ULTRALIGHT—A vehicle as defined by 14 CFR 103.1. 

UNSTABILIZED APPROACH—The final approach of an aircraft that has not achieved a stable rate of descent or controlled flight track by a pre-deter- mined altitude, usually 500 feet AGL. 

UPWIND LEG—A flight path parallel to the landing runway in the direction of landing. 

VEHICLE—Man-made means of transportation; an ultralight aircraft (not a light-sport aircraft). 

VENTURI—A specially shaped restriction in a tube designed to speed up the flow of fluid passing through in accordance with Bernoulli’s principle. Venturis are used in carburetors and in many types of fluid control devices to produce a pressure drop proportional to the speed of the fluid passing through them. 

VENTURI EFFECT—The effect of Bernoulli’s principle, which states that the pressure of a fluid decreases as it is speeded up without losing or gaining any energy from the outside. 

VERIFIED—Confirmation of information or con- figuration status. 

VERTICAL AXIS (YAW)—An imaginary line pass- ing vertically through the center of gravity of an aircraft. The vertical axis is called the z-axis or the yaw axis. 

VERTICAL SPEED INDICATOR (VSI)—An in- strument that uses static pressure to display a rate of climb or descent in feet per minute. The VSI can also sometimes be called a vertical velocity indicator (VVI). 

VERTIGO—A type of spatial disorientation caused by the physical senses sending conflicting signals to the brain. Vertigo is especially hazardous when flying under conditions of poor visibility and may cause pilot incapacitation, but may be minimized by confidence in the indication of the flight instru- ments. 

VFR—See VISUAL FLIGHT RULES. 

VFR TERMINAL AREA CHARTS—Charts desig- nated to depict Class B airspace in greater detail and greater scale than sectional charts. 

VISUAL FLIGHT RULES (VFR)—Code of Federal Regulations that govern the procedures for con- ducting flight under visual conditions. 

V LINES—See RISERS. 

VSI—See VERTICAL SPEED INDICATOR. 

WAKE TURBULENCE—Wingtip vortices that are created when an aircraft generates lift. When an aircraft generates lift, air spills over the wingtips from the high pressure areas below the wings 

to the low pressure areas above them. This flow causes rapidly rotating whirlpools of air called wingtip vortices or wake turbulence. 

WASHOUT—A condition in aircraft rigging in which a wing is twisted so its angle of incidence is less at the tip than at the root. Washout decreases the lift the wing produces to improve the stall characteristics of the wing. 

WEATHER BRIEFING—Means for pilots to gather all information vital to the nature of the flight. Most often obtained from FSS specialist. 

WEATHERVANE—The tendency to point into the wind. 

WEIGHT—A measure of the heaviness of an object. The force by which a body is attracted toward the center of the Earth (or another celestial body) by gravity. Weight is equal to the mass of the body times the local value of gravitational acceleration. One of the four main forces acting on an aircraft. Equivalent to the actual weight of the aircraft. It acts downward through the aircraft’s center of gravity toward the center of the Earth. Weight op- poses lift. 

WEIGHT-SHIFT CONTROL AIRCRAFT—Pow- ered aircraft with a framed pivoting wing and a fuselage controllable only in pitch and roll by the pilot’s ability to change the aircraft’s center of gravity with respect to the wing. Flight control of the aircraft depends on the wing’s ability to flex- ibly deform rather than the use of control surfaces. 

WIND CORRECTION ANGLE—Correction ap- plied to the course to establish a heading so that track will coincide with course. 

WIND DIRECTION INDICATORS—Indicators that include a wind sock, wind tee, or tetrahedron. Visual reference will determine wind direction and runway in use. 

WIND DRIFT CORRECTION—Correction applied to the heading of the aircraft necessary to keep the aircraft tracking over a desired track. 

WIND SHEAR—A sudden, drastic shift in wind- speed, direction, or both that may occur in the horizontal or vertical plane. 

WING—A ram-air inflated and pressurized fabric airfoil that produces the lift necessary to support the powered parachute in flight; including the lines that attach to the cart. Also called a parachute, chute, or airfoil. 

WING LOADING—The amount of weight that a wing must support to provide lift. 

WINGSPAN—The maximum distance from wingtip to wingtip. 

