{"id":"F2006B09889","name":"AD/F50/60 Amdt 1 - Bottom Hinged Cowl Door","slug":"ad-f50-60-amdt-1-bottom-hinged-cowl-door","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55030,"registerId":"commonwealth-F2006B09889-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F50/60 Amdt 1 - Bottom Hinged Cowl Door","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/F50/60\n\nAmdt 1\n\n  \nBottom Hinged Cowl Door 7/93\n\nApplicability: Model F27 Mk.050 with serial numbers 20103 through 20265. Requirement: Action in accordance with Fokker Service Bulletin F50-71-035 Revision 1.\n\nNote: RLD AD 93-032/2 (A) refers.\n\nCompliance: Within 650 hours time in service after 29 April 1993 or prior to 1 September 1993, whichever occurs first.\n\nThe compliance time of this Directive remains unchanged. This Amendment is effective from 24 June 1993.\n\nBackground: Reports have been received of fluid accumulating in the aft section of the engine bottom hinged cowl door. The introduction of a drain hole in the affected cowl door will prevent the accumulation of possibly flammable fluids.\n\nAmendment 1 is issued in response to a revision of the Requirement Document which requires a new (different) drain hole location.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The amendment does not change which aircraft are covered or the compliance deadline (Applicability, Compliance), but it does change the technical requirement: the drain hole location is different under the revised Requirement Document. In other words, the field of affected aircraft and the timing remain the same, but the exact modification to be performed was altered (Amendment 1)."},"complexity_factors":["Narrow applicability limited to a defined serial-number range (Applicability)","Mandatory technical action specified by reference to an external service bulletin (Requirement)","Short, fixed compliance window (650 hours TIS after 29 April 1993 or before 1 September 1993) (Compliance)","Amendment changes the technical specification (drain hole location) while leaving applicability and timing unchanged (Amendment 1)","Reference to another airworthiness directive (RLD AD 93-032/2 (A)) introduces cross-document checking (Note)","Operational impact: requires physical modification, parts, labour and scheduling of maintenance (Requirement, Compliance)"],"plain_english_summary":"Owners/operators of Fokker F27 Mk.050 aircraft (S/N 20103–20265) must install a drain hole in the aft area of the engine bottom‑hinged cowl door per the revised Fokker service bulletin, within the AD’s time window. The change prevents fluid accumulation (and potential fire risk); maintenance costs, downtime and use of the updated bulletin are the operators’ responsibility."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment maintains the original scope — a specific safety modification to Fokker F50 engine cowl doors. The amendment merely updates the technical specification (drain hole location) without expanding the applicability, adding new requirements, or broadening the regulatory reach."},"complexity_factors":["Very short document (approximately 150 words)","Only 1 defined term implicitly referenced (RLD AD 93-032/2)","Single, clear compliance requirement with straightforward deadline calculation","No nested exceptions or conditional logic","Minimal cross-referencing (only to manufacturer service bulletin and one related directive)","Plain language background explanation included"],"plain_english_summary":"This is a **safety instruction (Airworthiness Directive)** for a specific type of aircraft — the **Fokker F50** (also known as the F27 Mk 50).\n\n**What it does:**\n- Requires owners and operators of certain Fokker F50 planes (serial numbers 20103 to 20265) to modify the engine cowl door — specifically, to add or relocate a **drain hole**.\n- The drain hole prevents flammable fluids from pooling in the engine cowl, which could create a fire risk.\n\n**Why it matters:**\n- **Safety issue:** Reports showed fluids were collecting in the bottom-hinged engine cowl door. Without a drain, this creates a fire hazard.\n- **Mandatory action:** Aircraft operators must complete this modification within a set timeframe — either within 650 flight hours after 29 April 1993, or before 1 September 1993, whichever comes first.\n\n**What changed in this version (Amendment 1):**\n- The original directive required a drain hole, but this amendment updates the location of that hole based on a revised technical document from the manufacturer (Fokker Service Bulletin F50-71-035 Revision 1).\n- The deadline for completing the work stays the same.\n\n**Who it affects:**\n- Operators of Fokker F50 aircraft with specific serial numbers (20103–20265).\n- Maintenance engineers responsible for implementing the modification."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-60-amdt-1-bottom-hinged-cowl-door","history":"/api/acts/ad-f50-60-amdt-1-bottom-hinged-cowl-door/history","analysis":"/api/acts/ad-f50-60-amdt-1-bottom-hinged-cowl-door/analysis","conflicts":"/api/acts/ad-f50-60-amdt-1-bottom-hinged-cowl-door/conflicts","importantCases":"/api/acts/ad-f50-60-amdt-1-bottom-hinged-cowl-door/important-cases","documents":"/api/acts/ad-f50-60-amdt-1-bottom-hinged-cowl-door/documents"}}