{"id":"F2006B11448","name":"AD/P166/21 - Main Landing Gear Shock Absorber Strut - Modification","slug":"ad-p166-21-main-landing-gear-shock-absorber-strut-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":57393,"registerId":"commonwealth-F2006B11448-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/P166/21 - Main Landing Gear Shock Absorber Strut - Modification","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-description: CASA Airworthiness Directive\nmeta-generator: Aspose.Words for .NET 22.10.0\nmeta-keywords: Issue 12/1962,Aircraft below 5700 kg,Piaggio P166 Series Aeroplanes,Main Landing Gear Shock Absorber Strut - Modification,21\ntitle: Airworthiness Directive - AD/P166/21 - Main Landing Gear Shock Absorber Strut - Modification\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)  Piaggio P166 Series Aeroplanes\n\n \n\nAD/P166/21 Main Landing Gear Shock Absorber\n\nStrut - Modification\n\n\n12/62\n\n \n\nApplicability: All model P166. Document: Piaggio SB P166-25A. Compliance:  Forthwith.\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\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The supplied AD text does not indicate any change in scope from an earlier instrument or intent. It applies to all Piaggio P166 models, directs compliance with Piaggio SB P166-25A, and requires action forthwith (Applicability; Document; Compliance). No amendment or narrowing/expansion of applicability is described in the provided text."},"complexity_factors":["Narrow technical scope: applies only to the main landing gear shock absorber strut on Piaggio P166 aeroplanes (Applicability).","Single prescribed compliance method: requires following Piaggio SB P166-25A rather than multiple options (Document).","Immediate timing: compliance is required \"forthwith\", reducing scheduling flexibility (Compliance: Forthwith).","Regulatory enforcement: issued under Civil Aviation Regulations 1998 Part 39, which creates statutory enforcement and oversight (header).","Practical implementation complexity: while the directive text is brief, the actual modification may require specialist maintenance, parts, and downtime (implied by Document and Applicability)."],"plain_english_summary":"This Airworthiness Directive (AD) requires owners/operators of Piaggio P166 aeroplanes to modify the main landing gear shock absorber strut. It is issued by the Civil Aviation Safety Authority under the Civil Aviation Regulations 1998, Part 39 (see header).\n\nWhat the instrument does, mechanically\n- Mandates a modification to the main landing gear shock absorber strut on all Piaggio P166 models (Applicability: All model P166).\n- Specifies the technical instructions to follow: Piaggio Service Bulletin P166-25A is the referenced document (Document: Piaggio SB P166-25A).\n- Sets the timing: compliance is required forthwith (Compliance: Forthwith).\n\nWho it affects\n- Owners and operators of any Piaggio P166 aeroplane are directly affected (Applicability).\n- Maintenance organisations and engineers who perform the modification will carry out the work according to the referenced service bulletin (Document).\n- The Civil Aviation Safety Authority (CASA) is the regulator enforcing the directive (header: Civil Aviation Safety Authority; Civil Aviation Regulations 1998, PART 39 - 105).\n\nWhy it matters (stated purpose and practical implications)\n- ADs are regulatory instruments that require specific maintenance or modification actions; this AD makes a specific modification mandatory for the listed aeroplanes. The AD itself does not set out a narrative explanation of the safety concern in the text supplied; it instead prescribes the required action and the approved procedure to be used (Document).\n\nCosts, incentives, and implementation mechanics\n- Who pays: aircraft owners/operators pay for parts, labour, and any associated downtime to carry out the modification (the AD places the obligation on operators by applicability and compliance timing).\n- How it is to be done: the modification must be done following Piaggio SB P166-25A (Document). That ties compliance to the manufacturer’s procedure and any parts or tooling the bulletin requires.\n- Timing pressure: the instruction to comply \"forthwith\" creates immediate compliance pressure, meaning operators must schedule and complete the work without a deferred compliance window (Compliance: Forthwith).\n- Compliance burden: includes locating the service bulletin, arranging certified maintenance capacity, sourcing parts if required, and managing aircraft unavailability during the work.\n- Regulatory discretion and enforcement: CASA issues and enforces the AD under Part 39 of the Civil Aviation Regulations 1998; CASA has the authority to require and monitor compliance (header).\n\nTrade-offs and risks implied by the instrument (mechanisms, not value judgments)\n- Concentrated payer: the direct financial burden falls on individual owners/operators (Applicability), while the regulatory burden and monitoring rest with CASA (header).\n- Dependence on a manufacturer's bulletin: compliance requires following Piaggio SB P166-25A, so operators must rely on that document for technical detail and possibly on supply chains for any replacement parts (Document).\n- Operational impact: immediate compliance may cause short-term aircraft downtime and scheduling disruption for operators (Compliance: Forthwith).\n\nReference sections from the AD text used above: Applicability: All model P166; Document: Piaggio SB P166-25A; Compliance: Forthwith; Authority: Civil Aviation Regulations 1998, PART 39 - 105, Civil Aviation Safety Authority."},"kimi_summary":{"content_quality":"ok","complexity_score":1,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive focused specifically on one mechanical component of one aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Extremely short document (approximately 100 words of substantive content)","No defined terms section","No cross-references to other legislation beyond the enabling regulation (CAR 1998 Part 39)","No conditional logic or exceptions","Simple command structure: applicability + document reference + compliance deadline","Single operational requirement with no alternatives or phased implementation"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) issued by the Civil Aviation Safety Authority (CASA). An AD is a mandatory safety notice that requires aircraft owners or operators to fix a specific problem.\n\n**What it does:** It orders immediate modification of the main landing gear shock absorber strut on all Piaggio P166 series aircraft. A shock absorber strut is the hydraulic/pneumatic component in the landing gear that cushions the impact when an aircraft touches down.\n\n**Who it affects:** Anyone who owns or operates any model of the Piaggio P166 aircraft (a twin-engine utility aircraft originally designed in Italy).\n\n**What must be done:** Aircraft operators must follow the instructions in Piaggio Service Bulletin P166-25A \"forthwith\" — meaning immediately, without delay.\n\n**Why it matters:** This directive addresses a safety-critical component. If the shock absorber strut fails, it could cause landing gear collapse, potentially resulting in aircraft damage, injury, or death. The \"forthwith\" compliance requirement indicates CASA considers this an urgent safety issue."}},"importantCases":[],"_links":{"self":"/api/acts/ad-p166-21-main-landing-gear-shock-absorber-strut-modification","history":"/api/acts/ad-p166-21-main-landing-gear-shock-absorber-strut-modification/history","analysis":"/api/acts/ad-p166-21-main-landing-gear-shock-absorber-strut-modification/analysis","conflicts":"/api/acts/ad-p166-21-main-landing-gear-shock-absorber-strut-modification/conflicts","importantCases":"/api/acts/ad-p166-21-main-landing-gear-shock-absorber-strut-modification/important-cases","documents":"/api/acts/ad-p166-21-main-landing-gear-shock-absorber-strut-modification/documents"}}