{"id":"F2006B09650","name":"AD/F100/48 Amdt 4 - Main Landing Gear Main Fitting","slug":"ad-f100-48-amdt-4-main-landing-gear-main-fitting","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54493,"registerId":"commonwealth-F2006B09650-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F100/48 Amdt 4 - Main Landing Gear Main Fitting","content":"![](image.001.png)\n\nAIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/F100/48 Amdt 3 and issues the following AD under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)  \n\nFokker F100 (F28 Mk 100) Series Aeroplanes\n\nAD/F100/48\n\nAmdt 4\n\n  \nMain Landing Gear Main Fitting 11/2003\n\nApplicability: Model F.28 Mk.0100 aircraft, all serial numbers, if equipped with Messier-Dowty Main Landing Gear Units part numbers as listed in Messier-Dowty Service Bulletin F100-32-102, dated 24 February 2003.\n\nRequirement: 1. Inspect in accordance with the requirements of Netherlands CAA AD 2001-141.\n\n    2. Accomplish either of the following:\n\n    Replace the main landing gear in accordance with Section B. Part 1 of the Accomplishment Instructions of Fokker Services Service Bulletin F100-32- 134, dated 24 March 2003; or,\n\n    b. Inspect and rework, if necessary, the Main Landing Gear Main Fitting Sub- Assembly “on aircraft” in accordance with Part C. “Procedure on Aircraft” (alternative option) of Section 3 Accomplishment Instructions of Messier- Dowty Service Bulletin F100-32-102.\n\nNote 1: Accomplishment of the requirements of either Requirement 2.a. or 2.b.of this Directive constitutes terminating action for the inspection requirements of Requirement 1.\n\nNote 2: Messier-Dowty Service Bulletins SB F100-32-101 and SB F100-32-100 Revision 1 refer.\n\nNote 3: Netherlands CAA AD 2003-040 refers.\n\nCompliance: 1. Inspect as specified in the Requirement document, until accomplishment of Requirement 2.\n\n2. Before or during the next scheduled overhaul of the affected Main Landing Gear Main Fitting.\n\nThis Amendment becomes effective on 30 October 2003.\n\nFokker F100 (F28 Mk 100) Series Aeroplanes\n\nAD/F100/48 Amdt 4 (continued)\n\nBackground: A Fokker 100 aircraft experienced a main landing gear main fitting failure on landing, resulting in failure of the lower part of the main fitting, including the main landing gear sliding member, wheels and brakes.\n\nAmendment 1 corrected a compliance time typographical error.\n\nAmendment 2 required a conditional initial inspection and two repeat inspections, as a consequence of seven more main landing gears with an Eddy-Current indication in the affected area at the original inspection.\n\nAmendment 3 required the accomplishment of an etch penetrant inspection to terminate the necessity for further repetitive eddy-current inspections, and rework or replacement of any fitting when cracks are found. Recent tests and analysis have shown that a limited number of repeat inspections, combined with a final etch penetrant inspection during overhaul (or “on aircraft”) is sufficient to restore the safe life condition of the Main Landing Gear Main Fitting.\n\nAmendment 4 is issued to correct the Requirement 2.a. document number. Amendment 3 of this Airworthiness Directive became effective on 2 October 2003\\. Amendment 2 of this Airworthiness Directive became effective on 18 April 2002.\n\nAmendment 1 of this Airworthiness Directive became effective on 27 December 2001.\n\nThe original issue of this Airworthiness Directive became effective on 29 November 2001.\n\n![Signature of David Villiers, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\nDavid Villiers\n\nDelegate of the Civil Aviation Safety Authority 16 September 2003\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 8 October 2003.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"This amendment sequence expanded the AD beyond the original one-off inspection. The original AD required initial inspection after the reported failure. Subsequent amendments introduced mandatory repeat inspections, an etch‑penetrant inspection as a terminating test, and finally a formal choice between full replacement or on-aircraft rework as the terminating action (Requirement 2; Note 1; Background). Amendment 4 itself corrects a document number, but the cumulative effect of earlier amendments broadened the AD from inspection-only to include repair/replacement options and a clear terminating-action regime tied to overhaul scheduling."},"complexity_factors":["Multiple external cross-references: Netherlands CAA AD 2001-141; Messier-Dowty SB F100-32-102; Fokker SB F100-32-134; plus references to other Messier-Dowty SBs (SB F100-32-101 and SB F100-32-100 Revision 1).","Conditional compliance path: operator must choose either replacement (2.a) or on-aircraft inspection/rework (2.b) as terminating action.","Repetitive inspections until a terminating action is taken (Requirement 1 + Note 1) — creates ongoing compliance tracking.","Timing linkage to maintenance programme: terminating action must be before or during next scheduled overhaul (Compliance), which depends on operator scheduling.","Amendment history with corrected document numbers and evolving inspection/termination policy (Background) — requires attention to which AD/SB revision applies.","Applicability depends on part numbers listed in an external SB rather than a simple in-AD list — requires record checks against SB."],"plain_english_summary":"**What this instrument does (mechanically)\n\n- This is an Airworthiness Directive (AD) requiring checks and corrective action on the main landing gear main fitting of certain Fokker F100 (F28 Mk 100) aeroplanes.\n\n- Which planes are affected: All F.28 Mk.0100 aircraft that have Messier-Dowty main landing gear units whose part numbers are listed in Messier-Dowty Service Bulletin F100-32-102 (see \"Applicability\"). Operators must check their maintenance records and the SB list to confirm whether a particular aircraft is in scope. (Applicability)\n\n- What operators must do:  \n  - Requirement 1: Carry out inspections as required by Netherlands CAA AD 2001-141. (Requirement 1)  \n  - Requirement 2: Then take one of two terminating actions: either (a) replace the main landing gear in accordance with Fokker Services Service Bulletin F100-32-134 Part B; or (b) inspect and, if needed, rework the main fitting on the aircraft following Messier-Dowty Service Bulletin F100-32-102 Part C. Completing either option stops the need for the repetitive inspections required by Requirement 1. (Requirement 2; Note 1)\n\n- Timing: Continue the inspections required by Requirement 1 until you do the replacement or rework. The replacement or on-aircraft rework must be completed before, or during, the next scheduled overhaul of the affected main landing gear main fitting. (Compliance)\n\n- Background / why this was issued: A Fokker 100 suffered a main fitting failure on landing causing loss of the lower fitting and wheel/brake components. The AD has been revised several times to correct errors and to broaden inspection and repair options as analysis and test results evolved. (Background)\n\nWho pays, who decides, and what changes in behaviour\n\n- Who pays: Aircraft owners/operators pay the cost of the inspections, any rework, or replacement parts and labour. Maintenance organisations carry out the work to the specified Service Bulletins (SBs).\n\n- Who decides: The Civil Aviation Safety Authority (through its delegate) mandates the requirement. Operators choose between the two compliance options (replacement or on-aircraft rework) but must follow the referenced SB procedures and timing. Maintenance providers decide the technical execution in accordance with the SBs and regulatory oversight. (Requirement 2; Compliance)\n\n- Behaviour changes required: Operators must (a) check whether an aircraft is covered by the AD, (b) perform the required inspections repeatedly until a terminating action is done, and (c) either install replacement landing gear or perform the prescribed on-aircraft rework during overhaul.\n\nPractical trade-offs, costs and risks (mechanisms, not value judgements)\n\n- Direct costs and downtime: Replacement is likely to be costlier in parts and possibly quicker to achieve the terminating effect; rework on-aircraft may be cheaper in parts but could require more inspection effort and repeated checks until overhaul. Both options involve labour and aircraft downtime; the AD fixes the time window by linking the terminating action to the next scheduled overhaul. (Requirement 2; Compliance)\n\n- Incentives and choices for operators: Operators face a trade-off between paying more now for replacement (to stop further inspections) or choosing rework that preserves the existing fitting but keeps inspection obligations until overhaul. That choice changes maintenance scheduling and cashflow for operators.\n\n- Implementation risks and compliance burden: The AD relies on several external documents (a Netherlands CAA AD and multiple service bulletins). Operators must locate and follow those documents exactly. Cross‑referencing increases administrative burden and creates risk where documentation numbers were amended (the current amendment corrects a document number). (Requirement; Notes; Background)\n\n- Effects on competition and private enterprise: The AD imposes a regulatory maintenance obligation on affected operators and requires maintenance to be performed to specific SB instructions. That channels work through qualified maintenance organisations capable of performing the SB procedures; it does not itself prescribe particular suppliers beyond referencing the SBs, but it does create demand for parts and technical services tied to the Messier-Dowty and Fokker SBs.\n\n- Safety benefit vs cost: The stated safety rationale is correcting an identified unsafe condition after a main fitting failure (Background). The AD moves from repeated non-destructive inspections to a final terminating repair or replacement strategy, which concentrates the safety benefit where the corrective action is completed. (Background; Requirement 2; Note 1)\n\nKey references inside the AD you will need to read to comply: Netherlands CAA AD 2001-141 (inspections), Messier-Dowty Service Bulletin F100-32-102 (inspection/rework procedures and P/N list), and Fokker Services Service Bulletin F100-32-134 (replacement procedure). (Requirement; Notes)\n\n"},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment remains tightly focused on its original purpose: addressing the unsafe condition of Fokker F100 main landing gear main fittings. While Amendment 4 corrects a document reference error from Amendment 3, and earlier amendments expanded inspection requirements based on new findings of cracked components, the scope has not grown beyond the specific safety issue of main landing gear structural integrity. The directive maintains its original applicability to specific aircraft models and part numbers."},"complexity_factors":["Multiple amendment history requiring cross-referencing (Amendments 1-4) to understand evolution of requirements","Nested conditional compliance paths: Requirement 2 offers two alternative actions (replacement OR inspect/rework), with Note 1 establishing terminating action logic","External document dependencies: references to Netherlands CAA AD 2001-141, Fokker Service Bulletin F100-32-134, and Messier-Dowty Service Bulletin F100-32-102","Technical aviation terminology requiring specialized knowledge (e.g., 'etch penetrant inspection', 'eddy-current indication', 'Main Landing Gear Main Fitting Sub-Assembly')","Dual compliance timelines: ongoing inspections until terminating action is completed, plus hard deadline at next overhaul"],"plain_english_summary":"This AD requires operators of Fokker F100 jets fitted with certain Messier‑Dowty main landing gear to inspect the main landing‑gear fitting for cracks and defects and to repair or replace it by the next scheduled overhaul. It responds to a prior catastrophic in‑service failure where the fitting fractured and landing hardware detached, and aims to prevent recurrence by detecting metal fatigue and ensuring corrective action for affected aircraft."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f100-48-amdt-4-main-landing-gear-main-fitting","history":"/api/acts/ad-f100-48-amdt-4-main-landing-gear-main-fitting/history","analysis":"/api/acts/ad-f100-48-amdt-4-main-landing-gear-main-fitting/analysis","conflicts":"/api/acts/ad-f100-48-amdt-4-main-landing-gear-main-fitting/conflicts","importantCases":"/api/acts/ad-f100-48-amdt-4-main-landing-gear-main-fitting/important-cases","documents":"/api/acts/ad-f100-48-amdt-4-main-landing-gear-main-fitting/documents"}}