{"id":"F2006B04456","name":"AD/BELL 206/141 - Hydraulic Relief Valves","slug":"ad-bell-206-141-hydraulic-relief-valves","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44293,"registerId":"commonwealth-F2006B04456-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 206/141 - Hydraulic Relief Valves","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) 206 and Agusta Bell 206 Series Helicopters\n\nAD/BELL 206/141 Hydraulic Relief Valves 14/98\n\nApplicability: Bell Helicopter Textron Canada(BHTC) Model 206L-4 helicopters Serial numbers 5201 through 52208.\n\nRequirement: Replace hydraulic relief valve P/N 206-076-036-101 with P/N 206-076-036-105 in accordance with BHTC Alert Service Bulletin (ASB) 206L-98-111.\n\nEnsure proper functioning of the flight controls in accordance with BHTC ASB 206L- 98-111 dated 24 July 1998.\n\nNote: Transport Canada AD CF-98-34 Bell refers.\n\nCompliance: Unless previously carried out within 300 hours Time in Service from the issue of this AD but no later then 31 December 1998.\n\nThis Airworthiness Directive becomes effective on 31 December 1998.\n\nBackground: There was a manufacturing defect found on hydraulic relief valve P/N 206-076-036- 101 which could lead to an intermittent loss of hydraulic pressure to the flight controls.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive is corrective and targeted: it applies only to a defined set of Model 206L-4 helicopters (serial numbers 5201–52208) and requires a specific component replacement (P/N 206-076-036-101 replaced with P/N 206-076-036-105) following the manufacturer's ASB. It does not expand regulatory reach beyond those airframes or introduce ongoing obligations beyond the one-off replacement and verification specified in the Requirement and Compliance sections."},"complexity_factors":["Narrow applicability limited to a single model and serial number range (Applicability)","Single, prescriptive technical action: replace one part with a specified part number (Requirement)","Reference to an external manufacturer's Alert Service Bulletin for procedures introduces a dependency on another document (Requirement)","Time-limited compliance window with both flight-hours and calendar deadline (Compliance)","No additional procedural or enforcement complexity included in the text (Compliance)"],"plain_english_summary":"### What this instrument legally requires\n\n- It applies to Bell Helicopter Textron Canada (BHTC) Model 206L-4 helicopters with serial numbers 5201 through 52208. (Applicability)\n- Operators must replace hydraulic relief valve part number 206-076-036-101 with part number 206-076-036-105, following BHTC Alert Service Bulletin (ASB) 206L-98-111. Operators must also \"ensure proper functioning of the flight controls\" as described in that ASB. (Requirement)\n- The replacement must be done within 300 hours time in service from the issue of the directive, and in any event no later than 31 December 1998. The directive became effective on 31 December 1998. (Compliance; Effective date)\n\n### Official reason given\n\n- The directive says a manufacturing defect was found in hydraulic relief valve P/N 206-076-036-101 that could lead to an intermittent loss of hydraulic pressure to the flight controls. That safety risk is the stated reason for ordering the part replacement. (Background)\n\n### Who pays and who decides\n\n- Owners/operators of the listed Model 206L-4 helicopters must carry out and pay for the valve replacement and any associated work required by the ASB. (Applicability; Requirement)\n- The directive specifies the exact part numbers to remove and install and refers to a manufacturer's ASB for the detailed procedure, which constrains how the work must be done. (Requirement)\n\n### Compliance burden and timing\n\n- The directive creates a measurable compliance burden: locating affected airframes (by serial number), sourcing the specified replacement part (P/N 206-076-036-105), scheduling maintenance, performing the swap and verifying flight-control function per the ASB. (Applicability; Requirement)\n- The compliance window is short and binding: within 300 hours time in service or by the calendar deadline 31 December 1998, whichever comes first. This imposes scheduling and possible downtime costs on operators. (Compliance)\n\n### Implementation discretion and enforcement\n\n- The instrument leaves little regulatory discretion about the technical remedy: it prescribes a specific replacement part and refers to the ASB for the method, so regulator and manufacturer involvement is directive rather than discretionary. (Requirement)\n- The directive does not specify who (licensed engineers, the manufacturer, third-party maintenance organisations) must perform the work; the ASB is referenced for procedural detail but the AD itself mandates the end result. (Requirement)\n\n### Effects on businesses and market choices\n\n- The immediate economic effect falls on operators of the identified helicopters: they incur parts and labour costs and must schedule maintenance downtime. (Applicability; Requirement)\n- The measure constrains equipment choices for affected operators by mandating a particular part replacement rather than a range of corrective options. (Requirement)\n- The source does not specify subsidies, reimbursements, or who supplies the replacement parts; therefore the cost and procurement responsibility appears to rest with operators unless another arrangement exists outside this text. (Requirement)\n\n### Trade-offs, risks and substitution effects\n\n- The stated safety benefit (reduced risk of intermittent hydraulic pressure loss) is the motivating trade-off for the compliance costs. (Background)\n- Operators may have to pull aircraft out of service earlier than planned to meet the hours or calendar deadline, causing schedule or revenue impacts. (Compliance)\n- The directive does not describe monitoring, follow-up inspections, or penalties for non-compliance in this text; compliance is time-bound and prescriptive but enforcement mechanisms are not detailed here. (Compliance; Requirement)\n\n### What the source does not say\n\n- The directive does not give estimated costs, who supplies or pays for replacement parts, whether maintenance must be performed by particular providers, or whether any temporary operational restrictions apply while waiting for parts. (Requirement; Compliance)\n- The text does not indicate broader regulatory changes or permanent changes to design approval beyond the single-part replacement for the listed serial numbers. (Applicability; Requirement)\n\nSummary: Mechanically, this Airworthiness Directive requires owners/operators of specified Bell 206L-4 helicopters to replace a particular hydraulic relief valve with a newer part number and to verify flight-control function per the manufacturer's ASB within a defined time window. The stated purpose is to address a manufacturing defect that could cause intermittent loss of hydraulic pressure to the flight controls (Background). The concrete effects are direct compliance costs, scheduling/downtime requirements, and a mandatory technical remedy with limited regulatory discretion over method (Requirement; Compliance)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a standard airworthiness directive with a narrow, targeted scope addressing a specific manufacturing defect in a specific helicopter model. It has not expanded beyond its original safety purpose."},"complexity_factors":["Single, specific mechanical action required (valve replacement)","Only one defined applicability criterion (serial number range)","Single cross-reference to manufacturer service bulletin","Clear, unambiguous compliance deadline (300 hours or fixed date)","No nested exceptions, conditional logic, or alternative compliance methods","Background explanation provided in plain language"],"plain_english_summary":"This is a **safety order for specific Bell helicopters** that fixes a dangerous manufacturing fault.\n\n**What it does:**\nOrders owners and operators of certain Bell 206L-4 helicopters (serial numbers 5201 to 52208) to replace a faulty hydraulic relief valve with a new, corrected part. The old valve (part number 206-076-036-101) has a manufacturing defect that could cause flight controls to lose hydraulic pressure intermittently — a serious safety risk.\n\n**Who it affects:**\n- Owners and operators of Bell 206L-4 helicopters with serial numbers between 5201 and 52208\n- Maintenance engineers working on these aircraft\n\n**What must be done:**\n- Replace the faulty valve with part number 206-076-036-105\n- Follow the specific instructions in Bell Helicopter's Alert Service Bulletin 206L-98-111\n- Test that the flight controls work properly after the replacement\n\n**When it must be done:**\nWithin 300 flight hours of this directive being issued, or by 31 December 1998 — whichever comes first. The directive itself takes effect on 31 December 1998.\n\n**Why it matters:**\nHydraulic pressure keeps helicopter flight controls working. An intermittent loss could mean the pilot suddenly loses control of the aircraft, creating a crash risk. This directive forces a fix before that can happen."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-206-141-hydraulic-relief-valves","history":"/api/acts/ad-bell-206-141-hydraulic-relief-valves/history","analysis":"/api/acts/ad-bell-206-141-hydraulic-relief-valves/analysis","conflicts":"/api/acts/ad-bell-206-141-hydraulic-relief-valves/conflicts","importantCases":"/api/acts/ad-bell-206-141-hydraulic-relief-valves/important-cases","documents":"/api/acts/ad-bell-206-141-hydraulic-relief-valves/documents"}}