{"id":"F2006B11260","name":"AD/M20/9 - Rudder Drain Hole - Modification","slug":"ad-m20-9-rudder-drain-hole-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":57042,"registerId":"commonwealth-F2006B11260-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/M20/9 - Rudder Drain Hole - 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)  Mooney M20 Series Aeroplanes\n\n \n\nAD/M20/9 Rudder Drain Hole - Modification 9/67\n\nApplicability: All model M20F with S/Nos. 660003, 660004 and 670001 to 670030. Document:  Mooney SB No. M20-149.\n\nCompliance: Within 100 hours time in service after 7 September 1967.\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\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-issue airworthiness directive from 1967 addressing a specific manufacturing defect in a limited production run. It has not expanded beyond its original scope of requiring a rudder drain hole modification for 33 specific aircraft."},"complexity_factors":["Extremely short document (approximately 150 words)","Only 3 defined elements: applicability (specific serial numbers), reference document (Mooney SB M20-149), and compliance deadline","No cross-references to other legislation or regulations beyond the enabling authority (Civil Aviation Regulations 1998, Part 39)","Single unconditional requirement with clear deadline","No exceptions, exemptions, or conditional logic","Technical content limited to referencing external manufacturer service bulletin"],"plain_english_summary":"**What this is:** This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) under the Civil Aviation Regulations 1998.\n\n**What it requires:** Owners and operators of specific **Mooney M20F aircraft** (serial numbers 660003, 660004, and 670001 through 670030) must modify the **rudder drain hole** according to Mooney Service Bulletin M20-149.\n\n**Why it matters:** The rudder is the part of the tail that steers the aircraft left and right. A drain hole allows water to escape from inside the rudder structure. If this hole is improperly designed or located, water can accumulate, causing corrosion (rust) or freezing at altitude — either of which could weaken the rudder or cause it to jam, potentially leading to loss of control.\n\n**Who must comply:** Anyone operating the affected aircraft must complete this modification within **100 hours of flight time** after 7 September 1967.\n\n**Key takeaway:** This is a one-time safety fix for a specific batch of 1966–1967 Mooney aircraft to prevent rudder failure due to water damage."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD, as written, prescribes a specific modification for a defined list of M20F serial numbers and sets a compliance deadline; there is no indication in the text that the scope has been altered from that stated requirement. The directive remains limited to those serial numbers and requires compliance per Mooney SB No. M20-149 within 100 hours after 7 September 1967. (Applicability; Document; Compliance)"},"complexity_factors":["Narrow and specific applicability (only particular M20F serial numbers) reduces scope complexity (Applicability).","Single required action (rudder drain-hole modification) keeps procedural complexity low (AD/M20/9).","Reliance on an external document (Mooney SB No. M20-149) for technical detail adds a layer of operational complexity because implementers must obtain and follow the SB (Document).","A short, absolute compliance window (100 hours after 7 September 1967) imposes scheduling pressure and increases practical compliance complexity (Compliance).","The AD does not state technical rationale or expected outcomes, requiring implementers/regulators to consult the SB or other sources for justification and technical specifics (AD/M20/9; Document)."],"plain_english_summary":"This Airworthiness Directive orders a rudder drain‑hole modification on specific Mooney M20F aeroplanes (serials 660003, 660004, 670001–670030) by following Mooney Service Bulletin M20‑149. Owners/operators of those aircraft must have the work done within 100 hours TIS after 7 September 1967, bearing the cost and arranging compliance to meet the regulator’s airworthiness requirement."}},"importantCases":[],"_links":{"self":"/api/acts/ad-m20-9-rudder-drain-hole-modification","history":"/api/acts/ad-m20-9-rudder-drain-hole-modification/history","analysis":"/api/acts/ad-m20-9-rudder-drain-hole-modification/analysis","conflicts":"/api/acts/ad-m20-9-rudder-drain-hole-modification/conflicts","importantCases":"/api/acts/ad-m20-9-rudder-drain-hole-modification/important-cases","documents":"/api/acts/ad-m20-9-rudder-drain-hole-modification/documents"}}