{"id":"F2006B06563","name":"AD/RB211/33 - High Speed Gearbox and Dedicated Generator - Modifications","slug":"ad-rb211-33-high-speed-gearbox-and-dedicated-generator-modifications","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":48314,"registerId":"commonwealth-F2006B06563-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/RB211/33 - High Speed Gearbox and Dedicated Generator - Modifications","content":"![](image.001.png)\n\nAIRWORTHINESS DIRECTIVE\n\n![](image.001.png)  \n\nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CASR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n![](image.001.png)  \n\nRolls Royce Turbine Engines \\- RB211 Series\n\nAD/RB211/33 High Speed Gearbox and Dedicated\n\nGenerator \\- Modifications\n\n  \n10/2003\n\nDM\n\nApplicability: Rolls Royce RB211- 524G2, 524G2-T, 524G3, 524G3-T, 524H, 524H2, 524H-T and\n\n524H2-T series engines installed on Boeing 747 and 767 aeroplanes, as detailed in Rolls Royce Service Bulletin (SB) RB.211-72-E037 dated 26 March 2003.\n\nRequirement: 1. Modify the High Speed Gearbox Rear Housing and fittings in accordance with Rolls Royce SB RB.211-72-E037 dated 26 March 2003 on:\n\n    All RB211-524H-36 and 524H-T-36 series engines; and\n\n    b. All RB211 engines except 524H-36 and 524H-T-36 series engines.\n\n    2. As an alternative means of compliance with Requirement 1(a):\n\n    Carry out the actions required by Rolls Royce SB RB.211-73-D435 dated 6 July 2001; and\n\n    b. Carry out the actions required by Rolls Royce SB RB.211-72-E037 dated 26 March 2003\n\nNote 1: Requirement 2 offers an acceptable means of compliance (AMOC) by introducing a software modification in accordance with Rolls Royce SB RB.211-73- D435 to prevent uncommanded acceleration etc. in the event of erratic HP shaft signals. The incorporation of this software modification delays the need to comply with SB RB211-72-E037 and RB.211-73-C501 (a requirement contained in the body of SB RB211-72-E037 and Requirement 3 of this AD) until 31 December 2006.\n\n    3. Unless previously carried out in accordance with initial issue Rolls Royce SB RB.211-73-C501, dated 17 June 1998, or, Revision 1, dated 30 August 2000, modify Dedicated Generator Installation in accordance with Rolls Royce SB RB.211-73-C501, Revision 2, dated 19 June 2003.\n\nNote 2: CAA (UK) AD 004-03-2003 refers.\n\nRolls Royce Turbine Engines \\- RB211 Series\n\nAD/RB211/33 (continued)\n\nCompliance: For Requirement 1: (a) Prior to 31 December 2004.\n\n(b) Prior to 31 December 2008\\. For Requirement 2: (a) Prior to 31 October 2003.\n\n(b) Prior to 31 December 2006.\n\nFor Requirement 3: Prior to or concurrent with compliance with Requirement 1 or 2(b) as appropriate.\n\nThis Airworthiness Directive becomes effective on 6 August 2003.\n\nBackground: The dedicated generator rotor assembly has suffered a number of bearing failures due to the low fatigue life of the bearing material, resulting in possible oil loss and engine shut-down. Bearing failure can also lead to an erratic HP shaft speed signal being sent to the Full Authority Fuel Controller (FAFC) causing uncommanded engine acceleration with no throttle response, which could lead to uncontrolled thrust asymmetry during take-off or landing. The intention of this Directive is to introduce modifications to prevent the possibility of uncontrolled thrust asymmetry.\n\n![Signature of Jim Coyne Delegate of the Civil Aviation Safety Authority](image.002.png)  \n\nJim Coyne\n\nDelegate of the Civil Aviation Safety Authority 1 August 2003\n\n![](image.001.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 6 August 2003.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":false,"description":"The AD maintains the original safety scope: to eliminate bearing‑related failures and consequent erratic HP shaft signals on specified RB211‑524 engines by mandating gearbox and generator modifications or an interim software fix. It implements those corrective actions via specified Rolls‑Royce service bulletins and sets compliance deadlines; it does not expand applicability beyond the engine types and aeroplanes listed in the Applicability."},"complexity_factors":["Multiple engine variants listed in the Applicability (RB211‑524G2/G3/H series) increasing parts and fleet applicability.","Several interlocking Service Bulletins referenced (RB.211‑72‑E037, RB.211‑73‑D435, RB.211‑73‑C501) creating procedural and version dependencies.","Alternative Means of Compliance (AMOC) via software (Note 1) that defers physical modifications until later deadlines, requiring coordination between software and hardware actions.","Staggered compliance deadlines (2003, 2004, 2006, 2008) that require tracking different actions by date and by engine sub‑type.","Safety‑critical failure modes described in Background (bearing fatigue → oil loss/engine shutdown; erratic HP shaft signals → FAFC uncommanded acceleration) raise inspection, testing and certification burdens.","Cross‑reference to external regulator AD (CAA UK AD 004‑03‑2003) implies potential alignment or dependency on overseas approvals.","Requirement 3 must be done prior to or concurrent with Requirements 1 or 2(b), adding sequencing constraints."],"plain_english_summary":"This Airworthiness Directive requires physical modifications to the High Speed Gearbox rear housing/fittings and the Dedicated Generator installation on specified Rolls‑Royce RB211‑524 series engines fitted to Boeing 747 and 767 aeroplanes, and allows an alternative software modification as an interim compliance option. CASA’s delegate sets specific deadlines for these actions. Operators must carry out the prescribed service bulletin work or the software alternative to prevent bearing failures that can cause oil loss, engine shutdown or erratic HP shaft signals leading to uncommanded engine acceleration and thrust asymmetry."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD appears focused on its original safety purpose — addressing bearing failures in the dedicated generator and preventing uncommanded engine acceleration. The inclusion of an alternative compliance method (software patch as interim measure) is a standard regulatory flexibility mechanism rather than scope creep."},"complexity_factors":["Multiple compliance pathways with interdependent deadlines (Requirements 1, 2, and 3 with cross-referenced dates)","Nested applicability criteria distinguishing between RB211-524H-36/524H-T-36 series and all other RB211 engines","Reference to external technical documents (Rolls-Royce Service Bulletins) that are not reproduced in the AD itself","Conditional logic for Requirement 3 compliance ('unless previously carried out')","Cross-reference to UK aviation authority directive (CAA (UK) AD 004-03-2003)","Technical aviation terminology requiring specialised knowledge (e.g., 'Full Authority Fuel Controller', 'High Speed Gearbox Rear Housing')"],"plain_english_summary":"The Civil Aviation Safety Authority has issued a safety order after finding premature bearing failures in Rolls‑Royce RB211 dedicated generators on certain Boeing 747 and 767 engines. Failures can cause oil leaks that shut engines down or false speed signals that trigger uncommanded acceleration, risking asymmetric thrust during takeoff and landing.\n\nOperators must follow Rolls‑Royce technical instructions to modify the gearbox/generator—either by mandated hardware modifications by set deadlines or by installing an interim software patch to prevent false acceleration while awaiting the hardware fix."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-rb211-33-high-speed-gearbox-and-dedicated-generator-modifications","history":"/api/acts/ad-rb211-33-high-speed-gearbox-and-dedicated-generator-modifications/history","analysis":"/api/acts/ad-rb211-33-high-speed-gearbox-and-dedicated-generator-modifications/analysis","conflicts":"/api/acts/ad-rb211-33-high-speed-gearbox-and-dedicated-generator-modifications/conflicts","importantCases":"/api/acts/ad-rb211-33-high-speed-gearbox-and-dedicated-generator-modifications/important-cases","documents":"/api/acts/ad-rb211-33-high-speed-gearbox-and-dedicated-generator-modifications/documents"}}