Aeronautical Terms beginning with V
V-Bars
The flight director displays on the attitude indicator that provide control guidance to the pilot.
V-G Diagram
A chart that relates velocity to load factor. It is valid only for a specific weight, configuration, and altitude and shows the maximum amount of positive or negative lift the airplane is capable of generating at a given speed. Also shows the safe load factor limits and the load factor that the aircraft can sustain at various speeds.
V-Speeds
Designated speeds for a specific flight condition.
V-Tail
A design which utilizes two slanted tail surfaces to perform the same functions as the surfaces of a conventional elevator and rudder configuration. The fixed surfaces act as both horizontal and vertical stabilizers.
Va
The design maneuvering speed. This is the “rough air” speed and the maximum speed for abrupt maneuvers. If during flight, rough air or severe turbulence is encountered, reduce the airspeed to maneuvering speed or less to minimize stress on the airplane structure. It is important to consider weight when referencing this speed. For example, VA may be 100 knots when an airplane is heavily loaded, but only 90 knots when the load is light.
Vapor lock
A problem that mostly affects gasoline-fuelled internal combustion engines. It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult. The fuel can vaporise due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude.
Vector
A force vector is a graphic representation of a force and shows both the magnitude and direction of the force.
Velocity
The speed or rate of movement in a certain direction.
Vertical Axis
An imaginary line passing vertically through the center of gravity of an aircraft. The vertical axis is called the z-axis or the yaw axis.
Vertical Stability
Stability about an aircraft’s vertical axis. Also called yawing or directional stability.
Vfe
The maximum speed with the flaps extended. The upper limit of the white arc.
Vfo
The maximum speed that the flaps can be extended or retracted.
Vle
Landing gear extended speed. The maximum speed at which an airplane can be safely flown with the landing gear extended.
Vlo
Landing gear operating speed. The maximum speed for extending or retracting the landing gear if using an airplane equipped with retractable landing gear.
Vlof
Lift-off speed. The speed at which the aircraft departs the runway during takeoff.
Vmd
Minimum drag speed.
Vmo
Maximum operating speed expressed in knots.
Vne
Never-exceed speed. Operating above this speed is prohibited since it may result in damage or structural failure. The red line on the airspeed indicator.
Vno
Maximum structural cruising speed. Do not exceed this speed except in smooth air. The upper limit of the green arc.
Vp
Minimum dynamic hydroplaning speed. The minimum speed required to start dynamic hydroplaning.
Vr
Rotation speed. The speed that the pilot begins rotating the aircraft prior to lift-off.
Vs1
Stalling speed or the minimum steady flight speed obtained in a specified configuration. For most airplanes, this is the power-off stall speed at the maximum takeoff weight in the clean configuration (gear up, if retractable, and flaps up). The lower limit of the green arc.
Vso
Stalling speed or the minimum steady flight speed in the landing configuration. In small airplanes, this is the power-off stall speed at the maximum landing weight in the landing configuration (gear and flaps down). The lower limit of the white arc.
Vx
Best angle-of-climb speed. The airspeed at which an airplane gains the greatest amount of altitude in a given distance. It is used during a short-field takeoff to clear an obstacle.
Vy
Best rate-of-climb speed. This airspeed provides the most altitude gain in a given period of time.
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