What action is mandatory immediately after an engine is removed from an aircraft?

The mandatory action immediately after an engine is removed from an aircraft is conducting a performance review of the removed engine. This review is critical as it involves assessing the engine's condition and performance prior to its removal, allowing maintenance personnel to understand any issues that may have led to the engine's extraction. This analysis is essential for ensuring safety and reliability in aircraft operations, as it contributes to the evaluation of maintenance needs, potential repairs, and how such situations may affect future flight operations.

While immediate replacement of reserve engines may be a practical consideration, emphasizing the review of the removed engine is crucial for maintaining compliance with safety regulations and ensuring that the aircraft is operating at optimal efficiency.