Which aspect is NOT a part of preventative maintenance?

Preventative maintenance focuses on routine actions that help ensure equipment and systems operate efficiently and reliably, aiming to prevent unexpected failures and prolong the lifespan of components. In the context of aviation or similar industries, preventative maintenance activities often include routine servicing tasks that are performed regularly, regardless of whether an issue has been detected.

Servicing landing gear, replacing cabin air filters, and changing oil are all examples of preventative maintenance because they involve regular checks and replacements that prevent larger problems from developing. These tasks help in monitoring and maintaining the overall condition of the aircraft, ensuring that it remains safe and operational.

On the other hand, replacing engines is typically not part of preventative maintenance. It is often viewed as a corrective measure taken after a significant issue has arisen or when an engine has reached the end of its useful life. Engine replacement is a major task that occurs infrequently and usually only after serious considerations regarding performance, safety, and operational efficiency. Therefore, it does not fit the routine nature associated with preventative maintenance.