Plain English Meaning

These are the parts of the aircraft that produce the airflow needed to spin the gyros inside certain flight instruments. Some aircraft suck the air through; others blow the air through. Either way, the moving air is what keeps the gyros turning.

Full Definition

The systems on an aircraft that supply the moving air used to spin air-driven gyroscopic instruments. The two common arrangements are a vacuum (suction) system, which pulls air through the instrument by means of an engine-driven vacuum pump or a venturi, and a pressure system, which pushes air through the instrument from an engine-driven pressure pump. The moving airflow strikes small buckets on the and it .