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.

Valid Non-Alert

A situation in which the safety logic software correctly determines that an alert is not required, based upon the design specifications and the current set of Safety Logic parameters.

Validity

The extent to which a test measures what it is supposed to measure.

Vapor Lock

A condition in which air enters the fuel system and it may be difficult, or impossible, to restart the engine. Vapor lock may occur as a result of running a fuel tank completely dry, allowing air to enter the fuel system. On fuel-injected engines, the fuel may become so hot it vaporizes in the fuel line, not allowing fuel to reach the cylinders.

Vapor pressure

In meteorology, the pressure of water vapor in the atmosphere. Vapor pressure is that part of the total atmospheric pressure due to water vapor and is independent of the other atmospheric gases or vapors.

Vapor trail

Same as condensation trail—a cloud-like streamer frequently observed to form behind aircraft flying in clear, cold, humid air.

Variation

Compass error caused by the difference in the physical locations of the magnetic north pole and the geographic north pole.

Vector

A force vector is a graphic representation of a force and shows both the magnitude and direction of the force.

Vectoring

Navigational guidance by assigning headings.

Veering

Shifting of the wind in a clockwise direction with respect to either space or time; opposite of backing. Commonly used by meteorologists to refer to an anticyclonic shift (clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere).

Velocity

The speed or rate of movement in a certain direction.

Venturi tube

A specially shaped tube attached to the outside of an aircraft to produce suction to allow proper operation of gyro instruments.

Verify

Request confirmation of information; e.g., “verify assigned altitude.”

Verify Specific Direction Of Takeoff (Or Turns After Takeoff)

Used by ATC to ascertain an aircraft’s direction of takeoff and/or direction of turn after takeoff. It is normally used for IFR departures from an airport not having a control tower. When direct communication with the pilot is not possible, the request and information may be relayed through an FSS, dispatcher, or by other means.

Vertex

The last fix adapted on the arrival speed segments. Normally, it will be the outer marker of the runway in use. However, it may be the actual threshold or other suitable common point on the approach path for the particular runway configuration.

Vertex Time Of Arrival

A calculated time of aircraft arrival over the adapted vertex for the runway configuration in use. The time is calculated via the optimum flight path using adapted speed segments.

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 Card Compass

A magnetic compass that consists of an azimuth on a vertical card, resembling a heading indicator with a fixed miniature airplane to accurately present the heading of the aircraft. The design uses eddy current damping to minimize lead and lag during turns.

Vertical Navigation (VNAV)

Traditionally, the only way to get glidepath information during an approach was to use a ground-based NAVAID, but modern area navigation systems allow flight crews to display an internally generated descent path that allows a constant rate descent to minimums during approaches that would otherwise include multiple level-offs.

Vertical Navigation Planning

Included within certain STARs is information provided to help you reduce the amount of low altitude flying time for high performance aircraft, like jets and turboprops. An expected altitude is given for a key fix along the route. By knowing an intermediate altitude in advance when flying a high performance aircraft, you can plan the power or thrust settings and aircraft configurations that result in the most efficient descent, in terms of time, fuel requirements, and engine wear.

Vertical Separation

Separation established by assignment of different altitudes or flight levels.

Vertical Separation [ICAO]

Separation between aircraft expressed in units of vertical distance.

Vertical Speed Indicator (VSI)

An instrument 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).

Vertical Stability

Stability about an aircraft’s vertical axis. Also called yawing or directional stability.

Vertical Takeoff And Landing Aircraft

Aircraft capable of vertical climbs and/or descents and of using very short runways or small areas for takeoff and landings. These aircraft include, but are not limited to, helicopters.

Vertical visibility

The distance one can see upward into a surface based obscuration; or the maximum height from which a pilot in flight can recognize the ground through a surface based obscuration.

Very High Frequency

The frequency band between 30 and 300 MHz. Portions of this band, 108 to 118 MHz, are used for certain NAVAIDs; 118 to 136 MHz are used for civil air/ground voice communications. Other frequencies in this band are used for purposes not related to air traffic control.

Very High Frequency Omnidirectional Range Station

VOR.

Very Low Frequency

The frequency band between 3 and 30 kHz.

Very-high frequency (VHF)

A band of radio frequencies falling between 30 and 300 MHz.

Very-high frequency omnidirectional range (VOR)

Electronic navigation equipment in which the flight deck instrument identifies the radial or line from the VOR station, measured in degrees clockwise from magnetic north, along which the aircraft is located.

Very-high frequency omnidirectional range (VOR).

Vestibule

The central cavity of the bony labyrinth of the ear, or the parts of the membranous labyrinth that it contains.

VFR Aircraft

An aircraft conducting flight in accordance with visual flight rules.

VFR Conditions

Weather conditions equal to or better than the minimum for flight under visual flight rules. The term may be used as an ATC clearance/instruction only when: a. An IFR aircraft requests a climb/descent in VFR conditions. b. The clearance will result in noise abatement benefits where part of the IFR departure route does not conform to an FAA approved noise abatement route or altitude. c. A pilot has requested a practice instrument approach and is not on an IFR flight plan. Note: All pilots receiving this authorization must comply with the VFR visibility and distance from cloud criteria in 14 CFR Part 91. Use of the term does not relieve controllers of their responsibility to separate aircraft in Class B and Class C airspace or TRSAs as required by FAAO JO 7110.65. When used as an ATC clearance/instruction, the term may be abbreviated “VFR;” e.g., “MAINTAIN VFR,” “CLIMB/DESCEND VFR,” etc.

VFR Flight

VFR Aircraft.

VFR Military Training Routes

Routes used by the Department of Defense and associated Reserve and Air Guard units for the purpose of conducting low-altitude navigation and tactical training under VFR below 10,000 feet MSL at airspeeds in excess of 250 knots IAS.

VFR Not Recommended

An advisory provided by a flight service station to a pilot during a preflight or inflight weather briefing that flight under visual flight rules is not recommended. To be given when the current and/or forecast weather conditions are at or below VFR minimums. It does not abrogate the pilot’s authority to make his/her own decision.

VFR on top

ATC authorization for an IFR aircraft to operate in VFR conditions at any appropriate VFR altitude.

VFR over the top

A VFR operation in which an aircraft operates in VFR conditions on top of an undercast.

VFR over-the-top

A VFR operation in which an aircraft operates in VFR conditions on top of an undercast.

VFR terminal area chart

At a scale of 1:250,000, a chart that depicts Class B airspace, which provides for the control or segregation of all the aircraft within the Class B airspace. The chart depicts topographic information and aeronautical information including visual and radio aids to navigation, airports, controlled airspace, restricted areas, obstructions, and related data.

VFR Terminal Area Charts

Aeronautical Chart.

VFR Terminal Area Charts (1:250,000)

Depict Class B airspace which provides for the control or segregation of all the aircraft within the Class B airspace. The chart depicts topographic information and aeronautical information which includes visual and radio aids to navigation, airports, controlled airspace, restricted areas, obstructions, and related data.

VFR Waypoint

Waypoint.

VFR-on-top

ATC authorization for an IFR aircraft to operate in VFR conditions at any appropriate VFR altitude.

VHF Omnidirectional Range/Tactical Air Navigation

VORTAC.

Victor airways

Airways based on a centerline that extends from one VOR or VORTAC navigation aid or intersection, to another navigation aid (or through several navigation aids or intersections); used to establish a known route for en route procedures between terminal areas. Visual approach slope indicator (VASI). A visual aid of lights arranged to provide descent guidance information during the approach to the runway. A pilot on the correct glide slope will see red lights over white lights.

Video Map

An electronically displayed map on the radar display that may depict data such as airports, heliports, runway centerline extensions, hospital emergency landing areas, NAVAIDs and fixes, reporting points, airway/route centerlines, boundaries, handoff points, special use tracks, obstructions, prominent geographic features, map alignment indicators, range accuracy marks, minimum vectoring altitudes.

Virga

Water or ice particles falling from a cloud, usually in wisps or streaks, and evaporating before reaching the ground.

Virtual Reality (VR)

A form of computer-based technology that creates a sensory experience allowing a participant to believe and barely distinguish a virtual experience from a real one. VR uses graphics with animation systems, sounds, and images to reproduce electronic versions of real-life experience.

Visibility

The greatest distance one can see and identify prominent objects.

Visibility [ICAO]

The ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night.

Visual Approach

A visual approach is an ATC authorization for an aircraft on an IFR flight plan to proceed visually to the airport of intended landing; it is not an IAP. Also, there is no missed approach segment. When it is operationally beneficial, ATC may authorize pilots to conduct a visual approach to the airport in lieu of the published IAP. A visual approach can be initiated by a pilot or the controller.

Visual Approach Slope Indicator

Airport Lighting.

Visual Approach Slope Indicator (VASI)

The most common visual glidepath system in use. The VASI provides obstruction clearance within 10° of the extended runway centerline, and to 4 nautical miles (NM) from the runway threshold.

Visual Approach [ICAO]

An approach by an IFR flight when either part or all of an instrument approach procedure is not completed and the approach is executed in visual reference to terrain.

Visual Climb Over Airport (VCOA)

A departure option for an IFR aircraft, operating in visual meteorological conditions equal to or greater than the specified visibility and ceiling, to visually conduct climbing turns over the airport to the published “climb-to” altitude from which to proceed with the instrument portion of the departure. VCOA procedures are developed to avoid obstacles greater than 3 statute miles from the departure end of the runway as an alternative to complying with climb gradients greater than 200 feet per nautical mile. These procedures are published in the `Take-Off Minimums and (Obstacle) Departure Procedures’ section of the Terminal Procedures Publications.

Visual Climb Over the Airport (VCOA)

An option to allow an aircraft to climb over the airport with visual reference to obstacles to attain a suitable altitude from which to proceed with an IFR departure.

Visual Descent Point

A defined point on the final approach course of a nonprecision straight-in approach procedure from which normal descent from the MDA to the runway touchdown point may be commenced, provided the approach threshold of that runway, or approach lights, or other markings identifiable with the approach end of that runway are clearly visible to the pilot.

Visual descent point (VDP)

A defined point on the final approach course of a nonprecision straight-in approach procedure from which normal descent from the MDA to the runway touchdown point may be commenced, provided the runway environment is clearly visible to the pilot.

Visual Flight Rules

Rules that govern the procedures for conducting flight under visual conditions. The term “VFR” is also used in the United States to indicate weather conditions that are equal to or greater than minimum VFR requirements. In addition, it is used by pilots and controllers to indicate type of flight plan.

Visual Flight Rules (VFR)

Code of Federal Regulations that govern the procedures for conducting flight under visual conditions.

Visual Holding

The holding of aircraft at selected, prominent geographical fixes which can be easily recognized from the air.

Visual Meteorological Conditions

Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling equal to or better than specified minima.

Visual meteorological conditions (VMC)

Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling meeting or exceeding the minimums specified for VFR.

Visual range

Runway visual range. An instrumentally derived horizontal distance a pilot should see down the runway from the approach end; based on either the sighting of high intensity runway lights or on the visual contrast of other objects, whichever yields the greatest visual range.

Visual Segment

Published Instrument Approach Procedure Visual Segment.

Visual Separation

A means employed by ATC to separate aircraft in terminal areas and en route airspace in the NAS. There are two ways to effect this separation: a. The tower controller sees the aircraft involved and issues instructions, as necessary, to ensure that the aircraft avoid each other. b. A pilot sees the other aircraft involved and upon instructions from the controller provides his/her own separation by maneuvering his/her aircraft as necessary to avoid it. This may involve following another aircraft or keeping it in sight until it is no longer a factor.

Voice Switching And Control System

The VSCS is a computer controlled switching system that provides air traffic controllers with all voice circuits (air to ground and ground to ground) necessary for air traffic control.

VOR test facility (VOT)

A ground facility which emits a test signal to check VOR receiver accuracy. Some VOTs are available to the user while airborne, while others are limited to ground use only.

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.

Vortex

In meteorology, any rotary flow in the atmosphere.

Vortices

Circular patterns of air created by the movement of an airfoil through the air when generating lift. As an airfoil moves through the atmosphere in sustained flight, an area of area of low pressure is created above it. The air flowing from the high pressure area to the low pressure area around and about the tips of the airfoil tends to roll up into two rapidly rotating vortices, cylindrical in shape. These vortices are the most predominant parts of aircraft wake turbulence and their rotational force is dependent upon the wing loading, gross weight, and speed of the generating aircraft. The vortices from medium to heavy aircraft can be of extremely high velocity and hazardous to smaller aircraft.

Vorticity

Turning of the atmosphere. Vorticity may be imbedded in the total flow and not readily identified by a flow pattern. Types are: absolute, negative, positive, and relative vorticity.

Vs1

The 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

The 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.

VTOL Aircraft

Vertical Takeoff And Landing Aircraft.

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.

Vyse

Best rate-of-climb speed with one engine inoperative. This airspeed provides the most altitude gain in a given period of time in a light, twin-engine airplane following an engine failure.