{"id":"F2006B06551","name":"AD/RB211/20 - Fuel Flow Governor","slug":"ad-rb211-20-fuel-flow-governor","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":48271,"registerId":"commonwealth-F2006B06551-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/RB211/20 - Fuel Flow Governor","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nRolls Royce Turbine Engines \\- RB211 Series\n\nAD/RB211/20 Fuel Flow Governor 11/96\n\nApplicability: Rolls Royce RB211-535E4 series engines not incorporating Rolls Royce Service Bulletin RB. 211-73-B869 or RB.211-73-B876.\n\nRequirement: Incorporate a revised fuel flow governor (FFG) in accordance with Rolls Royce Service Bulletin RB.211-73-B869 or modify existing FFG in accordance with RB211-73-B876.\n\nNote: CAA (UK) AD 005-05-96 refers.\n\nCompliance: No later than 28 February 1997.\n\nNote: Incorporation of RR SB RB.211-73-B869 or RB211-73-B876 on both engines of an aircraft is terminating action on that particular aircraft for the AFM and MMEL amendments introduced by FAA AD 96-04-11 for Boeing 757 aircraft.\n\nThis Airworthiness Directive is effective from 10 October 1996.\n\nBackground: The manufacturer has advised that engine surge and run down may occur when an engine acceleration is commanded from low idle during aircraft descent at altitudes above 25,000'.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The Directive's scope is consistent with its stated purpose in the source text: it targets RB211-535E4 engines that have not incorporated the specified Rolls Royce service bulletins and requires incorporation or modification of the fuel flow governor to address the manufacturer-identified risk of engine surge/run down during a particular flight regime. The instrument does not expand or narrow applicability beyond that described (Applicability; Requirement; Background)."},"complexity_factors":["Technical specificity: Mandates work in accordance with specific Rolls Royce service bulletins (RB.211-73-B869 or RB.211-73-B876), requiring technical maintenance actions rather than simple administrative steps (Requirement).","Conditional applicability: Applies only to RB211-535E4 engines that do not already incorporate the listed service bulletins, so operators must verify engine configuration before acting (Applicability).","Deadline-driven compliance: A firm compliance date (28 February 1997) imposes scheduling and logistical constraints on operators and maintenance providers (Compliance).","Interactions with other airworthiness documents: References to FAA AD 96-04-11 (terminating action) and a CAA (UK) AD create cross-regulatory effects operators must understand (Note).","Operational-technical risk: The AD addresses a specific in-flight engine behaviour (surge/run down during acceleration from low idle above 25,000') which may require precise technical work to mitigate (Background)."],"plain_english_summary":"### What this directive does\n\nThis Airworthiness Directive (AD) requires operators of certain Rolls Royce RB211-535E4 series turbine engines to install or modify the engine's fuel flow governor (FFG). Specifically, engines that have not already had Rolls Royce Service Bulletin RB.211-73-B869 or RB.211-73-B876 incorporated must have the revised or modified FFG fitted in accordance with one of those service bulletins. (Requirement; Applicability)\n\n### Who it affects\n\n- Aircraft operators and maintenance organisations that operate or service aircraft equipped with Rolls Royce RB211-535E4 series engines that do not already incorporate the specified Rolls Royce service bulletins. (Applicability; Requirement)\n\n### Deadlines and legal status\n\n- The work must be completed no later than 28 February 1997. (Compliance)\n- The Directive is effective from 10 October 1996. (Effective date)\n\n### Why the change was ordered (as stated by the source)\n\n- The manufacturer advised that engine surge and run down may occur when an engine acceleration is commanded from low idle during aircraft descent at altitudes above 25,000 feet. The AD implements an FFG change to address that operational concern. (Background)\n\n### How it works mechanically and operationally\n\n- Operators must follow the technical instructions in Rolls Royce Service Bulletin RB.211-73-B869 (for replacement) or RB.211-73-B876 (for modification) to fit the revised or modified FFG. Compliance with one of those service bulletins satisfies the AD for the affected engines. (Requirement)\n- If both engines on an aircraft are modified or replaced in accordance with the service bulletins, that action also serves as a terminating action for certain Airplane Flight Manual (AFM) and Master Minimum Equipment List (MMEL) amendments introduced by FAA AD 96-04-11 for Boeing 757 aircraft. That means the AFM/MMEL changes required by that FAA AD no longer apply once both engines are modified as described. (Note)\n\n### Who pays, who decides, and what changes in behaviour\n\n- Who pays: Aircraft operators (or their maintenance providers) are responsible for the cost of parts, labour and any associated aircraft downtime required to incorporate the revised or modified FFG. (Requirement; Compliance)\n- Who decides: The Civil Aviation Safety Authority issued this AD under the Civil Aviation Regulations 1998 framework; operators decide how and when to schedule the mandated work so long as it is completed by the compliance date. (Header; Compliance)\n- Behaviour changes: Operators must schedule and carry out the FFG installation/modification per the specified service bulletin instructions by the stated deadline. Maintenance organisations must perform the modification in line with Rolls Royce's technical directions. Operators who complete the SB on both engines may remove the AFM/MMEL restrictions referenced. (Requirement; Note)\n\n### Costs, incentives, and implementation considerations\n\n- Direct costs and burdens: The AD creates a compliance cost for affected operators: acquiring parts, paying for labour, and allocating aircraft downtime to perform the work. (Requirement; Compliance)\n- Incentive structure: Completing the SBs on both engines removes the AFM/MMEL amendments imposed by an FAA AD for Boeing 757s, which may provide an operational benefit (fewer operational limitations/paperwork) that partially offsets the modification costs. (Note)\n- Implementation risks and compliance burden: Correct technical execution is required to achieve the intended mitigation of surge/run down; operators depend on Rolls Royce service bulletin instructions and competent maintenance actions to do so. Timing and parts availability could affect scheduling before the compliance date. (Requirement; Background; Compliance)\n\n### Cross-references and regulatory interaction\n\n- The AD cites a related United Kingdom CAA AD and notes interaction with an FAA AD (FAA AD 96-04-11) for Boeing 757 aircraft — operators should consider those documents where relevant to aircraft-specific AFM/MMEL requirements. (Note; Applicability)\n\n### Trade-offs and opportunity costs\n\n- The AD imposes an immediate maintenance obligation on a defined subset of engines, concentrating costs on operators of affected aircraft. The stated safety rationale is the mitigation of surge/run down in a specific flight regime (descent above 25,000 ft when accelerating from low idle). Operators must weigh scheduling and cashflow effects of performing the required work against the operational benefit of removing AFM/MMEL amendments when both engines are done. (Background; Requirement; Note)\n\n(References in parentheses refer to the labelled parts of the Directive: Applicability; Requirement; Compliance; Note; Background; Effective date.)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific engine fuel system defect identified by the manufacturer. It has not expanded beyond its initial safety purpose."},"complexity_factors":["Single, specific technical requirement with two alternative compliance paths","Only 3 defined technical references (the two Service Bulletins and the FAA AD)","No nested conditional logic or exceptions","Straightforward applicability test (engine series + absence of prior modifications)","Fixed, non-negotiable compliance date","Total length under 200 words"],"plain_english_summary":"**What this is:** An Airworthiness Directive (AD) — essentially a mandatory safety order issued by Australia's aviation regulator (CASA) requiring specific repairs or modifications to aircraft engines.\n\n**What it does:** Forces airlines and aircraft operators to fix a dangerous fuel system problem in certain Rolls-Royce RB211-535E4 jet engines. The engines need either a completely new fuel flow governor (the device that controls how much fuel enters the engine) or a modification to the existing one.\n\n**Who it affects:** Anyone operating aircraft with Rolls-Royce RB211-535E4 engines that haven't already been updated with specific factory service bulletins (technical repair notices from the manufacturer).\n\n**Why it matters:** Without this fix, engines can \"surge and run down\" — meaning they could lose power or flame out when pilots try to accelerate from low idle during descent at high altitude (above 25,000 feet). This is extremely dangerous during landing approach.\n\n**The deadline:** All affected engines had to be fixed by 28 February 1997.\n\n**Key detail:** Once both engines on a Boeing 757 are fixed this way, operators no longer need to follow certain emergency procedures that were imposed by an earlier American safety order (FAA AD 96-04-11)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-rb211-20-fuel-flow-governor","history":"/api/acts/ad-rb211-20-fuel-flow-governor/history","analysis":"/api/acts/ad-rb211-20-fuel-flow-governor/analysis","conflicts":"/api/acts/ad-rb211-20-fuel-flow-governor/conflicts","importantCases":"/api/acts/ad-rb211-20-fuel-flow-governor/important-cases","documents":"/api/acts/ad-rb211-20-fuel-flow-governor/documents"}}