{"id":"F2006B09582","name":"AD/ENST 28/26 Amdt 2 - Tail Rotor Drive Shaft Couplings","slug":"ad-enst-28-26-amdt-2-tail-rotor-drive-shaft-couplings","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54282,"registerId":"commonwealth-F2006B09582-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ENST 28/26 Amdt 2 - Tail Rotor Drive Shaft Couplings","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)  \nEnstrom F-28 Series Helicopters\n\nAD/ENST 28/26\n\nAmdt 2\n\n  \nTail Rotor Drive Shaft Couplings 10/90\n\nApplicability: All F-28A, 280, F28C, F-28C-2, 280C , F-28F and 280F models equipped with part number 28-13609 couplings.\n\nRequirement: Part 1: Disassemble and inspect couplings in accordance with Service Directive Bulletin No. 0065 Rev B.\n\nPart 2: Partially disassemble and lubricate couplings in accordance with Service Bulletin No. 0065 Rev B.\n\nPart 3: Carry out a Rockwell “C” material hardness check in accordance with Service Bulletin No. 0065 Rev. B.\n\nNote: Use Aeroshell Grease 16 or 22, or an approved equivalent FAA AD 83-18-64 Amendment 39-4721 refers to Revision A of Service Directive Bulletin.\n\n| Compliance: | Part 1: | Within 25 hours time in service after 1st October 1983 or no later than the 31 October 1983, whichever occurs first and thereafter every 600 hours time in service or annually whichever occurs first. |\n| ----------- | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n|             | Part 2: | At each maintenance release inspection.                                                                                                                                                                |\n|             | Part 3: | Unless already accomplished, prior to the issue of the next maintenance release after 31 January 1985.                                                                                                 |\n\nAny coupling which fails the material hardness test must be retired from service. Couplings must be retired from service at a total time in service of 1200 hours.\n\nThose couplings with more than 1200 hours time in service, retire within 50 hours time in service after 31 January 1985.\n\nBackground: This directive is amended to include a one time material hardness inspection, and the retirement life of the couplings in accordance with the manufacturers recommended revised Service Bulletin 0065. This amendment requires all couplings failing the hardness test to be retired from service\".","sortOrder":0}],"analysis":{"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"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Yes. The amendment adds a one-time material hardness inspection and formal retirement life for the couplings, and requires retirement of any coupling failing the hardness test — changes set out to align with the manufacturer’s revised Service Bulletin No. 0065 Rev B (Background; Requirement). It also fixes specific compliance deadlines (Compliance) and prescribes allowable lubricants (Note), expanding the directive’s operational and replacement obligations compared with the prior issuance."},"complexity_factors":["Multiple discrete technical tasks required (disassembly/inspection, lubrication, Rockwell C hardness test) increasing operational steps (Requirement: Parts 1–3).","Several different compliance timings and trigger events (within 25 hours or by date; recurring 600 hours or annual; at each maintenance release; one‑time prior-to-next-release deadline) increasing scheduling complexity (Compliance table).","Hardness test requires calibrated equipment and technical judgment to determine pass/fail, creating inspection capability and record-keeping burdens (Requirement: Part 3).","Mandatory retirement life (1,200 hours TIS) plus a short-window retirement for items already beyond that limit imposes asset‑replacement costs and logistics (Retirement rules).","Applicability limited to specific part number and aircraft models, requiring fleet-level tracking of affected components (Applicability).","Dependence on a specific service bulletin revision (0065 Rev B) and cross-reference to an FAA AD introduces dependency on external documents for correct procedure (Requirement/Note/Background).","Specified allowable lubricants narrows acceptable maintenance supplies (Note)."],"plain_english_summary":"This directive requires disassembly, inspection, lubrication and a Rockwell “C” hardness test of tail-rotor drive-shaft couplings (P/N 28-13609) on Enstrom F‑28 series helicopters, carried out to *Service Directive Bulletin No. 0065 Rev B*. Operators must retire couplings that fail the hardness test and retire all couplings at 1,200 hours total time-in-service (with specific short deadlines for items already beyond that limit). Maintenance organisations perform the work; owners/operators bear the cost and scheduling burden."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"This is Amendment 2 to an existing directive originally issued in October 1983. The original directive (implied by the background note) required inspections and lubrication. This amendment significantly expanded the scope by adding: (1) mandatory one-time material hardness testing, (2) absolute retirement life limits (1,200 hours), and (3) immediate retirement requirements for failed parts. The directive evolved from routine maintenance requirements to a more comprehensive safety-critical retirement scheme based on updated manufacturer data about material failure risks."},"complexity_factors":["Multiple compliance deadlines with 'whichever occurs first' conditional logic (3 separate timing rules)","Cross-reference to external technical documents (Service Bulletin No. 0065 Rev B, FAA AD 83-18-64)","Nested applicability criteria (specific helicopter models AND specific part number)","Three distinct maintenance parts with different frequencies (one-time, recurring, and conditional)","Retirement rules with grandfathering for existing high-time parts (1200-hour limit with 50-hour grace period for already-overdue parts)"],"plain_english_summary":"Owners and operators of Enstrom F‑28 series helicopters with tail rotor drive shaft couplings part no. 28‑13609 must follow a CASA airworthiness directive requiring enhanced inspection, maintenance, a one‑time hardness test, and mandatory retirement of couplings after specified flight hours.  \n\nIt’s intended to prevent tail‑rotor coupling failure and loss of directional control by addressing metal fatigue risk identified by the manufacturer."}},"importantCases":[],"_links":{"self":"/api/acts/ad-enst-28-26-amdt-2-tail-rotor-drive-shaft-couplings","history":"/api/acts/ad-enst-28-26-amdt-2-tail-rotor-drive-shaft-couplings/history","analysis":"/api/acts/ad-enst-28-26-amdt-2-tail-rotor-drive-shaft-couplings/analysis","conflicts":"/api/acts/ad-enst-28-26-amdt-2-tail-rotor-drive-shaft-couplings/conflicts","importantCases":"/api/acts/ad-enst-28-26-amdt-2-tail-rotor-drive-shaft-couplings/important-cases","documents":"/api/acts/ad-enst-28-26-amdt-2-tail-rotor-drive-shaft-couplings/documents"}}