What is a "mechanical failure" during flight?

A "mechanical failure" during flight refers to an unexpected malfunction of an aircraft's components, systems, or instruments. This can include issues such as a sudden engine failure, a problem with the flight control systems, or a fault in navigation instruments that occurs without prior warning. Such failures can significantly impact the safety and operation of the aircraft, often requiring immediate corrective actions from the flight crew.

In contrast to this, expected maintenance issues that can be scheduled are part of routine care that pilots and maintenance crews anticipate and plan for, which means they do not fall under the definition of a mechanical failure. While computer errors in navigation systems can lead to problems, they are specifically categorized under software or system errors rather than mechanical failures. Deliberate actions taken by the pilot, such as executing a maneuver or making decisions in response to specific circumstances, are not defined as mechanical failures either, as those actions are intentional and based on the operational state of the aircraft rather than a malfunction.