{"id":"F2006B10599","name":"AD/HU 269/28 Amdt 3 - Main Rotor Thrust Bearing P/N 269A5050-50 or -51 Nut and Mast - Inspection and Modification","slug":"ad-hu-269-28-amdt-3-main-rotor-thrust-bearing-p-n-269a5050-50-or-51-nut-and-mast-inspection-and-modi","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116461,"registerId":"commonwealth-F2006B10599-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 269/28 Amdt 3 - Main Rotor Thrust Bearing P/N 269A5050-50 or -51 Nut and Mast - Inspection and Modification","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)  \n![](image.002.png)  \nSchweizer (Hughes) 269 Series Helicopters\n\nAIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/HU 269/28 Amdt 2 and issues the following AD under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\nAD/HU 269/28\n\nAmdt 3\n\n  \nMain Rotor Thrust Bearing P/N 269A5050-50 or\n\n\\-51 Nut and Mast \\- Inspection and Modification\n\n  \n8/2000\n\nApplicability: Model 269A helicopters, S/N 0011 to 1109, Model 269A-1 helicopters, S/N 0001 to 0041, Model 269B helicopters, S/N 0001 to 0444 and model TH-55A with main rotor thrust bearing P/No 269A5050-50, -51 or -73 installed.\n\nRequirement: 1. Examine the helicopter records to determine P/N of main rotor thrust bearing.\n\n    (a) If bearing P/No 269A5050-50 or -51 is fitted, inspect in accordance with Step II, paragraph b. of Schweizer Service Notice (SSN) No N-59, dated October 9, 1968.\n    (b) If bearing P/No 269A5050-73 is fitted. Inspect for corrosion, rust, freedom of rotation, looseness, binding, nicks, burrs, cracks and lubrication. Repack the bearing cavity in accordance with Schweizer Aircraft Corporation CKP-C-41 “Installation Instructions for 269 Series Helicopters, SA-269K-057-1 Main Rotor Thrust Bearing Kit,” dated June 9, 1994.\n\nNote 1: Bearing P/N 269A5050-50 and 269A5050-51 have a 300 hour retirement life while bearing P/N 269A5050-73 has a 3000 hour retirement life.\n\n    2. Inspect the thrust bearing nut P/N 269A1306-5 for corrosion and physical damage and confirm nut has been modified in accordance with Step III of SSN No 59. Replace any nut found damaged, corroded or not modified.\n    3. Inspect interior of main rotor mast for corrosion, damage, foreign material, moisture or inadequate drainage due to a build up of zinc chromate paste and determine whether the mast has been modified in accordance with Step II of SSN No 59. If mast has not been modified, modify mast in accordance with Step III of SSN No 59.\n\nIf corrosion or damage is found, replace mast with serviceable mast modified in accordance with Step III of SSN No 59. If mast interior has foreign material, moisture or inadequate drainage due to chromate build-up, then clean in accordance with Step II of SSN No59.\n\nNote 2: FAA AD 97-05-06 Amendment 39-9950 supersedes FAA AD 68-21-05\n\nAmendment 39-1055 and 39-672.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nCompliance: 1 (a). Unless previously accomplished, within 25 hours time in service (TIS) from the effective date of this Directive. Re-inspect bearing after 150 hours TIS. Replace bearing before further flight if TIS equals or exceeds 300 hours. If bearing TIS equals or exceeds 275 hours and is less than 300 hours replace within next 25 hours. If bearing TIS is less than 275 hours replace on or before 300 hours.\n\n(b) Unless previously accomplished, within 25 hours TIS from the effective date of this Directive. Thereafter, re-inspect at intervals not exceeding 600 hours TIS.\n\n    2. Unless previously accomplished within 25 hours time in service from the effective date of this Directive.\n\n    3. Unless previously accomplished within 25 hours time in service from the effective date of this Directive.\n\nThis Amendment becomes effective on 10 August 2000.\n\nBackground: This amendment has been raised to align the mast bearing inspection requirements with the country of origin Airworthiness Directive.\n\n![](image.003.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 5 June 2000\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 12 July 2000.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This is Amendment 3 to an existing Airworthiness Directive. The background explicitly states the amendment was raised to align inspection requirements with the country of origin (US FAA) directive. This represents technical harmonisation rather than scope creep — the directive remains tightly focused on the specific thrust bearing, nut, and mast issues for the Schweizer 269 helicopter series as originally intended."},"complexity_factors":["Multiple part number variants (-50, -51, -73) with different inspection intervals and retirement lives (300 vs 3000 hours)","Nested conditional logic: different actions required depending on which bearing is installed, whether prior modifications were done, and accumulated flight hours","Cross-references to external documents (Schweizer Service Notice N-59, CKP-C-41 installation instructions) that are not reproduced in the text","Tiered compliance deadlines based on 'time in service' (TIS) with multiple thresholds (25 hours, 150 hours, 275 hours, 300 hours, 600 hours)","Four distinct aircraft models with specific serial number ranges in the applicability section","Amendment structure revokes previous version (Amdt 2) and references superseded FAA directives in background"],"plain_english_summary":"This CASA Airworthiness Directive mandates immediate inspection and, if needed, replacement or modification of key main-rotor components on certain Schweizer/Hughes 269 series helicopters and TH-55A trainers. It targets the rotor thrust bearing, bearing nut, and hollow mast to eliminate corrosion, wear, or drainage issues that could cause catastrophic rotor failure.\n\nIt affects owners/operators of applicable 269/TH-55A helicopters and requires action within a short 25-flight-hour compliance window to address the urgent safety risk."},"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":true,"description":"This amendment (Amdt 3) revokes AD/HU 269/28 Amdt 2 and updates mast bearing inspection requirements to align with the country‑of‑origin Airworthiness Directive (Background). The underlying unsafe condition addressed remains the same, but inspection intervals, part‑number‑specific requirements and referenced service‑document procedures have been modified (Requirement; Compliance; Note 1)."},"complexity_factors":["Multiple affected part numbers with different retirement lives and inspection intervals (269A5050‑50/‑51 vs 269A5050‑73) (Requirement; Note 1; Compliance)","Cross‑references to external service documents (Schweizer Service Notice No. N‑59 and CKP‑C‑41 installation instructions) that operators must follow exactly (Requirement)","Conditional actions based on time‑in‑service thresholds (replace if ≥300 hours; replace within next 25 hours if between 275–299) (Compliance)","Short mandatory compliance windows (generally within 25 hours TIS) increasing operational disruption risk (Compliance)","Applicability limited by model and serial number ranges, requiring record checks to determine applicability (Applicability; Requirement)","Multiple inspection and remediation tasks (examine records, inspect bearings, inspect/modify nut and mast, clean or replace mast) with decision forks based on findings (Requirement)","Revokes a prior amendment and aligns with foreign (FAA) ADs, creating inter‑jurisdictional reference and potential for differing historical operator compliance (Background; Note 2)"],"plain_english_summary":"This Airworthiness Directive requires operators of specified Schweizer (Hughes) 269‑series and TH‑55A helicopters to inspect, modify or replace main rotor thrust bearings, the thrust bearing nut and the mast to address corrosion, damage, drainage and retirement‑life issues. CASA (the regulator) mandates the checks and actions and revokes the prior amendment. Operators must examine records to identify part numbers, follow Schweizer Service Notice No. N‑59 and the specified installation instructions, and carry out inspections/modifications/replacements within the hours‑in‑service windows in the Requirement and Compliance sections."},"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-269-28-amdt-3-main-rotor-thrust-bearing-p-n-269a5050-50-or-51-nut-and-mast-inspection-and-modi","history":"/api/acts/ad-hu-269-28-amdt-3-main-rotor-thrust-bearing-p-n-269a5050-50-or-51-nut-and-mast-inspection-and-modi/history","analysis":"/api/acts/ad-hu-269-28-amdt-3-main-rotor-thrust-bearing-p-n-269a5050-50-or-51-nut-and-mast-inspection-and-modi/analysis","conflicts":"/api/acts/ad-hu-269-28-amdt-3-main-rotor-thrust-bearing-p-n-269a5050-50-or-51-nut-and-mast-inspection-and-modi/conflicts","importantCases":"/api/acts/ad-hu-269-28-amdt-3-main-rotor-thrust-bearing-p-n-269a5050-50-or-51-nut-and-mast-inspection-and-modi/important-cases","documents":"/api/acts/ad-hu-269-28-amdt-3-main-rotor-thrust-bearing-p-n-269a5050-50-or-51-nut-and-mast-inspection-and-modi/documents"}}