{"id":"F2006B06687","name":"AD/RRT-S/6 - Malfunction of Bleed Valve Mechanism Featuring Mod. 5866 - Operational and Maintenance Action","slug":"ad-rrt-s-6-malfunction-of-bleed-valve-mechanism-featuring-mod-5866-operational-and-maintenance-actio","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":48727,"registerId":"commonwealth-F2006B06687-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/RRT-S/6 - Malfunction of Bleed Valve Mechanism Featuring Mod. 5866 - Operational and Maintenance Action","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 \\- Spey Series\n\nAD/RRT-S/6 Malfunction of Bleed Valve Mechanism Featuring Mod. 5866 \\- Operational and Maintenance Action\n\n  \n11/82\n\nApplicability: Rolls Royce Spey 555-15, 15H, 15N and 15P engines featuring MOD. 5866 (SB SP72-916).\n\nRequirement: Rolls Royce Spey Alert SB No. SP72-A963. Compliance: Forthwith.\n\nBackground: There have recently been reports of engines featuring Bleed Valve Mechanism MOD. 5866 showing an unacceptable rise in T.G.T. at low power conditions in the following cases:-\n\n    Immediately on throttle advance from a low power setting where HP RPM stagnates, particularly following engine deceleration.\n\n    B. Less frequently \\- during steady state running at low power settings.\n\nThis AD is issued to alert flight and maintenance crews of the possibility of this condition occurring and precautions which should be taken.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD implements the stated original purpose: to alert flight and maintenance crews and require immediate compliance with the Rolls Royce Alert SB because of reported T.G.T. rises at low power (Background; Requirement). The directive’s applicability, required action, and timing are consistent with that stated purpose and do not change the scope of affected engines or duties from what the AD describes (Applicability; Requirement; Compliance: Forthwith)."},"complexity_factors":["Narrow technical scope limited to specific engine models and a single modification (Applicability).","Immediate compliance requirement increases operational urgency but not legal ambiguity (Compliance: Forthwith).","Technical actions are delegated to a manufacturer Alert Service Bulletin, requiring technical interpretation by maintainers (Requirement).","Detection of the condition depends on monitoring specific engine parameters (T.G.T. and HP RPM), which is technical rather than legal complexity (Background).","Short, self-contained instrument with few cross-references to other provisions; no complex procedural framework or staged requirements."],"plain_english_summary":"# What this directive does\n\nThis airworthiness directive (AD) applies to Rolls Royce Spey 555-15, 15H, 15N and 15P turbine engines that have had Modification 5866 installed (identified as SB SP72-916) (Applicability). It requires operators and maintenance organisations to follow the instructions in Rolls Royce Spey Alert Service Bulletin No. SP72-A963 (Requirement) and says that compliance must be carried out immediately (Compliance: Forthwith).\n\n# How it works mechanically\n\n- Engines fitted with Mod. 5866 have been reported to show an unacceptable rise in turbine gas temperature (T.G.T.) at low power in two situations: (a) immediately on advancing the throttle from a low power setting when high-pressure (HP) RPM momentarily stagnates, particularly after deceleration; and (b) less frequently, during steady running at low power (Background).\n- The AD directs flight crews and maintenance crews to take the precautions and maintenance actions described in the Rolls Royce Alert SB (Requirement). The AD itself is an instruction to comply with that manufacturer bulletin and to be alert to the described condition (Requirement; Background).\n\n# Stated purpose and how it maps to costs and incentives\n\n- The AD explicitly states its purpose as alerting flight and maintenance crews to the possibility of the condition and the precautions to take (Background).\n- Who pays: aircraft operators and their maintenance providers will bear the direct cost of reading and applying the Alert SB, performing any inspections, adjustments, or repairs that the SB requires, and any operational changes that follow (Applicability; Requirement; Compliance: Forthwith).\n- Who decides: the Civil Aviation Safety Authority issues the AD under the civil aviation regulatory framework and the manufacturer provides the technical instructions to be followed (title and Requirement).\n- Behaviour change required: flight crews must adopt operational precautions when advancing throttle from low power and monitor for T.G.T./HP RPM anomalies; maintenance personnel must perform actions set out in the Alert SB and any follow-up work it specifies (Background; Requirement).\n\n# Trade-offs, opportunity costs and implementation risks (mechanical and administrative)\n\n- Immediate compliance (Compliance: Forthwith) can impose short-term scheduling and resource costs on operators and maintenance organisations because actions must be taken without delay (Compliance: Forthwith; Requirement).\n- The technical work is defined by the manufacturer Alert SB; implementing those instructions requires that maintenance organisations interpret and carry out the SB, which may require parts, specialised labour, or additional inspections (Requirement). Those are concrete compliance costs borne by operators or their contracted MROs.\n- Detecting the described condition depends on monitoring T.G.T. and HP RPM behavior at low power settings (Background). If crews or maintenance personnel do not have procedures or equipment in place to detect the phenomenon reliably, there is implementation risk that the condition will be missed until an adverse effect appears (Background).\n- The AD centralises the decision to require action (the regulator issues the AD, the manufacturer issues the SB) but leaves technical implementation to maintenance organisations. That creates an administrative compliance burden (Requirement).\n\n# Effects on private enterprise and market considerations\n\n- Affected operators face direct compliance costs and potential short-term operational impacts; independent maintenance providers must allocate labour and possibly inventory to perform the SB work (Applicability; Requirement).\n- The AD does not itself mandate a specific commercial provider; it requires following the manufacturer Alert SB, so independent MROs can comply provided they implement the SB instructions (Requirement). Any competitive effects arise from the technical requirements and specialised capability needed to perform the SB.\n\n# Summary statement\n\nThis AD instructs operators of Rolls Royce Spey 555-15 series engines fitted with Mod. 5866 to immediately follow Rolls Royce Alert SB SP72-A963 because of reported T.G.T. rises at low power. The directive shifts compliance costs to operators and maintenance providers, requires immediate procedural and maintenance action (Compliance: Forthwith; Requirement), and relies on crews and maintainers to detect and address the described T.G.T./HP RPM behaviour (Background)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical issue in specific engine models. It has not expanded beyond its original purpose of addressing the bleed valve malfunction."},"complexity_factors":["Very short document (under 200 words)","Only 4 engine models specified in applicability","Single requirement referencing an external document (the Service Bulletin)","No defined terms section","No cross-references to other legislation","Simple conditional logic: if engine has MOD. 5866, then comply with SB","Background section uses technical aviation terminology but explains the operational context clearly"],"plain_english_summary":"**What this is:** An Airworthiness Directive (AD) — essentially a mandatory safety notice for aircraft operators.\n\n**What it does:** This directive requires immediate action on specific Rolls Royce Spey jet engines (models 555-15, 15H, 15N, and 15P) that have a particular modification called \"MOD. 5866\" installed.\n\n**The safety problem:** Some engines with this modification have been experiencing dangerous temperature spikes (T.G.T. stands for Turbine Gas Temperature) when running at low power. This happens in two scenarios:\n- When the pilot increases throttle from low power, especially after slowing the engine down\n- Less commonly, during steady low-power operation\n\n**Who must act:** Airlines and operators using these specific Rolls Royce Spey engines with MOD. 5866.\n\n**What they must do:** Follow the instructions in Rolls Royce Alert Service Bulletin SP72-A963 immediately (\"forthwith\" means right away, not when convenient).\n\n**Why it matters:** Temperature spikes can damage engines or cause them to fail. This AD warns flight crews to watch for this condition and maintenance crews to take specific precautions."}},"importantCases":[],"_links":{"self":"/api/acts/ad-rrt-s-6-malfunction-of-bleed-valve-mechanism-featuring-mod-5866-operational-and-maintenance-actio","history":"/api/acts/ad-rrt-s-6-malfunction-of-bleed-valve-mechanism-featuring-mod-5866-operational-and-maintenance-actio/history","analysis":"/api/acts/ad-rrt-s-6-malfunction-of-bleed-valve-mechanism-featuring-mod-5866-operational-and-maintenance-actio/analysis","conflicts":"/api/acts/ad-rrt-s-6-malfunction-of-bleed-valve-mechanism-featuring-mod-5866-operational-and-maintenance-actio/conflicts","importantCases":"/api/acts/ad-rrt-s-6-malfunction-of-bleed-valve-mechanism-featuring-mod-5866-operational-and-maintenance-actio/important-cases","documents":"/api/acts/ad-rrt-s-6-malfunction-of-bleed-valve-mechanism-featuring-mod-5866-operational-and-maintenance-actio/documents"}}