{"id":"F2006B03169","name":"AD/B747/273 - Thrust Reverser Flow Restrictor","slug":"ad-b747-273-thrust-reverser-flow-restrictor","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42541,"registerId":"commonwealth-F2006B03169-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.001.png)\n\n![](image.001.png)  \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 CAR 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\nBoeing 747 Series Aeroplanes","sortOrder":0},{"sectionNumber":"AD/B747/273 Thrust Reverser Flow Restric","sectionType":"part","heading":"AD/B747/273 Thrust Reverser Flow Restrictor 7/2002","content":"# AD/B747/273 Thrust Reverser Flow Restrictor 7/2002\n\nApplicability: Model 747-400 series aeroplanes up to and including line position 1022, powered by Pratt and Whitney PW 4000 series engines.\n\nRequirement: Replace the thrust reverser flow restrictor devices with one-way (check) valve restrictors in accordance with Boeing Alert Service Bulletin 747-78A2128, dated 10 March, 1994; or Revision 1, dated 26 May, 1994.\n\nNote: FAA AD 94-20-11 Amdt 39-9040 refers.\n\nCompliance: Prior to further flight.\n\nThis Amendment becomes effective on 11 July 2002.\n\nBackground: The manufacturer has reported several instances of thrust reverser sleeve actuator piston seal leakage during overhaul. Testing done by Boeing suggests that if there is sufficient seal leakage in two of the three actuators on a single sleeve, then a sleeve deployment could occur. This Directive introduces a modification to prevent the possibility of an uncommanded in- flight deployment of a thrust reverser.\n\n![Signature of James Coyne, Delegate of the Civil Aviation Safety Authority.](image.002.png)  \n\nJames Coyne\n\nDelegate of the Civil Aviation Safety Authority 28 May 2002\n\n![](image.001.png)","sortOrder":1}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD applies only to the specified 747-400/PW4000 subset and mandates replacement of flow restrictors before further flight to mitigate the identified seal-leakage risk. The text limits the measure to that aircraft/engine population and does not broaden or narrow the stated safety purpose beyond the Background and Applicability sections."},"complexity_factors":["Narrow technical applicability: limited to Model 747-400 up to line position 1022 with Pratt & Whitney PW4000 engines (Applicability).","Immediate mandatory compliance: action must be done 'prior to further flight', increasing operational disruption and scheduling pressure (Compliance).","Reliance on an external Boeing Alert Service Bulletin for the technical procedure and parts specification (Requirement).","Safety-critical failure mode: addresses actuator piston seal leakage that could cause uncommanded deployment (Background), creating low tolerance for partial compliance or delay.","Cross-reference to FAA AD for related regulatory context, implying alignment with overseas authority and possible coordination on parts/engineering data (Note).","Administrative allocation of decision-making and enforcement to the CASA delegate under CAR 1998 subregulation 39.1(1) (preamble/signature)."],"plain_english_summary":"This Airworthiness Directive requires operators of Boeing 747-400 aeroplanes (line positions up to 1022) with Pratt & Whitney PW4000 engines to replace existing thrust reverser flow restrictors with one-way (check) valve restrictors, following Boeing Alert Service Bulletin 747-78A2128. CASA requires the work prior to further flight to address actuator piston seal leakage that could allow an uncommanded in‑flight thrust reverser deployment."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific mechanical defect in a defined aircraft population. The scope remains precisely limited to the thrust reverser modification as originally intended."},"complexity_factors":["Single, clearly defined applicability (specific aircraft model, production line range, and engine type)","One straightforward requirement with reference to external technical document (Boeing Service Bulletin)","Simple compliance condition ('prior to further flight' — immediate, no phased schedule)","Minimal defined terms (only standard aviation terminology like 'line position')","No nested exceptions, conditional logic, or cross-references to other legislation beyond a single related FAA directive","Short document (approximately 250 words excluding headers and images)"],"plain_english_summary":"This CASA Airworthiness Directive mandates immediate replacement of thrust-reverser flow restrictor devices with one-way check-valve restrictors on Boeing 747-400s (P&W PW4000 engines, production line ≤1022).  \n\nBoeing found seal leaks in actuators could allow an in-flight thrust-reverser deployment—risking catastrophic loss of control—so operators must comply before the aircraft’s next flight per Boeing ASB 747-78A2128."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-273-thrust-reverser-flow-restrictor","history":"/api/acts/ad-b747-273-thrust-reverser-flow-restrictor/history","analysis":"/api/acts/ad-b747-273-thrust-reverser-flow-restrictor/analysis","conflicts":"/api/acts/ad-b747-273-thrust-reverser-flow-restrictor/conflicts","importantCases":"/api/acts/ad-b747-273-thrust-reverser-flow-restrictor/important-cases","documents":"/api/acts/ad-b747-273-thrust-reverser-flow-restrictor/documents"}}