{"id":"F2006B02807","name":"AD/B737/103 - Rudder Power Control Unit Replacement","slug":"ad-b737-103-rudder-power-control-unit-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42149,"registerId":"commonwealth-F2006B02807-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/103 - Rudder Power Control Unit Replacement","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nBoeing 737 Series Aeroplanes\n\nAD/B737/103 Rudder Power Control Unit Replacement 6/97\n\nDM\n\nApplicability: Model 737 series aeroplanes, having a main rudder power control unit (PCU) that is identified in Boeing Service Letter 737-SL-27-112-B, dated February 6, 1997, certificated in any category.\n\nRequirement: To prevent cracking and seizing of the internal summing lever assembly bearing of the main rudder power control unit (PCU), remove the main rudder PCU and replace with a serviceable unit in accordance with Boeing Service Letter 737-SL-27-112-B dated February 6, 1997.\n\nNote: FAA AD 97-05-10 refers.\n\nCompliance: Requirement to be completed within 90 days of the effective date of this Directive.\n\nThis Airworthiness Directive becomes effective on 1 April 1997.\n\nBackground: The FAA has received a report of cracking of the internal summing lever of the main rudder PCU on a model 737 airplane. Investigation showed that a Hi-Lock bolt had been installed in the lever assembly by a repair station instead of the correct specification bolt (Boeing Part No. 66-22749-1). The larger bolt radius of the Hi Lock bolt in the shoulder to shank transition area was such as to create an interference fit with the bearing that caused the inner race of the bearing to crack. Such cracking, if not detected and corrected could lead to seizure of the bearing and possible uncommanded rudder movement. This Directive removes from service all main rudder PCUs which could possibly have had an incorrect bolt fitted.\n\nA separate directive has been raised to address the second part of the FAA AD 97-05- 10 which is the on-going inspection of all main rudder PCUs prior to fitment to an aircraft.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The Directive removes from service all main rudder PCUs that could possibly have an incorrect bolt fitted, consistent with the FAA report and referenced FAA AD. It does not expand applicability beyond the PCUs identified in Boeing Service Letter 737-SL-27-112-B; a separate directive addresses the on‑going inspection requirement prior to fitment (Background; Requirement; Applicability)."},"complexity_factors":["Technical specificity: applies only to main rudder PCUs identified in Boeing Service Letter 737-SL-27-112-B (Applicability; Requirement).","Mandatory hardware replacement within a fixed 90‑day window creates logistical, parts‑supply and aircraft downtime costs for operators (Compliance).","Reliance on external documents and actions (Boeing Service Letter; FAA AD 97-05-10) adds compliance steps and cross‑jurisdictional references (Requirement; Note).","Safety‑critical maintenance action requiring qualified maintenance facilities to remove and fit serviceable PCUs (Requirement; Background).","Split obligations: a separate directive covers pre‑fitment inspections, so operators must track multiple instruments to remain compliant (Background).","Enforcement under Civil Aviation Regulations Part 39 gives regulatory backing but does not itself specify penalties or supply arrangements (heading; schedule text)."],"plain_english_summary":"This directive requires operators of Boeing 737s fitted with main rudder power control units (PCUs) specified in Boeing Service Letter 737-SL-27-112-B to remove those PCUs and replace them with serviceable units within 90 days. It addresses a reported incorrect bolt fit that can crack a bearing and cause possible uncommanded rudder movement. Aircraft operators bear the cost of replacement and must change maintenance and parts‑sourcing practices; the Civil Aviation Safety Authority enforces compliance."},"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":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow safety directive targeting a specific mechanical defect in a specific aircraft part. The scope remains tightly focused on the original safety concern — replacement of suspect rudder PCUs on Boeing 737s. The reference to a 'separate directive' for ongoing inspections actually preserves the narrow scope by splitting distinct requirements into separate instruments."},"complexity_factors":["Single, specific mechanical action required (remove and replace one component)","Only one defined term of note ('serviceable unit' implied by reference to Boeing documentation)","No nested exceptions or conditional logic — applies to all listed aircraft without exemptions","Clear 90-day compliance deadline with no alternative methods or phased implementation","Short document (approximately 250 words) with straightforward structure: applicability, requirement, compliance, background","Single cross-reference to FAA AD 97-05-10 for context only, not for operational requirements"],"plain_english_summary":"This CASA Airworthiness Directive mandates removal and replacement of certain Boeing 737 main rudder Power Control Units (PCUs) within 90 days of 1 April 1997. It targets PCUs listed in Boeing Service Letter 737-SL-27-112-B.\n\nA wrong bolt used in past repairs can crack the PCU bearing and cause uncommanded rudder movement, risking loss of control; affected operators must install serviceable replacements to remain legal to fly."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-103-rudder-power-control-unit-replacement","history":"/api/acts/ad-b737-103-rudder-power-control-unit-replacement/history","analysis":"/api/acts/ad-b737-103-rudder-power-control-unit-replacement/analysis","conflicts":"/api/acts/ad-b737-103-rudder-power-control-unit-replacement/conflicts","importantCases":"/api/acts/ad-b737-103-rudder-power-control-unit-replacement/important-cases","documents":"/api/acts/ad-b737-103-rudder-power-control-unit-replacement/documents"}}