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TEC. See Tower En Route Control.
Technique. The manner in which procedures are executed.
Telephone information briefing service (TIBS). An FSS
service providing continuously updated automated telephone
recordings of area and/or route weather, airspace procedures,
and special aviation-oriented announcements.
Temporary flight restriction (TFR). Restriction to flight
imposed in order to:
1. Protect persons and property in the air or on the surface
from an existing or imminent flight associated hazard;
2. Provide a safe environment for the operation of
disaster relief aircraft;
3. Prevent an unsafe congestion of sightseeing aircraft
above an incident;
4. Protect the President, Vice President, or other public
figures; and,
5. Provide a safe environment for space agency
operations.
Pilots are expected to check appropriate NOTAMs during
flight planning when conducting flight in an area where a
temporary flight restriction is in effect.
Tension. Maintaining an excessively strong grip on the control
column, usually resulting in an overcontrolled situation.
Terminal aerodrome forecast (TAF). A report established
for the 5 statute mile radius around an airport. Utilizes the
same descriptors and abbreviations as the METAR report.
Terminal arrival area (TAA). A procedure to provide a
new transition method for arriving aircraft equipped with
FMS and/or GPS navigational equipment. The TAA contains
a “T” structure that normally provides a NoPT for aircraft
using the approach.
Terminal instrument approach procedure (TERP).
Prescribes standardized methods for use in designing
instrument flight procedures.
TERP. See terminal instrument approach procedure.
Terminal radar service areas (TRSA). Areas where
participating pilots can receive additional radar services. The
purpose of the service is to provide separation between all
IFR operations and participating VFR aircraft.
Terrain awareness and warning system (TAWS). A
timed-based system that provides information concerning
potential hazards with fixed objects by using GPS positioning
and a database of terrain and obstructions to provide true
predictability of the upcoming terrain and obstacles.
TFR. See temporary flight restriction.
Thermosphere. The last layer of the atmosphere that begins
above the mesosphere and gradually fades away into space.
Threshold crossing height (TCH). The theoretical height
above the runway threshold at which the aircraft’s glideslope
antenna would be if the aircraft maintained the trajectory
established by the mean ILS glideslope or MLS glidepath.
Thrust. The force which imparts a change in the velocity of a
mass. This force is measured in pounds but has no element of
time or rate. The term “thrust required” is generally associated
with jet engines. A forward force which propels the airplane
through the air.
Thrust (aerodynamic force). The forward aerodynamic
force produced by a propeller, fan, or turbojet engine as it
forces a mass of air to the rear, behind the aircraft.
Thrust line. An imaginary line passing through the center of
the propeller hub, perpendicular to the plane of the propeller
rotation.
Time and speed table. A table depicted on an instrument
approach procedure chart that identifies the distance from the
FAF to the MAP, and provides the time required to transit
that distance based on various groundspeeds.
Timed turn. A turn in which the clock and the turn
coordinator are used to change heading a definite number
of degrees in a given time.
TIS. See traffic information service.
Title 14 of the Code of Federal Regulations (14 CFR).
Includes the federal aviation regulations governing the
operation of aircraft, airways, and airmen.
Torque. (1) A resistance to turning or twisting. (2) Forces that
produce a twisting or rotating motion. (3) In an airplane, the
tendency of the aircraft to turn (roll) in the opposite direction
of rotation of the engine and propeller. (4) In helicopters with
a single, main rotor system, the tendency of the helicopter
to turn in the opposite direction of the main rotor rotation.
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Torquemeter. An instrument used with some of the larger
reciprocating engines and turboprop or turboshaft engines to
measure the reaction between the propeller reduction gears
and the engine case.
Total drag. The sum of the parasite drag and induced drag.
Touchdown zone elevation (TDZE). The highest elevation
in the first 3,000 feet of the landing surface, TDZE is
indicated on the instrument approach procedure chart when
straight-in landing minimums are authorized.
Touchdown zone lights. Two rows of transverse light bars
disposed symmetrically about the runway centerline in the
runway touchdown zone.
Tower En Route Control (TEC). The control of IFR
en route traffic within delegated airspace between two
or more adjacent approach control facilities, designed to
expedite traffic and reduce control and pilot communication
requirements.
TPP. See United States Terminal Procedures Publication.
Track. The actual path made over the ground in flight.
Tracking. Flying a heading that will maintain the desired
track to or from the station regardless of crosswind conditions.
Traffic Alert Collision Avoidance System (TCAS).
An airborne system developed by the FAA that operates
independently from the ground-based Air Traffic Control
system. Designed to increase flight deck awareness of
proximate aircraft and to serve as a “last line of defense” for
the prevention of midair collisions.
Traffic information service (TIS). A ground-based service
providing information to the flight deck via data link using
the S-mode transponder and altitude encoder to improve the
safety and efficiency of “see and avoid” flight through an
automatic display that informs the pilot of nearby traffic.
Trailing edge. The portion of the airfoil where the airflow
over the upper surface rejoins the lower surface airflow.
Transcribed Weather Broadcast (TWEB). An FSS service,
available in Alaska only, providing continuously updated
automated broadcast of meteorological and aeronautical data
over selected L/MF and VOR NAVAIDs.
Transponder. The airborne portion of the ATC radar
beacon system.
Transponder code. One of 4,096 four-digit discrete codes
ATC assigns to distinguish between aircraft.
Trend. Immediate indication of the direction of aircraft
movement, as shown on instruments.
Tricycle gear. Landing gear employing a third wheel located
on the nose of the aircraft.
Trim. To adjust the aerodynamic forces on the control
surfaces so that the aircraft maintains the set attitude without
any control input.
Trim tab. A small auxiliary hinged portion of a movable
control surface that can be adjusted during flight to a position
resulting in a balance of control forces.
Tropopause. The boundary layer between the troposphere
and the stratosphere which acts as a lid to confine most of the
water vapor, and the associated weather, to the troposphere.
Troposphere. The layer of the atmosphere extending from
the surface to a height of 20,000 to 60,000 feet, depending
on latitude.
True airspeed. Actual airspeed, determined by applying a
correction for pressure altitude and temperature to the CAS.
True altitude. The vertical distance of the airplane above
sea level—the actual altitude. It is often expressed as feet
above mean sea level (MSL). Airport, terrain, and obstacle
elevations on aeronautical charts are true altitudes.
Truss. A fuselage design made up of supporting structural
members that resist deformation by applied loads. The truss-
type fuselage is constructed of steel or aluminum tubing.
Strength and rigidity is achieved by welding the tubing
together into a series of triangular shapes, called trusses.
T-tail. An aircraft with the horizontal stabilizer mounted on
the top of the vertical stabilizer, forming a T.
Turbine discharge pressure. The total pressure at the
discharge of the low-pressure turbine in a dual-turbine axial-
flow engine.
Turbine engine. An aircraft engine which consists of an
air compressor, a combustion section, and a turbine. Thrust
is produced by increasing the velocity of the air flowing
through the engine.
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Turbocharger. An air compressor driven by exhaust gases,
which increases the pressure of the air going into the engine
through the carburetor or fuel injection system.
Turbofan engine. A fanlike turbojet engine designed to
create additional thrust by diverting a secondary airflow
around the combustion chamber.
Turbojet engine. A turbine engine which produces its thrust
entirely by accelerating the air through the engine.
Turboprop engine. A turbine engine which drives a
propeller through a reduction gearing arrangement. Most of
the energy in the exhaust gases is converted into torque, rather
than using its acceleration to drive the aircraft.
Turboshaft engine. A gas turbine engine that delivers power
through a shaft to operate something other than a propeller.
Turn-and-slip indicator. A flight instrument consisting
of a rate gyro to indicate the rate of yaw and a curved glass
inclinometer to indicate the relationship between gravity and
centrifugal force. The turn-and-slip indicator indicates the
relationship between angle of bank and rate of yaw. Also
called a turn-and-bank indicator.
Turn coordinator. A rate gyro that senses both roll and
yaw due to the gimbal being canted. Has largely replaced
the turn-and-slip indicator in modern aircraft.
TWEB. See Transcribed Weather Broadcast.
U
UHF. See ultra-high frequency.
Ultra-high frequency (UHF). The range of electromagnetic
frequencies between 300 MHz and 3,000 MHz.
Ulitimate load factor. In stress analysis, the load that
causes physical breakdown in an aircraft or aircraft
component during a strength test, or the load that according
to computations, should cause such a breakdown.
Uncaging. Unlocking the gimbals of a gyroscopic instrument,
making it susceptible to damage by abrupt flight maneuvers
or rough handling.
Uncontrolled airspace. Class G airspace that has not been
designated as Class A, B, C, D, or E. It is airspace in which
air traffic control has no authority or responsibility to control
air traffic; however, pilots should remember there are VFR
minimums which apply to this airspace.
Underpower. Using less power than required for the purpose
of achieving a faster rate of airspeed change.
United States Terminal Procedures Publication (TPP).
Booklets published in regional format by FAA Aeronautical
Navigation Products (AeroNav Products) that include DPs,
STARs, IAPs, and other information pertinent to IFR flight.
Unusual attitude. An unintentional, unanticipated, or
extreme aircraft attitude.
Useful load. The weight of the pilot, copilot, passengers,
baggage, usable fuel, and drainable oil. It is the basic empty
weight subtracted from the maximum allowable gross weight.
This term applies to general aviation aircraft only.
User-defined waypoints. Waypoint location and other data
which may be input by the user, this is the only GPS database
information that may be altered (edited) by the user.
V
V1. See takeoff decision speed.
V2. See takeoff safety speed.
VA. See maneuvering speed.
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 vaporize due to being heated by the engine, by the
local climate or due to a lower boiling point at high altitude.
Variation. Compass error caused by the difference in
the physical locations of the magnetic north pole and the
geographic north pole.
VASI. See visual approach slope indicator.
VDP. See visual descent point.
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.
VEF. Calibrated airspeed at which the critical engine of a
multi-engine aircraft is assumed to fail.
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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.
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 speed indicator (VSI). A rate-of-pressure change
instrument that gives an indication of any deviation from a
constant pressure level.
Vertical stability. Stability about an aircraft’s vertical axis.
Also called yawing or directional stability.
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.
Vestibule. The central cavity of the bony labyrinth of the
ear, or the parts of the membranous labyrinth that it contains.
VFE. The maximum speed with the flaps extended. The upper
limit of the white arc.
VFR. See visual flight rules.
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 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.
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.
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
glideslope will see red lights over white lights.
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 (VFR). Flight rules adopted by the
FAA governing aircraft flight using visual references. VFR
operations specify the amount of ceiling and the visibility the
pilot must have in order to operate according to these rules.
When the weather conditions are such that the pilot cannot
operate according to VFR, he or she must use instrument
flight rules (IFR).
Visual meteorological conditions (VMC). Meteorological
conditions expressed in terms of visibility, distance from
cloud, and ceiling meeting or exceeding the minimums
specified for VFR.
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.
VMC. Minimum control airspeed. This is the minimum
flight speed at which a light, twin-engine airplane can be
satisfactorily controlled when an engine suddenly becomes
inoperative and the remaining engine is at takeoff power.
VMC. See visual meteorological conditions.
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VNE. The 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. The maximum structural cruising speed. Do not
exceed this speed except in smooth air. The upper limit of
the green arc.
VOR. See very-high frequency omnidirectional range.
VORTAC. A facility consisting of two components, VOR
and TACAN, which provides three individual services: VOR
azimuth, TACAN azimuth, and TACAN distance (DME)
at one site.
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.
VOT. See VOR test facility.
VSI. See vertical speed indicator.
VS0. 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.
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.
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.
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.
W
WAAS. See wide area augmentation system.
Wake turbulence. Wingtip vortices that are created when
an airplane generates lift. When an airplane 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.
Warm front. The boundary area formed when a warm air
mass contacts and flows over a colder air mass. Warm fronts
cause low ceilings and rain.
Warning area. An area containing hazards to any aircraft
not participating in the activities being conducted in the
area. Warning areas may contain intensive military training,
gunnery exercises, or special weapons testing.
WARP. See weather and radar processing.
Waste gate. A controllable valve in the tailpipe of an aircraft
reciprocating engine equipped with a turbocharger. The valve
is controlled to vary the amount of exhaust gases forced
through the turbocharger turbine.
Waypoint. A designated geographical location used for route
definition or progress-reporting purposes and is defined in
terms of latitude/longitude coordinates.
WCA. See wind correction angle.
Weather and radar processor (WARP). A device that
provides real-time, accurate, predictive, and strategic weather
information presented in an integrated manner in the National
Airspace System (NAS).
Weather depiction chart. Details surface conditions as
derived from METAR and other surface observations.
Weight. The force exerted by an aircraft from the pull of
gravity.
Wide area augmentation system (WAAS). A differential
global positioning system (DGPS) that improves the accuracy
of the system by determining position error from the GPS
satellites, then transmitting the error, or corrective factors,
to the airborne GPS receiver.
Wind correction angle (WCA). The angle between the
desired track and the heading of the aircraft necessary to
keep the aircraft tracking over the desired track.
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Wind direction indicators. Indicators that include a
wind sock, wind tee, or tetrahedron. Visual reference will
determine wind direction and runway in use.
Wind shear. A sudden, drastic shift in windspeed, direction,
or both that may occur in the horizontal or vertical plane.
Winds and temperature aloft forecast (FB). A twice daily
forecast that provides wind and temperature forecasts for
specific locations in the contiguous United States.
Wing area. The total surface of the wing (in square feet),
which includes control surfaces and may include wing area
covered by the fuselage (main body of the airplane), and
engine nacelles.
Wings. Airfoils attached to each side of the fuselage and are
the main lifting surfaces that support the airplane in flight.
Wing root. The wing root is the part of the wing on a fixed-
wing aircraft that is closest to the fuselage. Wing roots
usually bear the highest bending forces in flight and during
landing, and they often have fairings to reduce interference
drag between the wing and the fuselage. The opposite end
of a wing from the wing root is the wing tip.
Wing span. The maximum distance from wingtip to wingtip.
Wingtip vortices. The rapidly rotating air that spills over an
airplane’s wings during flight. The intensity of the turbulence
depends on the airplane’s weight, speed, and configuration.
Also referred to as wake turbulence. Vortices from heavy
aircraft may be extremely hazardous to small aircraft.
Wing twist. A design feature incorporated into some wings
to improve aileron control effectiveness at high angles of
attack during an approach to a stall.
Work. A measurement of force used to produce movement.
World Aeronautical Charts (WAC). A standard series
of aeronautical charts covering land areas of the world at a
size and scale convenient for navigation (1:1,000,000) by
moderate speed aircraft. Topographic information includes
cities and towns, principal roads, railroads, distinctive
landmarks, drainage, and relief. Aeronautical information
includes visual and radio aids to navigation, airports, airways,
restricted areas, obstructions and other pertinent data.
Z
Zone of confusion. Volume of space above the station where
a lack of adequate navigation signal directly above the VOR
station causes the needle to deviate.
Zulu time. A term used in aviation for coordinated universal
time (UTC) which places the entire world on one time standard.
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