Overview

The Airworthiness Directive AD/CESSNA 170/70 was enacted in 2001 by the Civil Aviation Safety Authority (CASA) to address a safety concern related to the engine idle speed and fuel mixture setting in Cessna 172R and 172S models. The directive was introduced to mitigate the risk of rough engine operation due to improper engine servo fuel mixture settings, as reported in the background information. The objective of the directive is to ensure that the fuel mixture settings are correct and that the Pilot’s Operating Handbook (POH) includes proper procedures for engine restart with a rich mixture. The directive mandates that a specific engine idle speed and fuel mixture setting check must be performed and recorded in the Aircraft Log Book, and that the POH and Pilot’s Check List must be amended accordingly. Compliance with these requirements must be achieved within 10 hours of the directive's effective date.

Scope and Application

The Airworthiness Directive (AD) issued under subregulation 39.1 (1) of the Civil Aviation Safety Regulations 1998 mandates specific actions for correcting identified unsafe conditions in certain Cessna aircraft models, namely the Cessna 170, 172, F172, FR172, and 175 Series Aeroplanes. This directive applies to Cessna models 172R and 172S of all serial numbers. The AD requires the pilot in command, excluding student pilots, to perform an engine idle speed and fuel mixture setting check under specific conditions, including an engine oil temperature between 120 and 150 degrees Fahrenheit, with the throttle hard at the ground idle stop, ensuring the engine revolutions per minute (RPM) fall between 575 and 625 RPM, and checking that RPM rises between 10 and 50 RPM when the mixture control is rotated slowly counter clockwise to idle cut-off. Any discrepancies found during this check must be recorded in the aircraft log book and maintenance release. Furthermore, the certificate of registration holder is required to amend the applicable Pilot’s Operating Handbook (POH) and Pilot’s Check List as per the instructions in Cessna Service Bulletin SB01-11-02, with compliance required within 10 hours from the effective date of this Directive. The directive, effective from 1 November 2001, ensures that the engine idle speed and fuel mixture setting is correct and that the POH provides pilots with the necessary procedures for restarting the engine with a rich mixture, addressing reported issues of rough engine operation due to improper engine servo fuel mixture settings.

Key Provisions

The Airworthiness Directive (AD) issued under subregulation 39.1 (1) of CASR 1998 (section 1) mandates specific actions for certain Cessna aeroplanes to address unsafe conditions. The AD applies to Cessna 172R and 172S models of all serial numbers (section 1(a)). The requirement section outlines two main actions: first, to perform an engine idle speed and fuel mixture setting check, which involves checking the engine revolutions per minute (RPM) and ensuring it rises appropriately when the mixture control is adjusted (section 1(b) to (d)). This check must be done with the engine oil temperature between 120 and 150 degrees Fahrenheit and the throttle at the ground idle stop. Second, it requires amending the Pilot’s Operating Handbook (POH) and Pilot’s Check List to reflect the new procedures, as detailed in Cessna Service Bulletin SB01-11-02 (section 1(2)). Compliance with these requirements must be recorded in the Aircraft Log Book or in the “Maintenance required” column of the aircraft maintenance release (section 1). The AD imposes several obligations on the parties involved. The pilot in command, excluding student pilots, is responsible for conducting the engine idle speed and fuel mixture setting check (section 1(b)). The certificate of registration holder can amend the POH and Pilot’s Check List (section 1(2)). These tasks must be completed within 10 hours of the aircraft being in service from the effective date of the Directive, which is 1 November 2001 (section 1). Failure to comply with the AD may result in unsafe conditions, potentially leading to violations of aviation safety regulations. Failure to comply with the AD may result in civil or criminal consequences. The AD does not specify particular penalties in the text, but non-compliance with such directives typically leads to enforcement actions by the Civil Aviation Safety Authority (CASA). This could include fines, revocation of the aircraft's airworthiness certificate, or other regulatory actions to ensure compliance with safety standards. The severity of the penalties depends on the extent of non-compliance and any resultant safety risks.