{"id":"F2007L02194","name":"AD/ATR 42/6 - Vertical Stabiliser Fin Tip","slug":"ad-atr-42-6-vertical-stabiliser-fin-tip","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":67439,"registerId":"commonwealth-F2007L02194-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Avions de Transport Regional ATR 42 Seri","sectionType":"division","heading":"Avions de Transport Regional ATR 42 Series Aeroplanes","content":"### Avions de Transport Regional ATR 42 Series Aeroplanes\n\n| AD/ATR 42/6 | Vertical Stabiliser Fin Tip | 8/2007 |\n| ----------- | --------------------------- | ------ |\n\n| Applicability: | Model ATR 42-500 aircraft, with modification No. 4440 incorporated, and on which modification No. 5426 or Service Bulletin ATR42-55-0012 has not been incorporated; except aircraft serial numbers 618 through 623.                                                                                                                                                                                    |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement:   | Action in accordance with the requirements of EASA AD 2006-0303.Note: ATR Service Bulletin ATR42-55-0011 original issue, or later EASA approved revision, refers.                                                                                                                                                                                                                                      |\n| Compliance:    | As specified in the Requirement document, with a revised effective date of2 August 2007.                                                                                                                                                                                                                                                                                                               |\n|                | This Airworthiness Directive becomes effective on 2 August 2007.                                                                                                                                                                                                                                                                                                                                       |\n| Background:    | A report was received of rudder operation difficulties on an ATR 42-500 aircraft. An investigation determined that the upper closing rib could be subject to fatigue cracks induced by installation stress. This Directive changes the interval of the current repetitive inspection requirement, and requires incorporation of a modification which terminates the repetitive inspection requirement. |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n22 June 2007","sortOrder":0},{"sectionNumber":"AD/ATR 42/6","sectionType":"part","heading":"AD/ATR 42/6","content":"## AD/ATR 42/6","sortOrder":1},{"sectionNumber":"Vertical Stabiliser Fin Tip","sectionType":"part","heading":"Vertical Stabiliser Fin Tip","content":"## Vertical Stabiliser Fin Tip","sortOrder":2},{"sectionNumber":"8/2007","sectionType":"part","heading":"8/2007","content":"## 8/2007","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"The Directive alters the prior inspection regime by changing the interval for repetitive inspections and adds a mandatory modification that, once incorporated, terminates the repetitive inspections (Background: \"This Directive changes the interval... and requires incorporation of a modification which terminates the repetitive inspection requirement\")."},"complexity_factors":["External cross-reference: requires compliance with EASA AD 2006-0303 and ATR Service Bulletin ATR42-55-0011 (or later EASA-approved revision), so operators must obtain and follow external documents (Requirement).","Applicability carve-outs: applies only to ATR 42-500 aircraft with mod No. 4440 and without mod No. 5426 (or SB ATR42-55-0012), excluding serial numbers 618–623, requiring operators to verify modification and serial-status for applicability (Applicability).","Change to inspection regime: changes the interval of existing repetitive inspections and then mandates a modification that terminates those inspections, creating a two-stage compliance path (Background / Requirement).","Operational impact: inspection and modification impose direct costs, labour and aircraft downtime; scheduling and access to parts/service may affect operators differently (Background / Compliance).","Approval constraint: terminating modification must be an EASA-approved revision where applicable, introducing regulatory approval dependency (Requirement note).","Effective-date enforcement: revised effective date (2 August 2007) fixes the compliance start and limits operator discretion on timing (Compliance).","Delegated enforcement: directive issued by CASA’s delegate, so domestic enforcement and interpretation rest with the regulator’s delegate (signature/cover).","Potential ambiguity: the AD refers to the Requirement document for inspection intervals rather than stating them directly, requiring cross-checking of the referenced AD for procedural detail (Requirement / Compliance)."],"plain_english_summary":"This Airworthiness Directive applies to ATR 42-500 aircraft with modification No. 4440 that have not had modification No. 5426 (or Service Bulletin ATR42‑55‑0012) incorporated, excluding serial numbers 618–623. It requires operators to carry out inspections as specified in EASA AD 2006‑0303 and to incorporate ATR Service Bulletin ATR42‑55‑0011 (or a later EASA‑approved revision) to terminate the repetitive inspections; effective 2 August 2007.\n\nThe measure responds to reported rudder operation difficulties caused by potential fatigue cracking in the upper closing rib. Operators pay for inspections and the terminating modification, incur aircraft downtime, must follow an externally referenced EASA document, and comply under CASA’s delegate-issued directive."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard, narrow-scope Airworthiness Directive addressing a specific safety-of-flight issue with a particular aircraft component. The scope remains tightly focused on the vertical stabiliser fin tip fatigue cracking problem as originally identified. There is no evidence of scope creep or expansion beyond the original safety purpose."},"complexity_factors":["Single-issue directive focused on one specific structural component","Limited applicability with three clear conditions (modification 4440 present, modifications 5426/0012 absent, serial number exclusion)","Only one substantive requirement (comply with referenced EASA AD)","No nested exceptions or conditional logic beyond the applicability criteria","Short document (approximately 200 words of substantive content)","Cross-references only two external documents (EASA AD 2006-0303 and ATR Service Bulletin ATR42-55-0011)","Clear compliance deadline and effective date"],"plain_english_summary":"This CASA Airworthiness Directive mandates more frequent inspections and a mandatory modification to the vertical stabiliser fin tip on ATR 42-500 aircraft fitted with factory modification No. 4440 (excluding aircraft with MOD 5426 or SB ATR42-55-0012 and serials 618–623). It responds to fatigue cracking in the upper closing rib that could impair the rudder and jeopardise directional control, and adopts requirements from the related EASA AD and manufacturer service bulletin. Effective 2 August 2007."},"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-atr-42-6-vertical-stabiliser-fin-tip","history":"/api/acts/ad-atr-42-6-vertical-stabiliser-fin-tip/history","analysis":"/api/acts/ad-atr-42-6-vertical-stabiliser-fin-tip/analysis","conflicts":"/api/acts/ad-atr-42-6-vertical-stabiliser-fin-tip/conflicts","importantCases":"/api/acts/ad-atr-42-6-vertical-stabiliser-fin-tip/important-cases","documents":"/api/acts/ad-atr-42-6-vertical-stabiliser-fin-tip/documents"}}