{"id":"F2006B08254","name":"AD/CESSNA 337/9 - Rear Engine Idle RPM - Adjustment and Placard Installation","slug":"ad-cessna-337-9-rear-engine-idle-rpm-adjustment-and-placard-installation","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":115556,"registerId":"commonwealth-F2006B08254-current","compilationNumber":null,"startDate":"2026-04-03","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/CESSNA 337/9 - Rear Engine Idle RPM - Adjustment and Placard Installation","content":"---\nmeta-content-style-type: text/css\nmeta-content-type: application/xhtml+xml; charset=utf-8\nmeta-generator: Aspose.Words for .NET 22.10.0\n---\n\n?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"no\"?>\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n \n\n![](image.001.png)  Cessna 337 Series Aeroplanes\n\n \n\nAD/CESSNA 337/9 Rear Engine Idle RPM - Adjustment\n\nand Placard Installation\n\n\n8/71\n\n \n\nApplicability: All models.\n\n \n\nRequirement: 1. Readjust the rear engine idle setting from 600 + 25 RPM to 650 + 25 RPM and readjust the idle mixture accordingly.\n\n \n\n2. Install a permanent placard adjacent to the tachometer as follows:\n\n \n\nTAKE AND TAKE-OFF LEAD WITH REAR ENGINE POWER CHECK RPM AND FUEL FLOW.\n\n \n\nNote: The operator may make and install a temporary placard, using letters of 1/8\" minimum height, until a permanent placard as detailed in Cessna SL No. ME71-21 is obtained from the manufacturer and installed.\n\n \n\nCompliance: Within 10 hours time in service after 25 August 1971.\n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n\n \n","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive's scope is limited and specific: it applies to all Cessna 337 models and requires a single mechanical adjustment (rear-engine idle and idle mixture) and installation of a specified placard, to be completed within the stated timeframe. There is no indication in the text that the directive expands or alters its original technical scope beyond those explicit requirements (Applicability; Requirement 1; Requirement 2; Compliance)."},"complexity_factors":["Technical maintenance task: requires someone able to set engine idle RPM and adjust mixture correctly (Requirement 1).","Regulatory specificity: exact RPM change and exact placard wording are prescribed (Requirement 1; Requirement 2).","Short compliance window: 10 hours time-in-service after a specified date creates scheduling pressure (Compliance).","Minor logistical issue: operator may fit temporary placard until manufacturer placard is available, requiring later replacement (Requirement 2; Note).","Applicability is broad but the actions are narrow: applies to all models but requires only two specific actions (Applicability; Requirement 1; Requirement 2)."],"plain_english_summary":"## What this directive does\n\n- It requires owners/operators of Cessna 337 series aeroplanes to change the rear (pusher) engine idle speed setting and to install a permanent placard next to the tachometer. (Applicability; Requirement 1; Requirement 2)\n\n- Mechanically, the rear-engine idle speed must be reset from 600 ± 25 RPM to 650 ± 25 RPM and the idle fuel/air mixture adjusted to suit the new idle setting. (Requirement 1)\n\n- A permanent placard must be installed adjacent to the tachometer bearing the following wording exactly as shown in the directive: \"TAKE AND TAKE-OFF LEAD WITH REAR ENGINE POWER CHECK RPM AND FUEL FLOW.\" Operators may temporarily make and fit a placard (letters at least 1/8\" high) until the manufacturer’s permanent placard (Cessna SL No. ME71-21) is obtained. (Requirement 2; Note)\n\n- The work must be completed within 10 hours time-in-service after 25 August 1971. (Compliance)\n\n## Who is affected\n\n- All Cessna 337 models are covered. The owner or operator of each aircraft is responsible for compliance. (Applicability)\n\n## Who pays and who decides\n\n- The owner/operator pays for the mechanical adjustment, any labour, and the permanent placard. The operator may decide to fit a temporary placard they make themselves until the manufacturer placard is available. (Requirement 1; Requirement 2; Note)\n\n## Why it matters (official claim and practical implications)\n\n- The directive’s stated mechanical change is an increase in rear-engine idle RPM and a placard to make pilots check rear-engine power and fuel flow for take and take-off. The document itself presents these as the required actions; it does not state an explicit narrative of operational safety rationale beyond the required adjustments. (Requirement 1; Requirement 2)\n\n- Practical implications and trade-offs to consider: the required adjustment must be done by someone with the skills and tools to set engine idle and mixture correctly; this creates a short-term maintenance cost and a brief aircraft downtime. The placard changes cockpit information and procedure memory — it is a low-cost, persistent reminder but requires physical installation and, if the manufacturer placard is not immediately available, an operator-made temporary placard is permitted. (Requirement 1; Requirement 2; Note)\n\n## Compliance burden and implementation risks\n\n- Time constraint: the AD sets a compliance deadline of 10 hours time-in-service from 25 August 1971, which imposes a tight period for making the adjustment and fitting the placard. Operators must schedule maintenance promptly. (Compliance)\n\n- Technical burden: resetting idle RPM and adjusting mixture is maintenance work that typically requires a qualified technician and tooling; incorrect adjustment could affect performance until corrected. (Requirement 1)\n\n- Supply/distribution: the manufacturer’s specified permanent placard (Cessna SL No. ME71-21) may not be immediately on-hand, so operators are explicitly permitted to fit a temporary placard that meets the minimum lettering requirement until the OEM placard is installed. This preserves immediate compliance options but requires replacement later. (Requirement 2; Note)\n\n## Discretion and enforcement\n\n- The directive prescribes specific mechanical settings and placard wording, leaving little technical discretion about what must be done. The only discretion explicitly granted to the operator is to make and install a temporary placard until the manufacturer’s placard is obtained. (Requirement 1; Requirement 2; Note)\n\n## Net effect on private choice and operations\n\n- Owners/operators must incur maintenance and placarding costs within a fixed short timeframe. The requirement changes a cockpit setting and the visible cockpit information; pilots and maintenance providers must incorporate the new idle setting and the placard instruction into pre-flight and power checks. (Requirement 1; Requirement 2; Compliance)\n\n(References in parentheses refer to the labeled parts of the directive: Applicability; Requirement 1; Requirement 2; Note; Compliance.)"},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue airworthiness directive issued in 1971 (as indicated by '8/71' and the compliance date). It addresses a specific technical safety issue (rear engine idle RPM) for a specific aircraft type. There is no evidence of scope creep; the directive remains tightly focused on its original safety purpose."},"complexity_factors":["Very short document (approximately 200 words)","Only 2 substantive requirements with clear, sequential numbering","Single defined term: 'time in service' (standard aviation term, not explicitly defined here)","No cross-references to other legislation or regulations beyond the enabling authority (Civil Aviation Regulations 1998, Part 39)","Simple conditional logic: temporary placard permitted as interim measure with one specific dimensional requirement (1/8\" minimum height)","No nested exceptions or sub-delegations"],"plain_english_summary":"**What this is:** This is an Airworthiness Directive (AD) — essentially a mandatory safety fix ordered by Australia's aviation regulator (CASA) for a specific aircraft type.\n\n**Who it affects:** Owners and operators of **Cessna 337 series aeroplanes** (twin-engine push-pull aircraft, nicknamed \"Skymaster\"). This applies to **all models** of this aircraft.\n\n**What it requires:** Two specific safety actions:\n- **Engine adjustment:** Mechanics must raise the rear engine's idle speed from 600 RPM (plus or minus 25) to **650 RPM (plus or minus 25)**, and adjust the fuel mixture accordingly. This prevents the rear engine from stalling or running rough at low power.\n- **Placard installation:** A warning label must be installed next to the tachometer (the RPM gauge) reading: *\"TAKE AND TAKE-OFF LEAD WITH REAR ENGINE POWER CHECK RPM AND FUEL FLOW.\"* This reminds pilots to verify rear engine performance before takeoff. Operators can use a temporary label (with letters at least 1/8 inch tall) until they get the official permanent placard from Cessna.\n\n**Why it matters:** Incorrect idle settings on the rear engine could cause engine failure during critical flight phases — particularly takeoff and landing — when pilots rely on both engines. The placard ensures pilots perform proper pre-flight checks.\n\n**Deadline:** Aircraft operators had to complete this work **within 10 hours of flying time after 25 August 1971**."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-337-9-rear-engine-idle-rpm-adjustment-and-placard-installation","history":"/api/acts/ad-cessna-337-9-rear-engine-idle-rpm-adjustment-and-placard-installation/history","analysis":"/api/acts/ad-cessna-337-9-rear-engine-idle-rpm-adjustment-and-placard-installation/analysis","conflicts":"/api/acts/ad-cessna-337-9-rear-engine-idle-rpm-adjustment-and-placard-installation/conflicts","importantCases":"/api/acts/ad-cessna-337-9-rear-engine-idle-rpm-adjustment-and-placard-installation/important-cases","documents":"/api/acts/ad-cessna-337-9-rear-engine-idle-rpm-adjustment-and-placard-installation/documents"}}