AD/HU 369/94 Amdt 2 - Main Rotor Blade Doublers

Applicability and identification: The Directive applies only to the listed blade part numbers and specified serial number ranges installed on enumerated helicopter models. The affected parts are P/N 369A1100-507 (S/N D139-D203, D209-D223), P/N 369D21100-517 (selected S/N ranges H664-H999, J000-J039, J041-J055 with some gaps), and P/N 369D21102-517 (S/N 1976-2100, 2106-2115). The helicopter models in the applicability statement include Model 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, 600N and OH‑6A (Applicability).

Inspection scope and method: The primary inspection is a visual check of the blade lower surface doubler and adjacent skin for chordwise cracking and for cracks on the doubler adjacent to the root end fitting. The blade must be lifted off the droop stop for the inspection and a minimum 10x magnifying glass must be used, with procedures given in specific Service Bulletins (SB369H-243R3, SB369E-088R3, SB500N-015R3, SB369D-195R3, SB369F-075R3, SB600N-007R2) (Requirement 1). For adhesive/paint bond-line defects, the Directive refers to paragraph 3.E. of Part II of the relevant Service Information Notices (HN‑239, DN‑188, EN‑81, FN‑67, NN‑008).

Removal and replacement rules: If cracks are found, remove the blade and replace it with a serviceable blade (Requirement 1). For disbonding beyond allowable margins specified in the Service Information Notices, remove and replace (Requirement 1). For 600N blades specifically, the Directive requires replacing any affected blade with a blade not listed in the applicability, and removed 600N blades cannot be used on any rotorcraft (Requirement 2).

Life limits and torque events: The Directive establishes retirement lives for specified P/Ns as either a stated hours time in service cap or a stated number of torque events (TE), whichever occurs first (Requirement 3). It defines TE as the transition to a hover from forward flight, with forward flight being any airspeed after attaining translational lift. Where TE has not been logged historically, operators must record TE before further flight using either known TE counts or, if unknown, conversion factors: for non-cargo hook operations, log 6 TE per hour time in service; for cargo hook/external load operations or mixed operations, log 20 TE per hour time in service (Requirement 3). The new life limits are: P/N 369A1100-507 , 1,750 hours or 10,600 TE; P/N 369D21100-517 , 2,500 hours or 15,000 TE; P/N 369D21102-517 , 2,500 hours or 15,000 TE (Requirement 3).

Recordkeeping and maintenance manual change: Operators must enter the new life limits into the component record or equivalent and thereafter maintain a running daily log of TE and hours, adding them to accumulated totals at the end of each day (Requirements 3 and 4). The Directive revokes hours-only retirement for these blades and requires that the Airworthiness Limitations Section of the maintenance manual be revised to reflect the hours-or-TE retirement regime (Requirement 5).

Inspection periodicity and compliance timing: Initial threshold and recurring intervals are set. For affected blades with 600 or more hours, the initial inspection is required before further flight after 4 February 1998 and then every 25 hours time in service. For Model 600N affected blades, removal and replacement are required before further flight after 4 February 1998. The Amendment becomes effective on 8 October 1998, with earlier amendments already in force on specified dates (Compliance; Amendment history).

Interplay with service documents: The Directive does not reproduce inspection techniques or allowable margins; it mandates adherence to the Accomplishment Instructions in the listed Service Bulletins and Service Information Notices for the detailed inspection procedures and acceptance criteria. Operators must consult those documents to determine allowable disbonding margins and the detailed steps for inspection and removal (Requirement 1, Requirement 1.b).

Rationale: The Directive attributes the actions to an accident-caused blade failure associated with chordwise fatigue cracks originating at the lower inboard doubler, possibly caused by residual stresses from non‑conforming doublers. Amendments adjusted scope, serial numbers, inspection thresholds, model applicability and introduced TE‑based life limits (Background; Amendment notes).

Operators and owners of the listed helicopter models: The Directive directly binds operators, owners and maintenance organisations responsible for Model 369A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM, 369HS, 500N, 600N and OH‑6A helicopters when those aircraft have installed the affected main rotor blade part numbers and serial numbers specified in the Applicability. If an operator does not have any of the listed P/Ns/S/Ns installed, the Directive does not apply to that aircraft (Applicability).

Maintenance organisations and maintenance engineers: The Directive requires physical inspection actions (visual inspection with 10x magnifier with blade lifted off the droop stop), adherence to specified Service Bulletins and Service Information Notices for inspection technique and acceptance criteria, and updates to component records and the Airworthiness Limitations Section of the maintenance manual. These tasks fall to licensed maintenance personnel and the accountable maintenance organisation (Requirement 1; Requirement 3; Requirement 5).

Aircraft logbook custodians and record keepers: The Directive imposes a recording obligation. Operators must log TE counts and hours in the aircraft/component records. For blades without previous TE logs, the operator must back‑log TE using the conversion rules (6 TE per hour for non-cargo hook ops; 20 TE per hour for cargo hook/external load ops or combinations) or log known TE if those figures are known (Requirement 3). At the end of each day’s operations operators must add the day’s TE and hours to accumulated totals (Requirement 4). The component record must be updated to show the new retirement life for each affected P/N (Requirement 3).

Parts suppliers and the spares market: The Directive restricts the reuse of certain blades. Specifically, blades removed from Model 600N are stated to be ineligible for use on any rotorcraft (Requirement 2). For 600N operators the Directive mandates replacement with a blade not listed in the applicability. Consequently suppliers of replacement blades for affected models and operators of 600N machines are stakeholders, as replacement demand will shift to non‑affected blade inventories (Requirement 2).

Regulator and inspectorate: The Civil Aviation Safety Authority (CASA) or equivalent national regulator enforces compliance with the Directive. The document itself is a Schedule of Airworthiness Directives issued under Commonwealth regulation (header). The regulator will rely on the Directive’s compliance clauses (including the specified dates) when auditing operator maintenance programmes or when investigating maintenance records following an incident (Compliance).

Aircraft lessors, fleet managers and insurers: Any party with an economic interest in the affected aircraft must ensure compliance because the Directive imposes mandatory removal/retirement thresholds and inspection intervals that change aircraft availability and asset life. The requirement to replace affected blades and to update life limits in component records alters the asset’s remaining useful life profile (Requirement 3; Requirement 5).

Aircraft manufacturers and design approval holders: The Directive requires adherence to specific Service Bulletins and Notices published by Boeing McDonnell Douglas Helicopter Systems and refers to FAA AD material. The manufacturer’s SBs and Service Information Notices are incorporated by reference for specific inspection and acceptance criteria (Requirement 1).

Personnel performing external load operations: Where an operator performs cargo hook or external load work, the Directive imposes a different TE logging conversion factor (20 TE per hour) compared to non‑cargo operations (6 TE per hour). This changes recordkeeping burden and accelerates TE accumulation for external load operators (Requirement 3).

Airworthiness managers responsible for maintenance manuals: The Directive explicitly revises the Airworthiness Limitations Section of the maintenance manual by replacing hours‑only retirement with an hours-or-TE retirement life for specific P/Ns. The maintenance manual author or custodian must implement that manual change as part of compliance (Requirement 5).

Duties , inspection and defect-driven removal: Operators must perform the visual inspections specified in Requirement 1. The inspection must be done with each blade lifted off the droop stop and using a 10x or higher magnifying glass, following the Accomplishment Instructions in the listed Service Bulletins and Notices (Requirement 1). If chordwise cracking or cracks on the doubler adjacent to the root end fitting are found, the operator must remove the blade and replace it with a serviceable blade (Requirement 1). For missing or cracked adhesive or paint at the bond line, the operator must remove and inspect the blade as per paragraph 3.E. of Part II of the applicable Service Information Notice; if disbonding exceeds the allowable margins specified there, remove and replace the blade (Requirement 1.b).

Duties , removal and replacement for Model 600N: For Model 600N helicopters, the duty is categorical: remove any affected blade from service and replace it with a serviceable blade not listed in the Directive’s applicability before further flight after 4 February 1998. Removed 600N blades are explicitly declared ineligible for use on any rotorcraft (Requirement 2; Compliance).

Duties , life limits, logging, record entries and daily accounting: Operators must, on or before reaching the new life limits, remove affected blades from service (Requirement 3). They must make entries in the component record that show the new retirement lives for each P/N (Requirement 3.b). They must log TE counts for blades lacking TE history by either logging known TE or applying the conversion rules (6 TE per hour for non‑cargo hook ops; 20 TE per hour for cargo hook operations or mixtures) before further flight (Requirement 3.a.i-iii). After initial compliance, operators must maintain and add daily counts of TE and hours to the accumulated totals in the aircraft logbook or equivalent (Requirement 4). Requirement 5 requires revising the Airworthiness Limitations Section of the maintenance manual to reflect the hours‑or‑TE retirement policy.

Duties , inspection periodicity: For blades that had accumulated 600 or more hours by the earlier Amendment, the initial inspection was required before further flight after 4 February 1998 and thereafter inspections must be conducted at intervals not to exceed 25 hours time in service (Compliance).

Rights , serviceable replacement choice limitations and eligibility: The Directive sets out limitations rather than rights. Operators have the ability to choose the replacement blade within the constraint that the replacement must be a serviceable blade. For Model 600N the Directive restricts acceptable replacement blades to those not listed in the applicability; operators cannot re‑fit the same affected P/N/SN on 600N aircraft, nor may removed 600N blades be reused on any rotorcraft (Requirement 2). This is an operational constraint on replacement choices rather than a conferment of positive rights.

Recordkeeping obligations and accountability: Operators and maintainers have a duty to update component records and the Airworthiness Limitations Section of the maintenance manual. Those records are the metric for compliance and will serve as evidence the Directive has been complied with; operators bear responsibility for completeness and accuracy of TE counts and hours entries (Requirements 3 and 4; Requirement 5).

Interaction with Service Bulletins and Notices: The detailed inspection techniques, figures (e.g., Figure 1), and allowable disbonding margins are located in the cited Service Bulletins and Service Information Notices. The operator’s right to determine compliance is therefore exercised by following those documents; the Directive mandates their use (Requirement 1).

Temporal duties and effective dates: The Directive prescribes specific time thresholds and intervals. Operators had to comply with initial inspection and removal timing that began on and around 4 February 1998 for the earlier Amendment; this Amendment became effective on 8 October 1998 and leaves compliance for Requirements 1 and 2 unchanged from the previous issue (Compliance; Amendment history). Operators must ensure that their records show compliance as of those dates.

Liability and enforcement consequences: The Directive is a mandatory regulatory instrument issued under the Commonwealth’s Civil Aviation safety framework (header). Non‑compliance would therefore expose the operator to regulatory enforcement action by the aviation authority, and the remedial obligations (removal and replacement, life limits, recordkeeping) are duties under the AD. The Directive itself does not specify penalties; enforcement falls to the administering authority under its statutory powers (document header and Compliance clauses).

Regulatory status and enforcement regime: The Directive is issued as a Schedule of Airworthiness Directives under the Commonwealth of Australia (Civil Aviation Regulations 1998), Part 39. As such, it is a mandatory regulatory instrument; the document establishes prescriptive duties for inspection, removal, replacement, recordkeeping and maintenance manual changes (header; Requirements 1-5). The Directive does not include a separate penalty schedule in its text; enforcement and sanctions therefore rest with the regulator’s statutory enforcement powers under the Civil Aviation Regulations 1998 and associated enforcement policy, not reproduced in this Directive text (header).

Compliance timing as an enforcement tool: The Directive sets clear compliance triggers and intervals that create audit points. Examples: initial inspection before further flight after 4 February 1998 for blades at or above 600 hours and recurring inspections every 25 hours thereafter (Compliance). For Model 600N, removal and replacement was required before further flight after 4 February 1998 (Requirement 2). The regulator will use those timing rules as objective compliance yardsticks when reviewing maintenance logs or following an incident.

Recordkeeping and evidentiary function: The Directive requires operators to make component record entries reflecting the new life limits (Requirement 3.b) and to maintain daily accumulated TE and hours in the aircraft logbook or equivalent (Requirement 4). These records are the primary evidence of compliance and will be reviewed by the regulator during inspections or investigations. The Directive’s explicit conversion rules for logging TE where none exist further reduce ambiguity in enforcement (Requirement 3.a).

Remedial actions mandated by the Directive: Where inspections reveal cracks or disbonding beyond allowable limits, the Directive mandates removal and replacement with serviceable blades (Requirement 1). For Model 600N affected blades, removal is mandatory and removed blades are not eligible for any rotorcraft use (Requirement 2). The regulator may expect corrective and follow‑up actions in cases of detected defects, and may require proof of replacement parts and disposal of ineligible parts.

Implied enforcement consequences of non‑compliance: While the Directive text does not list specific fines, licence suspensions or criminal penalties, non‑compliance with an AD is typically an aviation regulatory breach. The Directive’s status as an airworthiness directive under Commonwealth regulation creates a statutory obligation; enforcement actions would be determined by the regulator under its enforcement framework and the underlying Civil Aviation Regulations (header and Compliance). The Directive itself does not set those penalties.

Cross‑reference to FAA AD: The Directive notes that FAA AD 98‑15‑26 refers. That cross-reference signals alignment with FAA requirements and may influence joint regulatory scrutiny or bilateral enforcement cooperation where applicable (Note; Amendment notes).

Practical enforcement levers: The recordkeeping and airworthiness manual amendment duties create observable compliance markers: (1) component record entries showing the new retirement lives, (2) daily TE and hours totals, (3) records that inspections were performed at the required intervals and per the specified SBs/Notices, and (4) evidence that replaced blades are serviceable and, for 600N, that removed blades were not re‑used. Regulators monitoring maintenance records can use these items as enforcement evidence (Requirements 1-5).

No civil litigation clauses in the Directive text: The Directive does not provide a private right of action nor discuss civil liability allocation between parties. It is a regulatory instrument imposing mandatory safety obligations; enforcement and penalties are left to the regulator’s statutory powers (document text).

Relationship to the Commonwealth Civil Aviation framework: The Directive is issued under the Commonwealth of Australia (Civil Aviation Regulations 1998), Part 39, and sits within that regime of mandatory airworthiness directives. The text cites that regulatory source in its header; the Directive’s duties (inspection, removal, recordkeeping and maintenance manual amendment) thus operate as regulatory obligations under those Civil Aviation Regulations (header).

Interaction with manufacturer service documents: The Directive mandates compliance with specific Boeing McDonnell Douglas Helicopter Systems Service Bulletins (SB369H-243R3, SB369E-088R3, SB500N-015R3, SB369D-195R3, SB369F-075R3, SB600N-007R2) and Service Information Notices (HN-239, DN-188, EN-81, FN-67, NN-008) for the detailed inspection steps, figures and allowable criteria. Those service documents are incorporated by reference as the source of technical procedures and acceptance limits; the Directive itself relies on them for operational detail (Requirement 1; Requirement 1.b). The obligation to follow those service documents places regulatory weight on manufacturer technical material.

Interaction with FAA ADs and foreign regulator actions: The Directive notes FAA AD 98‑15‑26 and states that Amendment 2 responds to the new FAA AD, adopting similar inspection requirements but removing Model 369 from applicability and adding TE recording and shorter retirement lives for certain blades (Amendment notes). This indicates cross‑jurisdictional coordination in safety actions; operators subject to both jurisdictions’ oversight must ensure compliance with each regulator’s applicable directives.

Impact on maintenance manuals and airworthiness limitations: The Directive expressly revises the Airworthiness Limitations Section of the maintenance manual by establishing new retirement lives based on hours or TE rather than hours-only (Requirement 5). That mandation requires maintenance manual updates and thus interacts with any legal or contractual obligations surrounding maintenance manual revisions and approvals under the Civil Aviation Regulations.

Recordkeeping obligations and statutory inspection powers: The Directive’s requirement to update component records and log TE/hours daily interfaces with statutory recordkeeping requirements under aviation law. Regulators exercise statutory inspection and audit powers; operators’ compliance records created pursuant to the Directive will be subject to regulator review under those powers (Requirements 3 and 4).

Parts eligibility and airworthiness approvals: The Directive imposes part eligibility rules for blades removed from Model 600N (they are not eligible for use on any rotorcraft) and requires replacement with blades not listed in the applicability for 600N helicopters (Requirement 2). This interacts with airworthiness and parts approval regimes by changing which parts are legally permissible for installation on certain aircraft. The Directive does not prescribe a specific substitute P/N; it only excludes the affected ones for 600N replacement use.

No explicit interaction with contract, tort or insurance law in the text: The Directive does not address contractual rights, warranties, or insurance coverage. It imposes operational and recordkeeping duties; any effects on contractual obligations or insurance policies are external consequences not addressed in the Directive itself.

No judicial review or appeal mechanism described: The AD text does not provide an internal appeal or review mechanism nor a process for exemptions; such processes would be governed by the broader regulatory framework and are not set out in the Directive text provided.

Chronology in the Directive text: The Directive was first issued as an Airworthiness Directive becoming effective on 8 January 1998 (original issue). Amendment 1 came into force on 4 February 1998, introducing new requirement documents, limiting affected blade serial numbers, and reducing the inspection threshold time. Amendment 2, the current amendment, became effective on 8 October 1998 and was issued to respond to a new FAA AD that required similar inspections but deleted Model 369 from applicability, required recording torque events (TE), and established shorter retirement lives for certain blades (Amendment notes; Compliance; Background).

Specific changes introduced by each amendment (as stated in the Directive):

• Original AD (effective 8 January 1998): Introduced mandatory inspections and removal actions after an identified in-service failure. The original text is summarised as having been prompted by an accident on a Model 369D.

• Amendment 1 (effective 4 February 1998): Narrowed the affected population by limiting the affected blade serial numbers, introduced new Requirement Documents (the SB and Service Information Notice references), and reduced inspection threshold time. The Compliance clause notes that the compliance of the previous issue remains unchanged for Requirements 1 and 2, implying Amendment 1 adjusted other aspects such as thresholds and documentation.

• Amendment 2 (effective 8 October 1998): Responded to the FAA AD 98‑15‑26. Amendment 2 kept inspection requirements equivalent to the previous FAA AD, removed Model 369 from the applicability list (the text of the current Applicability does not list Model 369 alone but lists specific 369 variants), added the obligation to record torque events and to set retirement lives based on hours or TE, and shortened retirement lives for specified P/Ns. The Directive states that Amendment 2 “deletes the Model 369, specifies recording torque events, and establishes a shorter retirement life for certain blades” (Amendment notes).

References to FAA action: The Directive includes an explicit note that FAA AD 98‑15‑26 refers. The Amendment 2 text states it is issued in response to the new FAA AD, signifying coordination between jurisdictions and that the changes align with FAA findings (Note; Amendment notes).

Effect on previously issued compliance: The Compliance paragraph states that the compliance requirements of the previous issue remain unchanged for Requirements 1 and 2. This implies Amendment 2 introduced new or changed Requirements 3-5 (the TE recording and retirement life items) while retaining earlier inspection/removal timing and procedures (Compliance).

No other amendment entries recorded: The Directive text records the original issue and two amendments. No further amendments, supersessions or revocations are noted in the provided text.

Temporal implication for operators: The effective dates create a compliance timeline: actions connected to the first Amendment had immediate effect from 4 February 1998 for certain initial inspections/removals, and Amendment 2’s new retirement and TE requirements took legal effect on 8 October 1998 (Compliance; Amendment history).

No litigation reported in the Directive: The Directive text contains no reference to judicial proceedings, appeals, or case law arising from this AD. It names the precipitating accident and references FAA AD 98‑15‑26 but does not record any legal challenges to the Directive or to the associated Service Bulletins or notices (Background; Note).

No private rights or causes of action created in the text: The AD is framed as a regulatory instrument setting out mandatory airworthiness requirements. It does not create or mention private enforcement mechanisms, statutory causes of action, or litigation pathways in the Directive text itself.

Probative value of recordkeeping in disputes: While no litigation is recorded in the Directive, its recordkeeping duties (component records, logbooks, daily TE/hours accounting) create documentary trails that would be central evidence in any future regulatory investigation or civil litigation. The Directive’s explicit methods for logging and calculating TE (including conversion factors where TE were not previously logged) standardise record entries and thus shape the evidentiary record (Requirement 3; Requirement 4). That said, the Directive text is silent on how those records would be treated in court or how liability might be established.

Cross-reference to FAA AD but not to litigated outcomes: The Directive refers to FAA AD 98‑15‑26 and takes action in response to it, but the text does not report any litigation connected to the FAA AD. The only named event is the accident that prompted the original AD (Background).

Implications for enforcement action rather than litigation: The absence of litigation in the document suggests the intended enforcement path is administrative (regulatory compliance), not judicial. Any court cases arising from incidents, enforcement notices, or disputes over compliance or technical acceptability would likely be external to the Directive text and are not recorded here.

No recorded judicial invalidation or stays: The Directive does not record any suspensions, stays, or orders altering its operation. The Amendment notes indicate sequential tightening of requirements rather than legal challenge outcomes (Amendment notes).

Applicability is serial-number specific: The Directive does not apply to all blades of the listed P/Ns universally. It applies only to the enumerated P/Ns coupled with specific serial number ranges. Operators must check component serial numbers carefully; failing to verify S/N ranges may lead to mistaken non‑compliance or unnecessary removals (Applicability). The serial number listings are non‑continuous (e.g., gaps and ranges), so a superficial P/N-only check is insufficient.

Inspection posture requires blade off the droop stop and 10x magnifier: The Directive mandates that inspections occur with each blade lifted off the droop stop and using a 10x or higher magnifying glass (Requirement 1). Inspections performed on a blade left on the droop stop or without the specified magnification level would not meet the specific requirement language.

Inspection and acceptance criteria are in the Service Bulletins and Notices: The Directive does not include detailed acceptance criteria or figures in full. It refers to the Accomplishment Instructions and Figure 1 in the Service Bulletins and to paragraph 3.E. of Part II of the Service Information Notices for disbond allowance margins (Requirement 1; Requirement 1.b). Operators must obtain and follow those documents; failure to follow the referenced SBs/Notices will be non‑compliance.

TE definition and conversion rules can substantially change retirement accounting: TE is defined as the transition to a hover from forward flight, with forward flight meaning any airspeed after attaining translational lift (Requirement 3). Where TE have not been logged historically, the Directive mandates back‑logging using either known TE or automatic conversion rates (6 TE/hour non‑cargo; 20 TE/hour for cargo hook/external load). Operators that previously tracked only hours will find accumulated TE counts can be much higher under the conversion for external load operations, accelerating retirement and replacement cycles (Requirement 3.a.ii-iii).

Daily accounting requirement creates ongoing administrative burden: Requirement 4 requires daily accumulation and addition of TE and hours to the aircraft/component logbook totals. This is not a periodic or end-of-month task; it is a daily administrative duty that must be reflected in the official records.

For Model 600N, removed blades are non‑reusable: The Directive states blades removed from Model 600N are "not eligible for use on any rotorcraft" and that replacements must be blades not listed in the applicability. This makes removed blades effectively scrap from an airworthiness eligibility perspective, which has disposal, traceability and procurement cost implications (Requirement 2).

Life limits switched from hours-only to hours-or-TE: Requirement 5 changes the retirement regime. Operators cannot rely on hours-only retirement; the TE cap can force earlier removal even if hours are below the P/N hours threshold. For P/N 369A1100-507, the limit is 1,750 hours or 10,600 TE; depending on operations, TE may reach the cap first (Requirement 3.b.i-iii).

Immediate initial thresholds for older blades: The Directive required initial inspections for affected blades that had already accumulated 600 or more hours before further flight after 4 February 1998 and set the recurring interval at 25 hours thereafter (Compliance). Operators with blades above the threshold needed to act immediately at that historical date; historical records must show that these inspections occurred.

Replacement blade eligibility nuance: For some models, the Directive requires replacement with “serviceable blade” , the text does not specify which P/Ns are acceptable beyond excluding the affected blades for 600N. For legal compliance the operator must ensure the replacement blade itself is airworthy and not among the affected S/Ns/P/Ns; the Directive does not list approved substitute part numbers (Requirement 1; Requirement 2).

Service Bulletins versus Directive instructions: The Directive mandates following the SBs/Notices for technique and acceptance testing. The SBs may contain additional or differing recommendations; operators must follow the Directive and the referenced SB instructions strictly. Where the SB provides optional actions, the Directive’s mandatory language prevails for the listed items; operators should not assume SB non‑mandatory wording suffices for compliance (Requirement 1).

No penalty specifics included: The Directive does not set out fines or sanctions in the text; enforcement relies on the regulator’s statutory toolkit. Operators should not assume absence of explicit penalties implies lax enforcement (header; Compliance).

Amendment sequencing: The current effective date is 8 October 1998 for Amendment 2, but earlier amendments (4 February 1998 and original 8 January 1998) set earlier compliance triggers. Operators with older records must ensure historical compliance aligned with those earlier dates, not only with the current effective date (Amendment history; Compliance).

Step 1 , Verify applicability precisely: Check each main rotor blade’s part number and serial number against the Directive’s Applicability list. Only blades with the specified P/N and within the listed S/N ranges are subject to the Directive. Document the P/N and S/N in the component record before proceeding (Applicability).

Step 2 , Consult and follow the referenced Service Bulletins and Service Information Notices: Obtain and use the stated Boeing McDonnell Douglas Helicopter Systems Service Bulletins (SB369H‑243R3, SB369E‑088R3, SB500N‑015R3, SB369D‑195R3, SB369F‑075R3, SB600N‑007R2) and the Service Information Notices (HN‑239, DN‑188, EN‑81, FN‑67, NN‑008). These documents contain the Accomplishment Instructions, Figure 1 and the paragraph 3.E. acceptance margins referenced in the Directive. Perform inspections strictly in accordance with those procedures (Requirement 1; Requirement 1.b).

Step 3 , Perform the mandated inspections: With each blade lifted off the droop stop and using a 10x or higher magnifying glass, visually inspect the blade lower surface doubler and adjacent skin for chordwise cracking emanating from the root fitting edge, and for cracks on the doubler adjacent to the root end fitting (Requirement 1). Also inspect the lower surface bond line for missing or cracked adhesive or paint at the root end fitting-to-doubler bond line (Requirement 1.b).

Step 4 , Take remedial action for defects: If any chordwise cracking is found, remove the blade and replace it with a serviceable blade. If missing or cracked adhesive/paint is discovered, remove and inspect the blade per paragraph 3.E. of Part II of the applicable Service Information Notice; if disbonding exceeds the allowable margins specified there, remove and replace the blade (Requirement 1; Requirement 1.b).

Step 5 , Special rule for Model 600N: If you operate a Model 600N and have an affected blade, remove and replace it with a serviceable blade that is not listed in this Directive’s applicability before further flight after 4 February 1998. Retire removed 600N blades from any rotorcraft use , they are not eligible for reuse on any rotorcraft (Requirement 2; Compliance).

Step 6 , Record and implement new retirement lives: For each affected blade part number, make an entry in the component record reflecting the new retirement life (Requirement 3.b):

• P/N 369A1100‑507: retire at 1,750 hours TIS or 10,600 TE, whichever occurs first.
• P/N 369D21100‑517: retire at 2,500 hours TIS or 15,000 TE, whichever occurs first.
• P/N 369D21102‑517: retire at 2,500 hours TIS or 15,000 TE, whichever occurs first.

Step 7 , Log TE and back‑log where necessary: TE is defined as the transition to a hover from forward flight (with forward flight any airspeed after attaining translational lift). If TE have not been logged historically, before further flight either log the known TE count or, if unknown, use the conversion rules: for non‑cargo hook operations log 6 TE per hour TIS; for cargo hook/external load operations (or combinations) log 20 TE per hour TIS. Make the TE entry in the aircraft/component logbook or equivalent record (Requirement 3.a.i-iii).

Step 8 , Maintain daily accumulation and update logs: After initial compliance with the new life limits, keep a daily count of TE and additional hours accumulated during operations. At the end of each day add those counts to the accumulated number of TE and hours in the aircraft logbook or equivalent record. Ensure totals are always current to determine impending retirement thresholds (Requirement 4).

Step 9 , Update the maintenance manual: Revise the Airworthiness Limitations Section of the maintenance manual to reflect the new retirement lives and the hours-or-TE retirement policy for the affected blade P/Ns. Ensure the revised maintenance manual is the edition used by maintenance personnel and aligns with the Directive (Requirement 5).

Step 10 , Implement inspection periodicity: For affected blades that had already accumulated 600 or more hours TIS by the date set in the earlier amendment, ensure the initial inspection was carried out before further flight after 4 February 1998 and thereafter at intervals not to exceed 25 hours TIS. For Model 600N affected blades, ensure removal/replacement was completed before further flight after 4 February 1998 (Compliance).

Step 11 , Preserve evidence of compliance: Keep records of inspection dates, inspector identity, magnification used, droop stop lift, SB/Notice reference and revision, defect findings, part numbers and serial numbers of replacement blades, and component log entries showing the new retirement lives and accumulating TE/hours. These records are primary proof of compliance and will be inspected by regulators (Requirements 1-4).

Step 12 , Procurement and disposal: For replacements, procure serviceable blades that are not in the affected applicability for 600N replacements. Dispose or dispose‑trace removed blades per regulatory and manufacturer guidance; note the explicit ineligibility for removed 600N blades to be used on any rotorcraft (Requirement 2).

Step 13 , Integrate into safety and maintenance management: Incorporate the Directive’s inspection interval, daily TE accounting and retirement thresholds into the operator’s maintenance programme and safety management system. Ensure training for flight crews and maintenance personnel on the TE definition and logging rules so that operational behaviours (for example, external load usage) are captured correctly in the TE counts (Requirement 3; Requirement 4).

Step 14 , Liaise with regulator if unclear: If there is uncertainty about interpretation (for example, how to treat mixed operation modes for TE conversion, or acceptable replacement blades for a specific airframe), consult the regulator and reference the specific Service Bulletins and Service Information Notices cited in the Directive for detailed technical guidance (Requirement 1; Requirement 3).

Adhering to these steps implements the Directive’s mandatory inspections, recordkeeping and retirement rules and ensures the operator can demonstrate compliance during regulator audits or incident investigations.