{"id":"F2006B04641","name":"AD/BELL 407/6 - Engine to Transmission Driveshaft Replacement","slug":"ad-bell-407-6-engine-to-transmission-driveshaft-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44393,"registerId":"commonwealth-F2006B04641-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 407/6 - Engine to Transmission Driveshaft Replacement","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)  \nBell Helicopter Textron Canada (BHTC) 407 Series Helicopters\n\nAD/BELL 407/6 Engine to Transmission Driveshaft Replacement 5/99\n\nApplicability: Bell (BHTC) Model 407 helicopters, serial numbers 53000 and 53002 through 53066\\. Requirement: Replace driveshaft part number 206-340-300-103 with driveshaft part number 206-\n\n340-300-105 in accordance with the instructions in BHTC Alerts Service Bulletin\n\n(ASB) 407-98-19 dated 19 June 1998. All removed driveshafts are to be rendered unusable or identified as unairworthy and quarantined from airworthy parts.\n\nNote: Transport Canada Airworthiness Directive CF-98-25R1 refers.\n\nCompliance: Within the next 50 hours flight time after the effective date of this Directive.\n\nThis Airworthiness Directive becomes effective on 20 May 1999.\n\nBackground: A recent evaluation of the engine to transmission driveshaft concluded that the current configuration does not meet certification criteria. Replacement of the driveshaft has therefore been mandated to remove the non compliant component.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue safety directive focused on one mechanical component. It has not expanded beyond its original purpose of addressing a specific airworthiness deficiency in the Bell 407 driveshaft."},"complexity_factors":["Single, unambiguous mechanical action required (part replacement)","Only 2 defined part numbers referenced","Narrow applicability (specific serial number range of one helicopter model)","Clear compliance deadline (50 flight hours)","No nested exceptions, conditional logic, or cross-references to other legislation","Background explanation included in plain language"],"plain_english_summary":"This CASA Airworthiness Directive mandates that operators of certain early-production Bell 407 helicopters (s/n 53000 and 53002–53066) replace a non‑compliant engine‑to‑transmission driveshaft with an improved unit within 50 flight hours after 20 May 1999, and render the old part unusable. It’s legally binding because shaft failure could sever power to the rotors and cause catastrophic loss."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive implements the stated objective in the Background: removing a driveshaft that does not meet certification criteria by mandating a part-for-part replacement for specified serial numbers. The action, affected fleet, compliance time and part-disposition requirements align with that stated intent."},"complexity_factors":["Narrow, clearly defined applicability (specific serial numbers 53000 and 53002–53066) (Applicability)","Single, discrete mechanical action: replace one driveshaft part number with another (Requirement)","Short mandatory compliance window: within 50 flight hours (Compliance) increases scheduling urgency","Mandatory disposition of removed parts: render unusable or quarantine (Requirement) adds supply-chain/parts-management burden","Dependence on external maintenance instructions: references BHTC ASB 407-98-19 for procedural detail (Requirement)","Operational cost and logistics fall to operators (implicit in Requirement/Compliance)","Clear safety rationale provided (Background) — limited scope for interpretation or discretionary relief"],"plain_english_summary":"This airworthiness directive orders operators of Bell 407 helicopters (serial nos. 53000 and 53002–53066) to replace driveshaft part number 206-340-300-103 with part number 206-340-300-105 under BHTC Alerts Service Bulletin ASB 407-98-19, within 50 flight hours (Requirement; Compliance). Removed driveshafts must be rendered unusable or quarantined. The directive’s stated reason is that the original driveshaft does not meet certification criteria (Background). Operators must fund and schedule the work."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-407-6-engine-to-transmission-driveshaft-replacement","history":"/api/acts/ad-bell-407-6-engine-to-transmission-driveshaft-replacement/history","analysis":"/api/acts/ad-bell-407-6-engine-to-transmission-driveshaft-replacement/analysis","conflicts":"/api/acts/ad-bell-407-6-engine-to-transmission-driveshaft-replacement/conflicts","importantCases":"/api/acts/ad-bell-407-6-engine-to-transmission-driveshaft-replacement/important-cases","documents":"/api/acts/ad-bell-407-6-engine-to-transmission-driveshaft-replacement/documents"}}