AD/HS 125/57 - Flight Manual - Change to Metric Units

Overview

The Civil Aviation Regulations 1998, as part of Part 39, address the need for a uniform metric system in aviation to ensure safety and operational efficiency across the industry. Enacted by the Commonwealth of Australia, these regulations were introduced to address the problem of inconsistent measurement systems in aviation documentation, which could lead to confusion and errors in operation and maintenance of aircraft. The Civil Aviation Safety Authority, under the authority of the Department of Transport, issued Airworthiness Directive AD/HS 125/57, requiring that all Hawker Siddeley HS-125 series aeroplanes update their flight manuals to metric units, including weight in kilograms, distances in metres, centre of gravity limits and moment arms in millimetres, fuel and oil quantities in litres, and pressures in kilopascals. This policy objective aims to standardise aviation practices in Australia, reducing the risk of misinterpretation and enhancing safety by ensuring all aviation personnel use a consistent measurement system.

Scope and Application

The Civil Aviation Regulations 1998, specifically Part 39 - 105 under the Civil Aviation Safety Authority Schedule of Airworthiness Directives, applies to all Hawker Siddeley HS-125 series aeroplanes operating within Australia. This legislative instrument mandates that the Department of Transport-approved flight manual for these aircraft must be amended to specify various quantities using the metric system. The directive applies to all entities operating these aeroplanes, ensuring a standardised approach to aircraft safety and operational data throughout the Commonwealth. Notably, the flight manual must use kilograms for weight, metres for distances, millimetres for centre of gravity limits and moment arms, litres for fuel and oil quantities, and kilopascals for pressures. If the aircraft's installed instrumentation is calibrated in non-metric units, both systems of units must be specified within the flight manual. The regulation aims to align with the broader national and international aviation standards that require metric units for airworthiness and operational consistency. Compliance with these amendments is required by 1 January 1984, and the scope of the Act is further extended through subordinate instruments as necessary to ensure adherence and safety across the industry.

Key Provisions

The key provisions of the Civil Aviation Regulations 1998, particularly under Part 39 - 105 and the specified Airworthiness Directive (AD/HS 125/57), focus on ensuring the uniformity of measurement units within flight manuals of the British Aerospace BAe 125 Series Aeroplanes. Section (a) mandates that all weight specifications in the approved flight manual be converted to kilograms. Section (b) requires that distances be measured in metres, while section (c) specifies that centre of gravity limits and moment arms must be in millimetres. Furthermore, section (d) requires fuel and oil quantities to be in litres, and section (e) stipulates that pressures should be in kilopascals. Where aircraft instrumentation is calibrated in different units, the flight manual must include both systems of measurement for clarity. Under these regulations, the obligations imposed on the parties, particularly aircraft operators and maintenance providers, are to ensure the flight manual of the BAe 125 Series Aeroplanes is updated in accordance with the specified metric units. This includes not only the conversion of existing data but also ensuring that any new information added to the manual adheres to these requirements. Operators must also ensure that any discrepancies between the installed aircraft instrumentation and the specified units are clearly noted within the flight manual. The Civil Aviation Regulations impose penalties and consequences for non-compliance with these directives. Any failure to amend the flight manual to comply with the specified units by the compliance date of 1 January 1984 may result in the aircraft being deemed non-airworthy. This could lead to grounding of the aircraft until compliance is achieved, which could have significant operational and financial implications for the operator. While specific penalties are not detailed within this directive, non-compliance with airworthiness directives can generally result in enforcement actions, including fines and potential criminal charges depending on the severity and impact of the non-compliance.