ABSTRACT
This chapter focuses on the creation of an aircraft system at its very highest level. Top-level sizing is the heart of the creative process in aircraft design. The basic requirements which are allocated to this function are the temperature, pressure, humidity, and air quality throughout the aircraft. Depreciation is the primary direct operating costs (DOC) component which accounts for the unit cost of the aircraft, although the hull insurance component is also dependent on the unit cost. The initial sizing set the aerodynamic parameters at the aircraft level to meet the performance and cost goals. The DOC will depend on the toplevel requirements and the parameters estimated in the initial sizing, for example, take-off weight and number of engines. A successful metric is the cost reduction from fewer redesigns and after drawing release, both in engineering and manufacturing. The engines are normally sized by the conditions at take-off.
