AD/B747/122 - Ice and Rain Protection - Pitot Static and Temperature Probe Icing

Overview

The Civil Aviation Regulations 1998, enacted by the Parliament of Australia, address the regulation of civil aviation safety, including the implementation of Airworthiness Directives. One such directive, AD/B747/122, pertains to Boeing 747 Series Aeroplanes, specifically model 747-400 series aircraft, and was introduced to address the problem of ice and rain protection issues related to pitot, static, and temperature probes. The directive was introduced to ensure compliance with Boeing Alert Service Bulletin 747-30A2069 dated 15 July 1993 and to mitigate incidents where aircraft entered the "ground mode" due to hydraulic system depressurisation. The policy objective is to ensure the safety of the aircraft by maintaining the integrity of essential systems such as pitot and total air temperature heat, which can be compromised during icing conditions. Compliance with this directive was mandated before 1 December 1993.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105, governs the safety directives concerning aircraft airworthiness, including the Boeing 747 Series Aeroplanes. This legislation applies to all model 747-400 series airplanes and is enacted under the authority of the Civil Aviation Safety Authority (CASA) as detailed in the Schedule of Airworthiness Directives. The Act mandates compliance with Boeing Alert Service Bulletin 747-30A2069 dated 15 July 1993, which includes action to mitigate risks associated with hydraulic system depressurisation that can cause the aircraft to enter the ground operating mode during flight. The directive was issued to address instances where operators reported aircraft entering ground mode while still airborne, leading to significant depressurisation of the number four hydraulic system. Compliance with this directive is mandatory, with a specified compliance date of 1 December 1993. This regulatory requirement extends to ensuring the functionality of the pitot and total air temperature heat systems in the event of an aircraft entering ground mode, thereby maintaining critical electrical and avionics system operations.

Key Provisions

The Civil Aviation Regulations 1998, specifically Part 39 - 105, addresses the safety requirements for maintaining the airworthiness of Boeing 747 series aeroplanes, particularly the 747-400 models. According to the Airworthiness Directive AD/B747/122 (paragraph 1), operators of these aircraft must comply with Boeing Alert Service Bulletin 747-30A2069 dated 15 July 1993, which pertains to ice and rain protection for the pitot, static, and temperature probes. This directive is crucial to prevent the aircraft from entering the ground operating mode while still airborne, a condition that can arise due to depressurisation of the number four hydraulic system. Such a condition can lead to severe consequences, including incorrect sensing of the aircraft's landing gear position and subsequent erroneous system inputs. Operators of the Boeing 747-400 series must ensure compliance with the directive by making necessary modifications before 1 December 1993. The primary requirement is adherence to the Boeing Alert Service Bulletin, which includes specific actions to safeguard against the risks associated with hydraulic system depressurisation. These actions likely involve installing or modifying components related to the pitot and static systems to maintain their functionality in adverse weather conditions. Compliance also entails ensuring that the aircraft’s Flight Manual is updated to reflect these changes, as mandated by a Flight Manual Amendment issued under Approval Number A/QF747-4/27. This amendment is essential to keep the pilots informed about the updated procedures and system functionalities post-modification. Failure to comply with the Airworthiness Directive AD/B747/122 can result in significant penalties and safety risks. The Civil Aviation Safety Authority (CASA) may impose penalties for non-compliance, which can include fines or other administrative actions. More critically, operating an aircraft that does not meet the airworthiness requirements can lead to dangerous situations, including the aforementioned ground mode entry while in flight. Such operational errors can have severe consequences, potentially leading to accidents. Therefore, it is imperative for operators to ensure full compliance to avoid both regulatory penalties and the risk of aviation accidents. In summary, the Airworthiness Directive AD/B747/122 mandates specific modifications to the pitot, static, and temperature probes of Boeing 747-400 series aircraft to prevent the aircraft from entering ground mode while airborne. Operators must ensure compliance by adhering to Boeing Alert Service Bulletin 747-30A2069 and updating the Flight Manual accordingly. Non-compliance not only risks regulatory penalties but also poses serious safety hazards that could lead to accidents. It is thus essential for operators to take prompt action to meet these regulatory requirements and maintain the highest standards of aviation safety.