{"id":"F2006B09652","name":"AD/F100/5 - Powerplant - Lower Cowl Door Engagement","slug":"ad-f100-5-powerplant-lower-cowl-door-engagement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115769,"registerId":"commonwealth-F2006B09652-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F100/5 - Powerplant - Lower Cowl Door Engagement","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 F100 (F28 Mk 100) Series Aeroplanes\n\nAD/F100/5 Powerplant \\- Lower Cowl Door Engagement 1/99\n\nApplicability: Fokker F28-100 and F28-70 series aircraft, serial numbers 11244 through 11469, 11471, 11474 through 11483, 11489, 11490, 11491, 11494, 11498, 11499, 11501,\n\n11502, 11504, 11506, 11507, 11512 through 11515, 11517, 11520, 11528, and\n\n11537.\n\nRequirement: 1. Modify the hook and latch assembly of the lower cowl doors in accordance with the instructions in Part 1 of the Accomplishment Instructions of Fokker Service Bulletin SB F100-71-019 dated 21 March 1996.\n\nNote: The accomplishment of Part 1 of Fokker SB F100-71-003, dated 14 April 1989, or Revision 1 dated 08 August 1989, or Revision 2 dated 21 November 1994 is considered an acceptable means of compliance for this requirement.\n\n    2. Inspect both engine’s lower cowling door hook and latch assemblies in accordance with Part 2 of the Accomplishment Instructions of Fokker SB F100-71-019 dated 21 March 1996.\n\n    3. Modify the lower cowl door’s mid clevis fitting in accordance with the Accomplishment Instructions of Fokker SB P41230-71-07 dated 15 February 1996.\n\nNote: RLD Airworthiness Directive 1989-049/3 (A) dated 28 June 1996 refers.\n\nCompliance: 1. Unless already accomplished, on a limited number of aircraft as applicable, within 2500 flight cycles of the last inspection performed in accordance with BLA 89- 049/2.\n\n    2. Within 2500 flight cycles since new or since last inspection in accordance with BLA 89-049/2 as applicable.\n\n    3. Following the discovery of a cowl mismatch during accomplishment of Requirement 2. above.\n\nThis Airworthiness Directive becomes effective on 28 January 1999.\n\nBackground: Experience has shown that an aerodynamic gap/mismatch may exist between the fixed engine cowl and the lower cowl door. Should this mismatch exceed a certain value, one or more hooks may not engage properly. This degrades the redundancy of the lower cowl door engagement in the closed position and could lead to an unsafe condition. This Directive introduces a one time inspection and corrective action if necessary, to measure the gap/mismatch on applicable aircraft. This Directive also introduces a modification to the hook and latch assembly on a limited number of the applicable aircraft.","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"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in a defined aircraft population. The scope remains tightly focused on the original safety issue (lower cowl door engagement) without expansion into broader operational or maintenance areas."},"complexity_factors":["Multiple compliance pathways with cross-references to alternative service bulletins (SB F100-71-003 revisions 1-2 acceptable as alternative compliance for Requirement 1)","Serial number-specific applicability list spanning 40+ discrete ranges and individual numbers","Three distinct requirements with different compliance triggers and timelines","Conditional compliance timing ('Unless already accomplished', 'as applicable', 'Following the discovery')","Reference to external Dutch aviation authority directive (RLD Airworthiness Directive 1989-049/3)","Technical aviation terminology requiring specialist knowledge (clevis fitting, flight cycles, service bulletins, cowl door engagement redundancy)"],"plain_english_summary":"This Airworthiness Directive from CASA mandates inspections and required modifications to the engine lower cowl door hook/latch assemblies on certain Fokker F100 series aircraft (specific serial numbers listed).  \n\nIt affects operators of those aircraft to prevent gaps that can stop hooks from engaging, reducing risk of cowl doors opening in flight and ensuring continued flight safety."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":false,"description":"The Directive implements inspection and corrective modifications targeted at the aerodynamic gap problem for the listed aircraft. It confines action to specific serial numbers and links compliance to defined service bulletin procedures and flight-cycle deadlines (see Requirements 1–3; Compliance; Background), rather than expanding scope beyond those aircraft or introducing new regulatory powers."},"complexity_factors":["Narrow, serial-number-specific applicability (many listed serials) — increases tracking and applicability checks (Applicability).","Multiple distinct actions: modify hook/latch assembly, inspect both engines' lower cowl door assemblies, and modify mid clevis fitting (Requirements 1–3).","References and reliance on external Fokker Service Bulletins and earlier AD/BLA documents as the means of compliance (Requirements; Note).","Conditional steps: some modifications only required for a limited subset of aircraft or following discovery of a mismatch (Requirement 1 note; Requirement 3; Compliance).","Compliance metric uses flight cycles rather than calendar time, requiring operators to monitor cycles and maintenance logs (Compliance).","Technical maintenance work requiring approved procedures, parts and possibly engineering assessment — imposes operational and supply costs on operators (Requirements; Background).","Cross-references to prior directives and service bulletin revisions increase interpretation workload for maintenance planners (Notes; Background)."],"plain_english_summary":"This Airworthiness Directive requires operators of specified Fokker F28/F100 serial numbers to inspect and, where needed, modify the lower engine cowl door hook-and-latch assemblies and the mid-clevis fitting following Fokker service bulletin instructions. Compliance is measured in flight cycles (typically within 2,500) or must occur immediately if a cowl mismatch is found. The measure addresses an aerodynamic gap that can prevent hooks from engaging; operators (aircraft owners) pay for inspections, repairs and parts and must record compliance."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f100-5-powerplant-lower-cowl-door-engagement","history":"/api/acts/ad-f100-5-powerplant-lower-cowl-door-engagement/history","analysis":"/api/acts/ad-f100-5-powerplant-lower-cowl-door-engagement/analysis","conflicts":"/api/acts/ad-f100-5-powerplant-lower-cowl-door-engagement/conflicts","importantCases":"/api/acts/ad-f100-5-powerplant-lower-cowl-door-engagement/important-cases","documents":"/api/acts/ad-f100-5-powerplant-lower-cowl-door-engagement/documents"}}