{"id":"F2006B02812","name":"AD/B737/108 - Rudder Standby Power Control Unit - Bearing Replacement","slug":"ad-b737-108-rudder-standby-power-control-unit-bearing-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42154,"registerId":"commonwealth-F2006B02812-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/108 - Rudder Standby Power Control Unit - Bearing Replacement","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)  Boeing 737 Series Aeroplanes\n\n \n\n# AD/B737/108 Rudder Standby Power Control Unit - Bearing Replacement\n\nApplicability: Model 737-100,-200,-300,-400, and 500 series aeroplanes.\n\n# 4/98\n\n \n\nRequirement: 1. Perform an inspection to detect galling on the input shaft in accordance with FAA AD 97-26-01.\n\n \n\n2. Replace the Rudder Standby Power Control Unit input shaft bearing on all applicable aircraft in accordance with Boeing Service Letter 737-SL-27-113 dated 19 February 1997 and Dowty Aerospace Service Bulletin 1150-27-04 dated\n\n1 November 1996.\n\n \n\nNote: FAA AD 97-26-01 Amdt 36-10244 refers.\n\n \n\nCompliance:  1. Within 18 months or 4,500 hours time-in-service after the effective date of this directive whichever occurs later and thereafter every 18 months or 4,500 hours time-in-service if requirement 2 has not been accomplished.\n\n \n\n2. Within 3 years of the effective date of this Directive.\n\n \n\nThis airworthiness directive becomes effective on 26 March 1998.\n\n \n\nBackground: The current Standby PCU input bearing utilises a lapped journal bearing. The design has been shown to gall in service (galling is defined as metal transfer from one surface to another of two similar materials). Galling in the bearing can increase the force required to move the input lever to the standby PCU. At high enough force levels, the galling can cause yaw damper inputs to backdrive the rudder pedals. This can also lead to increased yaw damper authority. The new lever installation is designed with rolling element bearings to eliminate the galling potential. Installation of this design improvement is considered terminating action for FAA AD 97-26-01. This AD also includes a lever force check and an inspection that must be accomplished at certain intervals until the bearing is incorporated.\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":4,"scope_assessment":{"changed":true,"description":"This AD adds a mandatory replacement of the Rudder Standby PCU input shaft bearing across the listed 737 models and requires recurring inspections until the bearing is replaced; once replacement is installed it serves as terminating action for FAA AD 97-26-01. In practical terms the directive converts a recurring inspection burden into a fleet-wide modification obligation, with separate short-term inspection intervals and a longer one-time compliance deadline (Requirement 1; Requirement 2; Compliance 1; Compliance 2; Background)."},"complexity_factors":["Technical maintenance action requiring replacement of a specific component (Rudder Standby PCU input shaft bearing) per manufacturer and supplier service documents (Boeing Service Letter 737-SL-27-113 and Dowty Aerospace Service Bulletin 1150-27-04) (Requirement 2).","Mandatory inspection to detect galling with a specified periodicity until the terminating modification is accomplished (every 18 months or 4,500 hours) (Requirement 1; Compliance 1).","Two different compliance timeframes to track: recurring inspection interval (18 months/4,500 hours) and a one‑time replacement deadline (within 3 years) (Compliance 1 and Compliance 2).","Cross-reference to FAA AD 97-26-01 as the related regulatory instrument and to its amendment (Note), including that the replacement is 'terminating action' for that FAA AD (Background; Note).","Applicability limited to specific airframe models (737-100/200/300/400/500), requiring fleet-level compliance tracking by operators (Applicability).","Operational consequence described in technical terms (galling, increased force, backdrive of rudder pedals, increased yaw damper authority), which requires judgment and measurement in inspections and lever force checks (Background).","Dependence on external service documents for the detailed workscope increases administrative coordination between operators, manufacturers and suppliers (Requirement 2 references Boeing/Dowty service documents).","Effective date and compliance counting (effective date 26 March 1998) require historical scheduling for operators to determine deadlines (effective date statement)."],"plain_english_summary":"Requires inspection for galling and replacement of the Rudder Standby Power Control Unit input‑shaft bearing on Boeing 737‑100, ‑200, ‑300, ‑400 and ‑500 series aeroplanes; inspections recur every 18 months or 4,500 flight hours until the bearing is replaced, and full replacement must be done within 3 years. This responds to reported galling that can increase control forces and allow yaw damper inputs to backdrive the rudder pedals; installing rolling‑element bearings removes the galling risk and terminates FAA AD 97‑26‑01."},"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":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific bearing defect in specific Boeing 737 models. There is no evidence of scope creep; it remains tightly focused on the rudder standby power control unit bearing replacement as originally intended."},"complexity_factors":["Single, specific mechanical component addressed (Rudder Standby PCU bearing)","Only 2 substantive requirements (inspection and replacement)","Clear, fixed compliance deadlines (18 months/4,500 hours and 3 years)","Minimal cross-referencing (only references one FAA AD and two manufacturer documents)","No nested exceptions or conditional logic — straightforward applicability to specific 737 models","Short document (approximately 250 words of substantive content)","Only 3 defined/model terms (737-100 through -500 series)"],"plain_english_summary":"Australia's Civil Aviation Safety Authority has issued a mandatory AD for Boeing 737-100/200/300/400/500 series requiring operators to inspect and ultimately replace a faulty bearing in the Rudder Standby Power Control Unit. The bearing can gall, stiffening rudder pedals and causing the yaw damper to push back against pilots, risking loss of control. The measure prevents this known failure by recurring inspections until installation of an improved rolling‑element bearing."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-108-rudder-standby-power-control-unit-bearing-replacement","history":"/api/acts/ad-b737-108-rudder-standby-power-control-unit-bearing-replacement/history","analysis":"/api/acts/ad-b737-108-rudder-standby-power-control-unit-bearing-replacement/analysis","conflicts":"/api/acts/ad-b737-108-rudder-standby-power-control-unit-bearing-replacement/conflicts","importantCases":"/api/acts/ad-b737-108-rudder-standby-power-control-unit-bearing-replacement/important-cases","documents":"/api/acts/ad-b737-108-rudder-standby-power-control-unit-bearing-replacement/documents"}}