{"id":"F2005L02841","name":"AD/F100/71 - Main Landing Gear Bay Fuel/Hydraulic Lines","slug":"ad-f100-71-main-landing-gear-bay-fuel-hydraulic-lines","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":37835,"registerId":"commonwealth-F2005L02841-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Fokker F100 (F28 Mk 100) Series Aeroplan","sectionType":"division","heading":"Fokker F100 (F28 Mk 100) Series Aeroplanes","content":"### Fokker F100 (F28 Mk 100) Series Aeroplanes\n\n| AD/F100/71 | Main Landing Gear Bay Fuel/Hydraulic Lines | 11/2005 |\n| ---------- | ------------------------------------------ | ------- |\n\n| Applicability: | Fokker Aircraft B.V. Model F28 Mark 0070 and Mark 0100 aeroplanes. |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement: | 1. Inspect the clearance between the fuel lines and hydraulic lines in the left hand (LH) and right hand (RH) main landing gear (MLG) Bays in accordance with Section 3 of the accomplishment instructions, Part 1, of Fokker Service Bulletin (SB) F100-28-041 dated 20 July 2005 or later CAA-NL approved revision and when clearances between the affected lines are found of 3 mm (0.118 inch) or more in both MLG Bays, no further action is required and the aircraft may be returned to service.(a) When a clearance between the affected lines is found of less than 3 mm (0.118 inch) and there are chafing marks on the fuel lines, replace the affected fuel line and modify or readjust, as applicable, the attachment of the affected fuel lines and hydraulic lines in accordance with Section 3 Accomplishment Instructions, Part 2, of Fokker SB F100-28-041 or later CAA-NL approved revision.(b) When a clearance between the affected lines is found of less than 3 mm (0.118 inch) and there are no chafing marks on the fuel lines, modify or readjust, as applicable, the attachment of the affected fuel lines and hydraulic lines in accordance with Section 3 Accomplishment Instructions, Part 2, of Fokker SB F100-28-041 or later CAA-NL approved revision.Note: CAA-NL AD NL-2005-010R1 EASA approval No. 2005-6232 dated7 September 2005 refers. |\n| Compliance: | 1. Within the next 6 months after the effective date of this directive.(a) Before further flight.(b) Within the next 6 months after the inspection as required by Requirement 1(a) of this Directive. |\n| | This Airworthiness Directive becomes effective on 27 October 2005. |\n\n| Background: | During regular operations with a Fokker 100 (F28 Mark 0100), a fuel leak was found in the LH MLG Bay. The subsequent investigation revealed that a fuel line was chafed through, caused by interference with a hydraulic line. During manufacturing of the aircraft, a minimum distance of three (3) mm (0.118 inch) was maintained between fuel and hydraulic lines. During operation of the aircraft or during the accomplishment of maintenance tasks, loads induced on these lines can reduce this distance sufficiently enough to cause interference between them. Interference between fuel lines and hydraulic lines can ultimately result in sufficient wear to the fuel lines to cause a fuel leak. This condition, if not corrected, could lead to further cases of fuel leakage in the MLG Bay, in the vicinity of hot brakes, potentially resulting in a MLG Bay fire. Since an unsafe condition has been identified that may exist or develop on aircraft of the same type design, this Airworthiness Directive requires a one-time inspection of the clearance between the fuel lines and hydraulic lines in the LH and RH MLG Bays and, if necessary, corrective action. |\n| ----------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png) \nJames Coyne \nDelegate of the Civil Aviation Safety Authority\n\n15 September 2005","sortOrder":0},{"sectionNumber":"AD/F100/71","sectionType":"part","heading":"AD/F100/71","content":"## AD/F100/71","sortOrder":1},{"sectionNumber":"Main Landing Gear Bay Fuel/Hydraulic Lin","sectionType":"part","heading":"Main Landing Gear Bay Fuel/Hydraulic Lines","content":"## Main Landing Gear Bay Fuel/Hydraulic Lines","sortOrder":2},{"sectionNumber":"11/2005","sectionType":"part","heading":"11/2005","content":"## 11/2005","sortOrder":3}],"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":3,"scope_assessment":{"changed":false,"description":"This is a standard Airworthiness Directive with focused scope — addressing a specific mechanical defect on a specific aircraft model. The scope remains tightly constrained to the identified safety issue (fuel/hydraulic line interference in main landing gear bays) and has not expanded beyond its original safety purpose."},"complexity_factors":["Single, specific technical requirement focused on one aircraft type","Clear conditional logic with only three outcome branches (≥3mm, <3mm with chafing, <3mm without chafing)","References external technical document (Fokker Service Bulletin) but provides specific section citations","Simple compliance timeline (6 months, or before next flight for urgent cases)","No nested definitions or extensive interpretation sections","Straightforward cause-and-effect background explanation"],"plain_english_summary":"This CASA Airworthiness Directive requires Australian-registered Fokker F100 (F28 Mk 0070/0100) operators to inspect fuel and hydraulic lines in both main landing gear bays to prevent chafing that caused a fuel leak and fire risk. \n\nIf the lines are closer than 3 mm crew must re‑secure them; damaged fuel lines must be replaced. The AD took effect 27 Oct 2005 with inspections due within six months."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"This directive is narrowly targeted: it requires a one-time inspection and corrective action to address observed chafing between fuel and hydraulic lines in the MLG bays of specified Fokker F100 models. The measure aligns with the stated original purpose (eliminate the identified fuel‑line chafing and associated leak/fire risk) and does not broaden the affected aircraft types, increase ongoing surveillance obligations, or add unrelated regulatory requirements. It references a manufacturer service bulletin and regulator-approved revisions for the method of compliance but does not expand the scope beyond the original safety corrective action."},"complexity_factors":["Short document focused on a single technical task (one-time inspection and corrective action)","Three conditional outcomes to apply: clearance >= 3 mm (no action); < 3 mm with chafing (replace + modify/readjust); < 3 mm without chafing (modify/readjust)","Single external normative reference: Fokker Service Bulletin F100-28-041 (Section 3, Parts 1 & 2) and later CAA‑NL approved revisions","Three compliance time conditions (within 6 months; replacement before further flight; modification/readjust within 6 months after inspection)","No extensive defined-terms or cross-references within the directive itself","Limited technical specificity (uses a simple numeric clearance threshold: 3 mm) which reduces interpretive complexity"],"plain_english_summary":"**What this directive does (mechanical change)\n\n- Requires a one-time physical inspection of the gap (clearance) between fuel lines and hydraulic lines in both the left-hand and right-hand main landing gear (MLG) bays of Fokker F28 Mark 0070 and Mark 0100 aeroplanes. The inspection must follow Section 3, Part 1 of Fokker Service Bulletin (SB) F100-28-041 (or a later Civil Aviation Authority of the Netherlands (CAA‑NL) approved revision). (Requirement 1)\n- If the measured clearance is 3 mm (0.118 inch) or greater in both MLG bays, no further action is required and the aircraft may return to service. (Requirement 1)\n- If the clearance is less than 3 mm and there are chafing marks on the fuel line, the affected fuel line must be replaced and the attachments of the fuel and hydraulic lines must be modified or readjusted per Section 3, Part 2 of the SB. Replacement must be done before further flight. (Requirement 1(a))\n- If the clearance is less than 3 mm but there are no chafing marks, the attachments must still be modified or readjusted per Section 3, Part 2 of the SB. (Requirement 1(b))\n\n**Who this affects\n\n- Aircraft owners/operators and maintenance organisations that operate or maintain Fokker Aircraft B.V. Model F28 Mark 0070 and Mark 0100 aeroplanes. They are responsible for carrying out the inspection and any required repairs or adjustments, and for complying with the stated time limits. (Applicability; Requirement; Compliance)\n\n**When it must be done (timing)\n\n- The inspection must be completed within 6 months of the directive’s effective date. If a fuel line is found chafed and must be replaced, that replacement must be accomplished before the next flight. Any required modification/readjustment (when no chafing is present) must be completed within 6 months after the inspection. (Compliance)\n\n**Why the authority requires it (stated safety rationale)\n\n- Investigators found a fuel leak caused by a fuel line chafing against a hydraulic line in an MLG bay. The manufacturer originally kept a 3 mm manufacturing clearance between those lines. Loads during operation or maintenance can reduce that clearance and allow abrasion, eventually producing a fuel leak near hot brakes. The directive’s stated purpose is to prevent fuel leaks and the potential for MLG bay fires by ensuring minimum clearance and repairing any interference. (Background)\n\n**How decisions are made under the directive\n\n- The inspection and any corrective actions must follow the steps and acceptable methods given in Fokker SB F100-28-041 (Section 3, Parts 1 and 2) or a later revision approved by CAA‑NL; the regulator’s approval of SB revisions controls which procedures are acceptable. (Requirement; Note)\n\n**Who pays and what behaviour changes\n\n- Aircraft owners/operators pay for the labour, inspection time, any replacement fuel lines, and the modification/readjustment work. Aircraft may be grounded while the inspection or corrective work is performed, creating operational downtime. Maintenance organisations decide how to schedule the work and which approved SB revision to use. Operators must prioritise inspection within the specified compliance window and act immediately to replace any chafed fuel lines (before further flight).\n\n**Implementation, compliance and operational trade-offs (practical points)\n\n- Compliance is a one‑time inspection and, if needed, corrective action. That limits recurring inspection cost but can cause a concentrated near-term maintenance burden (scheduling, parts, and possible aircraft downtime) for operators.\n- The directive references an external service bulletin and its later regulator-approved revisions; operators need access to the correct SB revision and to ensure work is done to that standard. This creates a dependence on manufacturer instructions and regulator approvals for acceptable repair methods.\n- If the attachment/modification work is not performed correctly, there remains a residual safety risk; conversely, conservative repairs (e.g. replacing lines rather than just readjusting) raise direct costs and parts lead times.\n\n**Text pointers (where to look in the directive)\n\n- The inspection requirement and outcomes are set out in Requirement 1 and its subparagraphs (a) and (b).\n- Timing is in the Compliance paragraph (inspection within 6 months; replacement before further flight; modifications within 6 months after inspection).\n- Background and rationale appear in the Background paragraph explaining the origin of the directive.\n\n(James Coyne, Delegate of the Civil Aviation Safety Authority: signature and dates are administrative; the procedural effect is the inspection and corrective-action requirements above.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-f100-71-main-landing-gear-bay-fuel-hydraulic-lines","history":"/api/acts/ad-f100-71-main-landing-gear-bay-fuel-hydraulic-lines/history","analysis":"/api/acts/ad-f100-71-main-landing-gear-bay-fuel-hydraulic-lines/analysis","conflicts":"/api/acts/ad-f100-71-main-landing-gear-bay-fuel-hydraulic-lines/conflicts","importantCases":"/api/acts/ad-f100-71-main-landing-gear-bay-fuel-hydraulic-lines/important-cases","documents":"/api/acts/ad-f100-71-main-landing-gear-bay-fuel-hydraulic-lines/documents"}}