{"id":"F2006B09822","name":"AD/F28/87 - Stub Wing Fuselage Structure","slug":"ad-f28-87-stub-wing-fuselage-structure","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54767,"registerId":"commonwealth-F2006B09822-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 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.","sortOrder":0},{"sectionNumber":"AD/F28/87 Stub Wing Fuselage Structure 1","sectionType":"part","heading":"AD/F28/87 Stub Wing Fuselage Structure 11/2001","content":"# ![](image.003.png)AD/F28/87 Stub Wing Fuselage Structure 11/2001\n\nApplicability: All Model F.28 Mk. 1000 through 4000 series aircraft.\n\nRequirement: Visually inspect the internal fuselage structure in the Stub Wing areas in accordance with Part 1 of the Accomplishment Instructions of Fokker Service Bulletin\n\nF.28/53-151, dated 4 June 2001.\n\nWhenever damage is found, repair or replace the affected parts within the limits set in Part 2 of the Accomplishment Instructions of the Requirement document.\n\nRepair or replacement of damaged parts does not terminate the required repetitive inspections.\n\nNote 1: Netherlands CAA AD 2001-093 refers.\n\nNote 2: Fokker Services Manual Change Notification – Maintenance Documentation (MCNM) F.28-025 dated 4 June 2001, also pertains to this subject.\n\nCompliance: Within 6,000 flight cycles after 20 August 2001; thereafter at intervals not to exceed 6,000 flight cycles.\n\nThis Airworthiness Directive becomes effective on 1 November 2001.\n\n![](image.004.png)Background: The CAA received several reports of heat damage found on the fuselage skin panels in the stub wing (engine pylon) areas. In both cases, the damage was discovered visually, evidenced by discolouration of the (yellow) primer paint on the inside of the fuselage, and is thought to have been caused by leakage of hot air from one of the bleed air ducts inside the stub wing. Undetected damage could lead to deterioration of the structural integrity of the Stub Wing assembly.\n\n![](image.005.png)  \n\nDavid Alan Villiers\n\nDelegate of the Civil Aviation Safety Authority 21 September 2001\n\n![](image.002.png)\n\nThe above AD is notified in the Commonwealth of Australia Gazette on 10 October 2001.","sortOrder":1}],"analysis":{"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":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific structural integrity issue in Fokker F.28 aircraft. It has not expanded beyond its initial safety purpose of detecting and managing heat damage in stub wing fuselage structures."},"complexity_factors":["Single, clearly defined applicability (one aircraft model series)","Straightforward two-part requirement: inspect, then repair if needed","Simple compliance timeline (initial deadline + fixed recurring interval)","Only 2 cross-references to external documents (Fokker Service Bulletin and Dutch CAA AD)","No nested exceptions or conditional logic — requirements apply uniformly to all affected aircraft","Short document (approximately 300 words of substantive text)"],"plain_english_summary":"This Airworthiness Directive from CASA applies to all Fokker F.28 (1000–4000 series) and requires regular visual inspections of the internal fuselage at the engine “stub wing” areas, with mandated repairs or replacements per Fokker instructions if heat damage is found.  \n\nIt responds to bleed-air leaks that can heat-damage and weaken the engine attachment structure; inspections repeat every 6,000 flight cycles and must continue even after repairs to ensure structural safety."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD remains narrowly focused on the stated safety issue: detecting and repairing heat damage in the stub wing internal fuselage areas believed to result from bleed‑air leakage. It requires inspections and corrective action, and establishes recurring monitoring. It does not broaden obligations beyond that original purpose, expand to other aircraft types, or add unrelated regulatory burdens."},"complexity_factors":["Short, single-issue directive focused on stub wing fuselage structure","Direct cross-reference to external document: Fokker Service Bulletin F.28/53-151 (4 June 2001)","Two further references/notes: Netherlands CAA AD 2001-093 and Fokker MCNM F.28-025 (4 June 2001)","Repetitive inspection requirement (every 6,000 flight cycles) with an initial compliance window tied to a fixed past date (within 6,000 cycles after 20 August 2001)","Repair/replacement requirement that does not terminate the inspection cycle (ongoing obligation)","Measurement in flight cycles (operator-dependent timing) rather than calendar time or flight hours"],"plain_english_summary":"**What the rule does (mechanically)\n\n- **Who is affected:** All Fokker F.28 Mk. 1000 through 4000 series aircraft and the operators/maintenance organisations that maintain them.\n\n- **What you must do:** Carry out a visual inspection of the internal fuselage structure in the stub wing (engine pylon) areas following Part 1 of the Accomplishment Instructions in Fokker Service Bulletin F.28/53-151 (4 June 2001). If you find damage, repair or replace the affected parts within the limits set out in Part 2 of those Accomplishment Instructions. Repairs or replacements do not stop the need for the repeated inspections.\n\n- **When to do it:** Do the first inspection within 6,000 flight cycles after 20 August 2001. After that, repeat the inspection at intervals no longer than every 6,000 flight cycles.\n\n- **Reference material:** The AD relies on Fokker Service Bulletin F.28/53-151 (4 June 2001) for the inspection and repair instructions. It also notes Netherlands CAA AD 2001-093 and Fokker Maintenance Documentation Notice MCNM F.28-025 (4 June 2001) as related documents.\n\n**Why the rule was issued (stated rationale)\n\n- The regulator received multiple reports of heat damage to internal fuselage skin panels in the stub wing areas. The damage showed as discolouration of primer paint and is believed to be caused by leakage of hot bleed air from ducts inside the stub wing. The stated safety concern is that undetected heat damage could degrade the structural integrity of the stub wing assembly.\n\n**Practical effects and who pays\n\n- **Who pays:** Aircraft operators bear the direct costs: inspection labour, possible non‑routine maintenance downtime, and parts and labour for repairs/replacements called for by the Service Bulletin.\n\n- **Who decides and how it's done:** The Civil Aviation Safety Authority (via its delegate) issued the mandatory AD. The actual inspections and repairs are carried out by the aircraft operator or their contracted maintenance organisations, using the procedures in the referenced Fokker Service Bulletin.\n\n- **What behaviour changes:** Operators must schedule recurring visual inspections of the stub wing internal structure every 6,000 flight cycles and must carry out repairs or part replacements where damage is found. Because repairs do not cancel the inspection requirement, the inspections are ongoing.\n\n**Costs, incentives and trade-offs (implementation lens)\n\n- **Direct costs vs safety benefit:** The rule creates recurring maintenance cost and aircraft downtime for operators in exchange for reducing the risk of structural deterioration from heat damage. The trade‑off is straightforward: routine monitoring and corrective work to avoid potential structural failure.\n\n- **Incentives and substitution effects:** Operators have an incentive to detect and fix bleed air leaks early (preventive action) because repairs and structural work are more costly and disruptive. Operators may also adapt inspection scheduling to align with existing heavy maintenance checks to reduce incremental downtime.\n\n- **Compliance burden and implementation risk:** The AD delegates the technical specifics to the Fokker Service Bulletin. That creates dependency on the bulletin’s clarity and availability of parts and qualified maintenance resources. Visual inspection can detect paint discolouration and obvious damage, but may miss hidden damage; the Service Bulletin’s instructions determine whether additional non‑destructive testing is required.\n\n- **Effects on third parties and markets:** Independent maintenance organisations can perform the inspections and repairs provided they follow the Service Bulletin. The AD does not prescribe a single supplier for parts or work, so competition among approved maintenance providers can continue. However, if specialised parts or expertise are scarce, costs could be concentrated on operators who must schedule fleet downtime.\n\n**Other implementation notes and constraints**\n\n- The AD sets intervals in flight cycles (not hours or calendar time). High‑utilisation operators will reach the 6,000‑cycle interval sooner, increasing their maintenance frequency relative to low‑utilisation operators.\n\n- Repair or replacement does not remove the need for continued periodic inspections (see Requirement). That maintains ongoing monitoring rather than a one‑time fix.\n\n- The AD cross‑references an overseas regulator (Netherlands CAA AD 2001‑093) and a Fokker maintenance notification. Operators need access to those documents to implement the AD exactly as intended.\n\n**Bottom line:** The AD mandates recurring visual inspections and corrective action for heat damage in the stub wing internal fuselage areas of F.28 Mk.1000–4000 aircraft to mitigate a risk caused by suspected bleed‑air leakage. It places recurring inspection and repair costs on operators, relies on Fokker's service instructions for technical detail, and requires ongoing monitoring rather than a one‑off repair."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f28-87-stub-wing-fuselage-structure","history":"/api/acts/ad-f28-87-stub-wing-fuselage-structure/history","analysis":"/api/acts/ad-f28-87-stub-wing-fuselage-structure/analysis","conflicts":"/api/acts/ad-f28-87-stub-wing-fuselage-structure/conflicts","importantCases":"/api/acts/ad-f28-87-stub-wing-fuselage-structure/important-cases","documents":"/api/acts/ad-f28-87-stub-wing-fuselage-structure/documents"}}