{"id":"F2006L00745","name":"AD/B737/229 Amdt 1 - Lavatory Drain System","slug":"ad-b737-229-amdt-1-lavatory-drain-system","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":136768,"registerId":"commonwealth-F2006L00745-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 737 Series Aeroplanes","sectionType":"division","heading":"Boeing 737 Series Aeroplanes","content":"### Boeing 737 Series Aeroplanes\n\n| AD/B737/229 Amdt 1 | Lavatory Drain System | 4/2006 |\n| ------------------ | --------------------- | ------ |\n\n| Applicability: | Boeing Model 737 -100, -200, -300, -400 and -500 series aeroplanes.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Action in accordance with the instructions as detailed in FAA AD 2004-06-18.Note 1: FAA AD 2004-06-18 Amdt 39-13544 refers which supersedes FAA AD89-11-03 Amdt 39-6223.Note 2: This Directive supersedes AD/B737/25 Amdt 1.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |\n| Compliance:    | As detailed in the compliance section of FAA AD 2004-06-18 with a revised effective date of 13 April 2006.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |\n|                | This Amendment becomes effective on 13 April 2006.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |\n| Background:    | The requirement to carry out certain checks of the lavatory drain system was originally detailed in AD/B737/25; however the content of those requirements has changed significantly. Subsequently this Directive has been issued to reflect those requirements. The requirements previously detailed are no longer considered satisfactory to prevent the build up of “blue ice” and the problems associated with the dislodgment of the “blue ice” from the aeroplane.This Directive requires in addition to the existing leak checks, periodic replacement of the seals, replacement of “donut valves” with other valves and a revision to the leak check interval.This Amendment changes the title by removing “Forward” from the title of the AD with no change to the technical content. This is to reduce confusion as to which lavatory drain systems are affected.The original issue of this AD became effective on 28 October 2004. |\n\n![](image.001.png)  \nJayaprakashan Ambali  \nDelegate of the Civil Aviation Safety Authority\n\n21 February 2006","sortOrder":0},{"sectionNumber":"AD/B737/229 Amdt 1","sectionType":"part","heading":"AD/B737/229 Amdt 1","content":"## AD/B737/229 Amdt 1","sortOrder":1},{"sectionNumber":"Lavatory Drain System","sectionType":"part","heading":"Lavatory Drain System","content":"## Lavatory Drain System","sortOrder":2},{"sectionNumber":"4/2006","sectionType":"part","heading":"4/2006","content":"## 4/2006","sortOrder":3}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Scope has expanded from the earlier AD/B737/25 requirements. The new directive not only keeps leak checks but adds periodic seal replacement, requires replacement of “donut” valves with alternative valves, and revises leak‑check intervals to address continued risk of “blue ice”. The title change (removing “Forward”) does not alter technical scope."},"complexity_factors":["Cross-reference to external instrument (FAA AD 2004-06-18) creates dependency on foreign regulatory text for detailed requirements","Applies to multiple 737 series models, requiring fleet-wide planning and parts compatibility checks","Mandates both inspection regime changes (revised leak-check intervals) and hardware replacements (seals and valve swaps), increasing maintenance scope","Operational disruption and scheduling complexity from periodic replacements and inspections (aircraft downtime and line maintenance coordination)","Supply/parts availability and sourcing for replacement valves and seals affect implementation timing","Record-keeping and compliance tracking to demonstrate adherence to revised intervals and replacements","Supersession of prior AD requires transitional management of previously compliant configurations"],"plain_english_summary":"This airworthiness directive requires operators of Boeing 737-100/200/300/400/500 series to follow FAA AD 2004-06-18: carry out lavatory drain leak checks, periodically replace seals, replace “donut” valves with other valves, and use revised leak‑check intervals to reduce the risk of dislodged “blue ice”. Airlines and maintenance providers pay for parts and labour and must schedule the work to meet the revised compliance date. The directive supersedes an earlier AD and removes “Forward” from the title without changing technical effect."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This amendment represents a minor administrative clarification (removing \"Forward\" from the title) with no change to technical scope. The underlying directive maintains its original narrow purpose: regulating lavatory drain maintenance on specific Boeing 737 variants. The substantive scope was established in the original October 2004 issue and this amendment does not expand it."},"complexity_factors":["Short, single-purpose directive (approximately 300 words of substantive content)","Only 2 defined terms implicitly referenced (FAA AD numbers treated as external standards)","Heavy reliance on external document (FAA AD 2004-06-18) — actual technical requirements not reproduced in full","Simple conditional structure: applicability test → compliance requirement → reference to external standard","No nested exceptions or complex logical operators","Clear, linear compliance timeline (single effective date)","Minimal cross-referencing (only 2 superseded directives noted)"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections and maintenance of lavatory drain systems on Boeing 737-100/200/300/400/500 aircraft to prevent \"blue ice\" (frozen sewage/disinfectant) from forming and falling off in flight. It requires operators to follow the FAA’s AD procedures for leak checks, seal and valve replacements, and shorter inspection intervals.\n\nThe update removes \"Forward\" from the title to clarify all lavatory drain systems are covered; technical requirements remain unchanged."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-229-amdt-1-lavatory-drain-system","history":"/api/acts/ad-b737-229-amdt-1-lavatory-drain-system/history","analysis":"/api/acts/ad-b737-229-amdt-1-lavatory-drain-system/analysis","conflicts":"/api/acts/ad-b737-229-amdt-1-lavatory-drain-system/conflicts","importantCases":"/api/acts/ad-b737-229-amdt-1-lavatory-drain-system/important-cases","documents":"/api/acts/ad-b737-229-amdt-1-lavatory-drain-system/documents"}}