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vortex generators (aerodynamics). Small rectangular, low aspect ratio airfoils mounted on the upper
surface of the wings of some high-speed airplanes. Vortex generators are mounted in pairs, and the air
spilling over their upper ends forms swirls, or vortices. These vortices pull high-energy air down to the
surface of the wing. Vortex generators prevent the air separating from the surface of the wing.
vorticity (meteorology). Turning of the atmosphere. Vorticity may be embedded in the total air-flow and
not readily identified by a flow pattern. See absolute vorticity, negative vorticity, positive vorticity, and
relative vorticity.
VOT (VOR test signal). A ground facility which emits a test signal to check VOR receiver accuracy.
Some VOTs are available to the user while airborne, and others are limited to ground use only.
V-speeds. A series of designators used by the FAA and listed in 14 CFR 1 to describe certain flight
conditions.
VA — design maneuvering speed.
VB — design speed for maximum gust intensity.
VC — design cruising speed.
VD — design diving speed.
VDF/MDF — demonstrated flight diving speed.
VF — design flap speed.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 623
VFC/MFC — maximum speed for stability characteristics.
VFE — maximum flap extended speed.
VH — maximum speed in level flight with maximum continuous power.
VLE — maximum landing gear extended speed.
VLO — maximum landing gear operating speed.
VLOF — lift-off speed.
VMC — minimum control speed with the critical engine inoperative.
VMO/MMO — maximum operating limit speed.
VMU — minimum unstick speed.
VNE — never-exceed speed.
VNO — maximum structural cruising speed.
VR — rotation speed.
VS — the stalling speed or the minimum steady flight speed at which the airplane is controllable.
VS0 — the stalling speed or the minimum steady flight speed in the landing configuration.
VS1 — the stalling speed or the minimum steady flight speed obtained in a specific configuration.
VTOSS — takeoff safety speed for Category A rotorcraft.
VX — speed for best angle of climb.
VY — speed for best rate of climb.
V1 — takeoff decision speed (formerly denoted as critical engine failure speed).
V2 — takeoff safety speed.
V2min — minimum takeoff safety speed.
VSWR (voltage standing-wave ratio). A measure of reflected energy in an electrical transmission line
such as a waveguide or a coaxial cable. VSWR is the ratio of a voltage maximum to an adjacent voltage
minimum.
VTA (vertex time of arrival) (air traffic control). A calculated time of aircraft arrival over the adapted
vertex for the runway configuration in use. Vertex arrival time is calculated via the optimum flight path
using adapted speed segments.
VTOL (vertical takeoff and landing). Aircraft operation in which the aircraft rises and descends
vertically without requiring forward motion. A helicopter is capable of VTOL operation.
VTVM (vacuum-tube voltmeter) (electrical measuring instrument). A voltmeter that has a high input
impedance so that it does not load the circuit whose voltage is being measured. The voltage to be measured
is impressed on the grid of a vacuum tube amplifier, and the resulting plate current is measured.
Vacuum-tube voltmeters (VTVM) are being replaced with solid-state field-effect transistor (FET)
voltmeters.
vulcanize. A method of treating crude rubber with heat to give it such useful properties as elasticity,
strength, and chemical and dimensional stability.
W
wafer (semiconductor production). A thin slice of silicon or germanium used as the substrate on which
the components of an integrated circuit chip are formed. A wafer is also called a slice.
wafer-type selector switch (electrical component). A multicontact switch with the contacts arranged
around the outside of a circular wafer. A shaft through the center of the wafer is rotated by a knob to
connect a center contact, or wiper, to any one of the contacts around the wafer. Several wafers can be
stacked together with their center contacts rotated by the same shaft.
Printed from Summit Aviation's Computerized Aviation Reference Library, 2/7/2007
Page 624
waffle piston (reciprocating engine component). A reciprocating engine piston with fins cast or forged
on the bottom of the head, inside the piston. The fins cross to form a pattern that looks much like the
surface of a waffle. The fins strengthen the piston head and provide extra surface area to increase the
amount of heat the oil can carry away from the piston.
　
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