ensure personnel and tooling capability

    • Verify NDT/HFEC capability and personnel qualifications to perform the required HFEC and close internal inspections. These inspections have specific technique requirements referenced in the AD and Boeing manuals.

12. Monitor service bulletin revisions and approvals

    • Maintain a register of Boeing service bulletin revisions and of FAA AMOC approvals. Any claim of terminating action must be supported by the correct revision and approval documentation.

13. Audit and recordkeeping

    • Maintain auditable records of flight‑cycle counts (accounting for the 2.0 psi exclusion), inspection dates and methods, findings, repairs, and Authority communications/approvals.

These steps reproduce the AD’s technical and administrative requirements. The AD delegates technical workmanship standards to Boeing’s Service Bulletin and the NDT manual; compliance therefore requires integrating those documents into the operator’s maintenance control manual and ensuring that CASA and relevant authorities’ approvals and return‑to‑service processes are followed.