{"id":"F2005L00838","name":"AD/B737/185 Amdt 2 - Airframe Limit Cycle Oscillation","slug":"ad-b737-185-amdt-2-airframe-limit-cycle-oscillation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":113172,"registerId":"commonwealth-F2005L00838-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/B737/185 Amdt 2 | Airframe Limit Cycle Oscillation | 5/2005 |\n| ------------------ | -------------------------------- | ------ |\n\n| Applicability: | All Model 737-600, -700, -700BBJ, -700C, and -800 series aircraft, with line numbers up to and including 1174.Note 1: The FAA has approved an alternate method of compliance to the cleaning, modification, and AFM requirements of paragraphs (a) through (h) of FAA AD2002- 08-20 for line numbers 1175 and subsequent (refer FAA Letter 120S-02-683).                                                                                                                                                                                                                                                                                                                                    |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Action in accordance with the technical requirements of FAA AD 2002-08-20 Amdt 39-12732.The technical requirements of the Requirement document include revisions of the Limitations and Non-Normal Procedures sections of the Aircraft Flight Manual, and may be accomplished by inserting a copy of FAA AD 2002-08-20 into the specified Aircraft Flight Manual sections.Note 2: Boeing Alert Service Bulletin 737-55A1084 and Service Letter737-SL-12-017 refer.                                                                                                                                                                                                                          |\n| Compliance:    | As specified in the Requirement document, with a revised effective date of 5 June 2002.Compliance with paragraph (b) of FAA AD 2003-03-22 Amdt 39-13047 (CASA AD/B737/210 Amdt 1) is terminating action for this Airworthiness Directive.The compliance time remains unchanged by this issue.                                                                                                                                                                                                                                                                                                                                                                                               |\n|                | This Amendment becomes effective on 12 May 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |\n| Background:    | The FAA received reports of numerous incidents of severe airframe vibration, or limit cycle oscillation (LCO), in flight after the horizontal stabiliser had been de- iced/anti-iced on the ground. These events have been attributed to the accumulation of deicing/anti- icing fluid or other residue in the elevator balance panel cavities and on the external surfaces of the elevator tab. Fluid or residue accumulated in the balance bays, or foreign substances accumulated on the external surfaces of the elevator tab, in combination with normally recommended maximum operating airspeeds, can initiate LCO or flutter and result in loss of controllability of the aircraft. |\n\n|     | Amendment 1 was issued in response to the approval by the FAA of an alternate method of compliance for aircraft with the elevator and tab redesign, which was implemented on the production line at Line Number 1175.Amendment 2 is issued to identify that compliance with paragraph (b) of FAA AD 2003-03-33 (CASA AD/B737/210 Amdt 1) is considered terminating action for this Airworthiness Directive.The original issue of this Airworthiness Directive became effective on 5 June 2002. |\n| --- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n31 March 2005","sortOrder":0},{"sectionNumber":"AD/B737/185 Amdt 2","sectionType":"part","heading":"AD/B737/185 Amdt 2","content":"## AD/B737/185 Amdt 2","sortOrder":1},{"sectionNumber":"Airframe Limit Cycle Oscillation","sectionType":"part","heading":"Airframe Limit Cycle Oscillation","content":"## Airframe Limit Cycle Oscillation","sortOrder":2},{"sectionNumber":"5/2005","sectionType":"part","heading":"5/2005","content":"## 5/2005","sortOrder":3}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This amendment remains tightly scoped to its original purpose: addressing the specific airframe vibration risk caused by de-icing fluid accumulation in Boeing 737 elevator systems. Amendment 2 does not expand the substantive scope; it merely clarifies the relationship with another directive (allowing terminating action via AD/B737/210 Amdt 1). The applicability (specific models and line numbers) and core technical requirements remain unchanged from the original 2002 issue."},"complexity_factors":["Heavy reliance on external documents: the directive incorporates by reference an FAA AD (2002-08-20) and mentions multiple other documents (FAA AD 2003-03-22, Boeing Service Bulletin 737-55A1084, Service Letter 737-SL-12-017) without reproducing their contents","Conditional applicability based on production line numbers (up to and including 1174) with explicit exemption for subsequent line numbers","Cross-referencing termination condition — compliance with paragraph (b) of a different AD (CASA AD/B737/210 Amdt 1) terminates obligations under this directive","Multiple amendment history layers (original issue 2002, Amendment 1 for alternate compliance method, Amendment 2 for terminating action clarification)","Technical aviation terminology requiring domain knowledge (limit cycle oscillation, flutter, elevator balance panel cavities, line numbers)"],"plain_english_summary":"This AD requires operators of specified Boeing 737-600/-700/-700BBJ/-700C/-800 aircraft (built up to line number 1174) to follow FAA AD 2002-08-20 and update the Aircraft Flight Manual to prevent serious flight control vibrations caused by de-icing fluid residue in the tail that can lead to limit cycle oscillation or flutter. Amendment 2 clarifies that compliance with CASA AD/B737/210 Amdt 1 also satisfies this AD, letting one approved fix cover both requirements."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Amendment 2 does not broaden model or line-number applicability but clarifies compliance pathways: it recognises an alternate compliance method for post-line‑1174 production aircraft and declares that complying with a paragraph of a later FAA AD is terminating action for this AD. In practice this narrows ongoing obligations for aircraft already modified under that later FAA AD while leaving the original applicability intact."},"complexity_factors":["Cross-reference to FAA AD 2002-08-20 as the substantive requirement (external normative reference adds interpretive steps).","Applicability limited by aircraft model and line-number range (serial/line-number cut-off introduces conditional scope).","Incorporation of terminating-action language referencing another FAA AD paragraph (links compliance status to separate instrument).","Technical compliance requires both AFM revisions and physical cleaning/modification work (mix of documentation and maintenance tasks).","Alternate method of compliance approved for later line numbers (differentiated compliance pathways increases operational complexity).","Specified compliance and effective dates create scheduling and operational-availability constraints for operators."],"plain_english_summary":"This Airworthiness Directive requires operators of specified Boeing 737-600/700/700BBJ/700C/800 aircraft (line numbers up to 1174) to implement the technical measures in FAA AD 2002-08-20: revise Aircraft Flight Manual limitations/non‑normal procedures and carry out cleaning or modifications to prevent accumulation of deicing/anti‑icing fluid that can cause elevator limit cycle oscillation (LCO). It also recognises alternate compliance for later-production aircraft and that compliance with a later FAA AD paragraph is terminating action. Airlines and maintenance providers pay for the work and face related downtime and procedural changes."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-185-amdt-2-airframe-limit-cycle-oscillation","history":"/api/acts/ad-b737-185-amdt-2-airframe-limit-cycle-oscillation/history","analysis":"/api/acts/ad-b737-185-amdt-2-airframe-limit-cycle-oscillation/analysis","conflicts":"/api/acts/ad-b737-185-amdt-2-airframe-limit-cycle-oscillation/conflicts","importantCases":"/api/acts/ad-b737-185-amdt-2-airframe-limit-cycle-oscillation/important-cases","documents":"/api/acts/ad-b737-185-amdt-2-airframe-limit-cycle-oscillation/documents"}}