{"id":"F2006B02999","name":"AD/B737/99 - Main Rudder Power Control Unit (PCU)","slug":"ad-b737-99-main-rudder-power-control-unit-pcu","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42358,"registerId":"commonwealth-F2006B02999-current","compilationNumber":null,"startDate":"2026-04-01","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/99 - Main Rudder Power Control Unit (PCU)","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/B737/99 Main Rudder Power Control Unit (PCU) 1/97\n\nApplicability: All Boeing 737 models.\n\nRequirement: 1. Perform a test on the main rudder power control unit (PCU) in accordance with Boeing Alert Service Bulletin (ASB) 737-27A-1202 dated 01 November 1996 to verify proper operation.\n\n2. If, as a result of Requirement 1, the test gives unusual results as described in the referenced ASB, replace the main rudder PCU and perform the test of Requirement 1.\n\nNote: FAA AD T96-23-51 refers.\n\nCompliance: 1. For Requirement 1, prior to 14 November 1996 and there after at intervals not to exceed 250 hours time in service.\n\n2. For Requirement 2, before further flight.\n\nBackground: Recent tests on the main rudder PCU conducted by Boeing demonstrated a potential failure scenario that was previously unknown. These tests revealed that rudder pedal can cause deformation in the linkage leading to the primary and secondary slides of the servo valve of the main rudder PCU if the secondary slide of the PCU jams in certain positions. This situation could result in rudder motion in the opposite direction of the rudder command.","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1200},"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This directive maintains its original narrow scope addressing the specific rudder PCU failure mode discovered during Boeing testing. No expansion beyond the original safety-critical maintenance requirement is evident."},"complexity_factors":["Single, clearly defined applicability (all Boeing 737 models)","Only two operational requirements with straightforward conditional logic","Minimal cross-referencing (one Boeing Service Bulletin and one FAA AD reference)","No defined terms section or nested legislative references","Clear, unambiguous compliance deadlines"],"plain_english_summary":"This mandatory Airworthiness Directive requires all Boeing 737 owners/operators to perform Boeing’s specified test of the main rudder Power Control Unit at the first opportunity and then every 250 flight hours, and to replace any unit that shows abnormal results before the next flight. It addresses a discovered internal jam that can make the rudder deflect opposite pilot input, posing a serious loss-of-control risk."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-99-main-rudder-power-control-unit-pcu","history":"/api/acts/ad-b737-99-main-rudder-power-control-unit-pcu/history","analysis":"/api/acts/ad-b737-99-main-rudder-power-control-unit-pcu/analysis","conflicts":"/api/acts/ad-b737-99-main-rudder-power-control-unit-pcu/conflicts","importantCases":"/api/acts/ad-b737-99-main-rudder-power-control-unit-pcu/important-cases","documents":"/api/acts/ad-b737-99-main-rudder-power-control-unit-pcu/documents"}}