{"id":"F2006B04698","name":"AD/BELL 47/72 Amdt 2 - Main Rotor Hub Core P/N 47-120-117-1","slug":"ad-bell-47-72-amdt-2-main-rotor-hub-core-p-n-47-120-117-1","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44462,"registerId":"commonwealth-F2006B04698-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 47/72 Amdt 2 - Main Rotor Hub Core P/N 47-120-117-1","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBell Helicopter Textron 47 (All Variants) Series Helicopters\n\nAD/BELL 47/72\n\nAmdt 2\n\n  \nMain Rotor Hub Core P/N 47-120-117-1 3/87\n\nApplicability: All model 47 series fitted with P/N 47-120-117-1 hub core.\n\nRequirement: Irrespective of the dimensional exclusion given in Part I of Bell SB 47-04-1-73-2, inspect in accordance with Part II of the document.\n\nCompliance: At each issue of a new Maintenance Release, for all cores which have exceeded 1200 hours total time-in-service or for which the total time in service is unknown.\n\nBackground: A crack has been found in the web of a hub core which is exempted by dimensional criteria from the requirement for visual inspection at 100 hourly periods. Amendment 1 included all P/N 47-120-117-1 cores. This amendment brings the compliance periodicity into line with the inspection interval for Maintenance Release.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Yes. The amendment removes the dimensional exclusion in the Bell service bulletin and requires inspection of all P/N 47-120-117-1 hub cores (Amendment 1 noted in Background and Requirement). Amendment 2 adjusts the inspection timing so that inspections occur at each Maintenance Release for cores over 1,200 hours or with unknown hours, rather than the prior 100-hour visual inspection periodicity referenced in the service bulletin (Background; Compliance)."},"complexity_factors":["Cross-reference to external document (Bell SB 47-04-1-73-2) — compliance requires consulting Part II of that service bulletin (Requirement).","Record-keeping and determination of total time-in-service for each hub core — operators must know or treat unknown as requiring inspection (Compliance).","Change from a dimensional exclusion regime to mandatory inspection irrespective of dimensional exclusion increases the population of items to be inspected (Requirement; Background).","Timing tied to Maintenance Release intervals rather than a fixed hourly interval — inspection cadence depends on operator maintenance scheduling (Compliance; Background).","Regulatory amendment history (Amendment 1 and Amendment 2) requires attention to which version applies to a given core (Background)."],"plain_english_summary":"This AD requires owners/operators of Bell 47 series helicopters with main rotor hub core P/N 47-120-117-1 to carry out the Part II inspection in Bell SB 47-04-1-73-2, removing the SB’s dimensional exclusion. Inspections must be done at each Maintenance Release for cores over 1,200 hours or with unknown time‑in‑service.\n\nIt widens the inspection population, raises record‑keeping and maintenance costs, and may increase downtime and repair actions for affected operators."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original directive (implied by Amendment 1) expanded coverage to include all P/N 47-120-117-1 hub cores regardless of dimensions. Amendment 2 then significantly narrowed the practical scope by changing compliance from 'every 100 hours' to 'at each Maintenance Release issuance' — effectively reducing inspection frequency for low-time cores while maintaining safety focus on high-time or unknown-history parts. The scope has shifted from broad mandatory inspection to targeted risk-based inspection."},"complexity_factors":["Single specific part number targeted (P/N 47-120-117-1)","Conditional applicability based on two factors: hours-in-service (>1200) OR unknown hours","References external document (Bell SB 47-04-1-73-2) without reproducing its content","Amendment structure requires understanding of previous versions (Amendment 1 expanded scope, Amendment 2 changed compliance timing)","Technical aviation terminology requires domain knowledge (Maintenance Release, time-in-service, dimensional exclusion)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety notice issued by Australia's Civil Aviation Safety Authority (CASA) that requires specific maintenance actions on certain aircraft.\n\n**What it does:**\nThis directive orders owners and operators of **Bell 47 series helicopters** to conduct visual inspections of a specific part — the **main rotor hub core** (part number 47-120-117-1) — under certain conditions.\n\n**Who it affects:**\n- Anyone who owns or operates a Bell 47 helicopter fitted with this specific hub core part\n- Maintenance engineers who issue Maintenance Releases (official documents certifying an aircraft is safe to fly)\n\n**The specific requirement:**\nDespite an earlier exemption based on dimensions, operators must now inspect these hub cores **every time a new Maintenance Release is issued**, but **only for cores that have:**\n- Accumulated more than 1,200 flight hours, **or**\n- Have unknown flight hours (no reliable service history)\n\n**Why it matters:**\nA crack was discovered in one of these hub cores that had slipped through previous inspection requirements. The original safety bulletin allowed some cores to skip visual inspections based on their measurements. This directive closes that loophole — but only for high-time or mystery-history parts, and ties the inspection to the Maintenance Release cycle rather than fixed hourly intervals.\n\n**Key change from previous version:**\nEarlier versions required inspections at fixed 100-hour intervals. This amendment (Amendment 2) changes the timing to match whenever a Maintenance Release is renewed — typically annual or based on flight hours, whichever comes first."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-47-72-amdt-2-main-rotor-hub-core-p-n-47-120-117-1","history":"/api/acts/ad-bell-47-72-amdt-2-main-rotor-hub-core-p-n-47-120-117-1/history","analysis":"/api/acts/ad-bell-47-72-amdt-2-main-rotor-hub-core-p-n-47-120-117-1/analysis","conflicts":"/api/acts/ad-bell-47-72-amdt-2-main-rotor-hub-core-p-n-47-120-117-1/conflicts","importantCases":"/api/acts/ad-bell-47-72-amdt-2-main-rotor-hub-core-p-n-47-120-117-1/important-cases","documents":"/api/acts/ad-bell-47-72-amdt-2-main-rotor-hub-core-p-n-47-120-117-1/documents"}}