Swept wing

A swept wing angles backward or forward relative to an aircraft’s fuselage. Sweep reduces the airflow component perpendicular to the wing, delaying compressibility effects as speed approaches the speed of sound.

Sweep angle: The angle between a wing’s spanwise direction and a line perpendicular to an aircraft’s longitudinal axis. It quantifies how far the wing is angled and determines the reduction in perpendicular airflow.
Angle of attack: The angle between an airfoil’s reference line and the oncoming airflow. A swept wing responds to the airflow component normal to its leading edge.
Boeing 707: A four-engine swept-wing jet airliner that entered commercial service in 1958. Its success helped establish swept wings as standard on long-range jet airliners.
Straight wing: A wing with little sweep, commonly used where low-speed lift and efficiency matter most. It offers stronger low-speed performance but reaches compressibility effects sooner than a comparable swept wing.
Mach number: The ratio of an object’s speed to the local speed of sound. The benefits and penalties of sweep depend strongly on flight Mach number.
Boundary layer: The thin region of fluid next to a surface where viscosity strongly affects the flow. Spanwise flow on swept wings changes boundary-layer behavior and can promote tip stall.
North American F-86 Sabre: A swept-wing American jet fighter that fought in the Korean War. Its performance demonstrated the value of sweep in combat near transonic speeds.
Variable-geometry aircraft: An aircraft designed to change its aerodynamic configuration during flight. This broader design approach includes aircraft that vary wing sweep in flight.
Critical Mach number: The lowest free-stream Mach number at which airflow over an aircraft first reaches Mach 1. Sweep raises the speed at which local supersonic flow first appears on a wing.
Airfoil: A cross-sectional shape designed to produce aerodynamic forces as air flows around it. A swept wing combines airfoil sections with a planform angle to shape aircraft performance.

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