Maintainability assessment of an engine or unit helps in identifying and validating whether or not the actual design of an engine or unit meets the maintainability characteristics. Maintainability assessment is an important requirement while designing an aircraft engine because it determines whether Line Replaceable Units (LRUs) can be accessed for replacement or periodic inspection or on-wing adjustments. This white paper helps to understand the maintainability of the overall aircraft engine and systems engineering efforts. The paper describes the relationship between the maintainability and design process, presents the approach to understanding the maintainability of LRUs during the design phase, explains the associated tasks and activities, and proposes an alternate method to assess the maintenance tasks and activities.