AD/CESSNA 120/12 - Carburettor and Cabin air heater muffs

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COMMONWEALTH OF AUSTRALIA (Civil Aviation Safety Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY

SCHEDULE OF AIRWORTHINESS DIRECTIVES

 


AIRWORTHINESS DIRECTIVE


For 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 CASR 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.


 

Cessna 120 and 140 Series Aeroplanes

 

AD/CESSNA 120/12 Carburettor and Cabin Air Heater Muffs 12/2003

 

Applicability: All Cessna 120 and 140 aeroplanes equipped with Cessna welded exhaust muffler assemblies where the exhaust muffler assemblies are fabricated by welding the exhaust stacks to the muffler.

 

Requirement: 1. Remove the carburettor air heater muff and cabin heater muff and inspect the muffler assemblies for evidence of cracks paying particular attention to the areas of the mufflers and stacks adjacent to where the exhaust stacks and tailpipe are welded to the muffler assembly.

 

2. Any placard calling for an inspection of the mufflers every 100 flight hours should be revised to call for the inspection every 25 flight hours.

 

Note: FAA AD 48-25-02 refers.

 

Compliance: 1. Initial inspection within 25 flight hours from effective date of this Directive, or 25 flight hours from the last inspection, thereafter at intervals of 25 hours.

 

2. At the first inspection of the muffler assemblies detailed in this Directive. This Airworthiness Directive becomes effective on 27 November 2003.

Background: Cracking of the heater muff could lead to hazardous gases entering the cockpit.


Jim Coyne

Delegate of the Civil Aviation Safety Authority 14 October 2003

 

 

 

 

 

 


The above AD is notified in the Commonwealth of Australia Gazette on 5 November 2003.

 

 


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Overview

The Civil Aviation Safety Regulations 1998, enacted by the Commonwealth of Australia, aim to maintain and enhance the safety standards within the civil aviation sector. This legislative instrument, specifically Part 39 - 105, addresses the need to manage and rectify unsafe conditions that may affect the airworthiness of aircraft and aeronautical products. The regulation was introduced to ensure that any identified hazards, such as the cracking of muffler assemblies in certain Cessna aeroplanes, are addressed promptly and effectively. The policy objective is to maintain high safety standards by issuing directives that require corrective actions for specific aircraft models, thereby preventing potential hazards that could compromise flight safety. The enactment of this regulation by the Civil Aviation Safety Authority ensures that the aviation industry adheres to stringent safety protocols, thereby protecting the public and maintaining the integrity of civil aviation operations.

Scope and Application

The Civil Aviation Safety Regulations 1998, specifically Part 39 - 105, governs the safety standards for aeronautical products and aircraft within Australia. This legislation applies to all aircraft registered in Australia, including both private and commercial entities, ensuring they meet the prescribed safety standards. The regulations extend their reach to cover all types of aircraft operations, including manufacturing, maintenance, and airworthiness directives. One such directive, AD/CESSNA 120/12, issued under subregulation 39.1 (1), mandates actions to correct unsafe conditions for specific aircraft models, in this case, Cessna 120 and 140 aeroplanes equipped with certain muffler assemblies. The directive applies to all such aircraft and requires the inspection of muffler assemblies for cracks and the adjustment of inspection intervals. This Airworthiness Directive becomes effective on the date it is issued, ensuring timely compliance to enhance flight safety. The authority of the Civil Aviation Safety Authority extends through subordinate instruments, which can modify or expand the application of these regulations as necessary.

Key Provisions

The Civil Aviation Safety Regulations 1998, specifically Part 39 - 105, under the Civil Aviation Safety Authority Schedule of Airworthiness Directives, details an Airworthiness Directive (AD) that applies to all Cessna 120 and 140 aeroplanes equipped with specific muffler assemblies. This AD, issued by a delegate of the Civil Aviation Safety Authority (CASA), mandates certain actions to address an unsafe condition identified in the aircraft's muffler assemblies. The AD requires the removal and inspection of the carburettor air heater muff and cabin heater muff to check for cracks, particularly around the areas where the exhaust stacks and tailpipe are welded to the muffler assembly (section 1). Furthermore, any placards calling for a muffler inspection every 100 flight hours must be revised to call for inspections every 25 flight hours (section 2). This directive references FAA AD 48-25-02 for additional context. The AD imposes obligations on the owners and operators of the affected Cessna 120 and 140 aeroplanes. They are required to conduct the specified inspections within 25 flight hours from the effective date of this directive or from the last inspection, and subsequently at intervals of 25 hours. The initial inspection must be performed immediately upon the directive's effective date. Operators must also revise any relevant inspection placards to comply with the new requirements. These obligations ensure that the identified safety risks are mitigated effectively. Failure to comply with this Airworthiness Directive could lead to severe safety consequences. The potential for hazardous gases to enter the cockpit due to cracking in the muffler assemblies presents a significant risk to flight safety. The AD does not explicitly state penalties for non-compliance within the provided text, but non-compliance with CASA directives generally can result in enforcement actions by CASA, including fines and potential grounding of the aircraft. The seriousness of the safety issue addressed by this AD suggests that CASA may take stringent measures to ensure compliance.

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Sourced from the Federal Register of Legislation at 26 August 2026. For the latest information on Australian Government law please go to https://www.legislation.gov.au.