{"id":"F2006B02939","name":"AD/B737/4 Amdt 1 - Side of Body Rib","slug":"ad-b737-4-amdt-1-side-of-body-rib","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42281,"registerId":"commonwealth-F2006B02939-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/4 Amdt 1 - Side of Body Rib","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/B737/4\n\nAmdt 1\n\n  \nSide of Body Rib 2/86\n\nApplicability: Group A: All model 737 aircraft, Line Numbers 1 to 433 plus 436 and 437.\n\nGroup B: All model 737 aircraft, Line Numbers 434, 435 and 438 to 844.\n\nRequirement: Group A Aircraft:\n\n    FAA AD 85-01-07, Amendment 39-4983, Sections A to E.\n\n    2. Boeing SB 737-57-1087 Revision 4\\. Group B Aircraft:\n    3. FAA AD 85-22-02, Amendment 39-5159 Sections A to D.\n\n    4. Boeing SB 737-57-1137 Revision 2; or as otherwise agreed to by the Secretary.\n\nCompliance: Group A Aircraft: As detailed in Requirement Document No. 1\\. Group B Aircraft: As detailed in Requirement Document No. 3.\n\nBackground: Cracking has been reported in the side of body rib area, in particular the rib upper chord, skin and BS 663.75 bulkhead fitting. This has been attributed to localised cyclic stresses during approach and landing.\n\nThis Amendment introduces FAA AD 85-22-02 (similar to FAA AD 85-01-07) which addresses cracking in later production aircraft.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":true,"description":"The amendment expands the directive to cover later-production Boeing 737s by introducing FAA AD 85-22-02 (not previously included) in addition to FAA AD 85-01-07. It therefore extends explicit requirements to Group B line numbers and adds an additional Boeing service bulletin as an approved compliance path; it also preserves Secretary discretion to accept alternatives (Requirement 4)."},"complexity_factors":["Applicability split into two groups by specific line-number ranges (Group A: Line Numbers 1–433 plus 436–437; Group B: Line Numbers 434–435 and 438–844) — requires precise fleet identification.","Cross-reference to multiple external normative documents: FAA AD 85-01-07 (Amendment 39-4983) and FAA AD 85-22-02 (Amendment 39-5159), each with sections A–E or A–D respectively, rather than reproducing inspection/repair steps.","Dependence on Boeing service bulletins of particular revisions (SB 737-57-1087 Rev 4; SB 737-57-1137 Rev 2) as the practical means of compliance.","Compliance entries refer to 'Requirement Document No. 1' and 'Requirement Document No. 3' rather than listing actions, creating an additional layer for implementers to consult.","Discretionary provision: Requirement 4 allows 'or as otherwise agreed to by the Secretary', introducing case-by-case approval and administrative discretion.","Technical background ties cracking to localized cyclic stresses during approach and landing, implying recurring inspection/repair cycles and potential ongoing maintenance cost for operators.","Overlap and similarity between FAA ADs (the amendment notes FAA AD 85-22-02 is similar to 85-01-07) creates interpretation/selection complexity for later-production versus earlier-production aircraft."],"plain_english_summary":"This amendment requires inspections and corrective work for cracking in the side‑of‑body rib area on Boeing 737 aeroplanes. It applies to two groups of aircraft identified by line numbers and mandates compliance with specified FAA airworthiness directives and Boeing service bulletins. Aircraft operators and maintenance organisations must carry out the referenced inspections/repairs; the Secretary may accept alternative methods. The action responds to reported cracking attributed to cyclic stresses during approach and landing and aims to ensure structural integrity."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"This is Amendment 1 to an existing Airworthiness Directive. The original AD/B737/4 (issued 2/86) only applied to Group A aircraft. This amendment expands the scope to include Group B aircraft (later production line numbers) by incorporating FAA AD 85-22-02, effectively doubling the aircraft population covered by the directive. The amendment maintains the same technical subject matter (side of body rib cracking) but extends it to newer airframes that were previously exempt."},"complexity_factors":["Multiple reference documents required (FAA ADs and Boeing Service Bulletins) — the actual technical requirements are external to this instrument","Bifurcated applicability structure splitting aircraft into two groups based on production line numbers","Cross-references to US regulatory instruments (FAA ADs) rather than self-contained Australian requirements","Technical aviation terminology requiring domain knowledge (e.g., \"BS 663.75 bulkhead fitting\", \"upper chord\", \"side of body rib\")","Amendment structure indicating evolution of the directive over time"],"plain_english_summary":"This AD mandates inspections and repairs for cracks in the side‑of‑body rib (wing-to-fuselage support) on Australian‑registered Boeing 737s, caused by repeated landing/approach stress. It divides affected airplanes into two production groups and requires compliance with the corresponding FAA ADs and Boeing service bulletins. It prevents potentially catastrophic structural failure."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-4-amdt-1-side-of-body-rib","history":"/api/acts/ad-b737-4-amdt-1-side-of-body-rib/history","analysis":"/api/acts/ad-b737-4-amdt-1-side-of-body-rib/analysis","conflicts":"/api/acts/ad-b737-4-amdt-1-side-of-body-rib/conflicts","importantCases":"/api/acts/ad-b737-4-amdt-1-side-of-body-rib/important-cases","documents":"/api/acts/ad-b737-4-amdt-1-side-of-body-rib/documents"}}