Reference
Aviation glossary
Concise definitions for aviation terminology — from METAR and NOTAM to aerodynamics and airline operations. Search directly or scan alphabetically.
H
HeadwindWind blowing directly toward the front of an aircraft, opposing its direction of travel. Headwind increases airspeed relative to the air mass without increasing groundspeed, which shortens takeoff and landing distances. Hold-Short LineA painted marking on a taxiway that designates where an aircraft must stop before entering an active runway. It consists of four yellow lines (two solid facing the runway, two dashed facing the taxiway) and requires explicit ATC clearance to cross. Hoop StressHoop stress is the circumferential tension that develops in a cylindrical or spherical pressure vessel when internal pressure pushes outward against the walls. HubA hub is a central airport where an airline concentrates its operations and routes connecting passengers to a wider network of destinations. Hub airportA hub airport is a central airport where an airline concentrates operations and routes passengers through to connect to other destinations, following a hub-and-spoke network model. Hub-and-Spoke NetworkA hub-and-spoke network is an airline route structure where flights converge at a central hub airport, allowing passengers to connect onward to smaller spoke cities without requiring direct service between every city pair. HypoxiaHypoxia is a dangerous physiological condition in which the body's tissues do not receive enough oxygen to function normally, becoming a serious threat to pilots at high altitudes where air pressure drops.
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