{"id":"F2006B10633","name":"AD/HU 269/73 - Main Gearbox Ring Gear - Inspection and Increase of Bolt Torque","slug":"ad-hu-269-73-main-gearbox-ring-gear-inspection-and-increase-of-bolt-torque","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":116530,"registerId":"commonwealth-F2006B10633-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/HU 269/73 - Main Gearbox Ring Gear - Inspection and Increase of Bolt Torque","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)  \nSchweizer (Hughes) 269 Series Helicopters\n\nAD/HU 269/73 Main Gearbox Ring Gear \\- Inspection\n\nand Increase of Bolt Torque\n\n  \n9/82\n\nApplicability: All models 269A, 269A-1, 269B, 269C fitted with main gear box assembly P/N 269A5175-7, \\-9, \\-11, \\-13, \\-15 or \\-17, except those gearboxes identified with a letter “W” adjacent to the serial number on the identification plate.\n\nDocument: Hughes SIN N-181.\n\nFAA AD 82-15-01 refers.\n\nCompliance: Within 100 hours time in service after 30 September 1982.\n\nBackground: We are advised that there have been several reports of looseness to the main gearbox ring gear attach bolts. The possible resulting fatigue failure to bolts or ring gear carrier could cause loss of rotor drive, or jamming of the main gearbox.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in specific helicopter models. It has not expanded beyond its original purpose of mandating inspection and bolt torque correction for the identified gearbox assemblies."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined applicability criteria (part numbers and 'W' exclusion)","Single compliance requirement with clear deadline","No cross-references to other legislation (only references to manufacturer document Hughes SIN N-181 and FAA AD 82-15-01 for technical context)","No conditional logic or nested exceptions","Straightforward imperative language ('Compliance: Within 100 hours...')"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific helicopters.\n\n**What it does:**\nOrders owners and operators of certain Schweizer (formerly Hughes) 269 series helicopters to **inspect the main gearbox ring gear and tighten specific bolts** to a higher torque setting than originally specified.\n\n**Who it affects:**\n- All models 269A, 269A-1, 269B, and 269C helicopters\n- **Only those** with main gearbox assemblies having part numbers ending in -7, -9, -11, -13, -15, or -17\n- **Excludes** gearboxes marked with a \"W\" next to the serial number on the identification plate\n\n**Why it matters:**\nThere had been multiple reports of **loose bolts** attaching the ring gear in the main gearbox. If these bolts fail due to fatigue, the helicopter could suffer:\n- **Loss of rotor drive** (the rotor stops spinning — catastrophic)\n- **Jamming of the main gearbox** (sudden, uncontrolled mechanical seizure)\n\n**What must be done:**\nThe inspection and bolt torque increase must be completed **within 100 hours of flight time** after 30 September 1982.\n\n**Key point:** This is not optional. Airworthiness Directives are legally binding safety mandates. Non-compliance means the aircraft cannot legally fly."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive applies to a clearly defined set of helicopter models and gearbox part numbers, excluding gearboxes marked with a 'W' (Applicability). It prescribes inspection and torque increase within a set time window and references the manufacturer's service instruction for the technical procedure (Document; Compliance). Based on the text provided, the scope described (which aircraft and parts are covered and what action is required) aligns with the stated safety concern and does not indicate an expansion or contraction beyond that stated intent."},"complexity_factors":["Narrow, model- and part-number-based applicability with an explicit exclusion for gearboxes marked with 'W' (Applicability).","Mandated action references an external manufacturer service instruction (Hughes SIN N-181) for technical detail rather than specifying procedural steps or torque values directly in the directive (Document).","Fixed compliance window tied to airframe time in service introduces operational scheduling requirements (Compliance).","Cross-reference to a foreign regulator's AD (FAA AD 82-15-01) adds an external regulatory linkage (Document).","The directive is procedural (inspect and increase torque) rather than prescriptive about exact technical parameters in the text provided here, increasing reliance on external documents for execution (Document)."],"plain_english_summary":"The directive requires operators of Schweizer (Hughes) 269A/B/C-series helicopters with specified main gearbox part numbers (except gearboxes marked “W”) to inspect the main‑gearbox ring‑gear attachment bolts and increase bolt torque as needed, following Hughes SIN N‑181, within 100 hours after 30 September 1982. CASA issued it to reduce reported bolt looseness that can cause ring‑gear/carrier failure; owners/operators bear the inspection, maintenance and downtime costs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-hu-269-73-main-gearbox-ring-gear-inspection-and-increase-of-bolt-torque","history":"/api/acts/ad-hu-269-73-main-gearbox-ring-gear-inspection-and-increase-of-bolt-torque/history","analysis":"/api/acts/ad-hu-269-73-main-gearbox-ring-gear-inspection-and-increase-of-bolt-torque/analysis","conflicts":"/api/acts/ad-hu-269-73-main-gearbox-ring-gear-inspection-and-increase-of-bolt-torque/conflicts","importantCases":"/api/acts/ad-hu-269-73-main-gearbox-ring-gear-inspection-and-increase-of-bolt-torque/important-cases","documents":"/api/acts/ad-hu-269-73-main-gearbox-ring-gear-inspection-and-increase-of-bolt-torque/documents"}}