{"id":"F2006B09589","name":"AD/ENST 28/32 Amdt 1 - Tail Rotor Gearbox","slug":"ad-enst-28-32-amdt-1-tail-rotor-gearbox","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54295,"registerId":"commonwealth-F2006B09589-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/ENST 28/32 Amdt 1 - Tail Rotor Gearbox","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 28/32\n\nAmdt 1\n\n  \n\nTail Rotor Gearbox 3/90 DM\n\nApplicability: All model F28, F28A, F28C, F28C-2, F28F, 280, 280C, 280F and 280FX with tail rotor gearbox P/N 28-13500-1, 28-13525-1, \\-3 or \\-5 installed and containing spiral miter gear-set “Boston Gear XR-137-2YR or XR-137-2YL”.\n\nRequirement: Inspect in accordance with Enstrom Service Directive Bulletin 0078.\n\nNote: FAA AD 90-01-06 Amdt 39-6457 refers.\n\nCompliance: Unless already accomplished, within 10 hours time in service after 9 February 1990 or by 28 February 1990, whichever occurs first. Thereafter, reinspect ALL tail rotor gearboxes in accordance with the requirement document at intervals not exceeding 100 hours time in service.\n\nBackground: The manufacturer has received two reported cases of chipped or broken teeth in the tail rotor gearbox, and one case of total gear failure. This AD requires a precautionary inspection of the gearbox oil for particulate metal contamination.\n\nAlthough not called up in the Requirement document this Amendment extends compliance to the F-28 model and gearbox P/N 28-13500-1 in line with the now referenced FAA AD.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"This amendment explicitly expands the original directive's scope. The 'Background' section states that although the referenced technical requirement document (Enstrom Service Directive Bulletin 0078) doesn't mention them, this amendment adds the F-28 model and gearbox P/N 28-13500-1 to match the FAA's equivalent directive. This is a deliberate scope expansion beyond the original technical document's coverage."},"complexity_factors":["Multiple conditional applicability criteria (9 helicopter models, 4 part numbers, 2 specific gear-set types)","Dual compliance deadlines with 'whichever occurs first' logic","Cross-reference to external technical document (Enstrom Service Directive Bulletin 0078) without reproducing its contents","Cross-reference to US FAA AD 90-01-06 Amdt 39-6457 for alignment purposes","Amendment structure requires understanding of what changed from original AD (scope expansion to additional model/part number)"],"plain_english_summary":"This CASA Airworthiness Directive mandates owners/operators of certain Enstrom F‑28 series helicopters to inspect specified tail‑rotor gearboxes for metal particles in the oil (per Enstrom Service Directive Bulletin 0078), with an initial check within 10 flight hours after 9 Feb 1990 or by 28 Feb 1990 and recurring every 100 flight hours. Amendment 1 expands coverage to include the F‑28 model and gearbox part number 28‑13500‑1, aligning with the FAA’s equivalent action."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"This amendment expands the applicability to include the F‑28 model and gearbox P/N 28-13500-1 (not originally called up in the Requirement document) to align with the referenced FAA AD. Concretely, that increases the population of affected aircraft/gearboxes and thus the number of operators required to perform the immediate and recurring inspections, raising compliance obligations and costs for those operators."},"complexity_factors":["Technical subject matter: gearbox internal gear teeth and oil particulate contamination require mechanical/maintenance expertise.","Part-number and component specificity: multiple aircraft models and exact gearbox P/Ns plus specified Boston Gear spiral miter gear-set models determine applicability.","Cross-references: requires following Enstrom Service Directive Bulletin 0078 and references FAA AD 90-01-06, creating reliance on external documents.","Time-sensitive compliance window: initial inspection within 10 hours after 9 Feb 1990 or by 28 Feb 1990, whichever first, creates operational scheduling pressure.","Recurring inspection interval: ongoing reinspections every 100 hours impose repeated operational and maintenance cost burden.","Scope extension note: amendment explicitly expands applicability to an additional model and P/N, requiring operators to check affected aircraft ownership/parts records."],"plain_english_summary":"**Requires immediate and recurring inspections of specified Enstrom F‑28 series tail‑rotor gearboxes for metal particles in the oil.** Operators must inspect within 10 hours after 9 February 1990 or by 28 February 1990 (whichever is first) and re‑inspect every 100 flight hours thereafter; operators pay for and carry out the inspections and Civil Aviation Safety Authority enforces compliance. The directive responds to reported chipped/broken teeth and one total gear failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-enst-28-32-amdt-1-tail-rotor-gearbox","history":"/api/acts/ad-enst-28-32-amdt-1-tail-rotor-gearbox/history","analysis":"/api/acts/ad-enst-28-32-amdt-1-tail-rotor-gearbox/analysis","conflicts":"/api/acts/ad-enst-28-32-amdt-1-tail-rotor-gearbox/conflicts","importantCases":"/api/acts/ad-enst-28-32-amdt-1-tail-rotor-gearbox/important-cases","documents":"/api/acts/ad-enst-28-32-amdt-1-tail-rotor-gearbox/documents"}}