{"id":"F2006B02955","name":"AD/B737/55 - APU Power Feeder Cable Bundle Chafing","slug":"ad-b737-55-apu-power-feeder-cable-bundle-chafing","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42297,"registerId":"commonwealth-F2006B02955-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/55 - APU Power Feeder Cable Bundle Chafing","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 737 Series Aeroplanes\n\nAD/B737/55 APU Power Feeder Cable Bundle Chafing 4/91\n\nApplicability: All model Boeing 737 series aeroplanes listed in Boeing SB 737-35-1033 dated 15 March 1990.\n\nRequirement: Action in accordance with the technical requirements of FAA AD 90-25-12.\n\nNote: Boeing SB 737-35-1033 also refers.\n\nCompliance: As specified in the Requirement Document but with a revised effectivity date of 18 April 1991 for Australian registered aircraft.\n\nBackground: Boeing have advised that insufficient clearance may exist between the APU power feeder cable, the crew oxygen system tubing, and the horizontal stabiliser trim control cables in the area below the control cabin floor. This condition, if not corrected, could result in an oxygen fed fire caused by chafing and subsequent electrical arcing between the power feeder bundle and the crew oxygen system tubing.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard, narrow airworthiness directive addressing a specific technical defect in a specific aircraft type. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (approximately 150 words)","Only 1 defined term implicitly referenced (the Boeing service bulletin)","Single technical requirement: comply with existing FAA directive","No nested exceptions or conditional logic","Simple structure: applicability, requirement, compliance date, background","Cross-reference to only 2 external documents (FAA AD 90-25-12 and Boeing SB 737-35-1033)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for aircraft.\n\n**What it does:**\nOrders owners and operators of certain Boeing 737 aircraft to inspect and fix a specific safety problem. The issue involves electrical cables (the \"APU power feeder cable bundle\") rubbing against oxygen tubing and control cables beneath the cockpit floor. If left unfixed, this rubbing (\"chafing\") could cause electrical sparks near oxygen lines — creating a serious fire risk.\n\n**Who it affects:**\n- All Australian-registered Boeing 737 series aircraft covered by a specific Boeing service bulletin (SB 737-35-1033 from March 1990)\n- Airlines, maintenance organisations, and aircraft owners operating these planes in Australia\n\n**What must be done:**\nOperators must follow the technical instructions in an American FAA safety order (FAA AD 90-25-12), but with an Australian-specific deadline: **18 April 1991**.\n\n**Why it matters:**\nThis is a fire-prevention measure. Oxygen-fed fires are extremely dangerous and can spread rapidly. The directive forces operators to address the problem before it causes an accident."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"The AD does not expand the set of affected aircraft beyond those listed in Boeing SB 737-35-1033; instead it adopts the technical actions of FAA AD 90-25-12 for those aircraft but alters the compliance timing for Australian‑registered aeroplanes by specifying a revised effectivity date of 18 April 1991. The change in scope is therefore limited to the timing of mandatory compliance for Australian operators, not to the types of aircraft or the substantive technical requirements themselves."},"complexity_factors":["References external mandatory technical document (FAA AD 90-25-12) rather than containing full technical detail in the AD itself","Relies on an additional manufacturer service bulletin (Boeing SB 737-35-1033) for applicability and guidance","Safety‑critical aircraft maintenance actions that may require skilled labour, parts, and aircraft downtime","A revised effectivity date for Australian‑registered aircraft introduces a timing variance from the original FAA schedule","Potential need for interpretation where the FAA AD and Boeing SB overlap or differ"],"plain_english_summary":"This AD makes the actions of FAA AD 90‑25‑12 mandatory for Australian‑registered Boeing 737s: inspect and, if needed, repair/modify APU power feeder cable routing to prevent chafing with crew oxygen lines or trim control cables that could cause an oxygen‑fed fire. Operators must follow the FAA AD (with Boeing SB 737‑35‑1033 as guidance), comply from 18 April 1991, and bear associated costs and downtime."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-55-apu-power-feeder-cable-bundle-chafing","history":"/api/acts/ad-b737-55-apu-power-feeder-cable-bundle-chafing/history","analysis":"/api/acts/ad-b737-55-apu-power-feeder-cable-bundle-chafing/analysis","conflicts":"/api/acts/ad-b737-55-apu-power-feeder-cable-bundle-chafing/conflicts","importantCases":"/api/acts/ad-b737-55-apu-power-feeder-cable-bundle-chafing/important-cases","documents":"/api/acts/ad-b737-55-apu-power-feeder-cable-bundle-chafing/documents"}}