{"id":"F2006B04640","name":"AD/BELL 407/5 - Hydraulic Relief Valve Replacement","slug":"ad-bell-407-5-hydraulic-relief-valve-replacement","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44392,"registerId":"commonwealth-F2006B04640-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 407/5 - Hydraulic Relief Valve 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 407/5 Hydraulic Relief Valve Replacement 5/99\n\nApplicability: Bell (BHTC) Model 407 helicopters, serial numbers 53000 through 53266. Requirement: Replace hydraulic relief valves part number 206-076-036-101 with valve part number\n\n206-076-036-105 in accordance with the provisions of BHTC Alert Service Bulletin\n\n(ASB) No. 407-98-20, dated 3 July 1998.\n\nNote: Transport Canada Airworthiness Directive CF-98-28, dated 18 October 1998 refers.\n\nCompliance: Within the next 300 hours flight time after the effective date of this Directive, or by 20 August 1999, whichever occurs first.\n\nThis Airworthiness Directive becomes effective on 20 May 1999.\n\nBackground: A manufacturing defect has been found on hydraulic relief valve part number 206- 076-036-101 which could lead to an intermittent loss of hydraulic pressure to the flight controls. Replacement of the valve has been made mandatory to correct this safety of flight situation.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive addressing one specific safety defect in one aircraft model. It has not expanded beyond its original purpose of mandating replacement of a defective hydraulic valve."},"complexity_factors":["Single, specific technical requirement with no conditional logic or exceptions","Only 2 defined terms (part numbers) and 1 reference to an external technical document","Straightforward compliance deadline with simple 'whichever occurs first' logic","No cross-references to other legislation or regulations beyond the enabling Civil Aviation Regulations 1998","Short, single-purpose document (approximately 150 words of substantive content)","Clear applicability criteria (specific serial number range)"],"plain_english_summary":"This CASA Airworthiness Directive requires operators of Bell 407 helicopters (S/N 53000–53266) to replace a defective hydraulic relief valve (P/N 206-076-036-101) with the updated part (P/N 206-076-036-105) per Bell Service Bulletin 407-98-20. The replacement must occur within 300 flight hours after 20 May 1999 or by 20 August 1999. The change prevents intermittent hydraulic loss that could compromise flight control and safety."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The AD implements the manufacturer's Alert Service Bulletin for the specified helicopters and mandates the valve replacement without expanding or narrowing the affected fleet beyond the serial-number range given (Applicability/Requirement/Note)."},"complexity_factors":["Narrow applicability: specific Model 407 serial number range (Applicability)","Single, discrete technical action: replace one valve part number with another (Requirement)","Clear compliance deadline/options: 300 flight hours or fixed date (Compliance)","Dependence on manufacturer's service bulletin for procedure (Requirement)","Safety-critical operational impact may require immediate scheduling and downtime"],"plain_english_summary":"**This Directive requires owners/operators of Bell (BHTC) Model 407 helicopters, serial numbers 53000–53266, to replace hydraulic relief valve p/n 206-076-036-101 with p/n 206-076-036-105 per BHTC Alert Service Bulletin No. 407-98-20 (Requirement).** Compliance is due within 300 flight hours or by 20 August 1999, whichever is earlier (Compliance); the AD is effective 20 May 1999 (Effective date). It responds to a manufacturing defect that can cause intermittent loss of hydraulic pressure to flight controls (Background). Owners/operators pay for and arrange the replacement; the Authority prescribes timing and method."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-407-5-hydraulic-relief-valve-replacement","history":"/api/acts/ad-bell-407-5-hydraulic-relief-valve-replacement/history","analysis":"/api/acts/ad-bell-407-5-hydraulic-relief-valve-replacement/analysis","conflicts":"/api/acts/ad-bell-407-5-hydraulic-relief-valve-replacement/conflicts","importantCases":"/api/acts/ad-bell-407-5-hydraulic-relief-valve-replacement/important-cases","documents":"/api/acts/ad-bell-407-5-hydraulic-relief-valve-replacement/documents"}}