{"id":"F2006B10182","name":"AD/GAF-N22/35 - Horizontal Stabiliser Trim Tab System - Modification","slug":"ad-gaf-n22-35-horizontal-stabiliser-trim-tab-system-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55827,"registerId":"commonwealth-F2006B10182-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/GAF-N22/35 - Horizontal Stabiliser Trim Tab System - Modification","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  GAF N22 and N24 Series Aeroplanes\n\n \n\n# AD/GAF-N22/35  Horizontal Stabiliser Trim Tab System - Modification\n\nApplicability: All models N22, N22B and N22S with S/Nos. referenced in SB NMD-55-8. Document:               GAF SB No. NMD-55-8.\n\nCompliance: Before 1 August 1980.\n\n# 4/80\n\n \n\nBackground:  The modification is introduced to improve the durability of the stabilator trim tab control system.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-purpose airworthiness directive focused specifically on a mechanical modification to a particular aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (approximately 150 words)","Only 3 defined elements: applicability, document reference, and compliance date","No cross-references to other legislation or regulations beyond the parent Civil Aviation Regulations 1998","Single, unconditional mandate with no exceptions or conditional logic","Straightforward technical reference to a single service bulletin (SB NMD-55-8)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** issued by Australia's Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998. It mandates a specific safety modification for certain GAF aircraft models.\n\n**What it does:**\n- Requires owners/operators of specific GAF N22 series aeroplanes (including N22, N22B, and N22S models with particular serial numbers) to modify the horizontal stabiliser trim tab system\n- The modification must follow the technical instructions in GAF Service Bulletin NMD-55-8\n\n**Who it affects:**\n- Owners and operators of GAF N22 and N24 series aircraft with serial numbers listed in the referenced service bulletin\n- Specifically targets the \"stabilator\" (a combined stabiliser and elevator control surface) trim tab control system\n\n**Why it matters:**\n- The modification improves the **durability** (longevity and reliability) of the trim tab control system\n- Trim tabs are small adjustable surfaces that help pilots control the aircraft's pitch (nose up/down) without constant force on the controls\n- Without this modification, the system could fail prematurely, potentially affecting aircraft control and safety\n\n**Compliance deadline:** Before 1 August 1980 (this is a historical directive from April 1980)"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive sets a specific, time-limited requirement for a modification on identified aircraft serial numbers and delegates technical detail to GAF SB NMD-55-8. The text does not indicate any alteration or expansion of scope beyond that stated applicability; no change of scope from the instrument’s stated content is evident in the provided text. (Applicability; Document; Compliance)"},"complexity_factors":["Narrow and specific applicability (only GAF N22, N22B and N22S with S/Ns listed in SB NMD-55-8) (Applicability)","Single mandated action with a single deadline (Compliance)","Technical details are not contained in the AD but are delegated to an external document (GAF SB NMD-55-8), requiring cross-reference to implement (Document)","No alternative compliance paths, exemptions, or funding/compensation mechanisms specified in the AD (Compliance)","Implementation depends on the clarity and completeness of the referenced service bulletin, introducing implementation risk outside the AD text (Document; Background)"],"plain_english_summary":"# What this Airworthiness Directive does\n\n- This directive requires a modification to the horizontal stabiliser trim tab control system on certain GAF N22-series aeroplanes. (Applicability; Document)\n\n- Which aircraft are affected: all GAF N22, N22B and N22S aeroplanes whose serial numbers are listed in GAF Service Bulletin NMD-55-8. (Applicability; Document)\n\n- What must be done: the modification must be carried out in accordance with GAF SB No. NMD-55-8. (Document)\n\n- When it must be done: the modification must be completed before 1 August 1980. (Compliance)\n\n- Stated reason: the instrument states the modification is introduced to improve the durability of the stabilator trim tab control system. (Background)\n\nPractical mechanics, incentives and trade-offs\n\n- Who decides and who acts: the directive imposes an obligation on operators/owners of the listed aircraft (those with S/Ns in the referenced service bulletin) to implement the modification by the deadline. The AD points to the maker’s service bulletin as the implementing specification. (Applicability; Document; Compliance)\n\n- Who bears the burden: the directive requires that the modification be carried out; the text therefore creates a compliance obligation for the affected aircraft. The AD itself does not state who pays or how costs are allocated. (Applicability; Document; Compliance)\n\n- Compliance burden and operational effect: the AD creates a fixed deadline for a technical modification. That will typically require scheduling maintenance, allocating labour and parts, and aircraft downtime to complete the modification per SB NMD-55-8. The AD does not detail the work steps or parts — it relies on the referenced service bulletin for technical instructions. (Document; Compliance)\n\n- Implementation risk and discretion: the AD references the manufacturer’s service bulletin for the technical specification; the quality and completeness of that bulletin will determine implementation risk (for example, whether further interpretation by maintenance personnel or the regulator is required). The AD text does not itself create technical tolerances or alternative compliance pathways. (Document)\n\n- Effects on private choice and market participants: the directive changes operational choices available to owners/operators of the specified aircraft by requiring the modification. It does not address broader competitive or market measures (pricing, certification of alternative parts or providers), nor does it create explicit exemptions or funding arrangements in the text. (Applicability; Document; Compliance)\n\n- Trade-offs and opportunity costs: operators must prioritise this mandated modification relative to other maintenance and operational needs before the deadline. The AD does not mention compensating measures, staged compliance, or deferrals. (Compliance)\n\nConcise summary sentence\n\nThis airworthiness directive mandates, for listed GAF N22-series aeroplanes identified in GAF SB NMD-55-8, completion of a manufacturer-specified modification to the horizontal stabiliser trim tab control system before 1 August 1980, with the stated aim of improving system durability; the AD delegates technical detail to the referenced service bulletin and imposes a compliance obligation on affected aircraft without specifying cost allocation or alternative compliance routes. (Applicability; Document; Compliance; Background)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-gaf-n22-35-horizontal-stabiliser-trim-tab-system-modification","history":"/api/acts/ad-gaf-n22-35-horizontal-stabiliser-trim-tab-system-modification/history","analysis":"/api/acts/ad-gaf-n22-35-horizontal-stabiliser-trim-tab-system-modification/analysis","conflicts":"/api/acts/ad-gaf-n22-35-horizontal-stabiliser-trim-tab-system-modification/conflicts","importantCases":"/api/acts/ad-gaf-n22-35-horizontal-stabiliser-trim-tab-system-modification/important-cases","documents":"/api/acts/ad-gaf-n22-35-horizontal-stabiliser-trim-tab-system-modification/documents"}}