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Aviation Glossary
ABSOLUTE ALTITUDE - The
measurable height of an aircraft above the actual
terrain.
ABSOLUTE CEILING - The maximum altitude above sea level
at which an aircraft can maintain level flight under
Standard Air conditions.
ACCELERATED STALL - Any stall made to occur at other
than 1g.
ACCESSORY GROUP - Mechanical and electrical units
mounted on an engine necessary for its operation, such
as starter, magnetos, fuel pumps, etc.
ADCOCK RANGE - National low-frequency radio navigation
system (c.1930-c.1950) replaced by an omni range (VOR)
system. It consisted of four segmented quadrants
broadcasting Morse Code "A" (dot-dash) and "N"
(dash-dot) signals in opposing quadrants so that pilots
could orient their position relative to a "beam"
broadcasting a steady tone, and a Morse Code station
identifier. Using a "build-and-fade" technique, a pilot
could (ideally) pinpoint his location by the strength or
weakness of a signal. Read about it here.
ADF - Automatic Direction Finding via automated radio.
ADIABATIC LAPSE RATE - The rate at which ascending air
cools and descending air warms, given no heat is added
or taken away. The rate for dry air is based on 5.4° F
per 1000' altitude (1° per 100 meters); saturated rates
vary with barometric pressures and temperatures, and
must be adjusted for accuracy.
ADVERSE YAW - Yaw generated when the ailerons are used.
The lifting wing generates more drag, causing an
airplane to yaw (turn) toward it.
AGL - Above Ground Level, as a measurement of altitude
above a specific land mass, and differentiated from MSL.
AILERON - The movable areas of a wing form that control
or affect the roll of an aircraft by working opposite
one another—up-aileron on the right wing and
down-aileron on the left wing. French: aileron small
wing, diminutive of aile, from Latin: ala, wing. The
word "aisle" also derives from the same root. (Above pic
proves that birds invented ailerons long before man
did.)
AIR DEFENSE IDENTIFICATION ZONE (ADIZ) - The area of
airspace over land or water, extending upward from the
surface, within which the ready identification, the
location, and the control of aircraft are required in
the interest of national security.
Domestic Air Defense Identification Zone - An ADIZ
within the United States along an international boundary
of the United States.
Coastal Air Defense Identification Zone - An ADIZ over
the coastal waters of the United States.
Distant Early Warning Identification Zone (DEWIZ) - An
ADIZ over the coastal waters of the State of Alaska.
ADIZ locations and operating and flight plan
requirements for civil aircraft operations are specified
in FAR Part 99.
AIRFOIL - The shape of any flying surface, but
principally a wing, as seen in side-view
("cross-section"). Its characteristics are Center of
Pressure (CP), DRAG (CD), LIFT (CL), Lift-Drag Ratio
(L/D), and Moment (CM).
AIR ROUTE TRAFFIC CONTROL CENTER (ARTCC) or "CENTER" - A
facility established to provide air traffic control
service to aircraft operating on IFR flight plans within
controlled airspace and principally during the en route
phase of flight. When equipment capabilities and
controller workload permit, certain advisory/assistance
services may be provided to VFR aircraft.
AIR SPEED INDICATOR - An instrument or device that
measures the air speed of an aircraft through an air
mass, but not its ground speed.
AIR TAXI - An aircraft operator who conducts operations
for hire or compensation in accordance with FAR Part 135
in an aircraft with 30 or fewer passenger seats and a
payload capacity of 7,500# or less. An air taxi operates
on an on-demand basis and does not meet the "flight
scheduled" qualifications of a commuter.
AIR TRAFFIC CONTROL (ATC) - A service operated by the
appropriate authority to promote the safe, orderly, and
expeditious flow of air traffic.
AIRPORT TRAFFIC CONTROL TOWER (ATCT) - A terminal
facility that uses air/ground communications, visual
signaling, and other devices to provide ATC services to
aircraft operating in the vicinity of an airport or on
the movement area. Authorizes aircraft to land or
takeoff at the airport controlled by the tower or to
transit the Class D airspace area regardless of flight
plan or weather conditions (IFR or VFR). A tower may
also provide approach control services (radar or
non-radar).
ALCLAD - Trademark name of Alcoa for high-strength sheet
aluminum clad with a layer (approximately 5.5% thickness
per side) of high-purity aluminum, popularly used in
airplane manufacture.
ALPHABET (PHONETIC) - Devised for reasons of clarity in
aviation voice radio, this is the current NATO version
in global use:
ALFA BRAVO CHARLEY DELTA ECHO FOXTROT GOLF
HOTEL INDIA JULIET KILO LIMA MIKE NOVEMBER
OSCAR PAPA QUEBEC ROMEO SIERRA TANGO
UNIFORM VICTOR WHISKY X-RAY YANKEE ZULU
The original, from early in World War 2, was:
ABLE BAKER CHARLEY DOG EASY FOX GEORGE
HOW ITEM JIG KING LOVE MIKE NAN OBOE
PETER QUEEN ROGER SUGAR TARE UNCLE VICTOR
WILLIAM X-RAY YOKE ZEBRA
ALTIMETER - An adjustable aneroid-barometric cockpit
instrument used to measure an aircraft's altitude.
AMPHIBIAN, AMPHIBION - A SEAPLANE or FLOATPLANE with
retractable wheels for use on land, as well. The latter
spelling was used in the '20s and '30s but has since
fallen out of favor.
ANGLE OF ATTACK - The acute angle at which a moving
airfoil meets the airstream.
ANGLE OF INCIDENCE - The angle at which an airfoil is
normally fixed in relation to the longitudinal axis of
an aircraft.
ANHEDRAL - The downward angle of a wing in relation to a
horizontal cross-section line; aka CATHEDRAL. See
DIHEDRAL.
APPROACH CONTROL see RADIO NAVIGATION
APRON - The hard-surfaced or paved area around a hangar.
ARM - In aircraft weight and balance, as well as load
distribution, it is the distance from the CENTER OF
GRAVITY (c/g) to some point. For computations, arms
measured forward from the c/g are positive (+n) and
those measured aft of the c/g are negtive (-n).
ARSA see CONTROLLED AIRSPACE
ARTIFICIAL HORIZON - A vacuum-powered panel instrument
that displays pitch and roll movements about the lateral
and longitudinal axes; aka Attitude Indicator.
ASPECT RATIO - The ratio of the span to the chord of an
airfoil—a high-aspect ratio wing has wide span and
narrow chord, and vice-versa for a low-aspect ratio
wing.
ATA see CONTROLLED AIRSPACE
ATC - (1) Aircraft license as Approved Type Certificate,
see ATC; (2) AIR TRAFFIC CONTROL.
ATIS see AUTOMATIC TERMINAL INFORMATION SERVICE
AUTOGYRO, AUTOGIRO - An aircraft, often wingless, with
unpowered rotary airfoil blades that auto-rotate and
serve as wings as they move through the air when mounted
on a powered aircraft (or, in some cases, a glider). The
latter spelling is a trademark of the Autogiro
Corporation.
AUTO-ROTATION - Automatic rotation of rotary blades from
a helicopter in an unpowered glide or the forward
movement of an autogyro.
AUTOMATIC TERMINAL INFORMATION SERVICE (ATIS) -
Continuous broadcast of recorded non-control information
in selected terminal areas, to improve controller
effectiveness and to relieve frequency congestion by
automating repetitive transmissions of essential but
routine information.
BALANCED CONTROL SURFACE - A movable control surface, as
an aileron or rudder, having an added physical extension
or weights forward of the hinge-point to reduce forces
on a joystick or yoke. See ELEPHANT EARS (2).
BERNOULLI EFFECT (or LAW or THEOREM) - Since the
pressure of a fluid is proportional to its velocity,
airflow over the upper surface of an airfoil causes
suction [lift] because the airstream has been speeded up
in relation to positive pressure of the airflow on the
lower surface.
BLEED AIR - Hot air at high pressure, usually from the
bypass section of a gas turbine engine, for de-icing,
heating, and other uses.
BOUNDARY-LAYER CONTROL - The design or control of
slotted or perforated wings with suction methods to
reduce undesirable aerodynamic effects caused by the
boundary layer, that region adjacent to the boundary
where shear stresses dominate in the airflow over a
wingform.
BUMPED COWLING - An engine fairing, generally circular,
with welts or compound shapes in its surface to
accommodate cylinder heads.
CABANE STRUT - Wing strut attached to the fuselage.
CALIBRATED AIRSPEED (CAS) - The indicated airspeed of an
aircraft, corrected for position and instrument error.
CAS is equal to true airspeed in standard atmosphere at
sea level. Compare INDICATED AIRSPEED and TRUE AIRSPEED.
CAMBER - The convex or concave curvature of an airfoil.
CANARD - An arrangement in which the horizontal
stabilizer and elevators of an aircraft are mounted in
front of the main wing(s).
CAT - Clear-Air Turbulence.
CATHEDRAL see ANHEDRAL
CAVU - Ceiling and Visibility Unlimited; ideal flying
weather.
CEILING - (1) The heights above the earth's surface of
the lowest layer of clouds or obscuring phenomena that
is reported as "broken," "overcast," or "obscuration,"
and not classified as "thin" or "partial". (2) The
maximum height above sea level in Standard Air
attainable by an aircraft under given conditions—see
ABSOLUTE CEILING, SERVICE CEILING.
CENTER - An Air Route Traffic Control Center (ARTCC).
CENTER OF GRAVITY (c/g) - The longitudinal and lateral
point in an aircraft where it is stable; the static
balance point.
CERTIFICATED AIRPORT - An airport operating under FAR
Part 139. The FAA issues airport operating certificates
to all airports serving scheduled or unscheduled air
carrier aircraft designed for more than 30 passenger
seats. Certificated airports must meet minimum safety
standards in accordance with FAR Part 139.
CHORD - The measurable distance between the leading and
trailing edges of a wing form.
CLASS G AIRSPACE (Uncontrolled Airspace) - Airspace not
designated as Class A, B, C, D or E CONTROLLED AIRSPACE.
COAMING - A padded, protective rim around an open
cockpit.
COLLECTIVE PITCH - A cockpit control that changes the
pitch of a helicopter's rotor blades; used in climbing
or descending.
COLLECTOR RING - A circular duct on a radial engine into
which exhaust gases from its cylinders are safely
discharged.
COMMON TRAFFIC ADVISORY FREQUENCY (CTAF) - A frequency
designed for the purpose of carrying out airport
advisory practices while operating to or from an airport
without an operating control tower. The CTAF may be a
UNICOM, Multicom, FSS, or tower frequency and is
identified in appropriate aeronautical publications.
COMMUTER - An air carrier operator operating under 14
CFR 135 that carries passengers on at least five round
trips per week on at least one route between two or more
points according to its published flight schedules that
specify the times, day of the week, and places between
which these flights are performed. The aircraft that a
commuter operates has 30 or fewer passenger seats and a
payload capability of 7,500# or less.
COMPASS COURSE - A bearing as indicated by the
horizontal angle between the compass needle and the
centerline of the aircraft. A Compass Course is equal to
a True Course ± variation and deviation; also equal to a
Magnetic Course ± deviation.
COMPASS NORTH - The North point at which a liquid
compass needle points, rather than Geographical, or
True, North. Compare MAGNETIC NORTH.
CONE OF SILENCE - Click the Adcock page.
CONSTANT-SPEED PROPELLER - A hydraulically-controlled
propeller that governs an engine at its optimum speed by
the blade pitch being increased or decreased
automatically.
CONTACT FLIGHT - Navigation in which altitude and flight
path can be maintained by visual reference to the ground
and its landmarks. Similar to VFR.
CONTOUR FLIGHT - Contact Flight in and around
mountainous areas following visual reference to the
terrain's contours.
CONTRAILS - Trailing streaks of condensed water vapor
created in the air by aircraft engines at high
altitudes; aka Vapor Trails.
CONTROLLED AIRSPACE - An airspace of defined dimensions
within which air traffic control service is provided to
IFR flights and to VFR flights in accordance with the
airspace classification. Controlled airspace is a
generic term that covers Class A, B, C, D, and E
airspace. Controlled airspace is also that airspace
within which all aircraft operators are subject to
certain pilot qualifications, operating rules, and
equipment requirements in FAR Part 91. For IFR
operations in any class of controlled airspace, a pilot
must file an IFR flight plan and receive an appropriate
ATC clearance. Each B, C, and D airspace area designated
for an airport contains at least one primary airport
around which the airspace is designated (for specific
designations and descriptions of the airspace classes,
refer to FAR Part 71).
Class A (formerly PCA - Positive Control Area)
generally, that airspace from 18,000' mean sea level (MSL)
up to and including flight level (FL) 600 (60,000'
pressure altitude), including the airspace overlying the
waters within 12 nautical miles of the coast of the 48
contiguous States and Alaska. Unless otherwise
authorized, all persons must operate their aircraft
under IFR.
Class B (formerly TCA - Terminal Control Area)
Generally, that airspace from the surface to 10,000' MSL
surrounding the nation's busiest airports in terms of
airport operations or passenger enplanements. The
configuration of each Class B airspace area is
individually tailored and consists of a surface area and
two or more layers (some Class B airspace areas resemble
upside-down wedding cakes), and is designed to contain
all published instrument procedures once an aircraft
enters the airspace. An ATC clearance is required for
all aircraft to operate in the area, and all aircraft
that are so cleared receive separation services within
the airspace. The cloud clearance requirement for VFR
operations is "clear of clouds."
Class C (formerly ARSA - Airport Radar Service Area)
Generally, that airspace from the surface to 4,000' MSL
above the airport elevation surrounding those airports
that have an operational control tower, are serviced by
a radar approach control, and that have a certain number
of IFR operations or passenger enplanements. Although
the configuration of each Class C area is individually
tailored, the airspace usually consists of a surface
area with a 5 nautical mile (nm) radius, an outer circle
with a 10 nm radius that extends from 1,200' to 4,000'
above the airport elevation and an outer area. Each
person must establish two-way radio communications with
the ATC facility providing air traffic services prior to
entering the airspace and thereafter maintain those
communications while within the airspace. VFR aircraft
are only separated from IFR aircraft within the
airspace.
Class D (formerly ATA - Airport Traffic Area and CZ -
Control Zone) Generally, that airspace from the surface
to 2,500' MSL above the airport elevation surrounding
those airports that have an operational control tower.
The configuration of each Class D airspace area is
individually tailored and when instrument procedures are
published, the airspace will normally be designed to
contain the procedures. Arrival extensions for
instrument approach procedures may be Class D or E
airspace. Unless otherwise authorized, each person must
establish two-way radio communications with the ATC
facility providing air traffic services prior to
entering the airspace and thereafter maintain those
communications while in the airspace. No separation
services are provided to VFR aircraft.
Class E (formerly General Controlled Airspace)
Generally, if the airspace is not Class A, B, C, or D,
and is controlled airspace, it is Class E airspace.
Class E airspace extends upward from either the surface
or a designated altitude to the overlying or adjacent
controlled airspace. When designated as a surface area,
the airspace will be configured to contain all
instrument procedures. Also in this class are Federal
airways, airspace beginning at either 700' or 1,200' AGL
used to transition to/from the terminal or enroute
environment, enroute domestic, and offshore airspace
areas designated below 18,000' MSL. Unless designated at
a lower altitude, Class E airspace begins at 14,500' MSL
over the USA, including that airspace overlying the
waters within 12 nautical miles of the coast of the 48
contiguous States and Alaska, up to, but not including
18,000' MSL, and the airspace above Flight Level 600.
CONVENTIONAL GEAR - Having two main landing wheels at
the front and a tail wheel or tailskid at the rear as
opposed to having a tricycle gear with three main
wheels. Such an aircraft is popularly called a
TAILDRAGGER.
COWL, COWLING - A circular, removable fairing around an
aircraft engine (generally radial) for the purposes of
streamlining or cooling; aka RING COWLING.
COWL FLAP - A controllable louvre to regulating airflow
through an engine's cowling.
CRAB - A rudder-controlled yawing motion to compensate
for a crosswind in maintaining a desired flight path, as
in a landing approach.
CTAF see COMMON TRAFFIC ADVISORY FREQUENCY
DEAD RECKONING - In pioneer flight before radio,
beacons, and accurate maps, flying distances much by
instinct and guesswork, and referring to whatever
landmarks were below, was quite routine. The "dead" part
simply meant "straight," as in the nautical "dead
ahead," and pilots often relied heavily on the IRON
COMPASS for cross-country flights over unfamiliar
territory.
DEADSTICK - Descending flight with engine and propeller
stopped.
DECALAGE - The difference in angular settings [Angles of
Attack] of the wings of a biplane or multi-plane.
DECISION HEIGHT - With respect to the operation of
aircraft, the height at which point a decision must be
made during an instrument approach to either continue
the approach or to execute a missed approach [abort].
DELTA-WING - A triangularly-shaped aircraft wing having
a low aspect ratio, a sharply-tapered leading edge, a
straight trailing edge, and a pointed tip.
DEPARTURE CONTROL see RADIO NAVIGATION
DEPARTURE STALL - A stall in the takeoff configuration
with power.
DEVIATION (MAGNETIC) - The error of a Magnetic Compass
due to inherent magnetic influences in the structure and
equipment of an aircraft.
DEWIZ see AIR DEFENSE IDENTIFICATION ZONE
DIHEDRAL - The acute angle, usually upward, between the
wing of an airplane and a horizontal cross-section line.
Opposite of ANHEDRAL.
DIRECTIONAL GYRO - A panel instrument providing a
gyroscopic reading of an aircraft's compass heading.
DIRIGIBLE - A lighter-than-air craft capable of being
propelled and steered for controlled flight. Latin:
dirigo, to steer.
DME - Distance Measuring Equipment, a radio navigation
device that determines an aircraft's distance from a
given ground station, as well as its groundspeed and
time to/from the station.
DOPE - Preservative and pigmented coloring for fabric
aircraft covering and paints, generally nitrate lacquer
but generically used to denote all early shellac and
coal-tar mixtures on up to present-day acrylics.
DORSAL FIN - A lateral fin/rudder extension on the top
of a fuselage. Opposite of VENTRAL FIN.
DOWNWASH - The air deflected perpendicular to the
direction of movement of an airfoil.
DRAG - The resisting force exerted on an aircraft in its
line of flight opposite in direction to its motion.
Compare THRUST.
DRAG WIRE - A wire designed to resist DRAG forces,
usually running from a forward inboard point to an
outboard aft point.
DRIFT - The angle between the heading of an aircraft and
its Track [flight path] over the ground as affected by
winds.
DRY WEIGHT - The weight of an engine exclusive of any
fuel, oil, and coolant.
DURAL - Originally a trade name for a wrought
aluminum-copper alloy created by Bausch Machine Tool Co,
now fallen into generic use as any aluminum alloy
containing 3.0-4.5% copper, 0.4-1.0% magnesium, and
0.1-0.7% manganese. Alcoa's version is commonly referred
to as "Duraluminum," popularly used in aircraft
manufacture.
DZUS FASTENER - ("Zoose") Very singular to aircraft, a
patented slotted screw that binds to a wire for fast
release and securing of cowlings and inspection plates,
requiring no special tool other than a quarter coin.
EARTH-INDUCTOR COMPASS - One whose indications depend on
the current generated in a coil revolving in the earth's
magnetic field.
ELEPHANT EAR - (1) An air intake characterized by twin
inlets, one on each side of the fuselage. (2) A type of
balanced aileron in which the outer edges are noticeably
larger than the control itself. See BALANCED CONTROL
SURFACE and example Travel Air 4000.
ELEVATOR - The movable part of a horizontal airfoil
which controls the pitch of an aircraft, the fixed part
being the STABILIZER.
ELEVON - A hinged device on the rear portion of an
aircraft wing combining the functions of an elevator and
an aileron. Usually found on delta-wing aircraft, it can
be moved in the same direction on either side of the
aircraft to obtain longitudinal control, or
differentially to obtain lateral control. Also see
FLAPERON.
ELT - Emergency Locator Transmitter
EMPENNAGE - An aircraft's tail group, includes rudder
and fin, and stabilizer and elevator. Old French:
empenner, to feather an arrow, from Latin penna,
feather.
EN ROUTE AIR TRAFFIC CONTROL SERVICES - Air traffic
control services provided aircraft on IFR flight plans,
generally by centers, when these aircraft are operating
between departure and destination terminal areas. When
equipment, capabilities, and controller workload permit,
certain advisory/assistance services may be provided to
VFR aircraft.
ETA - Estimated Time of Arrival.
ETD - Estimated Time of Departure.
FAIRING - An added streamlining structure or auxiliary
member, most often of light metal, whose only purpose is
to reduce drag. Fairings are not load-bearing and,
therefore, are not meant to carry any principal air
loads placed on the airplane structure.
FBO - Fixed-Base Operator. A commercial operator
supplying fuel, maintenance, flight training, and other
services at an airport.
FAN MARKER see RADIO NAVIGATION
FEATHERING - In the event of engine failure, the process
of adjusting a controllable-pitch propeller to a pitch
position where the blade angle is about 90° to the plane
of rotation in order to to stop its wind milling and
lessen drag.
FEDERAL AIR REGULATION (FAR)
FAR Part 91 - General Aviation (portions apply to all
operators)
FAR Part 103 - Ultra light Vehicles
FAR Part 105 - Parachute Jumping
FAR Part 108 - Airplane Operator Security
FAR Part 119 - Certification: Air Carriers and
Commercial Operators
FAR Part 121 - Domestic, Flag, and Supplemental Air
Carriers and Commercial Operators of Large Aircraft
FAR Part 123 - Travel Clubs
FAR Part 125 - US Civil Airplanes, seating 20 or more
passengers or a maximum payload capacity 6,000# or more
FAR Part 127 - Air Carriers using helicopters for
scheduled interstate flights (within the 48 contiguous
states)
FAR Part 129 - Foreign Air Carrier and Foreign Operators
of US registered aircraft engaged in common carriage
FAR Part 133 - Rotorcraft External Load Operations
FAR Part 135 - Air Taxi Operators and Commercial
Operators
FAR Part 137 - Agricultural Aircraft Operations
FAR Part 141 - Pilot School
FERRY FLIGHT - A flight for the purpose of (1) returning
an aircraft to base; (2) delivering an aircraft from one
location to another; (3) moving an aircraft to and from
a maintenance base. Ferry flights, under certain
conditions, may be conducted under terms in a special
flight permit.
FIN - The fixed part of a vertical airfoil that controls
the yaw of an aircraft; the movable part being the
RUDDER. Sometime referred to as Vertical Stabilizer.
FIREWALL - A fire-resistant bulkhead that isolates the
engine from other parts of an airplane's structure.
FISHTAILING - A rudder-controlled side-to-side [yawing]
motion to reduce air speed, generally prior to landing.
FIVE-BY-FIVE (5x5) - In radio jargon, affirms that a
radioed transmission was received as clear and loud.
Rated one to five, with the first figure for clearness
and the second second for loudness.
FLAP - A movable, usually hinged AIRFOIL set in the
trailing edge of an aircraft wing, designed to increase
LIFT or DRAG by changing the CAMBER of the wing or used
to slow an aircraft during landing by increasing lift.
Also see FOWLER FLAP, SLOTTED FLAP, and SPLIT FLAP.
FLAPERON - A control surface combining the functions of
a FLAP and an AILERON.
FLARE - A simple maneuver performed moments before
landing in which the nose of an aircraft is pitched up
to minimize the touchdown rate of speed.
FLIGHT ENVELOPE - An aircraft's performance limits,
specifically the curves of speed plotted against other
variables to indicate the limits of speed, altitude, and
acceleration that a particular aircraft cannot safely
exceed.
FLIGHT LEVEL (FL) - A level of constant atmospheric
pressure related to a reference datum of 29.92 inches of
mercury. Each is stated in three digits that represent
hundreds of feet—flight level 250 represents a
barometric altimeter indication of 25,000', flight level
255 as 25,500'.
FLIGHT PLAN - Specified information relating to the
intended flight of an aircraft, filed orally or in
writing with an FSS or an ATC facility.
FLIGHT SERVICE STATION (FSS) - Air traffic facilities
which provide pilot briefing, enroute communications and
VFR search and rescue services, assist lost aircraft and
aircraft in emergency situations, relay ATC clearances,
originate Notices to Airmen, broadcast aviation weather
and NAS information, receive and process IFR flight
plans, and monitor NAVAIDs. In addition, at selected
locations, FSSs provide Enroute Flight Advisory Service
(Flight Watch), take weather observations, issue airport
advisories, and advise Customs and Immigration of
trans-border flights.
FLOATPLANE - A water-based aircraft with one or more
mounted pontoons, as differentiated from a hulled
SEAPLANE [Flying Boat], but often used generically.
FLYING WIRES - Inter-plane bracing wires that help
support wing-loads when the plane is in flight.
Direction of travel is upward and outward from the
fuselage to the inter-plane struts. Also known as LIFT
WIRES, the opposite of LANDING WIRES.
FOWLER FLAP - Trademark name of a split-flap attached to
a wing's trailing edge with a system of tracks and
rollers to roll the FLAP backward and downward,
increasing the wing area. Named for its inventor, USAAF
engineer Harland D Fowler.
FRISE AILERON - A type of aileron that has a beveled
leading edge projecting beyond its inset hinges. When
lowered, it forms an extension of the wing surface; when
raised, its nose protrudes below the wing, increasing
DRAG and reducing YAW. Named for its inventor, British
engineer Leslie George Frise.
FSS see FLIGHT SERVICE STATION
FUSELAGE - An aircraft's main body structure housing the
flight crew, passengers, and cargo and to which the
wings, tail and, in most single-engined airplanes,
engine are attached. French: fuselé, tapering.
g or G see LOAD FACTOR
GAP - The distance between two adjacent wings of a
biplane or multiplane.
GCA - Ground-Controlled Approach; part of ILS.
GENERAL AVIATION - That portion of civil aviation which
encompasses all facets of aviation except air carriers
holding a certificate of public convenience and
necessity from the Civil Aeronautics Board and large
aircraft commercial operators.
GEOGRAPHIC NORTH - The northern axis around which the
Earth revolves; aka "Map North" and TRUE NORTH. Also see
MAGNETIC NORTH.
GLASS COCKPIT - Said of an aircraft's control cabin
which has all-electronic, digital and computer-based,
instrumentation.
GLIDER - An un-powered aircraft capable of maintaining
altitude only briefly after release from tow, then
gliding to earth. Compare SAILPLANE.
GLIDE SLOPE - (1) The angle between horizontal and the
glide path of an aircraft. (2) A tightly-focused radio
beam transmitted from the approach end of a runway
indicating the minimum approach angle that will clear
all obstacles; one component of an instrument landing
system (ILS).
GPS - Global Positioning System; satellite-based
navigation.
GREEN LIGHT - Approval for landing. A carryover
expression from days when aircraft for the most part had
no radios, and communication from a control tower was by
means of a light-gun that beamed various green, red, and
yellow signals to pilots in the air and on the ground. A
popular phrase, "3 green lights," refers to the
instrument panel lights verifying that all three gears
(in a tri-gear aircraft) are down and locked for safe
landing.
GROSS WEIGHT - The total weight of an aircraft when
fully loaded, including fuel, cargo, and passengers; aka
Takeoff Weight.
GROUND CONTROL - Tower control, by radioed instructions
from air traffic control, of aircraft ground movements
at an airport.
GROUND CUSHION see GROUND EFFECT
GROUND EFFECT - Increased lift generated by the
interaction between a lift system and the ground when an
aircraft is within a wingspan distance above the ground.
It affects a low-winged aircraft more than a mid- or
high-winged aircraft because its wings are closer to the
ground; aka GROUND CUSHION.
GROUNDSPEED - The actual speed that an aircraft travels
over the ground—its "shadow speed"; it combines the
aircraft's AIRSPEED and the wind's speed relative to the
aircraft's direction of flight.
GULL-WING - Descriptive of wing in frontal view bent as
the wing of a seagull; a distinctive shallow, inverted
"V" shape—see Stinson SR-10 or inverted gull-wing Vought
F4U.
GYROPLANE - A rotorcraft whose rotors are not
engine-driven, except for initial starting, but are made
to rotate by action of the air when the rotorcraft is
moving and whose means of propulsion, usually a
conventional propeller, is independent of the rotor
system. Similar to AUTOGYRO.
HANGAR - An enclosed structure for housing aircraft.
Originated with lake-based floating homes of the
original German Zeppelins in which they were "hung" from
cables, which explains the erroneous, oft-seen spelling
of "hanger." French: hangar, shed, outbuilding, from
Latin: angarium, shed.
HELICOPTER - A wingless aircraft acquiring its lift from
revolving blades driven by an engine about a
near-vertical axis. A ROTORCRAFT acquiring its primary
motion from engine-driven rotors that accelerate the air
downward, providing a reactive lift force, or accelerate
the air at an angle to the vertical, providing lift and
thrust.
HIGH BLOWER - A blower-type supercharger set at high
rpm.
HIGH-SPEED STALL - Any stall made to occur at more than
1g, such as pulling out of a dive or while turning.
HORSEPOWER - The motive energy required to raise 550#
one foot in one second, friction disregarded.
HYPERSONIC - Speed of flight at or greater than Mach
5.0, exceeding SUPERSONIC.
HYPOXIA - Deprivation of oxygen, aka "altitude
sickness," which can adversely affect human judgment and
movement at altitudes above 12,000' with symptoms
ranging from light dizziness to unconsciousness, even
death at the extreme. It was a principal reason for
pressurized aircraft.
IFR - Instrument Flight Rules, governing flight under
instrument meteorological conditions.
ILS - Instrument Landing System. A radar-based system
allowing ILS-equipped aircraft to find a runway and land
when clouds may be as low as 200' (or lower for special
circumstances).
INDICATED AIRSPEED (IAS) - A direct instrument reading
obtained from an air speed indicator uncorrected for
altitude, temperature, atmospheric density, or
instrument error. Compare CALIBRATED AIRSPEED and TRUE
AIRSPEED.
INSTRUMENT METEOROLOGICAL CONDITIONS (IMC) -
Meteorological conditions expressed in terms of
visibility, distance from clouds, and ceiling less than
minima specified for visual meteorological conditions (VMC).
IRON COMPASS - Railroad tracks, favored by pilots of
yore as a dependable aid to surface navigation before
radio.
JOYSTICK - A single floor- or roof-mounted control
stick—sideways movement produces ROLL, and
forward/backward movement produces PITCH (rudder pedals
produce YAW).
KNOT - One nautical mile, about 1.15 statute miles
(6,080'); eg: 125kts = 143.9mph.
LAMINAR-FLOW AIRFOIL - A low-drag airfoil designed to
maintain laminar (smooth, continuous) flow over a high
percentage of the CHORD about itself. Often relatively
thin, especially along the leading edge, with most of
its bulk near the center of the chord.
LANDING WIRES - Interplane bracing wires that help
support wingloads when the plane is on the ground.
Direction of travel is downward and outward from the
fuselage. Opposite of FLYING WIRES.
LIFT - The force exerted on the top of a moving airfoil
as a low-pressure area [vacuum] that causes a wingform
to rise. AIRFOILs do not "float" on air, as is often
assumed—like a boat hull floats on water—but are "pulled
up" [lifted] by low air pressures trying to equalize.
LIFT-DRAG RATIO - The lift coefficient of a wing divided
by the drag coefficient, as the primary measure of the
efficiency of an aircraft; aka L/D Ratio.
LIFT WIRES - Interplane bracing wires that help support
wingloads when the plane is in flight. Direction of
travel is upward from the bottom of the fuselage to the
top of the interplane struts. Also known as FLYING
WIRES, the opposite of LANDING WIRES.
LIGHT SPORT AIRCRAFT - Special FAA certification class (LSA)
for an aircraft other than a helicopter or
powered-lift—single-engine aircraft, airship, balloon,
GLIDER, GYROCOPTER, ROTORCRAFT, weight-shift-control
aircraft. While limiting the types of aircraft that
could be flown by a Sport Pilot, it simplified
requirements for a obtaining a pilot license and did not
require a medical examination. See LSA feature.
LIQUID COMPASS - A non-electronic, calibratable compass
floating in a liquid as a panel instrument; aka WET
COMPASS.
LOAD FACTOR (g) - The proportion between lift and weight
commonly seen as g (sometimes capitalized)—a unit of
force equal to the force of gravity times one.
LOFTING - Design or fabrication of a complex aircraft
component, as with sheet metal, using actual-size
patterns or plans, generally laid out on a floor. The
term was borrowed from boat builders.
LONGERON - A principal longitudinal member of a
fuselage's framing, usually continuous across a number
of supporting points.
LOOP ANTENNA - A circular radio antenna, either in the
open or in a streamlined, teardrop housing, remotely
turned 360° to fine-tune a station in league with other
radio-directive devices. See also RADIO COMPASS, RADIO
DIRECTION FINDER.
LORAN - Long Range Navigation system, which utilizes
timing differences between multiple low-frequency
transmissions to provide accurate latitude/longitude
position information to within 50'.
LTA - Lighter-than-air craft, generally referring to
powered blimps and dirigibles, but often also includes
free balloons.
LUNKENHEIMER VALVE - A manual fuel drain placed handily
along a fuel line for checking avgas, such as for water
or sediment contaminations.
Mach or m. - A number representing the ratio of the
speed of an object to the speed of sound in the
surrounding air or medium in which it is moving.
MAGNETIC COMPASS - The most common liquid-type compass,
capable of calibration to compensate for magnetic
influences within the aircraft.
MAGNETIC COURSE - COMPASS COURSE ± deviation.
MAGNETIC NORTH - The magnetic North pole, located near
71° North latitude and 96° West longitude, that attracts
a magnetic compass which is not influenced by local
magnetic attraction, as opposed to GEOGRAPHIC NORTH.
MAGNETO, MAG - An accessory that produces and
distributes a high-voltage electric current for ignition
of a fuel charge in an internal combustion engine.
MAGNUS EFFECT - The effect on a spinning cylinder or
sphere moving through a fluid, in which force acts
perpendicular to the direction of motion and to the
direction of spin. This is used to advantage in
baseball, in which the trajectory of a pitched ball is a
distinct curve. Applied to aeronautics in experimental
wing forms, the Magnus Theory states that if air is
directed against a smooth, revolving cylinder, whose
circumferential speed is greater than that of the air
current, a force is directed against one side of the
cylinder—air compressed on one side and vacuum formed on
the other—creating lift. Named for physicist Heinrich
Gustav Magnus (1802-70).
MARKER BEACON see RADIO NAVIGATION
MEAN SEA LEVEL see MSL
METAR - Acronym in FAA pilot briefings and weather
reports simply means an "aviation routine weather
report," but nobody seems certain about the original
source. The format was introduced by the French on 1 Jan
1968, but was not adopted by USA and Canada until 1 July
1996, and is thought to be a contraction from
MÉTéorologique ("Weather") Aviation Règuliére
("Routine"). FAA and NOAA specifically define METAR as
"an approximate translation from the French."
MOA see SPECIAL USE AIRSPACE
MONOCOQUE - Type of fuselage design with little or no
internal bracing other than bulkheads, where the outer
skin bears the main stresses; usually round or oval in
cross-section. Additional classifications are (1) Semi-Monocoque,
where the skin is reinforced by longerons or bulkheads,
but with no diagonal web members, and (2) Reinforced
Shell, in which the skin is supported by a complete
framework or structural members. French: monocoque,
single shell.
MSL - Mean Sea Level. The average height of the surface
of the sea for all stages of tide; used as a reference
for elevations, and differentiated from AGL.
NACELLE - A streamlined enclosure or housing to protect
something such as the crew, engine, or landing gear.
French: nacelle, from Latin, navicella, little ship.
NATIONAL AIRSPACE SYSTEM (NAS) - The common network of
US airspace; air navigation facilities, equipment and
services, airports or landing areas; aeronautical
charts, information and services; rules, regulations and
procedures, technical information, and human resources
and material. Included are system components shared
jointly with the military.
NDB - Non-Directional Beacon. An LF, MF, or UHF radio
beacon transmitting non-directional signals whereby the
pilot of an aircraft equipped with direction finding
equipment can determine his bearing to or from the radio
beacon and "home" on or track to or from the station.
When the radio beacon is installed in conjunction with
the Instrument Landing System (ILS) marker, it is
normally called a Compass Locator.
ON THE BEAM - A leftover phrase from ADCOCK Radio Range
days still means the same thing today—"You are headed in
the right direction," as when you you hear a steady
broadcast tone beamed from your target radio
transmitter. Also as RIDING THE BEAM. Read about it
here.
OVERSHOOT - To land beyond a runway or planned spot.
Opposite of UNDERSHOOT.
PANTS - A popular word for streamlined, non-load bearing
fairings to cover landing wheels. Also sometimes called
Spats or, when fully enclosing the wheel struts, Skirts.
PAR - Precision Approach Radar, a ground-radar-based
instrument approach providing both horizontal and
vertical guidance
PATTERN - The path of aircraft traffic around an
airfield, at an established height and direction. At
tower-controlled fields the pattern is supervised by
radio (or, in non-radio or emergency conditions by red
and green light signals) by air traffic controllers.
PAYLOAD - Anything that an aircraft carries beyond what
is required for its operation during flight,
theoretically that from which revenue is derived, such
as cargo and passengers.
PCA see CONTROLLED AIRSPACE
PHONETICS see ALPHABET
PILOT IN COMMAND (PiC) - The pilot responsible for the
operation and safety of an aircraft during flight time.
PITCH - (1) Of the three axes in flight, this specifies
the vertical action, the up-and-down movement. Compare
ROLL and YAW. (2) The angle of a propeller or rotor
blade in relation to its arc; also the distance advanced
by a blade in one full rotation.
PITOT TUBE - More accurately but less popularly used,
Pitot-Static Tube, a small tube most often mounted on
the outward leading edge of an airplane wing (out of the
propeller stream) that measures the impact pressure of
the air it meets in flight, working in conjuction with a
closed, perforated, coaxial tube that measures the
static pressure. The difference in pressures is
calibrated as air speed by a panel instrument. Named for
French scientist Henri Pitot (1695-1771).
POSITIVE CONTROL - The separation of all air traffic
within designated airspace by air traffic control.
POWER LOADING - The GROSS WEIGHT of an airplane divided
by the rated horsepower, computed for Standard Air
density.
PUSHER - A propeller mounted in back of its engine,
pushing an aircraft through the air, as opposed to a
TRACTOR configuration.
QUADRAPLANE, QUADRUPLANE - An aircraft having four or
more wingforms.
RADAR APPROACH CONTROL FACILITY (RAPCON) - A terminal
ATC facility that uses radar and non-radar capabilities
to provide approach control services to aircraft
arriving, departing, or transiting airspace controlled
by the facility. This facility provides radar ATC
services to aircraft operating in the vicinity of one or
more civil/military airports in a terminal area. The
facility may provide services of a ground-controlled
approach (GCA). A radar approach control facility may be
operated by FAA or a military service, or jointly.
Specific facility nomenclatures are used for
administrative purposes only and are related to the
physical location of the facility and the operating
service generally:
Army Radar Approach Control (ARAC) (Army)
Radar Air Traffic Control Facility (RATCF) (Navy/FAA)
Radar Approach Control (RAPCON) (Air Force/FAA)
Terminal Radar Approach Control (TRACON) (FAA)
Tower/Airport Traffic Control Tower (ATCT) (FAA only
towers delegated approach control authority)
RAMJET - An aerodynamic duct in which fuel is burned to
produce a high-velocity propulsive jet. It needs to be
accelerated to high speed before it can become
operative.
RIDING THE BEAM see ON THE BEAM.
RING COWLING - A circular engine FAIRING.
ROGALLO WING - A flexible, delta-wing plan in which
three rigid members are shaped in the form of an
arrowhead and joined by a flexible fabric, which
inflates upward under flight loads. Originally specific
to paragliders, but now found on some powered aircraft.
ROLL - Of the three axes in flight, this specifies the
action around a central point. Compare PITCH and YAW.
ROTARY ENGINE - A power plant that rotates on a
stationary propeller shaft. An American invention by
Adams-Farwell Co (1896), it was first used for buses and
trucks in the US (1903), then copied by French engineers
for early aircraft engines (1914).
ROTORCRAFT - A heavier-than-air aircraft that depends
principally for its support in flight on the lift
generated by one or more rotors. Includes helicopters
and gyroplanes.
RUDDER - The movable part of a vertical airfoil which
controls the YAW of an aircraft; the fixed part being
the FIN.
SAILPLANE - An un-powered, soaring aircraft capable of
maintaining level flight for long periods of time after
release from tow and of gaining altitude using wind
currents, as opposed to a GLIDER.
SCRAMJET - Acronym for supersonic combustion ramjet, in
which combustion occurs at supersonic air velocities
through the engine.
SCUD - A low, fog-like cloud layer.
SEAPLANE - A water-based aircraft with a boat-hull
fuselage, often amphibious. The term is also used
generically to define a similar Flying Boat and a
pontoon FLOATPLANE.
SECONDARY STALL - Any stall resulting from pulling back
too soon and too hard while recovering from any other
stall. Usually a HIGH-SPEED or ACCELERATED STALL.
SERVICE CEILING - The height above sea level at which an
aircraft with normal rated load is unable to climb
faster than 100' per minute under Standard Air
conditions.
SESQUI-WING - A lesser-span additional wing form,
generally placed below the main planes of an aircraft,
generally a biplane.
SHOULDER-WING - A mid-wing monoplane with its wing
mounted directly to the top of the fuselage without use
of CABANE STRUTs.
SIDESLIP - A movement of an aircraft in which a relative
flow of air moves along the lateral axis, resulting in a
sideways movement from a projected flight path,
especially a downward slip toward the inside of a banked
turn.
SINK, SINKING SPEED - The speed at which an aircraft
loses altitude, especially in a glide in still air under
given conditions of equilibrium.
SKID - Too shallow a bank in a turn, causing an aircraft
to slide outward from its ideal turning path.
SLATS - Movable vanes or auxiliary airfoils, usually set
along the leading edge of a wing but able to be lifted
away at certain angles of attack.
SLIP - Too steep a bank in a turn, causing an aircraft
to slide inward from its ideal turning path.
SLIPSTREAM - The flow of air driven backward by a
propeller or downward by a rotor. Compare DOWNWASH.
SLOT - A long, narrow, spanwise gap in a wing, usually
near the leading edge, to improve airflow at high angles
of attack for slower landing speeds.
SLOTTED FLAP - A flap that, when depressed, exposes a
SLOT and increases airflow between itself and the rear
edge of the wing.
SMOH - "Since Major Overhaul," an acronym seen in
reference to the operating hours, or time remaining, on
an engine.
SPECIAL USE AIRSPACE (SUA) - Airspace of defined
dimensions identified by an area on the surface of the
earth wherein activities must be confined because of
their nature and/or wherein limitations may be imposed
upon aircraft operations that are not a part of those
activities:
Alert Area - Airspace which may contain a high volume of
pilot training activities or an unusual type of aerial
activity, neither of which is hazardous to aircraft.
Alert Areas are depicted on aeronautical charts for the
information of non-participating pilots. All activities
within an Alert Area are conducted in accordance with
Federal Aviation Regulations, and pilots of
participating aircraft as well as pilots transiting the
area are equally responsible for collision avoidance.
Military Operations Area (MOA) - Airspace established
outside of Class A airspace area to separate or
segregate certain non-hazardous military activities from
IFR traffic and to identify for VFR traffic where these
activities are conducted.
Prohibited Area - Airspace designated under part 73
within which no person may operate an aircraft without
the permission of the using agency.
Restricted Area - Airspace designated under FAR Part 73,
within which the flight of aircraft, while not wholly
prohibited, is subject to restriction. Most restricted
areas are designated joint use and IFR/VFR operations in
the area may be authorized by the controlling ATC
facility when it is not being utilized by the using
agency. Restricted areas are depicted on enroute charts.
Where joint use is authorized, the name of the ATC
controlling facility is also shown.
Warning Area - A warning area is airspace of defined
dimensions extending from 3 nautical miles outward from
the coast of the USA, that contains activity that may be
hazardous to non-participating aircraft. The purpose of
such warning area is to warn non-participating pilots of
the potential danger. A warning area may be located over
domestic or international waters or both.
SPLIT FLAP - A FLAP built into the underside of a wing,
as opposed to a Full Flap wherein a whole portion of the
trailing edge is used.
SPOILER - A long, movable, narrow plate along the upper
surface of an airplane wing used to reduce lift and
increase drag by breaking or spoiling the smoothness of
the airflow.
SPORT PILOT - Special FAA certification enabling
"budget" pilotry; see LIGHT SPORT AIRCRAFT and LSA
feature.
SPONSON - A short, winglike protuberance on each side of
a seaplane fuselage to increase lateral stability.
SQUAWK - A four-digit number dialed into his transponder
by a pilot to identify his aircraft to air traffic
controllers
STABILATOR - A movable horizontal tail that combines the
actions of a stabilizer and elevator, increasing
longitudinal stability while creating a pitching moment.
STABILIZER - The fixed part of a horizontal airfoil that
controls the pitch of an aircraft; the movable part
being the ELEVATOR.
STAGGER - The relative longitudinal position of the
wings on a biplane. Positive Stagger is when the upper
wing's leading edge is in advance of that of the lower
wing [e.g.: Waco YKS], and vice versa for Negative
Stagger [eg: Beech craft D17].
STALL - (1) Sudden loss of lift when the angle of attack
increases to a point where the flow of air breaks away
from a wing or airfoil, causing it to drop. (2) A
maneuver initiated by the steep raising of an aircraft's
nose, resulting in a loss of velocity and an abrupt
drop.
STANDARD AIR (Standard Atmosphere) - An arbitrary
atmosphere established for calibration of aircraft
instruments. Standard Air Density is 29.92 inches of
mercury and temperature of 59° F, equivalent to an
atmospheric air pressure of 14.7# per square inch.
STANDARD RATE TURN - A turn in which the heading of an
aircraft changes 3° per second, or 360° in one minute.
STATIC WIRE - A clip-on wire used to ground an aircraft
by drawing off static electricity, a potential fire
hazard, during refueling.
SUA see SPECIAL USE AIRSPACE
SUPERSONIC - Speed of flight at or greater than Mach
1.0; literally, faster than the speed of sound.
SWEEPBACK - A backward inclination of an airfoil from
root to tip in a way that causes the leading edge and
often the trailing edge to meet relative wind obliquely,
as wingforms that are swept back.
SWING-WING - A wing whose horizontal angle to the
fuselage centerline can be adjusted in flight to vary
aircraft motion at differing speeds.
TAILDRAGGER see CONVENTIONAL GEAR
TARMAC - (1) A bituminous material used in paving; a
trade name for Tar MacAdam. (2) An airport surface paved
with this substance, especially a runway or an APRON at
a hangar.
TAS - True Air Speed. Because an air speed indicator
indicates true air speed only under standard sea-level
conditions, true air speed is usually calculated by
adjusting an Indicated Air speed according to
temperature, density, and pressure. Compare CALIBRATED
AIR SPEED and INDICATED AIR SPEED.
TCA see CONTROLLED AIRSPACE
TERMINAL RADAR SERVICE AREA (TRSA) - Airspace
surrounding designated airports wherein ATC provides
radar vectoring, sequencing, and separation on a
full-time basis for all IFR and participating VFR
aircraft. Service provided at a TRSA is called Stage III
Service. TRSAs are depicted on VFR aeronautical charts.
Pilot participation is urged but is not mandatory.
TETRAHEDRON - Ground-based, free-rotating,
triangular-shaped wind direction indicator, generally
placed near a runway, often lighted at major airports.
THRUST - The driving force of a propeller in the line of
its shaft or the forward force produced in reaction to
the gases expelled rearward from a jet or rocket engine.
Opposite of DRAG.
TORQUE - A twisting, gyroscopic force acting in
opposition to an axis of rotation, such as with a
turning propeller; aka Torsion.
TOUCH-AND-GO - Landing practice in which an aircraft
does not make a full stop after a landing, but proceeds
immediately to another take-off.
TRACTOR - A propeller mounted in front of its engine,
pulling an aircraft through the air, as opposed to a
PUSHER configuration.
TRAILING EDGE - The rearmost edge of an AIRFOIL.
TRANSPONDER - An airborne transmitter that responds to
ground-based interrogation signals to provide air
traffic controllers with more accurate and reliable
position information than would be possible with
"passive" radar; may also provide air traffic control
with an aircraft's altitude.
TRIKE - Nickname for a weight-shift-control aircraft,
such as a para-glider.
TRIM TAB - A small, auxiliary control surface in the
trailing edge of a wingform, adjustable mechanically or
by hand, to counteract ("trim") aerodynamic forces on
the main control surfaces.
TRUE AIRSPEED - The speed of an aircraft along its
flight path, in respect to the body of air (air mass)
through which the aircraft is moving. Also see
CALIBRATED AIRSPEED, GROUND SPEED, INDICATED AIRSPEED.
TRUE NORTH - The northern direction of the axis of the
Earth; aka "Map North." GEOGRAPHIC NORTH, as opposed to
MAGNETIC NORTH.
TURBOJET - An aircraft having a jet engine in which the
energy of the jet operates a turbine that in turn
operates the air compressor.
TURBOPROP - An aircraft having a jet engine in which the
energy of the jet operates a turbine that drives the
propeller.
TURN & BANK INDICATOR - Primary air-driven gyro
instrument, a combined turn indicator and lateral
inclinometer to show forces on an aircraft in banking
turns. Also referred to as "needle & ball" indicator,
the needle as the gyro's pointer and a ball encased in a
liquid-filled, curved tube.
TWILIGHT ZONE - Long before Rod Serling's tv series was
this consumer-lever definition for a glitch in the
ADCOCK RANGE, officially called a Bi-Signal Zone. It was
a portion of the overlapping area of a beam where the
continuous monotone "on-course" signal became
temporarily overlaid with the "A" or "N" code signals.
Read more here.
ULTRA-LIGHT - An aeronautical vehicle operated for sport
or recreational purposes which does not require FAA
registration, an airworthiness certificate, nor pilot
certification. Primarily single-occupant vehicles,
although some two-place vehicles are authorized for
training purposes. Operation of an ultra-light vehicle
in certain airspaces requires authorization from ATC.
UNCONTROLLED AIRSPACE - Class G Airspace; airspace not
designated as Class A, B, C, D or E.
UNDERCARRIAGE - The landing gear of a land-based
aircraft, including struts, frames, and wheels. A very
British word that has limited use in the USA.
UNDERSHOOT - To land short of a runway or planned
landing spot. Opposite is OVERSHOOT.
UNICOM - Universal Communication. A common radio
frequency (usually 121.0 MHz) used at uncontrolled
(non-tower) airports for local pilot communication.
UPWASH - The slight, upward flow of air just prior to
its reaching the leading edge of a rapidly moving
airfoil.
UPWIND TURN - Long a point of contest among pilots,
there is in reality no such thing as far as the airplane
is concerned. Proponents claim that airplanes lose air
speed when turning upwind, while opponents (and the laws
of physics) argue that an airplane, like a boat in a
river whose speed is only relative to the water and not
the shore, is unaffected within the movement of an air
mass and that it loses only ground speed.
USEFUL LOAD - The weight of crew, passengers, fuel,
baggage, and ballast, generally excluding emergency or
portable equipment and ordnance.
V - Velocity, now used in defining air speeds:
VA = Maneuvering Speed (max structural speed for full
control deflection)
VD = Max Dive Speed (for certification only)
VFE = Max Flaps Extended Speed
VLE = Max Landing Gear Extended Speed
VLO = Max Landing Gear Operation Speed
VNE = Never Exceed Speed
VNO = Max Structural Cruising Speed
VS0 = Stalling Speed Landing Configuration
VS1 = Stalling Speed in a specified Configuration
VX = Best Angle of Climb Speed
VXSE = Best Angle of Climb Speed, one engine out
VY = Best Rate of Climb Speed
VYSE = Best Rate of Climb Speed, one engine out
VARIOMETER - A panel instrument, often as simple as a
tiny ball in a vertical tube, indicating subtle PITCH
movements of an aircraft. Popular use in SAILPLANES.
VENTRAL FIN - A fin/rudder extension on the bottom of a
fuselage. Opposite of DORSAL FIN.
VENTURI TUBE - A small, hourglass-shaped metal tube,
usually set laterally on a fuselage in the slipstream to
create suction for gyroscopic panel instruments. Now
outdated by more sophisticated means.
VFR - Visual Flight Rules that govern the procedures for
conducting flight under visual conditions. The term is
also used in the US to indicate weather conditions that
are equal to or greater than minimum VFR requirements.
Also used by pilots and controllers to indicate a type
of flight plan.
VFR ON TOP - Flight in which a cloud ceiling exists but
modified VISUAL FLIGHT RULES are in effect if the
aircraft travels above the cloud layer.
VISUAL METEOROLOGICAL CONDITIONS (VMC) - Meteorological
conditions expressed in terms of visibility, distance
from clouds, and ceiling equal to or better than
specified minima.
VOR - VHF OmniRange. A ground-based navigation aid
transmitting very high-frequency (VHF) navigation
signals 360° in azimuth, on radials oriented from
MAGNETIC NORTH. The VOR periodically identifies itself
by Morse Code and may have an additional voice
identification feature. Voice features can be used by
ATC or FSS for transmitting information to pilots.
VORTAC - VOR + TACAN (Tactical Air Navigation); combined
radio navigation aids.
VSI - Vertical Speed Indicator. A panel instrument that
gauges rate of climb or descent in feet-per-minute
(fpm). Also Rate Of Climb Indicator.
WASH-IN, WASH-OUT - A method of increasing lift by
increasing (Wash-In) or decreasing (Wash-Out) the angle
of incidence on the outer part of an airplane wing to
counteract the effects of engine torque.
WET COMPASS see COMPASS
WINGLET - A small, stabilizing, rudderlike addition to
the tips of a wing to control or employ air movement.
WING LOADING - The maximum take-off gross weight of an
aircraft divided by its wing area.
YAW - Of the three axes in flight, this specifies the
side-to-side movement of an aircraft on its vertical
axis, as in skewing. Compare PITCH and ROLL.
YOKE - The control wheel of an aircraft, akin to a
automobile steering wheel.
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