{"id":"F2006B08719","name":"AD/DART/6 Amdt 1 - Reduction Gear","slug":"ad-dart-6-amdt-1-reduction-gear","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":51926,"registerId":"commonwealth-F2006B08719-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/DART/6 Amdt 1 - Reduction Gear","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nRolls Royce Turbine Engines \\- Dart Series\n\nAD/DART/6\n\nAmdt 1\n\n  \nReduction Gear 5/98\n\nApplicability: All Dart series engines listed in Part 1A of Rolls Royce Service Bulletin Da72-348 Revision 12 dated November 1997.\n\nRequirement: Modify the Reduction Gear Assembly in accordance with Rolls Royce Service Bulletin Da72-348 Revision 12 dated November 1997.\n\nNote 1: Rolls Royce Service Bulletin Da72-348 Revision 12 dated November 1997 is re-issued to re-classify the Modification as Mandatory and extend the applicability.\n\nNote 2: CAA AD 1935 also refers.\n\nCompliance: As specified in Rolls Royce Service Bulletin Da72-348 Revision 12 dated November 1997.\n\nThis amendment becomes effective on 23 April 1998.\n\nBackground: The manufacturer has advised that a failed annulus gear resulted in the malfunctioning of an engine in service. Manual feathering was initiated but the propeller failed to feather, decoupling of the propeller occurred, followed by over speeding of the propeller to bursting point causing extensive damage to the adjacent engine and the aircraft fuselage.\n\nThe original issue of this airworthiness directive became effective on 31 October 1987.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":true,"description":"The original 1987 directive has been expanded via this amendment. The scope has grown from its original coverage to include more engine models (\"extend the applicability\" per Note 1), and the character of the requirement has changed from optional/ recommended to mandatory (\"re-classify the Modification as Mandatory\"). This represents a significant strengthening and broadening of the original safety measure."},"complexity_factors":["Single, unambiguous operative requirement (one modification task)","Only one defined applicability criterion (engine series listed in external document)","No nested exceptions or conditional logic","Minimal cross-referencing (only one related historical directive mentioned)","Short document (approximately 200 words)","Relies on external technical document (Service Bulletin) for actual implementation details"],"plain_english_summary":"This CASA Airworthiness Directive mandates modification of the reduction gear assembly on certain Rolls‑Royce Dart turbine engines, to be carried out per Rolls‑Royce Service Bulletin Da72‑348 Revision 12. It affects operators of aircraft equipped with the listed Dart engines and is intended to prevent a repeat of a serious incident where gear failure led to an unfeatherable, disintegrating propeller that damaged engine and airframe. Effective date: 23 April 1998."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"Rev 12 re‑issues the service bulletin to re‑classify the reduction‑gear modification as mandatory and to extend the engines to which it applies, expanding the directive's scope compared with the original 1987 AD."},"complexity_factors":["Reference to an external technical document (Rolls Royce Service Bulletin Da72‑348 Rev 12) as the operative compliance mechanism (Requirement / Compliance).","Re‑classification of the modification as mandatory and extension of engine applicability (Note 1) increases the pool of affected operators.","Safety‑critical technical nature of the reduction gear modification (Background: annulus gear failure led to propeller overspeed and damage).","Cross‑reference to another authority directive (CAA AD 1935) creates coordination and potential duplicate compliance checks.","Operational impacts on operators: parts procurement, maintenance labour, aircraft downtime and scheduling to perform the modification.","Clear effective date obliges action by a set time (becomes effective 23 April 1998), limiting discretionary delay."],"plain_english_summary":"This directive requires operators of Rolls‑Royce Dart series engines listed in Service Bulletin Da72‑348 Revision 12 (Nov 1997) to modify the reduction‑gear assembly in accordance with that bulletin; the requirement is mandatory and takes effect 23 April 1998.\n\nThe manufacturer reported an annulus‑gear failure that caused propeller overspeed and structural damage; the directive therefore makes the modification compulsory, shifting parts, labour and downtime costs to operators and imposing compliance with an external service bulletin (CAA AD 1935 is cross‑referenced)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-dart-6-amdt-1-reduction-gear","history":"/api/acts/ad-dart-6-amdt-1-reduction-gear/history","analysis":"/api/acts/ad-dart-6-amdt-1-reduction-gear/analysis","conflicts":"/api/acts/ad-dart-6-amdt-1-reduction-gear/conflicts","importantCases":"/api/acts/ad-dart-6-amdt-1-reduction-gear/important-cases","documents":"/api/acts/ad-dart-6-amdt-1-reduction-gear/documents"}}