Purpose: The purpose of this recommended practice is to establish a standard format for the presentation of helicopter mission data@ which will provide data required to establish airframe and/or engine component life. Application: The primary application of the data presented by the procedures of this document is in the preliminary design phases of a life cycle. Due to the lack of actual in-service data@ the information gives the designer the initial estimate of the expected engine duty cycle. The preliminary design data should be modified as additional data are obtained form service experience. Examination of flight recordings of the pertinent parameters will provide a more clear definition of the mission.