What is the distinction between 'life-limited' and 'TBO' parts?

The distinction between 'life-limited' and 'TBO' (Time Before Overhaul) parts is important for maintaining helicopter safety and airworthiness. Life-limited parts are components designated by the manufacturer that must be removed and replaced after a certain operational life or cycle limit, regardless of their condition at that time. This is done to ensure the integrity and safety of the helicopter, as these components may undergo stresses that can lead to failure.

On the other hand, TBO parts refer to components that must be overhauled or replaced after a specific time in service, but they may not necessarily have a fixed limit on their operational lifespan based on cycles or hours. TBO can indicate a time interval after which inspection and maintenance are required to ensure continued airworthiness, but the parts may sometimes be overhauled and returned to service if they meet certain condition requirements.

Thus, life-limited parts have a mandated replacement timeline based on their cumulative service life, while TBO parts establish performance thresholds for maintenance actions but allow for overhauling under specific conditions. This understanding helps pilots and maintenance personnel ensure compliance with safety standards and prolong the lifespan of critical helicopter components.