AD/B-2/32 - Tail Rotor Gearbox

This AD relies on a small number of interlocking technical concepts. Each concept translates to an operational requirement with a defined measurement tool or inspection methodology:

• Prescriptive component identification: The AD is part-number specific. It applies to particular part numbers for the vertical shaft assembly and related components (for example P/N 249-10 for the shaft; P/N 278-200 for the top gearbox; P/N 249-3 for the housing; P/N 252-4 bushing; P/N 15-8 bevel pinion; P/N 15-201 and P/N 249-11 bolts; P/N 249-9 male coupling; P/N 15-17 flange retainer). The Applicability clause limits the AD to Brantly B-2/B-2A/B-2B helicopters, serial number 2001 and larger, with shaft P/N 249-10, and any serial-numbered helicopter with that shaft P/N purchased after 1994. The specific enumeration of part numbers converts the AD into an inventory-driven compliance exercise.

• Dimensional tolerance enforcement: The AD sets precise dimensional tolerances for multiple components. Examples: flange retainer inside diameter 1.5050-1.5060 inches (Requirement 1(b)); shaft bolt-hole diameter 0.1894-0.1899 inch in several places (Requirements 1(e)(iii), 1(g)(iv), 1(h)(iii)); shaft outer diameter 0.6240-0.6250 inch (Requirement 1(h)(iv)); bushing length 0.292-0.302 inch (Requirement 1(d)); flared end outer diameter 1.844-1.875 inches for the housing (Requirement 1(c)(iii)); maximum straightness gap on the shaft 0.007 inch when rolled on a flat surface plate calibrated to work surface accuracy tolerance of 0.001 inch (Requirement 1(h)(v)). These tolerances require metric or imperial measuring instruments and calibrated metrology procedures.

• Material/finish and defect thresholds: The AD prescribes specific acceptance criteria for surface condition: nicks, scoring, fretting, burrs and misalignment are grounds for replacement unless removed by "light hand polishing using Scotch Brite (maroon or white)" whilst maintaining tolerances and a 32 rms finish (Requirements 1(e)(ii), 1(g)(iii), 1(h)(ii)). Magnetic particle inspection is required for crack detection of the shaft (Requirement 1(h)), and visual inspection concentrated on a 0.500 inch radius area from bolt-hole centres is specified.

• Assembly conformity to a defined service bulletin: Reassembly and verification steps must follow Brantly International Inc. Service Bulletin No. 105, Revision A, dated 3 August 2005, specifically Part 2 paragraph 2.6 for assembly/inspection and paragraphs 2.7.1 through 4 plus Figure SB-105-2 for gearbox installation inspections (Requirement 1(i) and Requirement 3). The AD interprets the SB’s wording: where the SB says "check", the AD treats that as "inspect" and removes the SB instruction to contact the factory for purposes of this AD.

• Airworthiness as a functional trigger for operational status: The AD expressly states if the assembly fails installation procedures or inspection tolerances, "the installation is not airworthy and the helicopter is grounded until the installation complies" (Requirement 3). Similarly, replacement parts must be "airworthy" before further flight (multiple subparagraphs of Requirement 1).

• Reporting and traceability: The AD requires service difficulty reporting for listed components and installation of the tail rotor gearbox assembly, with a seven-work-day reporting window and note to cite the AD number (Requirement 5 and Compliance 5). The AD thereby creates a data‑flow obligation back to the regulator or reporting system.

These core concepts translate into operational workstreams: parts identification and inventory, removal and inspection, dimensional measurement and non‑destructive testing (magnetic particle), replacement sourcing and certification of parts as airworthy, reassembly per the SB and maintenance manual, rigging check, and mandatory reporting. The AD combines prescriptive measurement tolerances and specific test/inspection techniques with assembly and reporting processes to achieve its stated safety objective.

The AD directly applies to the registered holders and operators of Brantly Helicopter, Inc. Model B-2, B-2A and B-2B helicopters meeting the Applicability criteria. Applicability is narrow and defined by serial number and the presence or procurement date of a particular shaft part number: it covers serial number 2001 and larger with shaft P/N 249-10, and any helicopter (regardless of serial number) with a shaft P/N 249-10 that was purchased after 1994. Thus an operator’s exposure depends on aircraft serial number and retrofit/repair parts history.

Within affected operators, specific personnel and organisations bear roles and obligations:

• Maintenance personnel and certificated maintenance organisations must perform the removal, inspection, measurement and assembly steps. The AD requires calibrated measurement techniques (flat surface plate tolerances of 0.001 inch, magnetic particle inspection, measurement of tight dimensional tolerances), so technicians must have the appropriate tools, calibration, skill and possibly third‑party NDT capability.
• Engineers or inspectors who certify an aircraft as airworthy after the work must ensure conformance with the AD and the relevant Service Bulletin procedures, including the AD’s clarification that "check" in the SB equals "inspect".
• Maintenance managers and operators must plan for parts replacement where tolerance or inspection failures arise; replacement parts must be "airworthy" prior to flight. The AD does not define airworthiness certification procedures for replacement parts; the operator must satisfy applicable airworthiness and supply-chain rules (the AD repeatedly requires replacement with an "airworthy" part).
• The organisation responsible for reporting (operator or maintenance organisation) must file service difficulty reports for the listed components and installations, noting the AD number, within seven work days of performing inspections (Requirement 5; Compliance 5).
• Regulators and CASA delegates are affected because the AD directs reporting into the service difficulty reporting system and establishes an enforceable compliance schedule. The AD itself is signed by a CASA delegate (James Coyne).

Indirectly affected parties include parts suppliers, overhaul facilities and aviation engineers:

• Suppliers of the specific parts listed face potential spikes in demand for replacement components (shaft, gear, housing, bushing, bolts, male coupling, bevel pinion, gearbox assembly) if inspections reveal failures.
• Overhaul and NDT service providers may see increased workload for magnetic particle inspections and precision machining or rework where allowable.
• Operators with limited spares inventory will incur operational disruption to obtain airworthy replacements or to ground the helicopter until parts/repair work is complete.

Operationally, all affected parties must accommodate the timing constraints: initial inspections are required within the next 10 hours TIS and before further flight after any hard landing or sudden rotor stoppage (Compliance 1), installation checks must precede gearbox installation (Compliance 2), and reporting must occur within seven work days after the inspections (Compliance 5). The AD thus creates short-term scheduling pressure for aircraft with recent hard landings or rotor stoppage events and for planned gearbox installations. The practical effect is that operators paying for maintenance, replacement parts and downtime bear the direct financial cost of compliance.

The AD sets out mandatory duties for identified parties; it does not present optional paths. Key duties flow from the numbered Requirements and Compliance statements.

Primary duties:

• Remove specific components for inspection (Requirement 1(a)). The specified items are: tail rotor vertical gearbox P/N 278-200, shaft P/N 249-10, shaft housing P/N 249-3, and intermediate gearbox bushing P/N 252-4.
• Conduct the sequence of component inspections, measurements and tests listed in Requirement 1(b) through 1(i). The document lists exact acceptance criteria and repair/replacement instructions for each component: flange retainer (1(b)), housing outer diameters and deformation (1(c)), bushing length and surface condition (1(d)), bevel pinion bore and bolt-hole diameter, surface finish requirement (1(e)), shaft attachment bolts for fretting and grip diameter (1(f)), male coupling bore, bolt-hole and keyway elongation (1(g)), shaft straightness, bolt-hole diameter, outer diameter, magnetic particle inspection and visual inspection of defined area (1(h)), and assembly/inspection per the SB (1(i)).
• Replace any component not meeting the specified dimensional, surface or NDT acceptance criteria with an airworthy part before further flight (various subparagraphs of Requirement 1).
• Assemble the intermediate gearbox and associated hardware without making any adjustment for the gearbox, vertical shaft or housing (Requirement 2). The AD instructs to follow the applicable maintenance manual for installation instructions.
• Install and inspect the gearbox per SB procedures and grounding the helicopter if any installation or inspection tolerance fails (Requirement 3).
• After airworthy installation, inspect and correct tail rotor rigging control as necessary (Requirement 4).
• Report specific discrepancies via the service difficulty reporting system within seven work days of conducting inspections and measurements, citing the AD number (Requirement 5; Compliance 5). The listed items to report include flange retainer P/N 15-17, shaft housing P/N 249-3, bushing P/N 252-4, bevel pinion P/N 15-8, bolts P/N 15-201 and 249-11, male coupling P/N 249-9, shaft P/N 249-10, the tail rotor gearbox assembly P/N 278-200 and installation of the tail rotor gearbox assembly.

Timing duties:

• Complete inspections within the next 10 hours TIS and before further flight after any hard landing or any main or tail rotor sudden stoppage (Compliance 1).
• Comply with installation inspection requirements before installing the gearbox (Compliance 2).
• Perform installation completion and rigging inspection before further flight after the AD’s effective date (Compliance 3 and 4).
• File reports within seven work days after inspections (Compliance 5).

Rights and clarifications expressly stated in the AD:

• The AD clarifies that when the SB uses the term "check", for purposes of the AD that term should be read as "inspect" (Requirement 1(i)). This narrows any ambiguity from the SB’s terminology.
• The AD explicitly states that "you are not required to contact the factory as stated in the SB" for purposes of complying with this AD (Requirement 1(i)). This is an explicit removal of a SB procedural step.
• The AD defines airworthiness outcomes: if installation fails inspection tolerances, the installation is "not airworthy and the helicopter is grounded until the installation complies with the requirements" (Requirement 3). That statement is operational in effect: it identifies a compliance-based state (grounded) that must be remedied by conforming to the AD.

The AD does not set out enforcement penalties, fines or criminal sanctions within its text. It also does not define how "airworthy" replacements are to be certified; operators must rely on existing airworthiness and certification processes outside the text. The AD does, however, create immediate operational duties and timing obligations that directly affect the right to operate the aircraft.

The AD itself prescribes operational consequences rather than legal sanctions. It explicitly states that if the gearbox installation "fails any portion of the installation procedures or any inspection tolerance required by this paragraph, the installation is not airworthy and the helicopter is grounded until the installation complies with the requirements of this paragraph" (Requirement 3). That is an operational enforcement mechanism embedded in the AD: non‑compliant installation equals non‑airworthiness and grounding until remedied.

Beyond that operational consequence, the AD text does not enumerate monetary penalties, administrative fines, licence actions or criminal sanctions. The instrument mandates reporting to the service difficulty reporting system and prescribes strict compliance times (for example inspections within 10 hours TIS after a specified event and reporting within seven work days), but it does not specify what formal penalties attach to failure to report or to fly a non‑airworthy aircraft. The AD was signed by a CASA delegate (James Coyne) and became effective 8 May 2006; the AD therefore has force as a regulatorily issued instrument requiring compliance of those aircraft within Applicability.

Because the AD does not list sanctions in its text, parties seeking to understand the full legal consequences of non‑compliance must consult CASA’s broader regulatory framework and statutory enforcement tools outside this AD. The AD references FAA AD 2006‑08‑07; however, the AD record does not include any enforcement provisions beyond the grounding statement and the reporting obligation. The practical enforcement risks for operators are therefore twofold and flow from the AD text:

• Operational enforcement: an aircraft that does not meet the AD’s inspection or installation tolerances is explicitly not airworthy and therefore must be grounded until compliant (Requirement 3). That grounding is an immediate operational restriction.
• Administrative or regulatory enforcement: although not set out in this AD, CASA retains regulatory authority to enforce civil aviation safety obligations under its statutory mandate; operators should assume CASA could use its general enforcement toolkit if it discovers non‑compliance. The AD itself does not describe those powers or procedures.

Finally, the AD requires the operator or maintainer to report discrepant parts or installation issues within seven work days via the service difficulty reporting system and to note the AD number (Requirement 5 and Compliance 5). Failure to report as required is non‑compliance with the AD’s terms even though the AD does not specify penalties for such failure. The reporting obligation creates a compliance trail that the regulator can use to monitor adherence.

In short, the text establishes a mandatory operational remedy (grounding where installation tolerances fail) and reporting requirements; it does not specify monetary or criminal penalties within the instrument. The AD should be read together with CASA’s broader enforcement authorities for a full picture of legal exposure.

The AD is a regulatory instrument issued by CASA and references a related United States Federal Aviation Administration (FAA) AD. The AD’s text explicitly notes FAA AD 2006‑08‑07 Amendment 39‑14562 as a relevant reference (Note 3). It also requires compliance with procedures set out in Brantly International Inc. Service Bulletin No. 105, Revision A, dated 3 August 2005 (Requirement 1(i)), and refers maintenance personnel to the applicable maintenance manual for installation instructions (requirements 2 and Note 1).

The AD supersedes or modifies parts of the service bulletin for the purposes of regulatory compliance. Two specific interactions are made explicit:

• Terminology alignment: where the SB uses the term "check", the AD treats that term as "inspect" (Requirement 1(i)). This adjustment aligns the SB’s language with the AD’s regulatory enforcement language.
• Removal of factory-contact requirement: the SB’s direction to contact the factory is expressly not required for purposes of complying with this AD (Requirement 1(i)). The AD therefore limits the SB’s scope in regulatory terms.

The AD otherwise prescribes technical procedures that must be done in accordance with the SB and the aircraft maintenance manual. The AD’s requirement that replacement parts be "airworthy" ties to the broader airworthiness and certification regime, although the AD does not specify how airworthiness is to be demonstrated; those certification requirements exist outside this AD in the broader aviation regulatory framework.

Because the AD references an FAA AD, operators should consider potential cross‑jurisdictional implications when part of the fleet operates in multiple regulatory environments. The text references FAA AD 2006‑08‑07, implying a degree of international harmonisation or mutual concern, but the AD does not specify how compliance with the FAA AD relates to satisfying CASA’s AD beyond the cross-reference.

The AD’s reporting requirement,file service difficulty reports within seven work days and note the AD number,interfaces with the regulatory reporting infrastructure. Operators must use the service difficulty reporting system designated by the regulator. The AD’s insistence on reporting specific P/Ns and the installation alerts CASA and other oversight bodies to component issues that may have broader regulatory consequences; however the AD itself does not create new statutory offences or modify civil code.

Finally, the AD does not state that compliance with it exempts operators from other legal obligations. It is therefore an additional, binding operational obligation layered on top of existing airworthiness, operational and safety law. Compliance with this AD must be integrated into operators’ broader maintenance programs, certification records and continuing airworthiness management systems.

The AD text provides a limited amendment and reference history contained within its own document. Key dated items that form the AD’s historical references are:

• Brantly International Inc. Service Bulletin No. 105, Revision A, dated 3 August 2005. The AD directs assembly and inspection actions to paragraphs and figures of this SB and clarifies the SB language in two respects (Requirement 1(i)).
• FAA Airworthiness Directive 2006‑08‑07 Amendment 39‑14562 is cited in Note 3 as a reference. The AD does not provide a cross‑walk between the FAA AD and the CASA AD beyond the reference.
• The AD itself was issued with an effective date of 8 May 2006 and signed on 4 May 2006 by James Coyne, Delegate of the Civil Aviation Safety Authority (signature block and effective date). The AD identifier is AD/B‑2/32, Tail Rotor Gearbox, 7/2006 TX.

The AD does not record any later amendment to its requirements within the text provided. No revisions, revocations or supersessions are noted in the document. The AD does not include transitional amendment provisions, nor does it list any subsequent modification dates or issued corrigenda in the text provided.

Because the AD incorporates and depends upon the SB, any future amendment to the SB could have operational significance. However, the AD expressly modifies two SB instructions for regulatory purposes (equating "check" to "inspect" and removing the factory contact requirement). Absent a later AD or amendment, those AD-specific clarifications remain controlling for compliance with the AD. Operators should note the dates and versions: the SB revision date (3 August 2005) and the AD effective date (8 May 2006). If the SB were later revised, compliance with the AD would still require meeting the AD’s stated obligations unless CASA issues an amending AD.

In summary, available documentary history within the AD is: SB No. 105 Rev A (3 Aug 2005), FAA AD 2006‑08‑07 (referenced), CASA AD AD/B‑2/32 effective 8 May 2006 (signed 4 May 2006). The AD text contains no further amendment record.

The AD text contains no litigation history, court decisions, appeals or legal challenges. It references technical documents (the SB and a FAA AD) and provides regulatory instructions, but there are no cases or judicial interpretations cited within the instrument. The AD is an administrative regulatory instrument issued by CASA and signed by a delegate; the text does not report any proceedings or disputes arising from it.

The absence of litigation history in the AD has several practical implications for legal and compliance professionals:

• No published judicial construction or interpretation of the AD’s technical language is provided in the source. Consequently, there is no authoritative court guidance on the AD’s scope, the practical meaning of particular tolerances, or disputes about whether specific maintenance actions satisfied the AD beyond what the AD itself states.
• Enforcement precedent is not recorded here. The AD prescribes inspection, replacement and reporting steps, and sets the operational legal consequence of non‑airworthiness for failed installations, but the AD does not document how CASA has applied enforcement actions in practice. Practitioners should therefore expect that any enforcement or contestation would be handled under broader regulatory enforcement mechanisms external to the AD text.
• Absence of litigation within the AD means that any legal questions about the AD,such as whether an operator’s replacement part was properly “airworthy”, whether a particular polishing technique satisfied the 32 rms requirement, or whether the SB’s instructions were properly followed,remain administrative factual disputes to be resolved between the operator and CASA or, if contested, in an appropriate judicial or administrative forum. The AD itself provides the technical benchmarks, but not judicially refined standards.

For risk management, operators should document compliance meticulously: record measurements, calibration certificates for measuring equipment (for example the flat surface plate tolerance of 0.001 inch used to test shaft straightness), NDT reports (magnetic particle inspection), photographs, and the service difficulty report submissions (which must note the AD number). That administrative trail will be the primary evidentiary basis if any regulatory or legal questions arise because no litigation precedents are supplied in the instrument.

In sum, the AD provides technical and timing obligations but contains no litigation history. Any legal disputes arising from compliance or enforcement will need to be tested against the AD’s written requirements and CASA’s broader enforcement regime outside the AD text.

The AD is detailed and prescriptive; several practical pitfalls and sources of non‑compliance arise directly from its wording. These are the concrete "gotchas" a compliance team should watch for, all grounded in the AD’s text.

1. Narrow Applicability and Part-Number Traps

   • The AD applies only to particular serial-number ranges and to helicopters containing shaft P/N 249-10 or where that shaft was purchased after 1994. Operators must verify airframe serial numbers and parts configuration records carefully. Operators with unclear parts provenance may inadvertently assume inapplicability; the AD places the onus on verifying whether P/N 249-10 exists on the helicopter (Applicability).

2. Short Compliance Window after a Hard Landing or Rotor Stoppage

   • The initial inspection requirement is within the next 10 hours TIS and before further flight after any hard landing or any main or tail rotor sudden stoppage (Compliance 1). Operations that continue to fly the helicopter without pausing for that short TIS window risk non‑compliance. The 10-hour timeframe is operationally tight.

3. Exacting Dimensional Tolerances and Measurement Methods

   • Tolerances are precise to four decimal places in inches (for example 1.5050-1.5060 inches for the flange retainer inside diameter; 0.6240-0.6250 inch outer diameter for the shaft). Measurement uncertainty and instrument calibration matter. The AD specifies a flat surface plate calibrated to work surface accuracy tolerance of 0.001 inch for shaft straightness tests (Requirement 1(h)(v)). If maintenance facilities lack suitably calibrated metrology equipment or cannot produce calibration certificates, measurements may be challenged.

4. Specific NDT and Surface-Finish Requirements

   • The AD mandates magnetic particle inspection for the shaft (Requirement 1(h)) and requires a 32 rms finish if polishing is used to remove defects (Requirements 1(e)(ii), 1(g)(iii), 1(h)(ii)). These are specialist requirements: magnetic particle inspection must be performed to applicable standards, and the finish specification (32 rms) requires instruments to measure surface roughness and personnel with the ability to certify finish. A common pitfall is thinking light polishing removes defects without verifying finish and tolerances afterwards.

5. Restricted Polishing Remedy

   • Light hand polishing using Scotch Brite (maroon or white) is permitted only if it removes defects and allows all tolerances and a 32 rms finish to be maintained (Requirements 1(e)(ii), 1(g)(iii), 1(h)(ii)). If polishing cannot achieve these outcomes, replacement is mandatory. That exception is conditional and enforceable.

6. Assembly and Installation Conformity

   • The AD requires assembly and inspection per SB Part 2 paragraph 2.6 and installation per SB paragraphs 2.7.1-4 and Figure SB-105-2 (Requirement 1(i) and Requirement 3). SB terminology is redefined by the AD: "check" equals "inspect", and contacting the factory is not required for compliance with the AD. Failing to follow the specified paragraphs or misinterpreting SB instructions could produce a non‑airworthy installation and result in grounding (Requirement 3).

7. No Definition of "Airworthy" Replacement in the AD

   • The AD requires replaced parts to be "airworthy" (multiple subparagraphs). The AD does not define how airworthiness is to be demonstrated; operators must use prevailing certification processes and documentation outside the AD. A common compliance pitfall is using parts with incomplete documentation or ambiguous provenance that do not meet airworthiness records requirements.

8. Grounding Trigger

   • Installation failures render the helicopter "not airworthy" and "grounded until" the installation complies (Requirement 3). If work is carried out by a third party and documentation is incomplete, the operator becomes exposed to immediate operational interruption through grounding, even absent explicit monetary penalties. The operator needs clear acceptance criteria and signed certification to resume flight.

9. Reporting Obligation and Deadline

   • Operators must report listed discrepancies via the service difficulty reporting system within seven work days of conducting inspections and measurements (Requirement 5 and Compliance 5). Forgetting the reporting requirement, mis‑labeling the AD number in the report or failing to declare specific P/Ns could generate regulatory follow‑up.

10. Maintenance Manual Dependencies

    • Several steps require reference to the "applicable maintenance manual" for installation or rigging instructions (Requirement 2 and Note 2). Operators should ensure they have the correct and current maintenance manual pages and record the manual revision used. Misalignment between SB instructions and the maintenance manual could create ambiguity during audits.

11. Mixed Metric/Imperial Dimensions

    • All tolerances are listed in imperial inches with high precision (for example 0.1894-0.1899 inch). Non‑US workshops or personnel more accustomed to metric measurements must use appropriately calibrated imperial tools and maintain traceable conversions where necessary.

12. Reporting Scope Includes Installation Itself

    • The AD requires reporting on the "Installation of Tail Rotor Gearbox Assembly" in addition to component parts (Requirement 5). That means process‑level reporting is required, not just part failure reporting.

13. Cross-reference to FAA AD

    • The AD references FAA AD 2006‑08‑07 (Note 3). If operators are dealing with multi‑jurisdictional operations, they should check whether the FAA AD contains differing requirements or timing.

Each of these gotchas arises directly from the AD’s text. Mitigation requires careful planning: confirm applicability, inventory affected aircraft, ensure calibrated measuring equipment and NDT capability, plan downtime and parts procurement, prepare reporting processes and documentation, and ensure technicians are clear on the SB paragraphs that control assembly and installation inspections.

This section converts the AD’s requirements into a practical compliance checklist and records strategy, strictly grounded in the AD’s text. It does not expand the AD’s obligations beyond what is stated; it organises steps and evidentiary practices that implement the AD’s mandatory actions.

1. Confirm Applicability and Schedule

   • Verify whether each helicopter has shaft P/N 249-10 and whether the airframe serial number is 2001 or larger, or whether the shaft P/N 249-10 was purchased after 1994. Only aircraft meeting these criteria fall under the AD (Applicability).
   • If the helicopter has experienced a hard landing or main/tail rotor sudden stoppage, schedule inspections immediately: the AD requires inspections within the next 10 hours TIS and before further flight after such events (Compliance 1).

2. Plan Logistics and Downtime

   • Allocate maintenance slots to remove the tail rotor vertical gearbox (P/N 278-200), shaft (P/N 249-10), shaft housing (P/N 249-3) and bushing (P/N 252-4) as required by Requirement 1(a).
   • Source calibrated measurement equipment and NDT capability. The AD requires a flat surface plate with work surface accuracy tolerance of 0.001 inch, magnetic particle inspection capability, instruments to measure bolt-hole diameters, bore diameters and outer diameters to the specified tolerances, and equipment to verify surface finish (32 rms) where polishing is used.

3. Perform Inspections and Measurements per Requirement 1

   • Flange retainer P/N 15-17: inspect for deformation and measure inside diameter. Replace before further flight if deformed or if inside diameter is not 1.5050-1.5060 inches (Requirement 1(b)).
   • Shaft housing P/N 249-3: inspect for deformation and measure outer diameters at each end and centre. Replace before further flight if deformed, any non‑flared outer diameter not 1.497-1.500 inches, or flared end outer diameter not 1.844-1.875 inches (Requirement 1(c)).
   • Bushing P/N 252-4: inspect for nicks or scoring and measure length. Replace before further flight if length not 0.292-0.302 inch or if nicks/scoring are found (Requirement 1(d)).
   • Bevel pinion gear P/N 15-8: inspect bore for nicks, scoring, burrs, misalignment; measure bolt-hole diameter and bore diameter. Replace if misaligned, if polishing cannot remove defects while maintaining tolerances and 32 rms finish, if bolt-hole diameter not 0.1894-0.1899 inch, or bore diameter not 0.6248-0.6250 inch (Requirement 1(e)).
   • Shaft attachment bolt P/N 15-201 and attachment bolt P/N 249-11: inspect for fretting/nicks where bolts contact shaft; measure grip diameter. Replace if fretting/nicks or grip diameter not 0.1889-0.1894 inch (Requirement 1(f)).
   • Male coupling P/N 249-9: inspect bore for nicks, scoring, keyway elongation, burrs or misalignment; measure bolt-hole diameter and bore diameter. Replace if misalignment, keyway elongation, if polishing cannot restore tolerances/32 rms finish, bolt-hole diameter not 0.1894-0.1899 inch, or bore diameter not 0.6250-0.6260 inch (Requirement 1(g)).
   • Shaft P/N 249-10: inspect for misalignment; measure bolt‑hole diameters; check straightness by rolling on a calibrated flat surface plate and measure maximum gap; magnetic particle inspect for cracks; visually inspect a 0.500 inch radius area from bolt-hole centre for nicks, scoring, fretting, burrs or misalignment. Replace shaft before further flight if any misalignment, if polishing cannot remove defects while keeping tolerances/32 rms finish, bolt-hole diameter not 0.1894-0.1899 inch, outer diameter not 0.6240-0.6250 inch at all points, maximum gap exceeds 0.007 inch, or if any crack, subsurface discontinuity or pitting is found (Requirement 1(h)).

4. Non-Destructive Testing and Surface Finish Controls

   • Ensure magnetic particle inspection (MPI) is performed to applicable practice (Requirement 1(h)). Record MPI reports, including acceptance/rejection findings and inspector signatures.
   • If using hand polishing (Scotch Brite maroon or white), verify post-polish that dimensional tolerances are maintained and measure surface finish to confirm 32 rms. Where polishing cannot restore both geometry and finish, replace the component (Requirements 1(e)(ii), 1(g)(iii), 1(h)(ii)).

5. Assembly and Installation per Service Bulletin and Maintenance Manual

   • Follow Part 2 paragraph 2.6 of Brantly SB No. 105 Rev A for assembly and inspection of gearbox P/N 278-200, shaft P/N 249-10 and housing P/N 249-3 (Requirement 1(i)). Before assembling pinion gear and male coupling to the shaft, clean and deburr the bore and inspect for foreign objects or burrs.
   • Note the AD’s instruction that where the SB uses "check" it should be treated as "inspect", and that contacting the factory is not required for AD compliance (Requirement 1(i)).
   • Align and bolt down the intermediate gearbox P/N 278-100, cover P/N 252-3, bushing P/N 252-4, long horizontal shaft housing P/N 14-13, and retainer flange P/N 15-17 without making any adjustment for the upper gearbox, vertical shaft, or housing (Requirement 2). Use the applicable maintenance manual for installation instructions (Note 1).
   • Install and inspect the top gearbox per SB paragraphs 2.7.1-4 and Figure SB-105-2 (Requirement 3). If any installation procedure or inspection tolerance fails, the installation is not airworthy and the helicopter must remain grounded until it complies.

6. Rigging and Final Checks

   • After achieving an airworthy installation, inspect the tail rotor rigging control and correct it if necessary, using the applicable maintenance manual’s rigging instructions (Requirement 4 and Note 2).

7. Record-Keeping and Reporting

   • File service difficulty reports for the listed items (flange retainer P/N 15-17; shaft housing P/N 249-3; bushing P/N 252-4; bevel pinion P/N 15-8; bolts P/N 15-201 and 249-11; male coupling P/N 249-9; shaft P/N 249-10; tail rotor gearbox assembly P/N 278-200; installation of tail rotor gearbox assembly) via the service difficulty reporting system within seven work days of conducting inspections and measurements, noting the AD number (Requirement 5 and Compliance 5). Archive a copy of the service difficulty report and cross-reference it to the aircraft maintenance logbook entry for the work performed.

8. Certification and Airworthiness Return-to-Service

   • Ensure that the certifying engineer or authorised person signs the release to service only after confirming all AD inspections pass, necessary parts are airworthy and installed and the tail rotor rigging is corrected and within limits. If installation fails any inspection tolerance, do not return the aircraft to service until the installation complies with the AD (Requirement 3).

9. Evidence and Audit Trail

   • Maintain calibration certificates for the flat surface plate and measurement tools, MPI NDT reports, photos of inspected areas (pre‑ and post‑polishing where applicable), parts traceability documents demonstrating the replacement parts are airworthy, service bulletin pages used (SB Rev A and the paragraphs/figures referenced), maintenance manual pages used, and copies of service difficulty reports filed. These documents form the primary evidence of compliance in the absence of case law or other precedents.

10. Cross-Jurisdictional Considerations

    • If the fleet operates in other jurisdictions, check FAA AD 2006‑08‑07 and other relevant ADs for harmonisation. The AD references the FAA AD (Note 3), and operators should ensure that any additional or differing non‑Australian AD obligations are reconciled with the CASA AD obligations.

11. Practical procurement considerations

    • Anticipate potential delays sourcing airworthy replacement parts for the specific P/Ns listed. Plan spares procurement in advance for minimal downtime. If parts need overhaul, ensure the overhaul process produces documentation of airworthiness consistent with applicable certification practices.

This compliance plan is tightly mapped to the AD text: perform the specified removals, inspections, measurements, NDT, replacement with airworthy parts where required, assembly and installation per SB and maintenance manual, rigging checks, and mandatory reporting within seven work days. Keep robust records and do not return the aircraft to service if installation tolerances fail the AD’s inspections.