{"id":"F2005L00211","name":"AD/ROTAX/21 Amdt 1 - Coolant \"Evans NPG+\" or Conventional Water-Glycol Coolant","slug":"ad-rotax-21-amdt-1-coolant-evans-npg-or-conventional-water-glycol-coolant","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":33738,"registerId":"commonwealth-F2005L00211-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Rotax Piston Engines","sectionType":"division","heading":"Rotax Piston Engines","content":"### Rotax Piston Engines\n\n| AD/ROTAX/21 Amdt 1 | Coolant \"Evans NPG+\" or ConventionalWater-Glycol Coolant | 3/2005 |\n| ------------------ | -------------------------------------------------------- | ------ |\n\n```html\n

Applicability:

Bombardier Rotax 912 A, 912 F, 912 S and 914 F series reciprocating aircraft engines.

Requirement:

1. Exchange current conventional engine coolant with a new coolant liquid type “Evans NPG+” per provisions of Bombardier Rotax Mandatory Service Bulletin SB-912-043 / SB-914-029 initial issue dated September 2004 or later revision approved by European Aviation Safety Agency (EASA). Operate the engine per Cylinder Head Temperature (CHT) limits specified in requirement 2 of this AD.

OR

Continue the use of conventional glycol / water coolant (mixing ratio 50/50). If you use this option, check the open-up pressure of the coolant pressure vessel cap. The open-up pressure is marked on the cap. If marked open-up pressure is any pressure other than “1.2 bar” or if marking is not legible or missing altogether, replace the cap with a new pressure vessel cap Rotax Part number 922.070. Operate the engine per CHT limits specified in requirement 2 of this AD.

2. Make the following changes to the engine installation and operating manuals:

i) Operator’s Manuals Rotax 912 A/F Series, Chapter 10, Operating Limits.

CHT

Use of EVANS NPG+

Max 150 Degree C

Use of Glycol / Water Coolant (50/50) and use of a 1.2 bar pressure vessel cap.

Max 120 Degree C

\n```\n\n```html\n

ii) Operator’s Manuals Rotax 912 S Series and 914 F series, Chapter 10, Operating Limits.

CHT

Use of EVANS NPG+

Max 135 Degree C

Use of Glycol / Water Coolant (50/50) and use of a 1.2 bar pressure vessel cap.

Max 120 Degree C

iii) Installation Manual Rotax 912 A Series, Chapter 7.1, Operating Limits.

CHT

Use of EVANS NPG+

Max 150 Degree C

Use of Glycol / Water Coolant (50/50) and use of a 1.2 bar pressure vessel cap.

Max 120 Degree C

iv) Installation Manual Rotax 912 F Series, Chapter 6.1, Operating Limits.

CHT

Use of EVANS NPG+

Max 150 Degree C

Use of Glycol / Water Coolant (50/50) and use of a 1.2 bar pressure vessel cap.

Max 120 Degree C

v) Installation Manual Rotax 912 S Series, Chapter 7.1, Operating Limits.

CHT

Use of EVANS NPG+

Max 135 Degree C

Use of Glycol / Water Coolant (50/50) and use of a 1.2 bar pressure vessel cap.

Max 120 Degree C

vi) Installation Manual Rotax 914 F Series, Chapter 8.1, Operating Limits.

CHT

Use of EVANS NPG+

Max 135 Degree C

Use of Glycol / Water Coolant (50/50) and use of a 1.2 bar pressure vessel cap.

Max 120 Degree C

\n```\n\n| | Note: Austrian ACG Airworthiness Directive A-2004-004 R1 as approved by EASA reference 2004-12534 dated 22 December 2004 refers. |\n| ----------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Compliance: | 1. Unless accomplished earlier, before 31 December 2005.2. Unless accomplished earlier, before 31 December 2005. |\n| | This Amendment becomes effective on 17 March 2005. |\n| Background: | During operation, conventional coolant liquid (mixture ratio of 50% water and 50% antifreeze) can vaporize or boil under certain circumstances before reaching of the maximum cylinder head temperature. Loss of cylinder head cooling may lead to engine over temperature, seizure or fire. This AD addresses the identified unsafe condition associated with engine fire or loss of power.The original issue of this AD required changing conventional engine coolant with a new coolant liquid type “Evans NPG+”. This amendment allows use of either coolant with revised maximum CHT Limits.The original issue of this AD became effective on 25 November 2004. |\n\n![](image.001.png) \nJames Coyne \nDelegate of the Civil Aviation Safety Authority\n\n4 February 2005","sortOrder":0},{"sectionNumber":"AD/ROTAX/21 Amdt 1","sectionType":"part","heading":"AD/ROTAX/21 Amdt 1","content":"## AD/ROTAX/21 Amdt 1","sortOrder":1},{"sectionNumber":"Coolant \"Evans NPG+\" or ConventionalWate","sectionType":"part","heading":"Coolant \"Evans NPG+\" or ConventionalWater-Glycol Coolant","content":"## Coolant \"Evans NPG+\" or Conventional \nWater-Glycol Coolant","sortOrder":2},{"sectionNumber":"3/2005","sectionType":"part","heading":"3/2005","content":"## 3/2005","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original AD (effective November 2004) mandated a single solution: switching to Evans NPG+ coolant. This amendment expands the scope to allow an alternative compliance path using conventional coolant with a specific 1.2 bar pressure cap, effectively doubling the regulatory options while maintaining safety standards. The scope has broadened from 'mandatory coolant replacement' to 'mandatory coolant replacement OR cap verification with temperature monitoring'."},"complexity_factors":["Two alternative compliance paths (Evans coolant vs. conventional coolant with cap replacement)","Multiple engine variants (912 A, 912 F, 912 S, 914 F) with slightly different temperature limits","Six separate manual updates required across operator and installation manuals","Specific part number requirement (Rotax 922.070) for pressure vessel cap","Cross-reference to European Aviation Safety Agency (EASA) approved service bulletin","Amendment structure requires understanding of what changed from original AD (November 2004) vs. this version (March 2005)"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to owners and operators of specific **Bombardier Rotax aircraft engines** (912 A, 912 F, 912 S, and 914 F series).\n\n**What the problem is:**\nConventional engine coolant (a 50/50 mix of water and antifreeze) can boil or vaporise before the engine reaches its maximum safe temperature. This can cause the engine to overheat, seize up, or even catch fire.\n\n**What you must do:**\nYou have **two options** to fix this safety issue:\n\n1. **Switch to a special coolant** called \"Evans NPG+\" (following the manufacturer's service bulletin), **OR**\n2. **Keep using conventional coolant** BUT you must:\n - Check that your coolant pressure cap opens at exactly **1.2 bar** pressure\n - Replace the cap if it's the wrong pressure, illegible, or missing (use Rotax part number 922.070)\n\n**New operating limits:**\nDepending on which coolant you choose and which engine model you have, you must update your manuals with new maximum **Cylinder Head Temperature (CHT)** limits:\n\n| Engine Type | Evans NPG+ Max Temp | Conventional Coolant Max Temp |\n|-------------|---------------------|-------------------------------|\n| 912 A/F Series | 150°C | 120°C |\n| 912 S Series | 135°C | 120°C |\n| 914 F Series | 135°C | 120°C |\n\n**When you must comply:**\nBefore **31 December 2005** (unless you've already done the work).\n\n**Why this matters:**\nThis amendment gives aircraft owners more flexibility than the original directive (which only allowed the Evans coolant). Now you can choose either option, but you must follow the specific temperature limits and equipment requirements for your choice. Ignoring this AD could lead to engine failure or fire in flight."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":true,"description":"Yes. The amendment broadened the original AD's scope. The original AD required changing conventional coolant to Evans NPG+ only. This amendment adds an alternative compliance path allowing continued use of conventional 50/50 glycol/water coolant provided the coolant pressure cap is verified (or replaced with Rotax part 922.070 if not marked 1.2 bar) and operators adopt lower CHT limits in manuals. Mechanically, the amendment moves the instrument from a single mandatory hardware/substance change to a two‑option regime that couples either a coolant conversion or a cap/operating‑limit control. That expands operator choice but imposes additional manual‑update and monitoring requirements."},"complexity_factors":["Applies to four engine series (Rotax 912 A, 912 F, 912 S, 914 F) with differing CHT limits","Two compliance paths (convert to Evans NPG+ per SB or retain conventional coolant with cap inspection/replacement)","Multiple manual amendments required across Operator's and Installation manuals (several chapters listed)","Different numeric CHT limits by engine series and by coolant option (120 °C, 135 °C, 150 °C)","External cross‑reference to Bombardier Rotax Mandatory Service Bulletin SB‑912‑043 / SB‑914‑029 and EASA approval","Specific part number mandated for cap replacement (Rotax part 922.070)","Compliance deadline and transitional allowance (deadline before 31 Dec 2005) adds temporal condition"],"plain_english_summary":"**What this airworthiness directive does (mechanically):**\n\n- It applies to Bombardier Rotax 912 A, 912 F, 912 S and 914 F series piston aircraft engines. \n- Operators must either: \n - Replace their existing conventional glycol/water coolant (50/50 mix) with the coolant product \"Evans NPG+\" following the Bombardier Rotax Mandatory Service Bulletin SB-912-043 / SB-914-029 (initial issue Sept 2004) or a later EASA‑approved revision; OR \n - Continue using conventional glycol/water coolant (50/50) but check the coolant pressure‑vessel cap’s marked open‑up pressure and, if it is anything other than \"1.2 bar\" (or the marking is illegible/missing), replace the cap with Rotax part number 922.070. \n- In all cases operators must update the engine installation and operating manuals to reflect revised Cylinder Head Temperature (CHT) limits (Requirement 2). The AD specifies different maximum CHTs depending on engine series and coolant choice (tables below). \n\n**The CHT (maximum) values required to be recorded in manuals:**\n- For Rotax 912 A / 912 F (and some Installation Manual entries):\n - Use of Evans NPG+: Max CHT 150 °C\n - Use of Glycol/Water (50/50) with a 1.2 bar cap: Max CHT 120 °C\n- For Rotax 912 S and 914 F (and corresponding Installation Manual entries):\n - Use of Evans NPG+: Max CHT 135 °C\n - Use of Glycol/Water (50/50) with a 1.2 bar cap: Max CHT 120 °C\n\n(These values must be inserted into the relevant chapters of the Operator’s and Installation manuals listed in the AD.)\n\n**Who this affects:**\n- Aircraft owners and operators that use the specified Rotax 912/914 engines. \n- Maintenance organisations that service those engines (they must perform the coolant swap or cap inspection/replacement and must update manuals). \n\n**Why it matters (stated safety rationale and what it changes):**\n- The AD addresses a thermal‑management safety problem: conventional 50/50 water/glycol coolant can boil under some operating conditions before the cylinder head reaches its maximum allowable temperature. If coolant vaporises, cylinder head cooling can be lost, increasing the risk of engine overheat, seizure, or fire. \n- The original AD required switching to Evans NPG+ only. This amendment gives operators a second option (keep conventional coolant) provided the cap opens at 1.2 bar and the operator uses the lower CHT limits for conventional coolant. The stated intent is to reduce the risk that coolant boiling will cause loss of cooling. \n\n**Who pays, who decides, and what behaviour changes:**\n- Operators pay for either the Evans NPG+ coolant and its installation, or for inspection and possible replacement of the pressure cap (Rotax part 922.070) and for updating manuals. \n- The operator or their maintenance organisation decides which option to take (change coolant or keep conventional coolant and verify/replace cap) and must ensure manuals reflect the required CHT limits. \n- Behavioural change: monitor and limit CHT to the new maximums depending on coolant choice; maintain the specified cap or use Evans NPG+.\n\n**Practical trade‑offs, costs and implementation risks:**\n- Costs: buying Evans NPG+ and performing a coolant conversion has a direct material and labour cost; alternatively, inspecting/replacing the cap and inserting new CHT limits into manuals is likely lower direct cost but imposes an operational restriction (lower maximum CHT when using conventional coolant). \n- Operational effect: Evans NPG+ allows higher permitted CHTs (135–150 °C depending on model), which may reduce operational constraints (fewer derates). Conventional coolant forces a lower CHT ceiling (120 °C), which may require different operating techniques or limit engine loading in some conditions. \n- Compliance burden: updating multiple operator and installation manual chapters (several engine series and chapters are named) and ensuring maintenance records reflect whichever option is chosen. \n- Implementation risk: failure to correctly inspect/replace the cap, failure to update manuals, or failure to comply with the lower CHT limit when using conventional coolant could leave the safety issue unaddressed. \n- Supply/market considerations: availability and price of Evans NPG+ versus conventional coolant, and availability of the specified replacement cap (Rotax 922.070), will affect operator choices and costs. \n\n**References inside the directive:**\n- Requirement 1: option to convert to Evans NPG+ per SB‑912‑043 / SB‑914‑029 (EASA approved) or to retain conventional coolant with cap check/replacement (Rotax part 922.070). \n- Requirement 2: mandatory manual amendments and the precise CHT values to be entered for each engine series.\n\n(Compliance dates and the AD's background are provided in the directive itself; operators must meet the stated compliance deadline in the AD.)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-rotax-21-amdt-1-coolant-evans-npg-or-conventional-water-glycol-coolant","history":"/api/acts/ad-rotax-21-amdt-1-coolant-evans-npg-or-conventional-water-glycol-coolant/history","analysis":"/api/acts/ad-rotax-21-amdt-1-coolant-evans-npg-or-conventional-water-glycol-coolant/analysis","conflicts":"/api/acts/ad-rotax-21-amdt-1-coolant-evans-npg-or-conventional-water-glycol-coolant/conflicts","importantCases":"/api/acts/ad-rotax-21-amdt-1-coolant-evans-npg-or-conventional-water-glycol-coolant/important-cases","documents":"/api/acts/ad-rotax-21-amdt-1-coolant-evans-npg-or-conventional-water-glycol-coolant/documents"}}