Contents 16.1 Introduction 16.2 Design features and functional aspects 16.2.1 Crankcase 16.2.2 Cylinder unit 16.2.3 Heat exchangers 16.2.4 Fan control 16.3 Cooling fan 16.3.1 General aspects 16.3.2 Layout and design of axial fans 16.3.3 Stators 16.3.4 Fan noise and its reduction 16.3.5 Other design considerations 16.3.6 Manufacturing considerations 16.4 Environmental aspects 16.4.1 Exhaust emissions 16.4.2 Engine noise 16.4.3 Noise characteristics of aircooled engines 16.4.4 Noise attenuation by secondary measures 16.5 Applications References and Bibliography 21761_16a