{"id":"F2006L03617","name":"AD/CT4/2 - Horizontal Stabiliser Rear Spar","slug":"ad-ct4-2-horizontal-stabiliser-rear-spar","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":137306,"registerId":"commonwealth-F2006L03617-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Pacific Aerospace Corporation CT/4 Serie","sectionType":"division","heading":"Pacific Aerospace Corporation CT/4 Series Aeroplanes","content":"### Pacific Aerospace Corporation CT/4 Series Aeroplanes\n\n| AD/CT4/2 | Horizontal Stabiliser Rear Spar | 12/2006 |\n| -------- | ------------------------------- | ------- |\n\n| Applicability: | Model CT/4E aircraft, serial numbers CT227 through CT240 and, all CT/4 series aircraft fitted with the new style hinge bracket part number 10-30031-1.                                                                                                                                                                                                                                                                                                                                        |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Inspect in accordance with Accomplishment Instruction 3 in Pacific Aerospace Corporation (PAC) Service Bulletin (SB) No. PACSB/CT/132.If cracks are detected, replace the horizontal stabiliser rear spar in accordance with SB No. PACSB/CT/132, and embody MOD PAC/CT/0303 Issue 2.If no cracks are detected, embody MOD PAC/CT/0303 Issue 2.Note 1: MOD PAC/CT/0303 Issue 2 revises the centre hinge attachment to the horizontal stabiliser rear spar.Note 2: NZ CAA AD DCA/CT4/7 refers. |\n| Compliance:    | Within 100 hours time in service after 23 November 2006.                                                                                                                                                                                                                                                                                                                                                                                                                                      |\n|                | This Airworthiness Directive becomes effective on 23 November 2006.                                                                                                                                                                                                                                                                                                                                                                                                                           |\n| Background:    | A report was received of a cracked horizontal stabiliser spar on a Model CT4-E aircraft fitted with a new style elevator centre hinge bracket part number 10-30031-1. The horizontal stabiliser rear spar is not repairable and must be replaced if cracking is detected.                                                                                                                                                                                                                     |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n12 October 2006","sortOrder":0},{"sectionNumber":"AD/CT4/2","sectionType":"part","heading":"AD/CT4/2","content":"## AD/CT4/2","sortOrder":1},{"sectionNumber":"Horizontal Stabiliser Rear Spar","sectionType":"part","heading":"Horizontal Stabiliser Rear Spar","content":"## Horizontal Stabiliser Rear Spar","sortOrder":2},{"sectionNumber":"12/2006","sectionType":"part","heading":"12/2006","content":"## 12/2006","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":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific structural defect reported on a particular aircraft model. The scope remains precisely limited to the identified safety issue and the affected aircraft population."},"complexity_factors":["Single, specific mechanical issue addressed (cracked spar)","Clear applicability criteria (specific serial numbers and part number)","Binary decision tree (cracks found / not found) with prescribed outcomes","Only 2 external documents referenced (Service Bulletin and Modification)","Single compliance deadline (100 hours time in service)","No nested exceptions or conditional sub-clauses","No defined terms section — uses standard aviation terminology"],"plain_english_summary":"This CASA Airworthiness Directive requires owners/operators of Pacific Aerospace CT/4E aircraft (S/N CT227–CT240) and any CT/4 fitted with the new-style hinge bracket (P/N 10‑30031‑1) to inspect the horizontal stabiliser rear spar for cracks and replace it if found. Regardless of findings, a strengthening modification to the centre hinge must be installed to prevent spar failure — addressing an actual crack discovery and reducing risk of tail structural loss."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD targets the population identified by the reported cracked spar: CT/4E serials CT227–CT240 and any CT/4 with the new-style hinge bracket (p/n 10-30031-1). It requires inspection, replacement if cracked, and embodiment of MOD PAC/CT/0303 Issue 2. There is no indication in the instrument text that the scope departs from that original safety-focused intent; it remains narrowly scoped to affected serials and the specific hinge-bracket fitment."},"complexity_factors":["Limited, specific applicability (serial numbers CT227–CT240 and any airframe with hinge bracket p/n 10-30031-1) — narrows the affected population.","Technical inspection requirement to be done per PAC Service Bulletin PACSB/CT/132 — introduces procedural reliance on a manufacturer SB.","Mandatory replacement if cracks found; spar stated as non-repairable — creates potential immediate parts cost and logistics burden.","Obligation to embody MOD PAC/CT/0303 Issue 2 (revises centre hinge attachment) even if no crack found — adds mandatory modification workload and parts/labour.","Short compliance window (within 100 hours TIS after 23 Nov 2006) — scheduling and operational disruption risk for operators.","Cross-reference to another regulator’s AD (NZ CAA AD DCA/CT4/7) and multiple documents increases administrative tracing.","Enforcement and effectivity dates set by CASA (delegate signature) — regulatory certainty but limited discretion for operators."],"plain_english_summary":"This Airworthiness Directive requires operators of Pacific Aerospace CT/4 aeroplanes (specific serial numbers CT227–CT240 and any CT/4 fitted with hinge bracket p/n 10-30031-1) to inspect the horizontal stabiliser rear spar for cracks and, if cracks are found, replace the spar. Regardless of findings, operators must also carry out a specified modification to the centre hinge attachment. Compliance is mandatory within 100 hours time in service from 23 November 2006. Owners/operators bear inspection, replacement and modification costs."}},"importantCases":[],"_links":{"self":"/api/acts/ad-ct4-2-horizontal-stabiliser-rear-spar","history":"/api/acts/ad-ct4-2-horizontal-stabiliser-rear-spar/history","analysis":"/api/acts/ad-ct4-2-horizontal-stabiliser-rear-spar/analysis","conflicts":"/api/acts/ad-ct4-2-horizontal-stabiliser-rear-spar/conflicts","importantCases":"/api/acts/ad-ct4-2-horizontal-stabiliser-rear-spar/important-cases","documents":"/api/acts/ad-ct4-2-horizontal-stabiliser-rear-spar/documents"}}