What defines a critical engine in aviation?

In aviation, the term "critical engine" refers to the engine whose failure most significantly impacts the performance of the aircraft. When an aircraft experiences the failure of a critical engine, it can lead to a loss of control, reduced aerodynamic performance, or difficulty in maintaining altitude.

Understanding this concept is essential for pilots and aviation professionals as it influences safety protocols, aircraft design, and emergency procedures. For instance, in multi-engine aircraft, identifying the critical engine allows pilots to make informed decisions, especially during takeoff or in emergency situations where an engine may fail.

Choosing an engine based on the criteria of thrust output, reliability, or maintenance needs does not necessarily address the implications that the failure of any given engine has on the aircraft's performance. Therefore, defining a critical engine emphasizes its direct effect on the aircraft's ability to operate safely and effectively when an engine is compromised.