A sharp and pointed spike normally inside the inlet air duct of supersonic aircraft. When supersonic airflow meets the spike, the incoming airflow is slowed down by formation of an oblique shock wave. The airflow may remain supersonic and is further slowed down by another normal shock wave before it meets the compressor. Airflow remains subsonic thereafter.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved