{"id":"F2006B04685","name":"AD/BELL 47/17 Amdt 1 - Tail Rotor Pitch Change Bearings - Inspection and Life Limitations","slug":"ad-bell-47-17-amdt-1-tail-rotor-pitch-change-bearings-inspection-and-life-limitations","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44437,"registerId":"commonwealth-F2006B04685-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 47/17 Amdt 1 - Tail Rotor Pitch Change Bearings - Inspection and Life Limitations","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 47/17\n\nAmdt 1\n\n  \n\nTail Rotor Pitch Change Bearings \\- Inspection and Life Limitations\n\n  \n11/67\n\nApplicability: All model 47D and D1, 47G, G2 and H1 helicopters.\n\nRequirement: 1. Inspection: Inspect pitch change control shaft P/N 47-641-034 or P/N 47-641-045 as follows:\n\n    (a) Remove shaft from tail rotor gear box in accordance with Bell Service Manual.\n\n    (b) Mount shaft at acme screw thread end in collet.\n\n    (c) Measure concentricity of bearing shaft diameter. This diameter must be concentric within 0.060 TIR.\n\n    (d) If diameters are not concentric within 0.060 shaft must be straightened within this tolerance.\n\n2. Life Limitation: Tail rotor pitch change bearings P/N R4AF4 also identified by Bell P/N 47-641-146-1 and alternate P/N SIRP and 7R4AXIC shall be retired from service after accumulation of 100 hours time in service; or\n\n3. FAA AD 58-23-1.\n\nCompliance: Inspect at intervals not exceeding 600 hours time in service after 1 September 1971.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is Amendment 1 to an existing Airworthiness Directive. The scope remains tightly focused on tail rotor pitch change bearings for specific Bell 47 variants. The amendment appears to maintain the original safety purpose — preventing tail rotor control failures — without expanding into unrelated systems or aircraft types."},"complexity_factors":["Short, single-purpose directive with only 3 substantive requirements","Minimal defined terms (only 'TIR' implied, not explicitly defined in text)","No nested conditional logic — requirements are numbered alternatives or sequential steps","Single cross-reference to external FAA AD 58-23-1 as alternative compliance path","Specific part numbers provided in full (no 'as amended' or dynamic referencing)","Clear applicability statement limiting scope to specific model variants","Fixed compliance dates and hours (no complex calculation formulas)"],"plain_english_summary":"This CASA Airworthiness Directive orders owners/operators of Bell 47D/D1, 47G/G2 and 47H1 helicopters to inspect the tail rotor pitch change control shaft (every 600 flight hours) and to replace a specified tail‑rotor bearing after 100 flight hours (no exceptions). Compliance via FAA AD 58‑23‑1 is allowed. It’s intended to prevent pitch‑link or bearing failures that could cause loss of directional control."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This amendment (Amdt 1) sets explicit inspection procedures, a 0.060\" concentricity tolerance, a 600‑hour inspection frequency and a 100‑hour retirement life limit for specified tail-rotor pitch-change bearings on listed Bell 47 models. The document itself is an amendment, indicating these inspection and life‑limit obligations were added or clarified compared with the prior directive text."},"complexity_factors":["Specific technical tolerance: concentricity requirement of 0.060\" total indicator reading (TIR) for shaft diameter","Procedural dependency: shaft removal and mounting steps reference the Bell Service Manual","Prescriptive life limit: mandatory retirement of listed bearing P/Ns after 100 hours time-in-service","Compliance scheduling: recurring inspection interval of every ≤600 hours (from a historical start date)","Multiple part-number references and alternates increase identification and inventory tasks","Alternate compliance path: permits following FAA AD 58-23-1, adding regulatory cross-reference"],"plain_english_summary":"This airworthiness directive requires operators of listed Bell 47 helicopter models to inspect tail-rotor pitch-change control shafts for bearing concentricity and to retire specified pitch-change bearings after 100 hours. Inspections require shaft removal, mounting in a collet and measuring concentricity to 0.060\" TIR; non-conforming shafts must be straightened.\n\nOperators bear the maintenance time, measurement-equipment and replacement costs, must meet 600‑hour inspection intervals (from 1 Sep 1971) and may comply via FAA AD 58-23-1; work follows the Bell Service Manual."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-47-17-amdt-1-tail-rotor-pitch-change-bearings-inspection-and-life-limitations","history":"/api/acts/ad-bell-47-17-amdt-1-tail-rotor-pitch-change-bearings-inspection-and-life-limitations/history","analysis":"/api/acts/ad-bell-47-17-amdt-1-tail-rotor-pitch-change-bearings-inspection-and-life-limitations/analysis","conflicts":"/api/acts/ad-bell-47-17-amdt-1-tail-rotor-pitch-change-bearings-inspection-and-life-limitations/conflicts","importantCases":"/api/acts/ad-bell-47-17-amdt-1-tail-rotor-pitch-change-bearings-inspection-and-life-limitations/important-cases","documents":"/api/acts/ad-bell-47-17-amdt-1-tail-rotor-pitch-change-bearings-inspection-and-life-limitations/documents"}}