{"id":"F2008L03052","name":"AD/HU 369/120 - Tail Rotor Blade Abrasion Strip","slug":"ad-hu-369-120-tail-rotor-blade-abrasion-strip","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":75089,"registerId":"commonwealth-F2008L03052-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"McDonnell Douglas (Hughes) and Kawasaki ","sectionType":"division","heading":"McDonnell Douglas (Hughes) and Kawasaki 369 Series Helicopters","content":"### McDonnell Douglas (Hughes) and Kawasaki 369 Series Helicopters\n\n| AD/HU 369/120 | Tail Rotor Blade Abrasion Strip | 10/2008 DM |\n| ------------- | ------------------------------- | ---------- |\n\n| Applicability: | Model 369A, OH-6A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM and 369HS, certificated in any category, with a tail rotor blade installed as follows, including all serial numbers and those T/R blades with an “M” or an “I” painted on the T/R blade root:Helicopter Technology Company, LLC (HTC) part number (P/N) 500P3100-101 and -103, or MDHI P/N 369D21640-501, -503, and -505.HTC P/N 500P3100-301 and -303, or MDHI P/N 369D21641- 501, -503, and -505.HTC P/N 500P3300-501 and -503, or MDHI P/N 369D21643- 501, -503, and -505.HTC P/N 500P3500-701 and -703, or MDHI P/N 369D21642- 501, -503, and -505.Note 1: An \"M'' or an \"I'' painted on the root of the T/R blade indicates compliance with an Alternate Method of Compliance (AMOC) to Emergency AD 2003-08-51 (AD/HU 369/111), issued by the FAA, Los Angeles Aircraft Certification Office (LAACO) on June 13, 2003 to HTC. The AMOC addressed shot peening of the pitch horn of the T/R assembly. CASA is not able to provide a copy of this AMOC. HTC should be approached for a copy if required. |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Accomplish the following actions:1. Inspect the abrasion strip-to-skin bond integrity on each T/R blade using a tap test method in accordance with Part 1- Inspection, in Helicopter Technology Company, LLC (HTC) Mandatory Service Bulletin Notice No. 3100-4R4, dated May 10, 2006 (SB) or later FAA approved revision.Note 2: MD Helicopters Service Bulletins (as applicable to model) SB369D-203R1, SB369E- 097R1, SB369F-082R1, and SB369H-246R1, dated January 23, 2006, refer.2. Modifying each T/R blade in accordance with Mandatory Service Bulletin Notice No. 3100-4R4 by installing a titanium rivet P/N 500P3124-13 at the outboard (tip) end and painting the letter \"T'' on the root-end of the T/R blade to indicate the terminating modification has been accomplished is terminating action for the inspection requirements of this AD.Note 3: FAA AD 2008-15-03, effective 3 September 2008 refers.                                                                                                                                                   |\n\n| Compliance: | 1. Within 25 hours time-in-service (TIS), unless accomplished previously, and thereafter at intervals not to exceed 25 hours TIS.2. Compliance optional, but completing the terminating modification removes the need for further 25 hourly inspections. |\n| ----------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n|             | This Airworthiness Directive becomes effective on 3 September 2008.                                                                                                                                                                                      |\n| Background: | This Airworthiness Directive is issued to prevent disbonding and subsequent separation of an abrasion strip from a Tail Rotor blade, which could result in vibration, loss of the Tail Rotor, and subsequent loss of control of the helicopter.          |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n11 August 2008","sortOrder":0},{"sectionNumber":"AD/HU 369/120","sectionType":"part","heading":"AD/HU 369/120","content":"## AD/HU 369/120","sortOrder":1},{"sectionNumber":"Tail Rotor Blade Abrasion Strip","sectionType":"part","heading":"Tail Rotor Blade Abrasion Strip","content":"## Tail Rotor Blade Abrasion Strip","sortOrder":2},{"sectionNumber":"10/2008 DM","sectionType":"part","heading":"10/2008 DM","content":"## 10/2008 DM","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific airworthiness concern (tail rotor blade abrasion strip disbonding) on specific helicopter models with specific part numbers. The references to prior AMOCs and FAA directives do not expand the substantive scope but rather provide regulatory context and alternative compliance pathways."},"complexity_factors":["Multiple manufacturer part number variations (8 different HTC/MDHI part number combinations) requiring careful cross-referencing to determine applicability","Reference to external documents: Mandatory Service Bulletin Notice No. 3100-4R4 and multiple MD Helicopters service bulletins (SB369D-203R1, SB369E-097R1, etc.) that are not reproduced in the AD itself","Conditional compliance logic: terminating action (modification) is optional but removes ongoing inspection obligations","Reference to prior regulatory history (Emergency AD 2003-08-51/AD/HU 369/111) and an FAA Alternate Method of Compliance (AMOC) that CASA cannot provide","Dual regulatory framework: references both CASA AD and FAA AD 2008-15-03, requiring operators to track both jurisdictions","Specific technical inspection method (tap test) defined only by reference to external service bulletin"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of certain McDonnell Douglas (Hughes) and Kawasaki 369-series helicopters with specific HTC or MDHI tail‑rotor blades to inspect the abrasion strip bond every 25 flight hours using the HTC tap‑test (per the service bulletin) because a loose strip can lead to catastrophic tail‑rotor failure. A permanent fix — installing a titanium rivet and marking the blade — removes the need for repeated 25‑hour inspections."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD is narrowly focused on preventing abrasion-strip disbonding on specified 369-series tail rotor blades. It prescribes inspections and offers a defined terminating modification. There is no material expansion beyond that corrective purpose in the text provided: the actions, affected parts, and incentives (inspect frequently or install the rivet) align with the stated safety objective and do not broaden the AD to unrelated components or operations."},"complexity_factors":["Targets a finite list of models (10 model designations) and an explicit set of tail rotor blade part numbers (20 P/N entries across HTC and MDHI), which clarifies applicability but requires careful cross‑checking of installed P/Ns.","One specific inspection method mandated (tap test) referenced to a single manufacturer Mandatory Service Bulletin (HTC SB 3100-4R4) and several MD Helicopters SB cross-references (adds a degree of dependency on external documents).","Short and repetitive compliance interval (every 25 hours TIS) until terminating action is taken — creates operational scheduling complexity though legally simple.","Single clearly‑defined terminating action (install titanium rivet P/N 500P3124-13 and paint 'T') — reduces conditional branching.","Cross-references to FAA AD 2008-15-03 and an AMOC (Note 1) where CASA cannot supply the AMOC text — creates a small additional documentary verification step for some operators.","Limited number of conditional exceptions/alternatives (inspection or terminate via modification); no deeply nested exceptions or multi-part compliance trees."],"plain_english_summary":"**What this instrument does (mechanically):**\n\n- It requires operators of certain McDonnell Douglas (Hughes) and Kawasaki 369-series helicopters to inspect the bond between the tail-rotor (T/R) blade and its abrasion strip using a \"tap test\" (a lightweight impact test that detects disbonding) and to repeat that inspection at fixed short intervals until a specified modification is fitted. (Requirement; Compliance)\n- As a permanent fix (called the \"terminating modification\"), each affected T/R blade may be modified by installing a titanium rivet (part number 500P3124-13) at the outboard (tip) end of the abrasion strip and marking the blade root with the letter \"T\" to show the modification has been done. Once the rivet/marking is fitted, the 25‑hour inspection requirement no longer applies. (Requirement; Compliance)\n\n**Which helicopters and parts are affected:**\n\n- The rule applies to Model 369A, OH-6A, 369D, 369E, 369F, 369FF, 369H, 369HE, 369HM and 369HS helicopters that have specific HTC or MDHI tail rotor blade part numbers installed. The AD lists those P/Ns explicitly (several HTC P/Ns such as 500P3100-101, -103, -301, -303, 500P3300-501, -503, 500P3500-701, -703 and corresponding MDHI P/Ns 369D21640/641/643/642 with suffixes -501, -503, -505). (Applicability)\n- The AD also notes blades painted with an \"M\" or an \"I\" on the blade root indicate a previous alternate compliance action (AMOC) relating to shot peening; operators may need to check records or contact the blade manufacturer for details. (Applicability, Note 1)\n\n**When it must be done (timing):**\n\n- Initial inspection must be done within 25 hours time-in-service (TIS) if not already done, and then repeated at intervals not to exceed every 25 hours TIS until the terminating modification is fitted. Fitting the rivet and marking the blade is optional, but if done it ends the recurring inspections. (Compliance)\n\n**Why the regulator requires this (stated safety risk):**\n\n- The stated purpose is to prevent failure of the abrasion strip bond on the tail rotor blade. If the abrasion strip disbonds and separates it can cause vibration, possible loss of the tail rotor or loss of control of the helicopter. (Background)\n\n**How operators, maintainers and regulators interact under this AD:**\n\n- Operators are responsible for ensuring compliance: scheduling and paying for the inspections and for the terminating modification if they choose to do it. Maintenance organisations (approved repair stations or appropriately certificated personnel) will carry out the tap tests and any rivet installation per the referenced service bulletin. The AD references Helicopter Technology Company (HTC) Mandatory Service Bulletin Notice No. 3100-4R4 (and certain MD Helicopters service bulletins) as the inspection/modification procedures; operators must follow those procedures or an FAA/CASA‑approved equivalent. (Requirement; Notes)\n\n**Practical costs, incentives and trade-offs (analyst notes):**\n\n- Who pays: helicopter owners/operators pay for the recurring inspections (labour, aircraft downtime) and for the cost of the terminating rivet modification (parts and labour).\n- Incentives: because inspections are frequent (every 25 flight hours), operators with high-utilisation aircraft face recurring labour and availability costs; this creates a clear economic incentive to elect the terminating modification to avoid the recurrent inspection burden.\n- Trade-offs and opportunity cost: choosing the terminating modification requires paying the upfront cost and scheduling downtime; choosing inspections preserves the original configuration but imposes repeated inspection cost and more frequent out-of-service time. Either route requires certified maintenance input.\n- Implementation risks: availability of the rivet part P/N 500P3124-13 or service bulletin access, and the need to verify prior AMOC work (the AD notes CASA cannot provide a copy of an AMOC; operators may need to source it from HTC). Any delay or difficulty obtaining parts or documents may extend operational restrictions or complicate proving compliance.\n- Effects on small businesses and competition: independent maintenance organisations that are certified to perform the SB work can compete to provide the inspection and modification services. The AD does not mandate a single supplier, but reliance on manufacturer service bulletin procedures and a specific rivet P/N concentrates demand for those parts and that technical procedure. (Requirement; Notes)\n- Enforcement and discretion: compliance is mandatory for affected helicopters; regulators (CASA/FAA references) will accept the modification/inspection per the referenced SBs or an approved AMOC. The AD cross‑references FAA AD 2008-15-03 and HTC/MD service bulletins, so some discretion exists only by approving alternate methods of compliance. (Requirement; Note 3)\n\n**Concrete behaviour changes imposed:**\n\n- Operators must perform a tap-test inspection every 25 flight hours until they either:\n  - continue the inspection regime indefinitely, or\n  - install the titanium rivet and mark the blade (the terminating action), after which the repetitive inspections stop. (Compliance; Requirement)\n\n**Primary documentation and cross‑references to follow:**\n\n- HTC Mandatory Service Bulletin Notice No. 3100-4R4 (dated May 10, 2006) or later FAA-approved revision (inspection and modification procedure).\n- MD Helicopters Service Bulletins (SB369D-203R1, SB369E-097R1, SB369F-082R1, SB369H-246R1) are referenced as applicable. (Requirement, Note 2)\n\n**Bottom line:** This AD targets a specific bonded abrasion-strip failure mode on specified 369-series tail rotor blades by imposing frequent short-interval inspections until an optional rivet retrofit is performed; operators bear the recurring inspection cost or the one-time retrofit cost and must follow the manufacturer's service bulletin procedures or an approved alternative."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-369-120-tail-rotor-blade-abrasion-strip","history":"/api/acts/ad-hu-369-120-tail-rotor-blade-abrasion-strip/history","analysis":"/api/acts/ad-hu-369-120-tail-rotor-blade-abrasion-strip/analysis","conflicts":"/api/acts/ad-hu-369-120-tail-rotor-blade-abrasion-strip/conflicts","importantCases":"/api/acts/ad-hu-369-120-tail-rotor-blade-abrasion-strip/important-cases","documents":"/api/acts/ad-hu-369-120-tail-rotor-blade-abrasion-strip/documents"}}