{"id":"F2006B04461","name":"AD/BELL 206/146 - Engine RPM Sensor - Limitations","slug":"ad-bell-206-146-engine-rpm-sensor-limitations","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":44298,"registerId":"commonwealth-F2006B04461-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"AIRWORTHINESS DIRECTIVE","sectionType":"part","heading":"AIRWORTHINESS DIRECTIVE","content":"# AIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.","sortOrder":0},{"sectionNumber":"AD/BELL 206/146 Engine RPM Sensor - Limi","sectionType":"part","heading":"AD/BELL 206/146 Engine RPM Sensor - Limitations 7/2001 DM","content":"# AD/BELL 206/146 Engine RPM Sensor \\- Limitations 7/2001 DM\n\nApplicability: All Model 206B and Series 206L helicopters equipped with Allison 250-C20R engine and Soloy engine power-out warning sensors, part number 206-075-545-001, in accordance with Supplemental Type Certificate (STC) SH 95-46 (FAA STC SH4179NM, applicable to Model 206B) and SH 95-45 (FAA STC SH4169NM, applicable to Model 206L).\n\nNote 1: This Directive is not applicable to helicopters with a part number (P/N) 680- 2551-1 engine out sensor.\n\nRequirement: If not previously accomplished, revise the Limitations Section of the applicable approved STC Rotorcraft Flight Manual Supplement by adding the following Warning Statement and Note:\n\nWARNING: For aircraft with an engine-out sensor other than P/N 680- 2551-1 only. To prevent false engine-out signals, the following procedure must be followed during practice auto-rotations. When entering a practice auto-rotation, avoid a pausing or creeping movement of any throttle decrease or increase between full open and idle. If movement is not made at a firm and continuous rate, N1 RPM undershoot and/or oscillation may occur causing a momentary false engine-out warning light and audio indication.\n\nNOTE: Ensure N1 RPM idle speed is set at 62-64%.\n\nThe Amendment may be accomplished by inserting a copy of this Directive into the Flight Manual Supplement.\n\nNote 2: Transport Canada AD CF-2001-13 refers.\n\nNote 3: The above amendment may have been previously accomplished in accordance with either FAA AD 95-24-06 Amdt 39-9438 which required a warning to be inserted in accordance with Soloy Corporation Service Bulletin (SB) 02-680 revised 8 December 1992 or Soloy Corporation SB 02-680R2 dated 25 May 2000 (this SB was approved by the FAA as an Alternate Method of Compliance to AD 95- 24-06 by FAA Transport Airplane Directorate Letter 140S-00-215 dated 16 May 2000).","sortOrder":1}],"analysis":{"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"},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD stays within the original safety focus: preventing false engine‑out warnings during practice autorotations by changing flight manual limitations and pilot procedure. It does not expand regulatory scope to require hardware modification, broader operational restrictions, or additional maintenance mandates. The measure is a procedural mitigation consistent with the underlying intent to correct the unsafe condition described in the Requirement section."},"complexity_factors":["Narrow applicability limited to specific airframe models (206B, 206L) and a single sensor part number (206‑075‑545‑001).","Single, short mandatory change: insert a warning and a note into the Flight Manual Supplement (simple procedural amendment).","One explicit exception (not applicable to P/N 680‑2551‑1).","Cross‑references to STCs (SH 95‑46, SH 95‑45) and to external documents (FAA AD 95‑24‑06, Soloy SB 02‑680/02‑680R2, Transport Canada AD) introduce minor external-document dependency.","Multiple notes describing prior possible compliance actions (creates slight ambiguity whether amendment already done).","No multi‑layered definitions, no nested exceptions, no complex conditional compliance schedules."],"plain_english_summary":"**What this directive does (mechanically)**\n\n- Applies to Bell Model 206B and 206L helicopters that have an Allison 250‑C20R engine and a Soloy engine power‑out warning sensor, part number 206‑075‑545‑001, installed under the listed Supplemental Type Certificates (STCs) (Applicability).\n- Requires the operator to amend the Limitations section of the approved STC Rotorcraft Flight Manual Supplement by adding a specific warning and a note (Requirement). The warning instructs pilots to avoid a pausing or creeping throttle movement between full open and idle when entering practice autorotations, because such slow/thin throttle inputs can cause N1 RPM undershoot or oscillation that may trigger a momentary false engine‑out light and audio warning. The note requires setting N1 idle speed to 62–64%.\n- The amendment may be done simply by inserting a copy of the AD into the Flight Manual Supplement (Requirement).\n- The AD does not apply to helicopters fitted with engine‑out sensor P/N 680‑2551‑1 (Note 1). It also cross‑references related FAA, Transport Canada and Soloy service bulletins and prior FAA airworthiness directives that addressed the same issue (Notes 2–3).\n\n**Who this affects**\n\n- Owners, operators and maintenance organisations of Bell 206B and 206L helicopters with the specified Allison engine and Soloy sensor (P/N 206‑075‑545‑001) installed via the cited STCs.\n- Pilots who perform practice autorotations in those aircraft, because their throttle handling during practice autorotations must follow the added warning.\n- Flight operations and training units that must update manuals and training syllabuses to reflect the new limitation.\n\n**Why it matters (purpose claim and practical effect)**\n\n- The stated purpose is to prevent false engine‑out warnings (a nuisance or potentially distracting alert) that are triggered by certain throttle movements during practice autorotations (Requirement). The AD achieves this by changing pilot behaviour (a procedural mitigation) and by prescribing an N1 idle speed range (62–64%) to limit the conditions that produce the erroneous signal.\n\n**Costs, incentives, trade‑offs and implementation considerations**\n\n- Compliance cost is small and largely administrative: inserting the AD text into the Flight Manual Supplement and briefing/retraining pilots. No hardware replacement is mandated.\n- The AD changes pilot procedure during training: pilots must adopt a firm, continuous throttle movement instead of a creeping/paused motion when entering practice autorotations. That is an operational constraint on how a training manoeuvre is flown.\n- The AD relies on procedural mitigation rather than correcting the sensor or its installation; so it reduces the likelihood of false warnings only when pilots follow the procedure. It does not eliminate the underlying sensor sensitivity or prevent false warnings in other circumstances.\n- There is a modest enforcement/verification burden on operators and maintenance authorities to ensure the Flight Manual Supplement reflects the change and that pilot training is updated.\n- Possible behavioural side effect: some operators or training units may alter training practice (e.g., how autorotations are taught or practised) to avoid conditions that have triggered false warnings.\n- The AD references prior FAA and manufacturer service bulletins and an FAA alternate compliance letter (Notes 2–3). That creates multiple acceptable compliance pathways but also requires operators to check those cross‑referenced documents for alternative methods of compliance.\n\n**Who decides and who pays**\n\n- The CASA delegate issued the AD (opening text). Operators are responsible for complying: updating manuals, implementing training, and ensuring N1 idle speed is set as specified. Costs fall primarily on the operator (administrative time, training time) rather than on the regulator.\n\n**Practical takeaway**\n\n- If you operate a Bell 206B or 206L with the specified Soloy sensor (P/N 206‑075‑545‑001), you must update your Rotorcraft Flight Manual Supplement to add the warning and note, and ensure pilots follow the described throttle technique during practice autorotations and set N1 idle to 62–64% (Requirement, Note 1). If your helicopter uses P/N 680‑2551‑1, the AD is not applicable (Note 1)."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific technical issue with a specific sensor on specific helicopter models. The references to prior FAA and Transport Canada directives (Notes 2-3) and alternative compliance methods do not expand the scope; they simply acknowledge related international safety actions and prior compliance options."},"complexity_factors":["Very short document (approximately 300 words)","Only 3 defined technical terms (STC, P/N, N1 RPM) with context provided","Single, straightforward requirement with clear applicability criteria","No nested exceptions or conditional logic beyond the basic applicability test","Cross-references to other ADs are informational only (Note 2 and 3), not operational dependencies","Simple binary applicability: either the sensor part number matches or it doesn't"],"plain_english_summary":"This AD requires operators of Bell 206B/206L helicopters fitted with Allison 250‑C20R engines and the Soloy power‑out warning sensor (P/N 206‑075‑545‑001) to add a flight‑manual warning. It instructs pilots to move the throttle firmly and continuously during autorotation practice, avoid slow/hesitant throttle movements, and maintain idle at 62–64% N1 to prevent false engine‑out warnings that could confuse emergency responses."}},"importantCases":[],"_links":{"self":"/api/acts/ad-bell-206-146-engine-rpm-sensor-limitations","history":"/api/acts/ad-bell-206-146-engine-rpm-sensor-limitations/history","analysis":"/api/acts/ad-bell-206-146-engine-rpm-sensor-limitations/analysis","conflicts":"/api/acts/ad-bell-206-146-engine-rpm-sensor-limitations/conflicts","importantCases":"/api/acts/ad-bell-206-146-engine-rpm-sensor-limitations/important-cases","documents":"/api/acts/ad-bell-206-146-engine-rpm-sensor-limitations/documents"}}