What is the speed range for the windmill relight envelope?

The windmill relight envelope refers to the range of airspeeds within which an aircraft's engines can be restarted in flight after experiencing a flameout. The correct answer specifies the windmill relight envelope extending from 250 KIAS to Vmo, which is the maximum operating maneuvering speed and typically varies depending on altitude and aircraft configuration.

This speed range is crucial for ensuring that the engine can restart effectively while maintaining sufficient airflow through the engine for relight, without exceeding the aircraft's aerodynamic limits. The lower limit of 250 KIAS ensures that the aircraft maintains an adequate speed for a successful windmill restart, as slower airspeeds can result in insufficient airflow to the engine. Additionally, the upper limit of Vmo provides a safety margin against potential structural limitations that could arise at higher speeds.

Understanding this windmill relight envelope is essential for pilots when dealing with engine failures and determining their best course of action in airborne scenarios.