{"id":"F2006B04584","name":"AD/BELL 212/52 - Main Driveshaft and Tail Rotor Drive Over-Temperature Indicators","slug":"ad-bell-212-52-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":114318,"registerId":"commonwealth-F2006B04584-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 212/52 - Main Driveshaft and Tail Rotor Drive Over-Temperature Indicators","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 212 Series Helicopters\n\nAD/BELL 212/52 Main Driveshaft and Tail Rotor Drive\n\nOver-Temperature Indicators\n\n  \n10/94\n\nApplicability: All model Bell 212 helicopters S/N 30501 through 30999, 31101 through 31311,\n\n32101 through 32142 and 35001 through 35066.\n\nRequirement: Action in accordance with Bell Helicopter Alert Service Bulletin 212-93-89 Rev A.\n\nNote: Transport Canada AD CF-94-07 dated 11 April 1994 refers.\n\nCompliance: As specified in the Requirement Document effective from 15 September 1994.\n\nNote: The Pilot in Command may carry out and certify in the maintenance release the Requirement Document Part II Serviceability Check required by this directive.\n\nBackground: Bell Helicopter has advised that the self adhesive temperature indicators are a more reliable means of over temperature indication than that provided by the zinc chromate primer stripe.","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 mechanical issue on a specific aircraft model. It has not expanded beyond its original purpose of mandating improved temperature monitoring."},"complexity_factors":["Very short document (under 300 words)","Only 4 defined elements: applicability (serial number ranges), requirement (single reference document), compliance date, and one permitted exception (Pilot in Command authorization)","No nested conditional logic or cross-references to other legislation","Single external reference to a manufacturer service bulletin and a Canadian equivalent AD","Straightforward command structure: identify aircraft → do this → by this date"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) for specific aircraft.\n\n**What it does:**\n- Requires owners and operators of certain Bell 212 helicopters to install or check **over-temperature indicators** on two critical parts: the main driveshaft and the tail rotor drive.\n- These indicators are small self-adhesive strips that change appearance if the components get dangerously hot — a more reliable warning system than the old zinc chromate primer stripes (a type of paint coating) that were previously used.\n\n**Who it affects:**\n- Owners and operators of Bell 212 helicopters with specific serial numbers (roughly 1970s-era twin-engine helicopters commonly used for firefighting, search and rescue, and offshore transport).\n\n**What must be done:**\n- Follow the instructions in **Bell Helicopter Alert Service Bulletin 212-93-89 Rev A** — a technical notice from the manufacturer.\n- The work must be completed by **15 September 1994**.\n- **Important flexibility:** The Pilot in Command (the pilot flying the aircraft) is allowed to perform and sign off on the \"Part II Serviceability Check\" themselves — they don't need to hire a separate mechanic for this specific check.\n\n**Why it matters:**\nOverheating in the main driveshaft or tail rotor drive can lead to catastrophic mechanical failure and loss of control. This directive ensures pilots have a clear, reliable visual warning of dangerous temperatures before they become critical."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive applies to a defined set of Bell 212 serial numbers and requires compliance with a specified Bell service bulletin (Applicability; Requirement). It implements the manufacturer's recommendation to replace or supplement the zinc chromate primer stripe with self-adhesive temperature indicators (Background). The instrument does not expand the fleet covered beyond the listed serial numbers and does not add additional unrelated obligations; it delegates procedural detail to the service bulletin and allows the Pilot in Command to perform and certify the Part II Serviceability Check (Note). Therefore, there is no indication in this document that the scope of applicability or the fundamental obligation has changed from the directive's stated intent."},"complexity_factors":["Narrow, explicit applicability by serial-number ranges reduces ambiguity (Applicability).","Procedural details are outsourced to an external Bell Helicopter Alert Service Bulletin (Requirement) — the AD does not contain technical steps itself.","Compliance depends on an external Requirement Document with an effective date, requiring operators to obtain and follow that document (Compliance).","Permission for the Pilot in Command to carry out and certify one part of the check reduces procedural complexity and cost for operators (Note: Pilot in Command may carry out and certify).","Cross-reference to another regulator's AD (Transport Canada) creates an additional documentary link but does not change the mechanical requirement (Note: Transport Canada AD CF-94-07)."],"plain_english_summary":"What this directive does (mechanical change)\n\n- Requires owners/operators of certain Bell 212 helicopters to install and use a specific type of temperature indicator on the main driveshaft and tail rotor drive. The work and checks must be carried out in accordance with Bell Helicopter Alert Service Bulletin 212-93-89 Rev A (Requirement).\n\nWho it affects\n\n- Applies only to Bell 212 helicopters with the serial numbers listed in the directive (S/N 30501–30999, 31101–31311, 32101–32142 and 35001–35066) (Applicability).\n\nWhy it matters (official rationale and a practical read)\n\n- The manufacturer (Bell Helicopter) advised that self-adhesive temperature indicators provide a more reliable over-temperature indication than the previous method using a zinc chromate primer stripe (Background). The directive implements that recommendation by requiring the actions specified in the referenced service bulletin (Requirement).\n\nWho pays, who decides, and what behaviour changes\n\n- Who pays: The costs of parts, labour and any checks fall on the aircraft owner/operator of the affected serial-number helicopters (Applicability; Requirement).\n- Who decides: The Civil Aviation Safety Authority issued the directive and sets the compliance requirement (Requirement; Compliance). The detailed method is delegated to the Bell Helicopter Alert Service Bulletin 212-93-89 Rev A, which contains the procedural steps operators must follow (Requirement).\n- Behavioural change: Operators must replace or fit the self-adhesive temperature indicators as directed and carry out the required serviceability checks. The directive also allows the Pilot in Command to perform and certify the Part II Serviceability Check in the maintenance release (Note: Pilot in Command may carry out and certify), which changes how at least that part of compliance can be executed and certified.\n\nCosts, incentives, trade-offs and compliance burden\n\n- Direct costs and concentration: Costs (parts, installation labour, record-keeping) are concentrated on operators of the specified serial-number helicopters; other Bell 212 operators are not affected (Applicability).\n- Procedural dependence and access cost: The directive does not include step-by-step instructions; it requires compliance with the external Bell Alert Service Bulletin (Requirement). Operators must obtain and follow that document, which concentrates the technical implementation and may create an administrative step to access and apply the bulletin.\n- Compliance burden and flexibility: The directive sets a fixed compliance regime (Compliance) but explicitly permits the Pilot in Command to carry out and certify the serviceability check required by Part II of the Requirement Document (Note). That permission reduces the need to use licensed maintenance organisations for that specific check and therefore lowers some compliance cost and scheduling constraints for operators.\n- Implementation risk and effectiveness: The safety outcome depends on correct installation and correct interpretation of the service bulletin. The source attributes improved reliability to the self-adhesive indicators (Background) — that is a manufacturer claim the directive adopts; the actual result in service will depend on workmanship, correct application, and ongoing inspection consistent with the bulletin.\n\nOther cross-references and regulatory context\n\n- The directive notes a related Transport Canada AD (CF-94-07) as a cross-reference (Note: Transport Canada AD CF-94-07), indicating another national regulator has issued related guidance. The Australian directive’s compliance timing is given by reference to the Requirement Document effective date (15 September 1994) (Compliance).\n\nNet operational effect (plain)\n\n- If you operate an affected helicopter, you must implement the specific temperature indicators and the serviceability checks set out in the Bell service bulletin. You will incur the cost of parts and installation, but you may have flexibility for one required check to be completed and certified by the Pilot in Command rather than by a maintenance organisation."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-212-52-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators","history":"/api/acts/ad-bell-212-52-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators/history","analysis":"/api/acts/ad-bell-212-52-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators/analysis","conflicts":"/api/acts/ad-bell-212-52-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators/conflicts","importantCases":"/api/acts/ad-bell-212-52-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators/important-cases","documents":"/api/acts/ad-bell-212-52-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators/documents"}}