The purpose of this section is to provide methods and a set of convenient working charts to estimate penalty values in terms of take-off fuel weight for any given airplane mission. The curves are for a range of specific fuel consumption (SFC) and lift/drag ratio (L/D) compatible with the jet engines and supersonic aircraft currently being developed. A typical example showing use of the charts for an air conditioning system is given. Evaluation of the penalty imposed on aircraft performance characteristics by the installation of an air conditioning system is important for two reasons: 1 It provides a common denominator for comparing systems in the preliminary design stage, thus aiding in the choice of system to be used. 2 It aids in pinpointing portions of existing systems where design improvements can be most readily achieved.