{"id":"F2006B04666","name":"AD/BELL 412/32 - Main Driveshaft and Tail Rotor Drive Over-Temperature Indicators","slug":"ad-bell-412-32-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":44418,"registerId":"commonwealth-F2006B04666-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/BELL 412/32 - 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 412 Series Helicopters\n\nAD/BELL 412/32 Main Driveshaft and Tail Rotor Drive\n\nOver-Temperature Indicators\n\n  \n10/94\n\nApplicability: All model Bell Helicopter Textron 412 Series Helicopters S/N 33001 through 33213, 34001 through 34024 and 36001 through 36086.\n\nRequirement: Action in accordance with Bell Helicopter Alert Service Bulletin 412-93-79 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, single-issue airworthiness directive focused specifically on temperature indicator installation. It has not expanded beyond its original safety purpose."},"complexity_factors":["Very short document (under 300 words)","Only 1 substantive requirement (comply with referenced service bulletin)","No defined terms section","No conditional logic or nested exceptions","Single cross-reference to Transport Canada AD for informational purposes only","Straightforward applicability criteria (specific serial number ranges)"],"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) that requires specific maintenance actions on certain aircraft.\n\n**What it does:** It orders owners and operators of specific Bell 412 helicopters to install or check **over-temperature indicators** on two critical parts: the main driveshaft and the tail rotor drive. These indicators are stickers that change appearance if the components get too hot, which could indicate dangerous mechanical stress.\n\n**Why it matters:** Overheating in these parts can lead to catastrophic failure in flight. The directive replaces an older, less reliable method (a painted stripe) with better adhesive temperature stickers.\n\n**Who must comply:** Anyone operating Bell 412 helicopters with serial numbers in the listed ranges (approximately 33001-33213, 34001-34024, and 36001-36086).\n\n**What must be done:** Follow the instructions in **Bell Helicopter Alert Service Bulletin 412-93-79 Rev A**. This includes a serviceability check that the pilot in command (the pilot flying the aircraft) is actually allowed to perform and sign off on themselves — unusually, this doesn't require a licensed aircraft mechanic for that specific check."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The instrument enforces the manufacturer’s specified modification/inspection method for the listed Bell 412 helicopters and does not expand or narrow the class of affected aircraft beyond the serial numbers stated. It prescribes compliance with the Service Bulletin and sets an effective compliance date; it does not add broader regulatory obligations or new aircraft categories beyond those listed. (Applicability; Requirement; Compliance)"},"complexity_factors":["Narrow applicability limited to a specific range of serial numbers (Applicability)","Requirement is a single prescriptive action: follow a named manufacturer Service Bulletin (Requirement)","Short compliance instruction with a fixed effective date reduces procedural complexity (Compliance)","Limited discretionary element: Pilot in Command may perform and certify one part of the check (Note)","Cross-reference to an external foreign AD (Transport Canada) adds minor cross-jurisdictional traceability (Requirement)"],"plain_english_summary":"What this instrument requires\n\n- It requires owners/operators of specified Bell Helicopter Textron 412 series helicopters (serial numbers listed) to carry out the work set out in Bell Helicopter Alert Service Bulletin 412-93-79 Rev A. (Applicability; Requirement)\n- The required work must be done as specified in the Service Bulletin and by the compliance timetable that took effect on 15 September 1994. (Requirement; Compliance)\n- The Pilot in Command is explicitly permitted to perform and sign off the Part II Serviceability Check required by the directive. (Note)\n\nWhat the manufacturer says and how that is tested here\n\n- The manufacturer’s stated reason is that self-adhesive temperature indicators provide a more reliable over-temperature indication than the earlier zinc chromate primer stripe. That statement is recorded as the Background for the directive. (Background)\n- Testing that claim against practical effects: if the self-adhesive indicators work as claimed, the direct benefit would be an improved method of detecting over-temperature conditions. The directive enforces the manufacturer’s method by requiring the actions in the Service Bulletin. (Requirement)\n\nWho pays, who decides, and what behaviour changes\n\n- Who pays: the helicopter owner/operator pays for the parts, labour and any related maintenance downtime needed to comply with the Service Bulletin. (Requirement; Compliance)\n- Who decides: the Civil Aviation Safety Authority (via this airworthiness directive) sets the requirement; the operator decides when and where to implement the Service Bulletin work subject to the AD’s compliance timing. (Requirement; Compliance)\n- Behavioural change required: replace or supplement the zinc chromate primer stripe method with self-adhesive temperature indicators and complete the required serviceability check. The Pilot in Command may perform and certify the specified serviceability check. (Requirement; Note)\n\nCosts, incentives and trade-offs\n\n- Direct costs are the purchase and installation of self-adhesive temperature indicators and any inspection or record-keeping the Service Bulletin requires. Those costs fall to operators (owners) of the affected serial-numbered helicopters. (Requirement; Applicability)\n- The permission for the Pilot in Command to carry out and certify one part of the serviceability check reduces the need to use external maintenance labour for that specific check, which lowers immediate labour cost or outsourcing for some operators. (Note)\n- The AD prescribes following the manufacturer’s Service Bulletin rather than leaving the choice of method to operators; that narrows operational choice but ensures uniformity in the corrective action specified. (Requirement)\n\nImplementation risk, compliance burden and discretion\n\n- Implementation risk is the standard risk that the required work is not carried out correctly if the Service Bulletin instructions are not followed; compliance is achieved by following the Service Bulletin and the AD’s schedule. (Requirement; Compliance)\n- Compliance burden is concentrated on the relatively small set of affected helicopters (identified by serial numbers), meaning the cost is concentrated on those owners/operators rather than broadly distributed. (Applicability)\n- Discretion is limited: the AD requires the actions in the Service Bulletin. The only expressly permitted operational discretion in the AD text is that the Pilot in Command may perform and certify the specified Part II Serviceability Check. (Requirement; Note)\n\nOther references\n\n- The AD records a cross-reference to a Transport Canada airworthiness directive (CF-94-07), cited in the instrument. (Requirement)\n\nBottom-line mechanics in one sentence\n\n- Specified Bell 412 helicopters must have the work described in Bell Helicopter Alert Service Bulletin 412-93-79 Rev A completed by the stated compliance timetable, with the Pilot in Command allowed to perform and sign off the Serviceability Check portion of the work. (Applicability; Requirement; Compliance; Note)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-412-32-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators","history":"/api/acts/ad-bell-412-32-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators/history","analysis":"/api/acts/ad-bell-412-32-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators/analysis","conflicts":"/api/acts/ad-bell-412-32-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators/conflicts","importantCases":"/api/acts/ad-bell-412-32-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators/important-cases","documents":"/api/acts/ad-bell-412-32-main-driveshaft-and-tail-rotor-drive-over-temperature-indicators/documents"}}