{"id":"F2006B06966","name":"AD/SF340/37 - Fuselage Structure Protective Shield","slug":"ad-sf340-37-fuselage-structure-protective-shield","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114872,"registerId":"commonwealth-F2006B06966-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/SF340/37 - Fuselage Structure Protective Shield","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  SAAB SF340 Series Aeroplanes\n\n \n\nAD/SF340/37 Fuselage Structure Protective Shield 13/92\n\nApplicability: 1. SAAB SF340A Serial Number 004 to159 inclusive.\n\n \n\n2. SAAB SF340B Serial Number 160 to 252 inclusive.\n\n \n\nRequirement: Action in accordance with the technical requirement of SAAB 340 Service Bulletin number SAAB 340-53-028 Mod 1948 dated 20 August 1992.\n\n \n\nNote: Swedish Airworthiness Directive No. 1-055 issued 4 September 1992 refers.\n\n \n\nCompliance: No later than 3 000 flight hours after 10 December 1992.\n\n \n\nBackground: Leakage of hot air from the Air Cycle Machine and ducts may cause damage to the structure. Should this continue for a prolonged time, the structure would be weakened below an acceptable level.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","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 structural vulnerability in defined aircraft models. It has not expanded beyond its original purpose of mandating a protective modification."},"complexity_factors":["Single, specific technical requirement referencing an external service bulletin","Limited applicability (two specific serial number ranges)","Simple compliance deadline (flight hours-based)","No nested exceptions, conditional logic, or extensive defined terms","Short document (approximately 200 words)","Straightforward background explanation with clear safety rationale"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific SAAB SF340 aircraft.\n\n**What it does:** It requires owners or operators of certain SAAB SF340A and SF340B aeroplanes to install a protective shield on the fuselage structure. This shield prevents hot air leaks from the Air Cycle Machine (part of the aircraft's air conditioning/pressurisation system) from damaging the airframe.\n\n**Who it affects:** \n- SAAB SF340A aircraft with serial numbers 004 through 159\n- SAAB SF340B aircraft with serial numbers 160 through 252\n\n**What must be done:** Aircraft operators must follow the technical instructions in SAAB Service Bulletin 340-53-028 (Modification 1948), dated 20 August 1992. This involves fitting a protective shield to prevent structural damage from hot air leakage.\n\n**When it must be done:** Within 3,000 flight hours after 10 December 1992.\n\n**Why it matters:** Without this fix, leaking hot air could gradually weaken the aircraft's structure below safe levels, creating a serious safety risk. The directive ensures structural integrity is maintained before damage becomes critical."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD's scope aligns with its stated intent: it targets specific SAAB SF340 serial-number ranges and mandates corrective work per the referenced service bulletin. There is no indication in the text that the AD widens or narrows the remedy beyond that Applicability and Requirement."},"complexity_factors":["Limited applicability to specific serial numbers (Applicability: SAAB SF340A Serial Number 004 to 159; SAAB SF340B Serial Number 160 to 252).","Technical method delegated to an external document (Requirement: 'Action in accordance with the technical requirement of SAAB 340 Service Bulletin number SAAB 340-53-028 Mod 1948 dated 20 August 1992').","Fixed compliance metric and deadline measured in flight hours from a calendar date (Compliance: 'No later than 3 000 flight hours after 10 December 1992').","Safety rationale tied to component leakage risk (Background: 'Leakage of hot air from the Air Cycle Machine and ducts may cause damage to the structure').","Execution and expense borne by operators/owners (implied by Requirement and Compliance — operators must carry out SB work and schedule maintenance).","No alternative compliance pathway stated in the AD text (the AD requires the service bulletin action and does not itself state acceptable alternatives or AMOCs).","Enforcement through the Airworthiness Directive mechanism (document header: AD/SF340/37), which creates a mandatory regulatory obligation."],"plain_english_summary":"Requires installation of a fuselage protective shield on specified SAAB SF340 aeroplanes to stop hot-air leakage from the Air Cycle Machine damaging the structure. The technical work must follow SAAB Service Bulletin SAAB 340-53-028 Mod 1948 (20 Aug 1992).\n\nOperators of SAAB SF340A (S/N 004–159) and SF340B (S/N 160–252) must complete the work within 3,000 flight hours after 10 December 1992. The cost, scheduling and execution fall to the aircraft owners/operators; compliance is judged against the referenced service bulletin and the AD's deadline."}},"importantCases":[],"_links":{"self":"/api/acts/ad-sf340-37-fuselage-structure-protective-shield","history":"/api/acts/ad-sf340-37-fuselage-structure-protective-shield/history","analysis":"/api/acts/ad-sf340-37-fuselage-structure-protective-shield/analysis","conflicts":"/api/acts/ad-sf340-37-fuselage-structure-protective-shield/conflicts","importantCases":"/api/acts/ad-sf340-37-fuselage-structure-protective-shield/important-cases","documents":"/api/acts/ad-sf340-37-fuselage-structure-protective-shield/documents"}}