{"id":"F2005L03888","name":"AD/HU 369/113 Amdt 1 - Main Rotor Blade Torque Events and Life Limit","slug":"ad-hu-369-113-amdt-1-main-rotor-blade-torque-events-and-life-limit","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":39654,"registerId":"commonwealth-F2005L03888-current","compilationNumber":null,"startDate":"2026-04-01","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 369/113 Amdt 1 | Main Rotor Blade TorqueEvents and Life Limit | 1/2006 DM |\n| -------------------- | -------------------------------------------- | --------- |\n\n```html\n

Applicability:

Models 369D, 369E, 369F, 369FF, 500N, or 600N helicopters with either an MD Helicopter Inc. (MDHI) main rotor blade installed or modified with Helicopter Technology Company, LLC (HTC), Supplemental Type Certificate (STC) No. SR09172RC, SR09074RC, or SR01050LA with an HTC blade installed, as listed below:

Model

MDHI blade part No. (P/N)

HTC blade P/N

HTC STC

369D

369D21100 Basic, -516, -517, -523

500P2100-BSC, -BSC-1

SR09172RC

369E

369D21120-501, -503

500P2100-101, -103

SR09074RC

369F, FF

369D21102 Basic, -503, -517, -523

500P2300-501, -503

SR01050LA

369D21121-501, -503

500N

369D21102-503, -517, -523

500P2300-501, -503

SR01050LA

369D21121-501, -503

600N

369D21102-517, -523

500P2300-501, -503

SR01050LA

369D21121-501, -503

Note: The terms “BSC” and “Basic” are interchangeable when identifying blades produced by MDHI and HTC.

Requirement:

1. Determine and record the number of torque events accumulated on each blade. A torque event (TE) is the transition to a hover from forward flight or any external lift operation. Each transition to a hover from forward flight is recorded as a TE, and any external lift operation is recorded as two TEs. Forward flight is considered to be flight at any airspeed (or direction) after attaining translational lift. If you cannot determine the number of TEs, use 13,720 TEs.

Continue to record the number of TEs accumulated (actual usage) throughout the life of the blades along with hours time in service. On or before accumulating an additional 200 TEs or at the end of each day’s operations, whichever occurs first, record and update the accumulated TEs total.

\n```\n\n| | 2. For each blade that has accumulated 13,720 or more TEs and 750 or more hours time in service, before further flight, unless already accomplished; and thereafter after at intervals not to exceed 200 TEs or 35 hours time in service, whichever occurs first, perform a main rotor blade torque event inspection.If a crack is found, before further flight, replace the affected blade with a serviceable blade.Note 1: MD Helicopters Inc. Maintenance Manual CSP-HMI-2, Revision 36, Section 62-10-00, paragraph 8, Main Rotor Blade Torque Event Inspection, pertains to the subject of this Directive.Note 2: MDHI Maintenance Manual CSP-HMI-2, Section 20-30-00 Main Rotor Blade Painting, pertains to the subject of this Directive. This section of the maintenance manual recommends painting the inboard 24-inches (not to be exceeded) of the blade gloss white to aid in detecting a crack; and if this is done, painting all blades alike and rebalancing them.Note 3: TEs are used only to establish an additional inspection interval and not to establish an alternate retirement life. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Compliance: | 1. Within 50 hours time in service after 7 December 2005, unless already accomplished.2. As specified in Requirement 2. |\n| | This Amendment becomes effective on 7 December 2005. |\n| Background: | The FAA required certain actions in response to several reports, including a recent report dated 24 July 2003, of blade cracks due to a high number of TEs per hour. The actions specified in this Directive are intended to prevent fatigue cracking of the blade, blade failure, and subsequent loss of control of the helicopter. |\n\n| | Amendment 1 is issued in response to a new FAA AD, which revises model applicability, adds MDHI part-numbered blades, removes any reference to the life limits of the blades, changes the requirements for inspecting the blades, and revises the STC applicability. The FAA AD also provides that compliance with portions of certain documents constitutes alternative methods of compliance, contains editorial changes for clarification, and makes some corrections. The FAA AD was prompted by additional reports of cracked blades and by comments received in response to FAA AD 2003-24-01. |\n| --- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png) \nDavid Villiers \nDelegate of the Civil Aviation Safety Authority\n\n1 December 2005","sortOrder":0},{"sectionNumber":"AD/HU 369/113 Amdt 1","sectionType":"part","heading":"AD/HU 369/113 Amdt 1","content":"## AD/HU 369/113 Amdt 1","sortOrder":1},{"sectionNumber":"Main Rotor Blade TorqueEvents and Life L","sectionType":"part","heading":"Main Rotor Blade TorqueEvents and Life Limit","content":"## Main Rotor Blade Torque \nEvents and Life Limit","sortOrder":2},{"sectionNumber":"1/2006 DM","sectionType":"part","heading":"1/2006 DM","content":"## 1/2006 DM","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"The amendment broadened and altered the original scope. Compared with earlier wording, Amendment 1 revises model and STC applicability and explicitly adds MDHI part-numbered blades to the applicability list, so more blade/airframe combinations are covered. It also removes any reference to blade life limits (so the instrument focuses on inspection intervals rather than mandatory retirement lives), revises inspection requirements (introducing the TE thresholds and recurring 200‑TE/35‑hour intervals), and adjusts STC applicability. These changes expand the operational reach of the directive (more blades/models affected) and shift the regulatory mechanism from life-limits to inspection-based monitoring."},"complexity_factors":["Applicability table listing 6 helicopter models and multiple blade part numbers and STCs (multiple rows to match parts to models)","Specific operational definition of a \"torque event\" with counting rules (1 TE for transition to hover; 2 TEs for external lift)","Default TE assumption if history unknown (13,720 TEs)","Dual threshold to trigger inspections (>=13,720 TEs AND >=750 flight hours)","Recurring inspection interval defined as the lesser of 200 TEs or 35 flight hours","Cross-references and dependencies on MDHI Maintenance Manual sections for inspection technique and painting guidance","Notes that TEs only set inspection intervals (not retirement life) — adds interpretive nuance","Amendment history described (revised applicability, added MDHI P/Ns, removed life limits) and references to FAA AD and possible alternative compliance methods"],"plain_english_summary":"**What this instrument requires (mechanics)**\n\n- It applies to McDonnell Douglas (Hughes) and Kawasaki 369-series helicopters (models 369D, 369E, 369F/FF, 500N, 600N) fitted with specified MD Helicopters Inc. (MDHI) main rotor blades or Helicopter Technology Company (HTC) blades installed under particular Supplemental Type Certificates (STCs). The affected blade part numbers and STCs are listed in the Applicability table.\n\n- Operators must count and record “torque events” (TEs). A TE is defined as a transition to hover from forward flight, or any external lift operation. Each transition to hover from forward flight = 1 TE; each external lift operation = 2 TEs. Forward flight means any flight after attaining translational lift. (See Requirement 1.)\n\n- If the TE history for a blade cannot be determined, treat that blade as having 13,720 TEs. Continue recording actual TEs and flight hours for each blade. Update the accumulated TE total at least every 200 TEs or at the end of each day’s operations, whichever happens first. (Requirement 1.)\n\n- Inspection trigger: For any blade that has already accumulated at least 13,720 TEs and at least 750 hours time in service, you must perform a Main Rotor Blade Torque Event Inspection before further flight (unless already done). After that, repeat the inspection at intervals not exceeding 200 TEs or 35 hours time in service, whichever occurs first. If a crack is found, replace the blade before further flight. (Requirement 2.)\n\n- Notes: the directive points operators to specific sections of the MDHI Maintenance Manual for the inspection procedure and for painting guidance. The manual recommends painting the inboard 24 inches of the blade gloss white (no more than 24 in.) to help detect cracks, but if you paint, paint all blades the same and rebalance them. The directive also clarifies that TEs are used only to set inspection intervals, not to set blade retirement lives. (Notes 1–3.)\n\n- Compliance timing: initial compliance actions must be completed within the time window specified in the instrument (the document provides a concrete short-term compliance deadline).\n\n**Who this affects**\n\n- Aircraft owners, operators and maintenance organisations responsible for the listed 369-series helicopters with the specified MDHI or HTC blade part numbers or STCs.\n\n- Maintenance personnel who must perform the torque-event inspections, record-keeping, and any blade replacements.\n\n**Why it matters (stated purpose and how the measure attempts to achieve it)**\n\n- The stated purpose is to prevent fatigue cracking of main rotor blades caused by a high number of torque events per hour, and to prevent blade failure and loss of control. The rule does this by: (a) mandating counting and traceability of TEs per blade, (b) requiring inspections after a defined exposure threshold (>=13,720 TEs and >=750 hours), and (c) imposing recurring inspections at short intervals (every 200 TEs or 35 hours) once thresholds are met.\n\n**Practical effects, costs and incentives**\n\n- Who pays: operators pay the direct costs — staff time to count and update TE logs, the labour and parts costs for recurring inspections, potential blade replacements, and any repainting and rebalancing required.\n\n- Who decides: operators and their maintenance organisations decide how to implement counting systems and when to schedule inspections within the required intervals. Certificated maintenance manuals and procedures (MDHI manuals cited in the notes) determine the inspection technique.\n\n- Behaviour changes required: keep per-blade TE and hour logs; inspect blades at the prescribed triggers; replace cracked blades; optionally paint the blade inboard area to aid crack detection (if painting is chosen, paint and rebalance all blades equally).\n\n- Compliance burden: adds frequent short-interval inspections (every 200 TEs or 35 hours once thresholds reached), which increase maintenance workload and downtime compared with baseline calendar- or hour-based maintenance. Operators with poor TE tracking face an immediate de facto additional cost because unknown-history blades are treated as having 13,720 TEs and therefore may require immediate inspection.\n\n- Risk of substitution effects: operators might change operational patterns (e.g. fewer transitions to hover, fewer external lift ops) to slow TE accumulation, or retire blades earlier to avoid inspection/replacement costs. Those operational responses could affect revenue or mission capability.\n\n- Concentrated benefits and diffuse costs: the safety benefit (reduced risk of blade failure) is concentrated on flight safety for any operator and their passengers; the costs (inspections, replacements, administrative tracking) fall directly and predictably on operators of the specified models.\n\n- Implementation risk and discretion: the directive references MDHI maintenance manual procedures as the inspection method; proper implementation relies on maintenance organisations following those procedures. There is limited administrative discretion: the rule sets thresholds and intervals; the maintenance manuals supply the inspection technique.\n\n**Notable design choices and trade-offs**\n\n- Uses an exposure metric (TEs) rather than only flight hours. That targets a specific stressor (repeated transitions/hovering) but increases record-keeping complexity.\n\n- Sets a large default TE value (13,720) for unknown-history blades, which shifts cost and precaution onto owners of aircraft without good records.\n\n- Clarifies that TEs do not determine retirement life, only inspection frequency — retirement rules remain separate.\n\n**Relevant cross-references in the instrument**\n\n- Requirement 1: TE counting and record-keeping rules.\n- Requirement 2: inspection trigger (>=13,720 TEs and >=750 hours) and recurring inspection intervals (<=200 TEs or <=35 hours); action on finding cracks.\n- Notes 1–3: refer to MDHI maintenance manual sections for inspection technique and painting guidance; note that TEs are only for inspection intervals.\n\n"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":true,"description":"This Amendment 1 significantly expanded scope from the original AD/HU 369/113. It added MDHI part-numbered blades to the applicability (previously limited to HTC-modified blades), removed life limit provisions (shifting to inspection-based safety), revised the Supplemental Type Certificate applicability, and changed inspection requirements based on additional field reports of cracked blades. The amendment responds to new FAA directives and operator feedback, indicating the original scope was insufficient to address the safety risk."},"complexity_factors":["Multiple overlapping applicability criteria (helicopter model, blade manufacturer part numbers, and Supplemental Type Certificate numbers)","Dual tracking requirements (torque events AND flight hours) with different thresholds for initial compliance versus ongoing inspections","Nested conditional logic: inspections triggered by combined thresholds (13,720 TEs + 750 hours), then subsequent intervals based on whichever comes first (200 TEs or 35 hours)","Cross-references to external maintenance manuals (MDHI CSP-HMI-2) for inspection procedures","Specific technical definitions required (\"translational lift\", \"torque event\" counting methodology)","Alternative compliance methods referenced but not fully detailed in the directive itself"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to specific McDonnell Douglas (Hughes) and Kawasaki helicopter models (369D, 369E, 369F, 369FF, 500N, and 600N) that use certain main rotor blades.\n\n**What it does:**\n- Requires helicopter operators to **track \"torque events\"** — specific flight manoeuvres that stress the main rotor blades. A torque event includes:\n - Every transition from forward flight to a hover (counts as 1 event)\n - Every external lift operation (counts as 2 events)\n- **Mandates inspections** once blades reach 13,720 torque events AND 750 flight hours, then repeatedly every 200 torque events or 35 flight hours (whichever comes first)\n- **Requires blade replacement** if cracks are found during inspection\n\n**Why it matters:**\nFatigue cracks have been discovered in these blades after repeated high-stress manoeuvres. Cracked blades can fail in flight, causing catastrophic loss of control. This directive prevents accidents by forcing operators to monitor blade stress and inspect before failure occurs.\n\n**Who must comply:**\nOwners and operators of affected helicopters must begin tracking torque events within 50 flight hours after 7 December 2005, and follow the inspection schedule thereafter."},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-369-113-amdt-1-main-rotor-blade-torque-events-and-life-limit","history":"/api/acts/ad-hu-369-113-amdt-1-main-rotor-blade-torque-events-and-life-limit/history","analysis":"/api/acts/ad-hu-369-113-amdt-1-main-rotor-blade-torque-events-and-life-limit/analysis","conflicts":"/api/acts/ad-hu-369-113-amdt-1-main-rotor-blade-torque-events-and-life-limit/conflicts","importantCases":"/api/acts/ad-hu-369-113-amdt-1-main-rotor-blade-torque-events-and-life-limit/important-cases","documents":"/api/acts/ad-hu-369-113-amdt-1-main-rotor-blade-torque-events-and-life-limit/documents"}}