{"id":"F2006B05320","name":"AD/P166/27 - Magnetic Compass Installation - Modification","slug":"ad-p166-27-magnetic-compass-installation-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":45768,"registerId":"commonwealth-F2006B05320-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/P166/27 - Magnetic Compass Installation - 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)  Piaggio P166 Series Aeroplanes\n\n \n\nAD/P166/27 Magnetic Compass Installation - Modification 2/64\n\nApplicability: All P166 series in which the maximum compass deviation and/or change in deviation due to electrical interference exceeds the limits prescribed in ANO 108.2.7.\n\n \n\nRequirement: 1. Modify the wiring to the pitot heaters, compass lighting and radio system if necessary, to reduce the interference to acceptable limits.\n\n \n\n2. Remove the compass from the windshield frame and relocate it on the flare shield. 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","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive's scope is confined to Piaggio P166 series aeroplanes where compass deviation due to electrical interference exceeds the limits in ANO 108.2.7 and requires specified corrective actions. The instrument text itself does not expand or narrow that scope beyond those criteria; it mandates wiring modification as necessary and relocating the compass, to be done forthwith. (Applicability; Requirement 1; Requirement 2; Compliance)"},"complexity_factors":["Narrow technical scope: applies only to Piaggio P166 aeroplanes whose compass deviation exceeds ANO 108.2.7 limits (Applicability).","Immediate compliance requirement increases operational urgency and scheduling complexity (Compliance).","Technical discretion: wiring changes are required \"if necessary\" to reduce interference, but the AD does not prescribe exact wiring procedures, requiring diagnostic work and engineering judgement (Requirement 1).","Cross-reference to an external standard (ANO 108.2.7) is necessary to determine applicability, adding an administrative/testing step (Applicability).","Physical modification and relocation tasks (wiring work and moving the compass) require parts, certified maintenance personnel and verification testing, generating variable cost and downtime (Requirement 1; Requirement 2)."],"plain_english_summary":"What this directive does mechanically:\n\n- Requires modification of wiring to the pitot heaters, compass lighting and radio system where needed to reduce magnetic interference to acceptable levels (Requirement 1). (Requirement 1)\n- Requires removal of the magnetic compass from the windshield frame and relocation of the compass to the flare shield. (Requirement 2)\n- Requires compliance immediately — the work is to be done \"forthwith.\" (Compliance)\n\nWho it applies to:\n\n- Applies to all Piaggio P166 series aeroplanes in which the maximum compass deviation and/or change in deviation caused by electrical interference exceeds the limits set out in ANO 108.2.7. Determination that the aircraft is within scope depends on measuring compass deviation against that ANO standard. (Applicability)\n\nWhy it matters and how it works in practice:\n\n- The directive is framed to reduce electrical interference that affects the magnetic compass. The measure it prescribes is physical: change wiring where needed and relocate the compass to a different mounting point. (Requirement 1; Requirement 2)\n- Who pays: aircraft owners/operators must pay for the wiring work, compass relocation, any associated parts and labour, and for the aircraft downtime while the work and any testing are carried out. (Applicability; Requirement 1; Requirement 2)\n- Who decides: the directive is issued under the Civil Aviation Safety Authority schedule of airworthiness directives; whether an individual aircraft falls within the directive depends on measured compass deviation exceeding the ANO 108.2.7 limits. (Applicability)\n- Behaviour change required: operators must test or otherwise establish whether compass deviation exceeds the ANO limits, and if so, arrange and complete the specified modifications and relocation immediately. (Applicability; Requirement 1; Requirement 2; Compliance)\n\nCosts, incentives and trade-offs to note (grounded in the directive text):\n\n- Direct cost and downtime: the directive creates a compliance cost (parts, technician labour, testing, and aircraft out-of-service time) borne by operators/owners. (Requirement 1; Requirement 2; Compliance)\n- Supplier effects: maintenance and avionics providers are the likely recipients of the work; the directive increases demand for such services for affected P166 aircraft. (Requirement 1; Requirement 2)\n- Measurement and implementation risk: the directive refers to deviation \"exceeding the limits\" in ANO 108.2.7; determining applicability requires deviation measurement against that standard. The wiring changes are specified only by function (reduce interference) and so will require technical judgement about what wiring actions are necessary and subsequent verification. (Applicability; Requirement 1)\n- Compliance burden and discretion: the directive requires work \"if necessary\" to reduce interference to acceptable limits, which gives operators and maintenance personnel a role in diagnosing the problem and deciding which wiring changes are needed; that technical discretion affects implementation complexity and verification steps. (Requirement 1)\n- Opportunity cost: immediate compliance (\"forthwith\") means operators must prioritise the corrective work, possibly displacing other maintenance or operational activities. (Compliance)\n\nLimited effects not specified in the text:\n\n- The directive does not set out detailed technical procedures, costs, or service instructions; it identifies the items to be modified and the new compass location, and relies on technical action to achieve compliance. (Requirement 1; Requirement 2)\n\nSource citations: Applicability; Requirement 1; Requirement 2; Compliance."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific technical defect in a specific aircraft series. It has not expanded beyond its original purpose of correcting magnetic compass interference in Piaggio P166 aircraft."},"complexity_factors":["Very short document (approximately 150 words of substantive content)","Only 2 specific technical requirements","Single defined term reference (ANO 108.2.7 — an external aviation navigation order)","No nested conditional logic or exceptions","Straightforward applicability test (maximum compass deviation exceeds prescribed limits)","Simple binary compliance requirement (do it immediately)"],"plain_english_summary":"This is an **Airworthiness Directive** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\nIt requires owners and operators of **Piaggio P166 series aeroplanes** (a type of Italian-made twin-engine aircraft) to fix a problem with their **magnetic compass** — the instrument that shows which direction the plane is heading.\n\n**The problem:**\nIn some of these aircraft, the compass readings are being thrown off by electrical interference from other systems (like pitot tube heaters, compass lighting, and radios). The interference is bad enough that it exceeds safety limits set out in another aviation rule (ANO 108.2.7).\n\n**What must be done:**\n1. **Rewire** the electrical systems causing the interference (pitot heaters, compass lighting, and radio systems) to reduce the magnetic interference to safe levels.\n2. **Move the compass** from its current location on the windshield frame to a new location on the \"flare shield\" (a different part of the aircraft structure).\n\n**Who it affects:**\nAnyone who owns or operates a Piaggio P166 aircraft where the compass deviation problem exists.\n\n**When it must be done:**\n**Immediately** (\"Forthwith\" in aviation-speak means right away — don't wait for the next scheduled maintenance).\n\n**Why it matters:**\nA faulty compass can give pilots wrong directional information, which is extremely dangerous — especially in poor visibility or when flying without modern GPS navigation. This directive prevents potential accidents caused by navigational errors."}},"importantCases":[],"_links":{"self":"/api/acts/ad-p166-27-magnetic-compass-installation-modification","history":"/api/acts/ad-p166-27-magnetic-compass-installation-modification/history","analysis":"/api/acts/ad-p166-27-magnetic-compass-installation-modification/analysis","conflicts":"/api/acts/ad-p166-27-magnetic-compass-installation-modification/conflicts","importantCases":"/api/acts/ad-p166-27-magnetic-compass-installation-modification/important-cases","documents":"/api/acts/ad-p166-27-magnetic-compass-installation-modification/documents"}}