What is one situation that prohibits engine restart during flight?

In aviation, an engine may be prohibited from restarting during flight for a variety of reasons, and one particular situation that stands out is the presence of Foreign Object Debris (FOD). FOD refers to any object, debris, or material that could potentially interfere with the operation of an aircraft's engine or systems. This could include anything from loose hardware to wildlife or rocks.

If an aircraft experiences FOD ingestion, the engine's internal components could be damaged, rendering a safe restart impossible. The likelihood of severe damage to the engine increases if it attempts to restart under these conditions, as the foreign objects could obstruct airflow or damage components further, posing a significant risk to safety.

In contrast, scenarios such as low fuel levels, engine malfunction, or high speed may lead to considerations regarding the engine's operational status but do not universally prohibit a restart in the same definitive way. Restarting an engine may still be a possibility in a low fuel situation, depending on how much fuel is actually present and the specific aircraft design. Similarly, while engine malfunction creates serious cases where restart might be advisable, it doesn't inherently mean that a restart cannot occur under certain conditions. Lastly, high speed could complicate the respawn process but does not automatically prevent it.