{"id":"F2006B09972","name":"AD/FSM/30 - Mixture Control Shaft Retention Screw","slug":"ad-fsm-30-mixture-control-shaft-retention-screw","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":55256,"registerId":"commonwealth-F2006B09972-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/FSM/30 - Mixture Control Shaft Retention Screw","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nFuel Supply and Metering Equipment\n\nAD/FSM/30 Mixture Control Shaft Retention Screw 3/95\n\nApplicability: Precision Airmotive Corporation Model HA-6 series carburettors as detailed in Precision Airmotive Corporation Mandatory Service Bulletin No. MSA-6.\n\nRequirement: Install retainer clip P/N 55-A239 in accordance with Precision Airmotive Corporation Mandatory Service Bulletin No. MSA-6 or Marvel Schebler Service Bulletin No. A1- 78.\n\nNote: FAA Airworthiness Directive 94-25-04 refers.\n\nCompliance: Effective 2 March 1995: Unless previously accomplished; prior to 31 December 1995.\n\nBackground: This Directive has been issued to require the installation of a retainer clip to the mixture control assembly. The requirement follows advice that excessive wear on the mixture control shaft retention screw can result in the mixture shaft moving out of position and a resultant interruption to fuel flow.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, single-issue safety directive focused solely on preventing fuel flow interruption in specific carburettor models. It has not expanded beyond its original mechanical safety purpose."},"complexity_factors":["Very short document (under 200 words)","Only 1 substantive requirement (install a specific part)","No defined terms section","Single cross-reference to FAA directive and manufacturer service bulletins","Clear, unconditional compliance deadline","No nested exceptions or conditional logic"],"plain_english_summary":"This is an **Airworthiness Directive** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA) that requires aircraft owners and operators to fix a specific mechanical problem.\n\n**What it does:**\nOrders the installation of a small metal clip (retainer clip part number 55-A239) on certain aircraft carburettors made by Precision Airmotive Corporation (Model HA-6 series). This clip prevents a screw from wearing out and letting the fuel mixture control shaft slip out of place.\n\n**Why it matters:**\nIf the retention screw wears down, the mixture shaft can move out of position and **cut off fuel flow to the engine** — potentially causing engine failure in flight.\n\n**Who must comply:**\nAnyone operating an aircraft with the affected Precision Airmotive HA-6 series carburettors. The directive references specific service bulletins that detail exactly which carburettors are affected.\n\n**When:**\nThe fix had to be done by 31 December 1995 (unless already completed).\n\n**Key point:** This directive adopts a US Federal Aviation Administration (FAA) safety order (AD 94-25-04) and applies it to Australian-registered aircraft."},"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The Directive's scope is consistent with its stated purpose in the text: it applies only to the Precision Airmotive HA-6 series carburettors identified in the referenced service bulletin and requires installation of a specific retainer clip to address wear of the mixture control shaft retention screw. There is no indication in the supplied text that the Directive alters that scope from the original stated intent (Applicability; Requirement; Background)."},"complexity_factors":["Narrow technical scope: single discrete retrofit (installation of one retainer clip mentioned as P/N 55-A239) (Requirement).","Clear applicability: limited to Precision Airmotive Model HA-6 series carburettors listed in the referenced service bulletin (Applicability).","Single specified method: installation must follow one of two identified service bulletins, reducing procedural ambiguity (Requirement).","Fixed compliance timeline with a single deadline and effective date (Compliance).","Safety-critical context increases stakes despite procedural simplicity (Background).","Dependence on accurate execution of manufacturer/OEM service bulletin procedures introduces implementation risk (Requirement)."],"plain_english_summary":"The Directive mandates fitting a metal retainer clip (P/N 55‑A239) to the mixture control shaft of specified Precision Airmotive HA‑6 carburettors to prevent shaft movement and possible fuel‑flow interruption. Owners/operators of affected aircraft must obtain and install the clip per the named service bulletin at their expense; the requirement took effect 2 Mar 1995 with compliance by 31 Dec 1995."}},"importantCases":[],"_links":{"self":"/api/acts/ad-fsm-30-mixture-control-shaft-retention-screw","history":"/api/acts/ad-fsm-30-mixture-control-shaft-retention-screw/history","analysis":"/api/acts/ad-fsm-30-mixture-control-shaft-retention-screw/analysis","conflicts":"/api/acts/ad-fsm-30-mixture-control-shaft-retention-screw/conflicts","importantCases":"/api/acts/ad-fsm-30-mixture-control-shaft-retention-screw/important-cases","documents":"/api/acts/ad-fsm-30-mixture-control-shaft-retention-screw/documents"}}