{"id":"F2006B07308","name":"AD/TB10/6 Amdt 1 - Horizontal Stabilizer Balance Weight Support","slug":"ad-tb10-6-amdt-1-horizontal-stabilizer-balance-weight-support","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":49303,"registerId":"commonwealth-F2006B07308-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/TB10/6 Amdt 1 - Horizontal Stabilizer Balance Weight Support","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)  Aerospatiale (Socata) TB9 and TB10 (Tobago) Series Aeroplanes\n\n \n\nAD/TB10/6\n\nAmdt 1\n\n\nHorizontal Stabilizer Balance Weight Support 11/85\n\n \n\nApplicability: All model TB9 and TB10 with S/Nos 001 to 474 inclusive. Requirement: Action in accordance with SOCATA S.B. No. 25 ATA 55-10.\n\nNote: Bureau Veritas AD 85-90-(A) refers.\n\n \n\nCompliance: Prior to 30 June 1986.\n\n \n\nBackground: The manufacturer has devised a modification to separate the natural frequencies of the balance weight support and the stabilizer thereby preventing the possibility of flutter. This amendment changes the compliance requirement to conform with the requirement document and French AD.\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":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":true,"description":"The amendment alters the compliance requirement to conform with the manufacturer’s requirement document and the French authority’s AD (Background). The applicability (TB9/TB10 s/n 001–474) remains specified in this text (Applicability), while the compliance timing is explicitly set (Compliance). The change described in the Background is a modification of the compliance requirement rather than an expansion of the aircraft population covered."},"complexity_factors":["Narrow applicability limited to Aerospatiale (Socata) TB9 and TB10 with serial numbers 001–474 (Applicability).","Single mandated action: implement SOCATA Service Bulletin No. 25 ATA 55-10; technical details are delegated to that external document (Requirement).","Clear compliance deadline (prior to 30 June 1986), which is a fixed, simple temporal requirement (Compliance).","References to an overseas airworthiness directive (Bureau Veritas AD 85-90-(A)) and alignment with a French AD add administrative cross-reference but not additional procedural layers in this text (Note; Background).","Technical nature of the modification (separating natural frequencies of balance weight support and stabilizer) requires certified maintenance capability and parts, introducing operational and cost considerations despite legal simplicity (Background).","The phrase “action in accordance with” creates reliance on the manufacturer’s service bulletin for implementation detail, which concentrates technical complexity in that external document (Requirement)."],"plain_english_summary":"What this instrument does mechanically:\n\n- It is an airworthiness directive (Schedule of Airworthiness Directives under the Civil Aviation Regulations) that requires a specific modification to certain Aerospatiale (Socata) TB9 and TB10 (Tobago) aeroplanes (Applicability).  \n- Specifically, every TB9 and TB10 with serial numbers 001 to 474 inclusive must have the horizontal stabilizer balance weight support modified in accordance with SOCATA Service Bulletin No. 25 (ATA 55-10) (Requirement).  \n- The modification must be completed by the compliance deadline: prior to 30 June 1986 (Compliance).\n\nWho is affected and who pays:\n\n- Aircraft owners and operators of the listed TB9/TB10 serial numbers are responsible for arranging and paying for the modification (Applicability; Requirement).  \n- Maintenance organisations or authorised mechanics will perform the work under the manufacturer’s service bulletin; those organisations receive the work and the revenue from it (Requirement).\n\nWhy it matters (claimed purpose and how that interacts with costs and incentives):\n\n- The manufacturer states the modification separates the natural frequencies of the balance weight support and the stabilizer to prevent the possibility of flutter; the Background attributes that as the reason for the change (Background).  \n- If operators want to keep these aircraft compliant with this directive, they must incur the direct costs of parts, labour and downtime to implement SOCATA S.B. No. 25 (Requirement; Compliance).  \n- The directive aligns the Australian requirement with the French authority’s action (Note; Background), so operators of the affected fleet face the same technical specification as in the referenced foreign AD.\n\nImplementation mechanics, incentives and risks:\n\n- The directive does not include technical detail in this text; it requires action “in accordance with” the manufacturer’s service bulletin, so the precise steps, parts and acceptance standards come from SOCATA S.B. No. 25 (Requirement).  \n- This creates a compliance process: obtain the service bulletin, schedule maintenance, perform the modification to the manufacturer’s instructions, and retain evidence of compliance by the stated date (Requirement; Compliance).  \n- The deadline (prior to 30 June 1986) imposes a time constraint on owners/operators; failure to comply by the deadline would leave an aircraft non-compliant with this AD (Compliance).  \n- The directive references an overseas authority’s AD (Bureau Veritas AD 85-90-(A)), indicating regulatory coordination rather than a separate technical approach (Note).\n\nTrade-offs, enforcement and discretion:\n\n- The directive transfers the immediate financial cost and operational downtime to private owners/operators (Applicability; Requirement).  \n- The enforcement mechanism is the airworthiness directive itself: compliance is required by the stated date; this text delegates the technical detail to the manufacturer’s service bulletin, so inspectors will check compliance against that document (Requirement; Compliance).  \n- The text does not allocate subsidies, exemptions, or compensations; it does not detail enforcement penalties or the process for approval of alternative methods—those matters would be handled under the regulator’s normal airworthiness oversight processes (Requirement; Compliance).\n\nNet procedural effect:\n\n- Operators of TB9/TB10 s/n 001–474 must follow SOCATA S.B. No. 25 ATA 55-10 and complete the modification before the stated deadline to meet this airworthiness directive (Applicability; Requirement; Compliance).  \n- The stated policy rationale is to prevent the possibility of flutter by separating natural frequencies (Background); the directive amended the compliance requirement to conform with the requirement document and the French AD (Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This amendment does not expand scope. It remains tightly focused on the original safety issue (flutter prevention in specific Socata aircraft) and merely harmonises the compliance deadline with international standards. The original intent — mandating a specific airframe modification — is unchanged."},"complexity_factors":["Single, specific applicability criterion (serial number range)","One clear compliance action (follow manufacturer's Service Bulletin)","No defined terms section","No cross-references to other legislation beyond a note about French AD","Simple conditional logic: if you own this specific aircraft, you must do this specific thing by this specific date","Amendment is administrative only — changes compliance date alignment, not technical requirements"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\n- Requires owners/operators of certain **Socata TB9 and TB10 Tobago aeroplanes** (serial numbers 001 to 474) to carry out a specific modification to the **horizontal stabilizer balance weight support** — a component at the tail of the aircraft that helps keep it stable in flight.\n\n**Why it matters:**\n- The manufacturer discovered that without this modification, the balance weight support could vibrate at the same frequency as the stabilizer itself. This matching of frequencies (called \"flutter\") can cause dangerous structural damage or even cause the tail to fail in flight. The fix separates these natural frequencies to prevent that risk.\n\n**What must be done:**\n- Aircraft owners must follow the manufacturer's **Service Bulletin No. 25** (referenced as ATA 55-10 — a standard numbering system for aircraft parts) to make the modification.\n- This had to be completed **before 30 June 1986**.\n\n**What's new in this version (Amendment 1):**\n- This update simply aligns Australia's compliance deadline with the French aviation authority's equivalent directive and the manufacturer's original requirement document. No technical change to the fix itself — just administrative harmonisation.\n\n**Who it affects:**\n- Owners and operators of early-production Socata TB9 and TB10 aircraft in Australia (roughly the first 474 built)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-tb10-6-amdt-1-horizontal-stabilizer-balance-weight-support","history":"/api/acts/ad-tb10-6-amdt-1-horizontal-stabilizer-balance-weight-support/history","analysis":"/api/acts/ad-tb10-6-amdt-1-horizontal-stabilizer-balance-weight-support/analysis","conflicts":"/api/acts/ad-tb10-6-amdt-1-horizontal-stabilizer-balance-weight-support/conflicts","importantCases":"/api/acts/ad-tb10-6-amdt-1-horizontal-stabilizer-balance-weight-support/important-cases","documents":"/api/acts/ad-tb10-6-amdt-1-horizontal-stabilizer-balance-weight-support/documents"}}