Installation design methods and results of an aircraft engine on the wing-mounted-nacelle type aircraft has been presented in this paper. The design process starts from design requirements and constraints and covers some major aspects of the engine installation design such as wing-nacelle interference drag, roll clearance, ground clearance, nose gear collapse margin, rotor burst and fuel tank capacity. The method was applied to 100-seat class airplane(K100). Results of the design suggest optimum nacelle location and nacelle installation angle(toe-in, incidence, droop angle) which satisfies in stalled engine performance and size/location of wing dry day.