Gerhard Neumann built an engine for supersonic flight by overcoming "compressor stall."
Top: the problem. The compressor tended to pull in more air than the engine could swallow.
Middle: Neumann gave attention to "strators." In a conventional engine, these were fixed in position and helped air in the compressor to flow properly.
Bottom: Neumann arranged for strators to turn, changing their position. This reduced the airflow in the compressor and prevented it from drawing in too much air.

Credits - NASA