{"id":"F2006B03276","name":"AD/B747/98 - Auxiliary Power Unit (APU) Pneumatic Ducts","slug":"ad-b747-98-auxiliary-power-unit-apu-pneumatic-ducts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42713,"registerId":"commonwealth-F2006B03276-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B747/98 - Auxiliary Power Unit (APU) Pneumatic Ducts","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 747 Series Aeroplanes\n\nAD/B747/98 Auxiliary Power Unit (APU) Pneumatic Ducts 11/91\n\nApplicability: Boeing 747 series aeroplanes as listed in FAA Airworthiness Directive 91-15-24 Amdt 39-7089.\n\nRequirement: Action in accordance with the Technical Requirements of FAA AD 91-15-24.\n\nNote: Boeing Service Bulletin 747-36-2081 and 747-36-2092 refers.\n\nCompliance: Required prior to the accumulation of 7 000 flight cycles or within the next 3 000 flight cycles after the 14 November 1991, which ever occurs later.\n\nBackground: FAA AD action prompted by reports of cracked or ruptured APU ducts that have caused damage to adjacent structure, pneumatic ducts, and hydraulic lines. This condition, if not corrected, could result in damage to the adjacent structure, pneumatic ducts, hydraulic lines and/or electrical wiring.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, targeted safety directive addressing a specific mechanical defect in a specific aircraft type. It has not expanded beyond its original purpose of mandating APU duct inspections and repairs."},"complexity_factors":["Very short document (under 200 words)","Only 1 defined term implicitly referenced (flight cycles — takeoff-landing pairs)","Single compliance pathway with simple 'whichever is later' timing calculation","No nested exceptions or conditional logic","Relies entirely on external documents (FAA AD and Boeing bulletins) for technical detail, keeping the instrument itself minimal","Clear applicability statement referencing a single FAA directive"],"plain_english_summary":"**What this is:** An Airworthiness Directive (AD) — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific Boeing 747 aircraft.\n\n**What it does:** Requires airlines and aircraft operators to inspect and fix a dangerous problem with the Auxiliary Power Unit (APU) pneumatic ducts. The APU is a small engine at the back of the plane that provides power when the main engines are off. The \"pneumatic ducts\" are pipes that carry hot, pressurised air from this unit. These ducts were cracking and bursting, which could damage nearby fuel lines, hydraulics, wiring, and the aircraft's structure — creating fire and safety risks.\n\n**Who it affects:** Operators of Boeing 747 series aircraft (the specific models covered by an equivalent US FAA directive 91-15-24).\n\n**What must be done:** Operators must follow the technical instructions in the US Federal Aviation Administration's AD 91-15-24, which references specific Boeing service bulletins (repair guides). The work must be completed before the plane reaches 7,000 flight cycles, or within 3,000 flight cycles after 14 November 1991 — whichever gives more time.\n\n**Why it matters:** Cracked air ducts can rupture without warning, spraying hot air onto fuel lines and electrical systems. This creates serious fire and flight safety hazards. The directive forces operators to fix the problem before catastrophic damage occurs."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The instrument adopts and enforces the FAA AD for the specified Boeing 747 aeroplanes and points to Boeing Service Bulletins for related technical information (Applicability; Requirement; Note). It does not expand the set of affected aircraft or alter the FAA AD’s technical scope in the text provided; it simply makes compliance mandatory under Australian Part 39 (header)."},"complexity_factors":["Narrow technical scope limited to APU pneumatic ducts on listed Boeing 747 series (Applicability)","Cross-reference to an external FAA Airworthiness Directive for the technical requirements (Requirement)","Reference to Boeing Service Bulletins for related technical detail, requiring operators to obtain additional documents (Note)","A clear, simple compliance deadline tied to flight cycles and a calendar date (Compliance)","Technical execution requires maintenance resources and potential aircraft downtime (Requirement; Note)"],"plain_english_summary":"This directive requires operators of the specified Boeing 747 models to carry out inspections and corrective actions set out in FAA AD 91‑15‑24 (and follow referenced Boeing service bulletins) to detect and repair cracked or ruptured APU pneumatic ducts. Compliance is mandatory by the stated flight‑cycle thresholds. It aims to prevent duct failures that can damage structure, systems and wiring. Operators bear inspection/repair costs; CASA enforces the requirement under Part 39."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-98-auxiliary-power-unit-apu-pneumatic-ducts","history":"/api/acts/ad-b747-98-auxiliary-power-unit-apu-pneumatic-ducts/history","analysis":"/api/acts/ad-b747-98-auxiliary-power-unit-apu-pneumatic-ducts/analysis","conflicts":"/api/acts/ad-b747-98-auxiliary-power-unit-apu-pneumatic-ducts/conflicts","importantCases":"/api/acts/ad-b747-98-auxiliary-power-unit-apu-pneumatic-ducts/important-cases","documents":"/api/acts/ad-b747-98-auxiliary-power-unit-apu-pneumatic-ducts/documents"}}