{"id":"F2008L02555","name":"AD/B747/299 Amdt 2 - Yaw Damper Actuator","slug":"ad-b747-299-amdt-2-yaw-damper-actuator","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":74554,"registerId":"commonwealth-F2008L02555-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 747 Series Aeroplanes","sectionType":"division","heading":"Boeing 747 Series Aeroplanes","content":"### Boeing 747 Series Aeroplanes\n\n| AD/B747/299 Amdt 2 | Yaw Damper Actuator | 8/2008 |\n| ------------------ | ------------------- | ------ |\n\n| Applicability: | Model 747-400, -400D, and -400F series aircraft, as identified in Boeing Alert Service Bulletin 747-27A2479, dated 8 November 2007, or later FAA approved revision.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement:   | Action in accordance with the technical requirements of FAA AD 2008-13-03 Amdt 39-15566.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |\n| Compliance:    | As specified in the Requirement document, with a revised effective date of31 July 2008.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |\n|                | This Amendment becomes effective on 31 July 2008.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |\n| Background:    | The original issue of this Airworthiness Directive required an ultrasonic inspection of the yaw damper portion of the upper and lower rudder power control modules main manifold for cracking. Such cracking, unless detected and corrected, could result in an uncommanded left rudder hardover, consequent increased pilot workload, and possible runway departure upon landing.Amendment 1 expanded the applicability and discontinued certain requirements of the previous Airworthiness Directive.Amendment 2 is issued in response to a new FAA AD, which was prompted by additional reports of failure or cracking of the power control module manifold in the area of the yaw damper cavity endcap at intervals well below the initial inspection threshold of the existing AD. This amendment limits applicability, reduces initial inspection threshold and repetitive interval, and requires installation of a secondary retention device for the yaw damper modulating piston. |\n\n|     | The original issue of this Airworthiness Directive became effective on22 January 2004. |\n| --- | -------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n20 June 2008","sortOrder":0},{"sectionNumber":"AD/B747/299 Amdt 2","sectionType":"part","heading":"AD/B747/299 Amdt 2","content":"## AD/B747/299 Amdt 2","sortOrder":1},{"sectionNumber":"Yaw Damper Actuator","sectionType":"part","heading":"Yaw Damper Actuator","content":"## Yaw Damper Actuator","sortOrder":2},{"sectionNumber":"8/2008","sectionType":"part","heading":"8/2008","content":"## 8/2008","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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original 2004 directive required ultrasonic inspections only. Amendment 1 expanded which aircraft were covered. Amendment 2 has narrowed applicability back down (limiting which aircraft are affected) but significantly deepened the technical requirements — adding mandatory installation of secondary retention devices and shortening inspection intervals. The scope has shifted from 'inspect and monitor' to 'inspect more frequently AND physically modify the aircraft with new safety hardware'."},"complexity_factors":["Short, single-purpose instrument (approximately 300 words)","Only 3 defined applicability criteria (specific Boeing 747 models)","Single cross-reference to external technical document (FAA AD 2008-13-03)","No nested conditional logic or exceptions within the instrument itself","Technical complexity is outsourced to referenced Boeing/FAA documents rather than contained in the instrument","Clear linear structure: Applicability → Requirement → Compliance → Background"],"plain_english_summary":"This CASA Airworthiness Directive mandates inspections and modifications to yaw damper actuators on specified Boeing 747-400 series aircraft after cracks were found in power control modules that can cause an uncommanded rudder \"hardover.\"  \n\nAmendment 2 tightens the requirements: it narrows applicability but requires earlier and more frequent ultrasonic inspections and installation of a secondary retention device to reduce loss-of-control risk during landing."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"Amendment 2 changes the original AD by limiting applicability to specific 747-400 variants, reducing the initial inspection threshold and repetitive intervals, and adding a mandatory secondary retention device installation for the yaw-damper modulating piston (as stated in the Background and Requirement). These adjustments alter which aircraft are covered and increase inspection/modification obligations for operators."},"complexity_factors":["External cross-references: requires strict compliance with FAA AD 2008-13-03 and Boeing Alert Service Bulletin 747-27A2479 (creates dependence on external technical documents).","Technical inspection method: mandates ultrasonic inspection of the power-control-module manifold (requires specialised equipment and skills).","Design modification requirement: compulsory installation of a secondary retention device for the yaw-damper modulating piston (parts procurement and modification planning).","Changed compliance parameters: reduced initial inspection threshold and shortened repetitive intervals increase operational impact and scheduling complexity.","Applicability adjustments: amendment both narrows and redefines which Model 747-400 variants are covered (requires careful fleet-by-fleet applicability checks).","Regulatory history and effective date: multiple amendments and an amended effective date (31 July 2008) require operators to reconcile prior AD obligations with the new requirements."],"plain_english_summary":"Requires operators of certain Boeing 747-400 family aircraft to perform more frequent ultrasonic inspections of the yaw-damper power-control-module manifold and to install a secondary retention device for the yaw-damper modulating piston, following FAA AD 2008-13-03 and Boeing Alert Service Bulletin 747-27A2479. Effective 31 July 2008. The amendment narrows which aircraft are covered, reduces initial and repeat inspection intervals after reports of manifold cracking, and places inspection and modification costs and scheduling obligations on aircraft operators."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-299-amdt-2-yaw-damper-actuator","history":"/api/acts/ad-b747-299-amdt-2-yaw-damper-actuator/history","analysis":"/api/acts/ad-b747-299-amdt-2-yaw-damper-actuator/analysis","conflicts":"/api/acts/ad-b747-299-amdt-2-yaw-damper-actuator/conflicts","importantCases":"/api/acts/ad-b747-299-amdt-2-yaw-damper-actuator/important-cases","documents":"/api/acts/ad-b747-299-amdt-2-yaw-damper-actuator/documents"}}