{"id":"F2006B09903","name":"AD/F50/73 - Hub Mounting Face Dowel Hole Inspection Following Propeller Overtorque","slug":"ad-f50-73-hub-mounting-face-dowel-hole-inspection-following-propeller-overtorque","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55086,"registerId":"commonwealth-F2006B09903-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/73 - Hub Mounting Face Dowel Hole Inspection Following Propeller Overtorque","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)  \nFokker F50 (F27 Mk 50) Series Aeroplanes\n\nAD/F50/73 Hub Mounting Face Dowel Hole Inspection\n\nFollowing Propeller Overtorque\n\n  \n4/97\n\nApplicability: All Fokker F27 Mk 50 series aircraft fitted with Dowty R352/6-123-F/1 or R352/6- 123-F/2 propellers.\n\nRequirement: Whenever a propeller is subject to an overtorque condition, as defined in Dowty Aerospace Mandatory SB F50-61-50 Revision 7 dated Dec 12, 1996, inspect the propeller in accordance with the reference SB.\n\nNote: RLD AD 89-079/3 dated December 31, 1996, which supersedes RLD AD 89-079/2 dated November 24, 1994 and UK CAA AD 023-05-89 refer.\n\nCompliance: Whenever a propeller overtorque occurs.\n\nThis Airworthiness Directive becomes effective on 27 March 1997.\n\nBackground: The manufacturer has reported several incidents of propellers being overtorque while in operational use. To enable operators to assess if propeller removal is required the propeller manufacturer has provided inspection procedures.\n\nThis Directive has been relocated from CAO 107 AD/PR/30 with an effective date of 27 March 1997.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a straightforward relocation of an existing airworthiness directive from the old CAO 107 system to the CASR Part 39 framework. The scope remains exactly as originally intended: a specific safety inspection requirement for a particular aircraft/propeller combination following a specific operational event. No expansion of scope has occurred."},"complexity_factors":["Very short document (approximately 150 words)","Only 2 defined applicability criteria (aircraft type and propeller model)","Single, clear trigger condition (propeller overtorque)","Single compliance action (inspect per referenced service bulletin)","No nested exceptions or conditional logic","Cross-references to external technical documents (service bulletin) but not to other legislation","No interpretation section or defined terms within the instrument itself"],"plain_english_summary":"This AD requires operators of Fokker F50 aircraft fitted with specific Dowty propellers to inspect the propeller hub after any overtorque event. It targets airlines and maintenance crews because reported overtorque incidents can damage the hub—especially dowel holes—risking propeller failure in flight. Compliance follows the Dowty Mandatory Service Bulletin procedures; the directive has been effective since 27 March 1997."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The Directive was relocated from CAO 107 AD/PR/30 with an effective date of 27 March 1997; the text gives no indication of a substantive change in obligations or expanded applicability compared with the prior reference."},"complexity_factors":["Event-driven compliance: obligation arises only after a propeller overtorque occurs, creating monitoring and reporting demands.","Reliance on external material: inspection procedures and the definition of 'overtorque' are contained in Dowty Mandatory SB F50-61-50 Rev 7 rather than the AD text (Requirement).","Narrow applicability: applies only to Fokker F27 Mk 50 aircraft with specific Dowty propeller models (Applicability).","Operational impact uncertainty: SB may require propeller removal or further work, creating variable downtime and cost for operators (Background).","Cross-references to prior ADs and foreign directives increase the record-keeping and compliance-check burden (Note).","Regulatory enforcement timing: AD effective date specified, requiring operators to apply procedures from that date (Compliance; effective date)."],"plain_english_summary":"This Airworthiness Directive requires operators of Fokker F27 Mk 50 aircraft fitted with Dowty R352/6-123-F/1 or F/2 propellers to inspect the hub mounting face dowel holes whenever a propeller experiences an overtorque, following Dowty's Mandatory Service Bulletin F50-61-50 Revision 7 (Requirement; Compliance). The manufacturer reported overtorque incidents and supplied the inspection procedure so operators can decide if propeller removal is needed; operators therefore bear the inspection and any follow-up costs (Background)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-73-hub-mounting-face-dowel-hole-inspection-following-propeller-overtorque","history":"/api/acts/ad-f50-73-hub-mounting-face-dowel-hole-inspection-following-propeller-overtorque/history","analysis":"/api/acts/ad-f50-73-hub-mounting-face-dowel-hole-inspection-following-propeller-overtorque/analysis","conflicts":"/api/acts/ad-f50-73-hub-mounting-face-dowel-hole-inspection-following-propeller-overtorque/conflicts","importantCases":"/api/acts/ad-f50-73-hub-mounting-face-dowel-hole-inspection-following-propeller-overtorque/important-cases","documents":"/api/acts/ad-f50-73-hub-mounting-face-dowel-hole-inspection-following-propeller-overtorque/documents"}}