{"id":"F2005L02428","name":"AD/BELL 430/2 - Power Turbine RPM Steady State Operation Avoidance","slug":"ad-bell-430-2-power-turbine-rpm-steady-state-operation-avoidance","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":36976,"registerId":"commonwealth-F2005L02428-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Bell Helicopter Textron Canada (BHTC) 43","sectionType":"division","heading":"Bell Helicopter Textron Canada (BHTC) 430 Series Helicopters","content":"### Bell Helicopter Textron Canada (BHTC) 430 Series Helicopters\n\n| AD/BELL 430/2 | Power Turbine RPM SteadyState Operation Avoidance | 10/2005 |\n| ------------- | ------------------------------------------------- | ------- |\n\n| Applicability: | Bell Helicopter Textron Canada (BHTC) Model 430 helicopters, serial numbers 49001 through 49111.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |\n| -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n| Requirement:   | 1. Unless previously accomplished incorporate BHT-430-FM-1 Temporary Revision (TR15) or later Transport Canada approved revision into the rotorcraft flight manual.2. Unless previously accomplished, install the decal as per Alert Service Bulletin 430-05-34, dated 10 June 2005, or later Transport Canada approved revision. It is permissible to locally manufacture the decal with white lettering on a black background, minimum 10 point font size.Requirements 1 and 2 may be accomplished by a pilot endorsed on the Bell 430.Note: Transport Canada AD CF-2005-25 refers.            |\n| Compliance:    | Within 10 calendar days after the effective date of this directive.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |\n|                | This Airworthiness Directive becomes effective on 29 September 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |\n| Background:    | Transport Canada has been advised of multiple reports of failure of the third stage turbine wheel used in both the Rolls-Royce 250-C30S and 250-C47B engines. A similar turbine wheel is also installed in the 250-C40B engine which is utilized by BHTC for the Model 430. Rolls-Royce has determined that detrimental vibrations can occur within a particular range of turbine speed as a potential contributing factor to these failures. BHTC revised their rotorcraft flight manual and provided a decal to inform pilots to avoid steady-state operations at these engine turbine speeds. |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n15 August 2005","sortOrder":0},{"sectionNumber":"AD/BELL 430/2","sectionType":"part","heading":"AD/BELL 430/2","content":"## AD/BELL 430/2","sortOrder":1},{"sectionNumber":"Power Turbine RPM SteadyState Operation ","sectionType":"part","heading":"Power Turbine RPM SteadyState Operation Avoidance","content":"## Power Turbine RPM Steady  \nState Operation Avoidance","sortOrder":2},{"sectionNumber":"10/2005","sectionType":"part","heading":"10/2005","content":"## 10/2005","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific mechanical defect in a specific helicopter model. It has not expanded beyond its safety-critical purpose of preventing turbine wheel failures through operational avoidance."},"complexity_factors":["Very short document (approximately 250 words)","Only 2 substantive requirements with clear alternatives (manufacture decal locally)","Single defined term: 'TR15' (Temporary Revision)","No nested exceptions or conditional logic","Simple compliance timeline (10 calendar days)","Minimal cross-referencing (only to Transport Canada AD CF-2005-25 and Alert Service Bulletin 430-05-34)","Straightforward applicability (specific serial number range)"],"plain_english_summary":"This mandatory AD applies to 43 Bell 430 helicopters (S/N 49001–49111) in Australia and requires, within 10 days of 29 Sept 2005, two pilot-performable actions: add Flight Manual TR15 to avoid specific turbine speeds and install a cockpit warning decal (or equivalent). Rolls‑Royce found those speeds cause damaging vibrations that have led to multiple third‑stage turbine‑wheel failures; compliance prevents in‑flight engine loss and potential crashes."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD stays within the original safety purpose: preventing turbine wheel failure by directing pilots to avoid a specific power‑turbine RPM steady‑state range and providing cockpit notice. It does not expand obligations beyond that narrow operational and documentation change; it does not add new inspection regimes, mandatory parts replacement, or broader applicability."},"complexity_factors":["Applies to a narrow, specific serial‑numbered fleet (49001–49111) — limits scope","Two straightforward required actions (insert temporary RFM revision; install decal)","Short compliance window (10 calendar days)","Permits pilot‑accomplishment (reduces procedural complexity)","Cross‑references external technical documents (BHT‑430‑FM‑1 TR15 and ASB 430‑05‑34) where the specific RPM band and procedural wording are located","Minimal conditional logic or nested exceptions","No large number of defined terms or multiple Parts/Clauses"],"plain_english_summary":"**What this instrument does**\n\n- This Airworthiness Directive (AD) applies only to Bell Helicopter Textron Canada (BHTC) Model 430 helicopters with serial numbers 49001 through 49111. (If your helicopter is not in that serial range, this AD does not apply.)\n\n- It requires two immediate, simple actions: 1) put a specific temporary revision (BHT-430-FM-1 Temporary Revision, TR15, or a later Transport Canada–approved revision) into the rotorcraft flight manual (RFM); and 2) install a cockpit decal that warns pilots to avoid certain steady‑state power turbine speeds. The decal may be locally made (white lettering on black, minimum 10‑point font) and the two tasks may be performed by a pilot who is endorsed to fly the Bell 430.\n\n- These actions had to be completed within 10 calendar days of the directive coming into force (the AD’s effective date is recorded as 29 September 2005).\n\n**Who is affected**\n\n- Owners, operators and pilots of Bell 430 helicopters with serial numbers 49001–49111. Maintenance providers and organisations that hold the flight manuals for those helicopters are also affected because the RFM must be revised.\n\n**Why it matters (mechanics and safety rationale)**\n\n- The AD was issued after multiple reports of failure of the third‑stage turbine wheel in Rolls‑Royce 250 series engines. Rolls‑Royce identified that harmful vibrations can occur at a particular range of power‑turbine rotational speeds (RPM), which can contribute to those failures. The Model 430 uses a similar turbine wheel.\n\n- The AD’s immediate mechanical effect is to change pilot procedure and cockpit information: pilots must avoid operating the power turbine at the specified steady‑state RPM range (details of the prohibited RPM range are provided in the TR15 flight manual revision and the manufacturer’s Alert Service Bulletin referenced by the AD). The decal is a visual reminder in the cockpit to support compliance.\n\n**How the rule works, practically**\n\n- The AD does not require engine modification or grounded inspections; it requires changes to documentation (RFM) and a physical decal.\n- A pilot endorsed on the Bell 430 may perform both tasks, so operators need not send the helicopter to a maintenance facility just to comply.\n- The AD references Transport Canada AD CF‑2005‑25 and Bell’s Alert Service Bulletin 430‑05‑34 (dated 10 June 2005) for the decal instructions, so the technical specifics are contained in those cross‑referenced documents.\n\n**Costs, incentives and trade‑offs (brief analytical lens)**\n\n- Who pays: the operator bears the direct, modest costs — updating the RFM and producing/installing the decal, and any short administrative time to record compliance. There is also an operational cost if pilots must routinely avoid an RPM range, which can alter fuel usage, flight profiles, or crew technique.\n\n- Who decides: the regulator (Civil Aviation Safety Authority delegate, via this AD) mandates the change; the manufacturer supplied the temporary revision and decal specifications; pilots and operators implement it.\n\n- Behaviour change induced: pilots will avoid keeping the power turbine at the specified steady‑state RPM range. That can mean more frequent transient power changes or operating at a different steady RPM outside the affected band.\n\n- Trade‑offs and opportunity costs: avoiding a specific steady‑state RPM range can increase pilot workload and may slightly increase fuel burn or cause other components to operate in different regimes. Those operational effects are indirect and depend on individual flight profiles.\n\n- Compliance burden and implementation risk: the direct burden is low and can be completed by a pilot. The directive relies on cross‑referenced documents (TR15 and the Alert Service Bulletin) for the technical RPM limits; if those documents are not clearly consulted, there is a risk of misinterpretation about what exactly constitutes 'steady‑state' operation and which RPMs to avoid.\n\n- Effects on private enterprise and competition: the AD imposes a narrow, safety‑driven operational constraint on a defined fleet segment. It does not change ownership, market access, or broader competitive conditions; it affects only operations of the specified serial‑numbered helicopters.\n\n**Where to look for the technical detail**\n\n- The AD names the specific RFM temporary revision (BHT‑430‑FM‑1 TR15) and the Alert Service Bulletin 430‑05‑34 for the decal instructions. The RPM band to avoid and any specific procedural language are contained in those cross‑referenced documents rather than fully restated in the short AD itself.\n\n(Information source: the AD sections titled Applicability, Requirement, Compliance and Background, and the AD’s references to the manufacturer TR and Alert Service Bulletin.)"},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-430-2-power-turbine-rpm-steady-state-operation-avoidance","history":"/api/acts/ad-bell-430-2-power-turbine-rpm-steady-state-operation-avoidance/history","analysis":"/api/acts/ad-bell-430-2-power-turbine-rpm-steady-state-operation-avoidance/analysis","conflicts":"/api/acts/ad-bell-430-2-power-turbine-rpm-steady-state-operation-avoidance/conflicts","importantCases":"/api/acts/ad-bell-430-2-power-turbine-rpm-steady-state-operation-avoidance/important-cases","documents":"/api/acts/ad-bell-430-2-power-turbine-rpm-steady-state-operation-avoidance/documents"}}