{"id":"F2005L01037","name":"AD/F50/91 - Elevator Leading Edge","slug":"ad-f50-91-elevator-leading-edge","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":34574,"registerId":"commonwealth-F2005L01037-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Fokker F50 (F27 Mk 50) Series Aeroplanes","sectionType":"division","heading":"Fokker F50 (F27 Mk 50) Series Aeroplanes","content":"### Fokker F50 (F27 Mk 50) Series Aeroplanes\n\n| AD/F50/91 | Elevator Leading Edge | 6/2005 |\n| --------- | --------------------- | ------ |\n\n| Applicability: | All Model F27 Mk 050, Mk 0502, and Mk 0604 aircraft.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |\n| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Inspect the elevator leading edge sections in accordance with Part 2 Accomplishment Instructions of Fokker Service Bulletin (SB) F50-55-012, dated 11 October 2004, or a later CAA-NL approved revision.2. For aircraft equipped with the “divided type” elevator leading edge sections, inspect in accordance with Part 2 Accomplishment Instructions of SB F50-55-12, or a later CAA-NL approved revision.3. For aircraft equipped with the “divided type” elevator leading edge sections, modify the leading edge sections in accordance with Part 2 Accomplishment Instructions of Fokker SB F50-55-13, dated 11 October 2004, or a later CAA-NL approved revision.Note: Netherlands CAA AD NL-2005-001 refers. |\n| Compliance:    | 1. Within 6 months after 9 June 2005.2. Within 6 months after the Requirement 1 inspection, and thereafter at intervals not to exceed 6 months; until accomplishment of Requirement 3 of this Directive.3. Within 2 years after 9 June 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |\n|                | This Airworthiness Directive becomes effective on 9 June 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |\n| Background:    | Reports were received of elevator leading edges (divided type) that appeared to be loose. Inspection revealed the fastener holes in the leading edge sections to be elongated and worn. Investigation has shown that vibration induced by the propeller slipstream as the most likely cause. This Directive requires inspections and eventual modification of the divided elevator leading edges.                                                                                                                                                                                                                                                                                                                      |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n26 April 2005","sortOrder":0},{"sectionNumber":"AD/F50/91","sectionType":"part","heading":"AD/F50/91","content":"## AD/F50/91","sortOrder":1},{"sectionNumber":"Elevator Leading Edge","sectionType":"part","heading":"Elevator Leading Edge","content":"## Elevator Leading Edge","sortOrder":2},{"sectionNumber":"6/2005","sectionType":"part","heading":"6/2005","content":"## 6/2005","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow Airworthiness Directive addressing a specific airframe defect. It has not expanded beyond its original purpose of ensuring elevator leading edge integrity on affected Fokker F50 aircraft."},"complexity_factors":["Single, specific aircraft type and limited model variants (3 models only)","Clear, sequential compliance deadlines (6 months, 6-monthly recurring, 2 years)","Only 3 technical requirements referencing external service bulletins","No nested exceptions or conditional logic — straightforward 'inspect then modify' pathway","Minimal defined terms (only 'divided type' requires technical understanding)","Short document (~250 words of substantive content)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's aviation regulator (CASA) to fix a specific mechanical problem on certain aircraft.\n\n**What it does:**\nOrders owners and operators of **Fokker F50 aircraft** (specifically models Mk 050, Mk 0502, and Mk 0604) to inspect and eventually modify the **elevator leading edge** — the front part of the horizontal tail surface that helps control the plane's pitch.\n\n**The problem:**\nThe \"divided type\" elevator leading edges were coming loose. Investigation found that vibration from the propellers was wearing out and elongating the fastener holes. This could potentially affect aircraft control.\n\n**What must be done:**\n- **First inspection:** Within 6 months of 9 June 2005\n- **Repeat inspections:** Every 6 months thereafter (for the \"divided type\" only), until the modification is done\n- **Permanent fix:** Modify the leading edge sections within 2 years of 9 June 2005\n\n**Who it affects:**\nAnyone who owns, operates, or maintains these specific Fokker F50 aircraft in Australia.\n\n**Why it matters:**\nAirworthiness Directives are legally binding. Failure to comply means the aircraft cannot legally fly. This particular AD prevents potential structural failure of a critical flight control surface."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive addresses the safety issue identified in the background (loose/divided elevator leading edges and elongated fastener holes due to vibration). It requires inspection and a structural modification for the affected sub‑type. The measures stay within that original safety-focused purpose and do not expand to unrelated systems, operators or obligations."},"complexity_factors":["Short, targeted directive limited to three aircraft model variants (clear applicability).","Two principal required actions: inspection (SB F50-55-012) and modification for a specific sub-type (SB F50-55-13).","Cross-reference to two Fokker Service Bulletins and any later Netherlands CAA-approved revisions (external dependencies).","Distinct treatment for the \"divided type\" leading edge (conditional path and recurring inspection requirement).","Three compliance timeframes (6 months for initial inspection, 6‑monthly repeat interval until modification for divided type, 2 years to complete modification).","No large number of defined terms, no nested exceptions beyond the divided-type distinction."],"plain_english_summary":"This directive requires owners, operators and maintenance organisations of Fokker F50 (F27 Mk 050/0502/0604) aeroplanes to inspect elevator leading edges (per Fokker SB F50‑55‑012) within six months of 9 June 2005, and — for aircraft with the “divided‑type” leading edge — repeat inspections every six months until a mandated modification (per Fokker SB F50‑55‑13) is completed within two years. It responds to worn/elongated fastener holes from prop‑wash vibration that can loosen leading edges; operators bear the inspection/modification costs and scheduling impact."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-91-elevator-leading-edge","history":"/api/acts/ad-f50-91-elevator-leading-edge/history","analysis":"/api/acts/ad-f50-91-elevator-leading-edge/analysis","conflicts":"/api/acts/ad-f50-91-elevator-leading-edge/conflicts","importantCases":"/api/acts/ad-f50-91-elevator-leading-edge/important-cases","documents":"/api/acts/ad-f50-91-elevator-leading-edge/documents"}}