The aircraft service air-ground-air environmental spectrum consists of two parts： flying environmental spectrum and ground parking environmental spectrum. To most military aircrafts, the ground parking time accounts for more than 90% of the aircraft service life. The service life of aircraft is greatly influenced by the severe environment of naval aircraft where there are 3-highs： high temperature, high humidity and high salt-fog corrosion. The service life of aircraft must be determined based on the environmental spectrum of aircraft service, in which factors such as flying time, calendar time and comprehensive service flying time are taken into account. As a typical example, based on the analysis of the axle neck crack of axial hinge in certain type of naval helicopter by utilizing an analytical method of structural fatigue, the overhaul life of the hinge is discussed in respect of flying time, calendar time and comprehensive service flying time.