Originally Posted by
beardy
...a windmilling engine is high drag, higher than idle thrust or a seized engine.
Must admit, that's always been my understanding.
The incoming airflow has to drive the engine to rotate which creates a lot of drag, whereas at idle, some of the turning force is taken up by the engine's idle thrust. In a seized engine, there are no moving parts for the airflow to turn so it passes through with drag only from the stationary parts.