{"id":"F2006B02948","name":"AD/B737/49 - Outboard Flaptrack Support Fitting Attach Bolts","slug":"ad-b737-49-outboard-flaptrack-support-fitting-attach-bolts","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":42290,"registerId":"commonwealth-F2006B02948-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/B737/49 - Outboard Flaptrack Support Fitting Attach Bolts","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)  Boeing 737 Series Aeroplanes\n\n \n\nAD/B737/49 Outboard Flaptrack Support Fitting Attach Bolts 12/90\n\nApplicability: Models 737 with line numbers 1 through 324.\n\n \n\nRequirement: Action in accordance with the technical requirements of FAA AD 90-17-20 Amdt 39- 6707.\n\n \n\nNote: Boeing SB 737-57A1079 Rev 4 refers.\n\n \n\nCompliance: In accordance with the Requirement document, except that the effective date of this AD is 29 November 1990.\n\n \n\nBackground: Country of origin AD. Failure of the subject bolts could result in loss of the flap and consequent control difficulties.\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\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD adopts the technical requirements of FAA AD 90-17-20 for Boeing 737 aeroplanes with line numbers 1–324 and sets an Australian effective date (29 November 1990). The instrument does not expand or narrow the affected population beyond the stated line number range, nor does it add technical requirements beyond those in the referenced FAA AD and Boeing service bulletin. (Applicability; Requirement; Note; Compliance; Background)"},"complexity_factors":["Cross-reference to an external FAA AD for all technical detail (Requirement)","Reference to a manufacturer service bulletin for supporting technical material (Note)","Applicability limited by aircraft line number range (1–324) (Applicability)","Single, clearly stated safety hazard drives the requirement (Background)","Compliance date specified but enforcement and cost details are not included (Compliance)"],"plain_english_summary":"What this instrument does mechanically\n\n- It requires owners/operators of certain Boeing 737 aeroplanes to carry out the technical actions set out in a specific FAA airworthiness directive (FAA AD 90-17-20 Amdt 39-6707). (Requirement)\n- It applies to Boeing 737 aeroplanes with line numbers 1 through 324. (Applicability)\n- The Civil Aviation Safety Authority (CASA) makes compliance subject to the FAA AD’s technical requirements, but sets the effective date for this Australian AD as 29 November 1990. (Compliance)\n- The AD also refers operators to Boeing Service Bulletin 737-57A1079 Revision 4 for related information. (Note)\n\nWho this affects and who pays\n\n- Aircraft owners and operators of the affected Boeing 737s must carry out the inspection/repair/replace actions required by the FAA AD (and any actions invoked by the Boeing service bulletin). The instrument itself points to those external documents for the specific technical steps. (Requirement; Note)\n- Practically, the direct costs (labour, parts, aircraft downtime) will fall on those owners/operators because they are required to implement the AD’s technical requirements. (Requirement)\n\nWhy it matters (stated safety rationale) and how it works\n\n- The expressed safety reason is that failure of the subject outboard flaptrack support fitting attach bolts could result in loss of a flap and consequent aircraft control difficulties. The AD therefore mandates actions intended to prevent that failure. (Background)\n- Mechanically the AD does not re-state the engineering steps; it adopts and makes mandatory the FAA’s technical directive for the Australian-registered aeroplanes identified. The Boeing service bulletin is referenced as further technical material. (Requirement; Note)\n\nImplementation, discretion and compliance points to note\n\n- The AD delegates the detailed technical prescription to an external FAA document (FAA AD 90-17-20) and to a Boeing service bulletin, so the specific inspections/repairs/part numbers or thresholds are contained in those documents rather than in this short Australian notice. (Requirement; Note)\n- CASA’s instrument fixes the population of affected aircraft (line numbers 1–324) and the effective date (29 Nov 1990), but does not itself set the technical methods or intervals—those are in the referenced FAA AD and Boeing SB. (Applicability; Compliance; Requirement; Note)\n- The AD creates an on-going compliance obligation for affected operators to follow the external documents; the AD does not describe enforcement, cost-recovery, or approval processes for alternative actions within this text. (Requirement; Compliance)\n\nTrade-offs, incentives and potential implementation effects (source-grounded)\n\n- Concentrated benefit: the safety benefit (reduced risk of flap loss) accrues mainly to operators and their passengers/crew on affected aeroplanes; the AD targets a clearly identified subset of aircraft by line number. (Applicability; Background)\n- Concentrated cost: the compliance costs (inspection, modification or replacement of bolts, parts and labour, plus downtime) are likely to be borne by those same operators because the AD requires them to take the actions. The AD text itself does not estimate those costs. (Requirement)\n- Administrative simplicity: by adopting an existing FAA AD and referencing a Boeing service bulletin, CASA keeps this instrument short and aligns the technical work with documents prepared by the aircraft manufacturer and the FAA. That reduces duplication but shifts substantive detail outside the Australian instrument. (Requirement; Note)\n\nBottom line in one sentence\n\nThis AD makes mandatory, for Boeing 737s line numbers 1–324, the technical actions specified in FAA AD 90-17-20 (and refers to Boeing SB 737-57A1079 Rev 4), effective 29 November 1990, in order to address the risk of outboard flaptrack support fitting attach bolt failure and potential flap loss. (Applicability; Requirement; Note; Compliance; Background)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard airworthiness directive adopting a foreign safety order. It maintains its original narrow scope: addressing a specific mechanical defect in specific aircraft models. No scope creep is evident."},"complexity_factors":["Extremely short document (under 200 words)","Only one substantive requirement: compliance with an external FAA document","Minimal defined terms (only 'line numbers' requires industry knowledge)","No nested conditional logic or exceptions","Single applicability criterion (line numbers 1-324)","Cross-reference to only one external technical document (FAA AD 90-17-20) and one advisory bulletin (Boeing SB 737-57A1079)"],"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 Boeing 737 aircraft.\n\n**What it does:** It requires owners and operators of certain Boeing 737 planes (specifically those with \"line numbers\" 1 through 324 — essentially the earlier production models) to inspect or replace specific bolts on the **outboard flap track support fitting**. These bolts attach the mechanism that helps control the aircraft's flaps (the movable surfaces on the wings that help with takeoff and landing).\n\n**Why it matters:** If these bolts fail, the aircraft could lose a flap during flight. This would cause serious **control difficulties** and potentially endanger the aircraft and everyone on board. The directive adopts a US Federal Aviation Administration (FAA) safety order (AD 90-17-20) and makes it legally binding in Australia.\n\n**Who must comply:** Airlines, aircraft owners, or maintenance organisations operating the affected Boeing 737 models in Australia.\n\n**When:** The directive took effect on **29 November 1990**."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-49-outboard-flaptrack-support-fitting-attach-bolts","history":"/api/acts/ad-b737-49-outboard-flaptrack-support-fitting-attach-bolts/history","analysis":"/api/acts/ad-b737-49-outboard-flaptrack-support-fitting-attach-bolts/analysis","conflicts":"/api/acts/ad-b737-49-outboard-flaptrack-support-fitting-attach-bolts/conflicts","importantCases":"/api/acts/ad-b737-49-outboard-flaptrack-support-fitting-attach-bolts/important-cases","documents":"/api/acts/ad-b737-49-outboard-flaptrack-support-fitting-attach-bolts/documents"}}