AD/CESSNA 177/5 Amdt 2 - Pneumatic Stall Warning System

Overview

The Civil Aviation Regulations 1998, enacted by the Australian Parliament, encompass a comprehensive regulatory framework governing various aspects of civil aviation, including airworthiness directives. One such directive, AD/CESSNA 177/5 Amendment 2, addresses a specific safety concern regarding the pneumatic stall warning system in certain Cessna 177 Series Aeroplanes. This directive was introduced to mitigate the risk of inadequate stall warning, which could compromise flight safety. The objective of this directive is to ensure that the pneumatic stall warning system operates correctly and remains audible to the pilot, thus enhancing overall aviation safety. The directive requires pilots to verify the functionality of the pneumatic stall warning system by applying slight suction at the stall warning opening in the left wing, ensuring the horn produces a clearly audible sound. Additionally, it mandates the installation of a placard reminding pilots to pre-flight test the pneumatic stall warning system. Compliance with these requirements must be achieved before each flight for the initial check and within 25 hours time in service after the directive's issuance. This amendment rectifies a typographical error and updates the part numbers to reflect the latest specifications from Cessna.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, encompasses the authority and directives related to airworthiness, including the Airworthiness Directives for various aircraft models such as the Cessna 177 Series Aeroplanes. This legislative instrument applies to all models of the Cessna 177 series equipped with a pneumatic stall warning system that does not incorporate the horn reed assembly parts numbers 0413483-2, 0713348-1 or subsequent, and does not have protective screens over the horn bell and stall warning system opening on the left wing. The regulation is applicable across the Commonwealth of Australia, overseen by the Civil Aviation Safety Authority (CASA). The directive mandates that the pneumatic stall warning system be checked for correct operation before each flight and requires the installation of a placard reminding the pilot to pre-flight test the system. Additionally, the directive outlines specific modifications that can be made to the aircraft to meet these requirements, such as replacing the stall warning reed assembly with the specified part numbers and installing a mesh screen over the horn bell and left wing opening. These modifications must be followed within 25 hours time in service after 5 September 1968. The regulations extend their application through subordinate instruments which may provide further specifications and enforcement details.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, outlines the requirements and procedures for ensuring the airworthiness of Cessna 177 series aeroplanes under the authority of the Civil Aviation Safety Authority (CASA). This part includes the Airworthiness Directive (AD) for Cessna 177 series aeroplanes, identified as AD/CESSNA 177/5 Amendment 2, which pertains to the pneumatic stall warning system. The AD applies to all models equipped with a pneumatic stall warning system that do not include the horn reed assembly P/N 0413483-2, P/N 0713348-1 or subsequent, and protective screens over the horn bell and stall warning system opening on the left wing (Section 39-105). The primary requirement outlined in this AD is that the pneumatic stall warning system must be checked for correct operation before each flight. This involves applying slight suction at the stall warning opening in the left wing using the mouth. The check must ensure that the horn produces a sound that is clearly audible. It may be advisable to cover the opening with a clean piece of cloth prior to the check. This procedure is referenced in the Cessna 100 Series Service Manual from 1963 to 1967, Section 16 (Section 39-105). Additionally, a placard must be installed in full view of the pilot stating "PRE-FLIGHT TEST THE PNEUMATIC STALL WARNING SYSTEM" (Section 39-105). These checks and placard requirements must be completed before each flight and within 25 hours time in service after 5 September 1968, respectively. The AD also provides an alternative to the initial requirements. If the stall warning reed assembly P/N 0413028-1 is replaced with the reed assembly P/N 0413483-2, P/N 0713348-1 or subsequent, and an 18 x 14 or 18 x 16 mesh screen is installed over the exposed horn bell inside the cabin and over the left wing opening, the requirements for the pre-flight checks and placard can be removed. The aircraft must then be flight tested to ensure that the stall warning horn sounds at 5 to 10 knots above the stalling speed (Section 39-105). Failure to comply with the provisions of the AD may result in various consequences. While the regulations do not explicitly state penalties, non-compliance with airworthiness directives can lead to enforcement actions by CASA. Such actions may include the grounding of the aircraft until the required modifications are made, and potential civil or criminal penalties if the non-compliance results in a safety breach. It is essential for operators to adhere to these requirements to ensure the continued airworthiness and safety of the aircraft.