{"id":"F2006B02604","name":"AD/B-2/31 - Main Rotor Mast - Inspection","slug":"ad-b-2-31-main-rotor-mast-inspection","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":41907,"registerId":"commonwealth-F2006B02604-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B-2/31 - Main Rotor Mast - Inspection","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)  \nBrantly B-2 Series Helicopters\n\nAD/B-2/31 Main Rotor Mast \\- Inspection 9/71\n\nApplicability: All model B-2, B-2A and B-2B. Requirement: 1. Remove mast plug P/N 151-18.\n\n    2. Visually inspect the inner bore surface over the entire length of the main rotor mast for presence of rust or corrosion using a light and mirror. The presence of any rust or corrosion which cannot be removed with a lint free cloth is cause for removal of the transmission assembly.\n\n    3. Prior to reinstallation or replacement of the mast accomplish the appropriate inspection items under the heading “Main Transmission” of the 1200 Hour Interval Inspection, Section 1.8.7, Brantly Maintenance Manual.\n\n    4. If the main rotor mast is free or can be freed of rust or corrosion following the inspections noted in Para. (2), apply a thin film of Esso Rust-Ban 626, Avrex 901 or equivalent preserving type lubricating oil to the entire length of the inner bore surface.\n\n    5. Re-install the mast plug with a new “O” ring packing P/N AN 6227-26 and retain in place with the clevis pin P/N AN 393-11 that retains the hub retaining nut P/N 150-1. Secure clevis pin by installing washer, P/N AN 960-10L and cotter pin AN 380-2-1; or\n\nFAA AD 71-17-5.\n\nCompliance: Within 10 hours time in service and thereafter at intervals not exceeding 50 hours time in service.","sortOrder":0}],"analysis":{"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"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused specifically on main rotor mast corrosion inspection for one helicopter series. It has not expanded beyond its original safety purpose."},"complexity_factors":["Single, discrete maintenance task with linear procedural steps (1-5)","Only 3 helicopter models affected (B-2, B-2A, B-2B)","Minimal defined terms (only standard aviation part numbers like P/N 151-18, AN 6227-26)","No cross-references to other legislation beyond citing parent Civil Aviation Regulations 1998, Part 39","Simple conditional logic: 'if rust found → remove transmission; if clean → apply oil'","Single compliance timeframe (10 hours initial, 50 hours recurring)","Short document (approximately 200 words)"],"plain_english_summary":"This CASA Airworthiness Directive mandates operators of Brantly B‑2, B‑2A and B‑2B helicopters in Australia to inspect the hollow main rotor mast for internal rust or corrosion, initially within 10 flight hours and then every 50 hours. It requires corrective action — cleaning and corrosion protection or removal and replacement of the transmission assembly if corrosion is not removable — to prevent catastrophic rotor failure."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive applies to all listed Brantly B‑2 variants and sets inspection, cleaning/oiling, and removal requirements with specified compliance intervals. There is no textual indication that the AD widens or narrows applicability relative to its stated subject matter; it operationalises inspection and corrective actions without changing the class of affected aircraft."},"complexity_factors":["Narrow applicability (specific models B‑2, B‑2A, B‑2B) limits scope but requires model-specific parts and procedures","Detailed parts and part numbers referenced (mast plug P/N 151‑18; O‑ring P/N AN 6227‑26; clevis pin P/N AN 393‑11; washer P/N AN 960‑10L; cotter pin AN 380‑2‑1)","Clear decision point: if corrosion cannot be removed with a lint‑free cloth (Para. (2)), transmission assembly must be removed","Specified inspection method (visual with light and mirror) and preservative options (Esso Rust‑Ban 626, Avrex 901 or equivalent)","Cross‑reference to Brantly Maintenance Manual, 1200 Hour Interval Inspection, Section 1.8.7, for pre‑reinstallation tasks","Fixed, frequent compliance intervals (within 10 hours then every 50 hours) impose recurring maintenance burden"],"plain_english_summary":"This airworthiness directive requires owners/operators of Brantly B‑2, B‑2A and B‑2B helicopters to remove the mast plug, visually inspect the inner bore of the main rotor mast for rust or corrosion, and either clean and preserve the bore or remove the transmission assembly if corrosion cannot be cleared. It names specific parts, preserving oils and re‑installation hardware.\n\nCompliance is within 10 hours time‑in‑service and then every 50 hours. Operators pay for inspections, cleaning/oiling and any replacements; maintenance personnel decide removability and must follow the Brantly Maintenance Manual (Section 1.8.7)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b-2-31-main-rotor-mast-inspection","history":"/api/acts/ad-b-2-31-main-rotor-mast-inspection/history","analysis":"/api/acts/ad-b-2-31-main-rotor-mast-inspection/analysis","conflicts":"/api/acts/ad-b-2-31-main-rotor-mast-inspection/conflicts","importantCases":"/api/acts/ad-b-2-31-main-rotor-mast-inspection/important-cases","documents":"/api/acts/ad-b-2-31-main-rotor-mast-inspection/documents"}}