glossary

航空

100-HOUR INSPECTION—
An inspection, identical in scope to an
annual inspection. Must be conducted
every 100 hours of flight on aircraft of
under 12,500 pounds that are used
for hire.
ABSOLUTE ALTITUDE—
The vertical distance of an airplane
above the terrain, or above ground
level (AGL).
ABSOLUTE CEILING—
The altitude at which a climb is no
longer possible.
ACCELERATE-GO DISTANCE—
The distance required to accelerate to
V1 with all engines at takeoff power,
experience an engine failure at V1 and
continue the takeoff on the remaining
engine(s). The runway required
includes the distance required to
climb to 35 feet by which time V2
speed must be attained.
ACCELERATE-STOP
DISTANCE—The distance required
to accelerate to V1 with all engines at
takeoff power, experience an engine
failure at V1, and abort the takeoff and
bring the airplane to a stop using braking
action only (use of thrust reversing
is not considered).
ACCELERATION—Force involved
in overcoming inertia, and which may
be defined as a change in velocity per
unit of time.
ACCESSORIES—Components that
are used with an engine, but are not a
part of the engine itself. Units such as
magnetos, carburetors, generators,
and fuel pumps are commonly
installed engine accessories.
ADJUSTABLE STABILIZER—
A stabilizer that can be adjusted in
flight to trim the airplane, thereby
even a trim tab, which provides
aerodynamic force when it interacts
with a moving stream of air.
AIRMANSHIP SKILLS—The skills
of coordination, timing, control touch,
and speed sense in addition to the
motor skills required to fly an aircraft.
AIRMANSHIP—
A sound acquaintance with the
principles of flight, the ability to
operate an airplane with competence
and precision both on the ground and
in the air, and the exercise of sound
judgment that results in optimal
operational safety and efficiency.
AIRPLANE FLIGHT MANUAL
(AFM)—A document developed by
the airplane manufacturer and
approved by the Federal Aviation
Administration (FAA). It is specific to
a particular make and model airplane
by serial number and it contains
operating procedures and limitations.
AIRPLANE OWNER/
INFORMATION MANUAL—A
document developed by the airplane
manufacturer containing general
information about the make and
model of an airplane. The airplane
owner’s manual is not FAA-approved
and is not specific to a particular serial
numbered airplane. This manual is not
kept current, and therefore cannot be
substituted for the AFM/POH.
AIRPORT/FACILITY
DIRECTORY—
A publication designed primarily as a
pilot’s operational manual containing
all airports, seaplane bases, and
heliports open to the public including
communications data, navigational
facilities, and certain special notices
and procedures. This publication is
issued in seven volumes according to
geographical area.
allowing the airplane to fly hands-off
at any given airspeed.
ADVERSE YAW—A condition of
flight in which the nose of an airplane
tends to yaw toward the outside of the
turn. This is caused by the higher
induced drag on the outside wing,
which is also producing more lift.
Induced drag is a by-product of the lift
associated with the outside wing.
AERODYNAMIC CEILING—
The point (altitude) at which, as the
indicated airspeed decreases with altitude,
it progressively merges with the
low speed buffet boundary where prestall
buffet occurs for the airplane at a
load factor of 1.0 G.
AERODYNAMICS—The science of
the action of air on an object, and with
the motion of air on other gases.
Aerodynamics deals with the
production of lift by the aircraft, the
relative wind, and the atmosphere.
AILERONS—Primary flight control
surfaces mounted on the trailing edge
of an airplane wing, near the tip.
Ailerons control roll about the longitudinal
axis.
AIR START—The act or instance of
starting an aircraft’s engine while in
flight, especially a jet engine after
flameout.
AIRCRAFT LOGBOOKS—
Journals containing a record of total
operating time, repairs, alterations or
inspections performed, and all
Airworthiness Directive (AD) notes
complied with. A maintenance
logbook should be kept for the
airframe, each engine, and each
propeller.
AIRFOIL—An airfoil is any surface,
such as a wing, propeller, rudder, or
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AIRWORTHINESS—A condition
in which the aircraft conforms to its
type certificated design including
supplemental type certificates, and
field approved alterations. The
aircraft must also be in a condition for
safe flight as determined by annual,
100 hour, preflight and any other
required inspections.
AIRWORTHINESS
CERTIFICATE—
A certificate issued by the FAA to all
aircraft that have been proven to meet
the minimum standards set down by
the Code of Federal Regulations.
AIRWORTHINESS
DIRECTIVE—A regulatory notice
sent out by the FAA to the registered
owner of an aircraft informing the
owner of a condition that prevents the
aircraft from continuing to meet
its conditions for airworthiness.
Airworthiness Directives (AD notes)
must be complied with within the
required time limit, and the fact of
compliance, the date of compliance,
and the method of compliance must be
recorded in the aircraft’s maintenance
records.
ALPHA MODE OF
OPERATION—The operation of a
turboprop engine that includes all of
the flight operations, from takeoff to
landing. Alpha operation is typically
between 95 percent to 100 percent of
the engine operating speed.
ALTERNATE AIR—A device
which opens, either automatically
or manually, to allow induction airflow
to continue should the primary
induction air opening become
blocked.
ALTERNATE STATIC SOURCE—
A manual port that when opened
allows the pitot static instruments to
sense static pressure from an alternate
location should the primary static port
become blocked.
ALTERNATOR/GENERATOR—A
device that uses engine power to generate
electrical power.
ALTIMETER—A flight instrument
that indicates altitude by sensing
pressure changes.
pitch, which is the up and down
movement of the airplane’s nose.
ATTITUDE— The position of an
aircraft as determined by the
relationship of its axes and a reference,
usually the earth’s horizon.
AUTOKINESIS—This is caused by
staring at a single point of light
against a dark background for more
than a few seconds. After a few
moments, the light appears to move
on its own.
AUTOPILOT—An automatic flight
control system which keeps an aircraft
in level flight or on a set course.
Automatic pilots can be directed by
the pilot, or they may be coupled to a
radio navigation signal.
AXES OF AN AIRCRAFT—Three
imaginary lines that pass through an
aircraft’s center of gravity. The axes
can be considered as imaginary axles
around which the aircraft turns. The
three axes pass through the center of
gravity at 90° angles to each other.
The axis from nose to tail is the
longitudinal axis, the axis that passes
from wingtip to wingtip is the lateral
axis, and the axis that passes vertically
through the center of gravity is the
vertical axis.
AXIAL FLOW COMPRESSOR—
Atype of compressor used in a turbine
engine in which the airflow through
the compressor is essentially linear.
An axial-flow compressor is made up
of several stages of alternate rotors
and stators. The compressor ratio is
determined by the decrease in area of
the succeeding stages.
BACK SIDE OF THE POWER
CURVE— Flight regime in which
flight at a higher airspeed requires a
lower power setting and a lower
airspeed requires a higher power
setting in order to maintain altitude.
BALKED LANDING—
A go-around.
BALLAST—Removable or permanently
installed weight in an aircraft
ALTITUDE (AGL)—The actual
height above ground level (AGL) at
which the aircraft is flying.
ALTITUDE (MSL)—The actual
height above mean sea level (MSL) at
which the aircraft is flying.
ALTITUDE CHAMBER—A device
that simulates high altitude conditions
by reducing the interior pressure. The
occupants will suffer from the same
physiological conditions as flight at
high altitude in an unpressurized
aircraft.
ALTITUDE ENGINE—
A reciprocating aircraft engine having
a rated takeoff power that is
producible from sea level to an
established higher altitude.
ANGLE OF ATTACK—The acute
angle between the chord line of the
airfoil and the direction of the relative
wind.
ANGLE OF INCIDENCE—
The angle formed by the chord line of
the wing and a line parallel to the
longitudinal axis of the airplane.
ANNUAL INSPECTION—
A complete inspection of an aircraft
and engine, required by the Code
of Federal Regulations, to be
accomplished every 12 calendar
months on all certificated aircraft.
Only an A& technician holding an
Inspection Authorization can conduct
an annual inspection.
ANTI-ICING—The prevention of
the formation of ice on a surface. Ice
may be prevented by using heat or by
covering the surface with a chemical
that prevents water from reaching the
surface. Anti-icing should not be confused
with deicing, which is the
removal of ice after it has formed on
the surface.
ATTITUDE INDICATOR—
An instrument which uses an artificial
horizon and miniature airplane to
depict the position of the airplane in
relation to the true horizon. The
attitude indicator senses roll as well as
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used to bring the center of gravity into
the allowable range.
BALLOON—The result of a too
aggressive flare during landing
causing the aircraft to climb.
BASIC EMPTY WEIGHT
(GAMA)—Basic empty weight
includes the standard empty weight
plus optional and special equipment
that has been installed.
BEST ANGLE OF CLIMB (VX)—
The speed at which the aircraft will
produce the most gain in altitude in a
given distance.
BEST GLIDE—The airspeed in
which the aircraft glides the furthest
for the least altitude lost when in
non-powered flight.
BEST RATE OF CLIMB (VY)—
The speed at which the aircraft will
produce the most gain in altitude in
the least amount of time.
BLADE FACE—The flat portion of a
propeller blade, resembling the
bottom portion of an airfoil.
BLEED AIR—Compressed air
tapped from the compressor stages of
a turbine engine by use of ducts and
tubing. Bleed air can be used for
deice, anti-ice, cabin pressurization,
heating, and cooling systems.
BLEED VALVE—In a turbine
engine, a flapper valve, a popoff
valve, or a bleed band designed to
bleed off a portion of the compressor
air to the atmosphere. Used to
maintain blade angle of attack and
provide stall-free engine acceleration
and deceleration.
BOOST PUMP—An electrically
driven fuel pump, usually of the
centrifugal type, located in one of the
fuel tanks. It is used to provide fuel to
the engine for starting and providing
fuel pressure in the event of failure of
the engine driven pump. It also
pressurizes the fuel lines to prevent
vapor lock.
CAMBERED—The camber of an
airfoil is the characteristic curve of its
upper and lower surfaces. The upper
camber is more pronounced, while the
lower camber is comparatively flat.
This causes the velocity of the airflow
immediately above the wing to be
much higher than that below the wing.
CARBURETOR ICE— Ice that
forms inside the carburetor due to the
temperature drop caused by the
vaporization of the fuel. Induction
system icing is an operational hazard
because it can cut off the flow of the
fuel/air charge or vary the fuel/air
ratio.
CARBURETOR—1. Pressure: A
hydromechanical device employing a
closed feed system from the fuel
pump to the discharge nozzle. It
meters fuel through fixed jets
according to the mass airflow through
the throttle body and discharges it
under a positive pressure. Pressure
carburetors are distinctly different
from float-type carburetors, as they do
not incorporate a vented float
chamber or suction pickup from a
discharge nozzle located in the venturi
tube. 2. Float-type: Consists
essentially of a main air passage
through which the engine draws its
supply of air, a mechanism to control
the quantity of fuel discharged in
relation to the flow of air, and a means
of regulating the quantity of fuel/air
mixture delivered to the engine
cylinders.
CASCADE REVERSER—A thrust
reverser normally found on turbofan
engines in which a blocker door and a
series of cascade vanes are used to
redirect exhaust gases in a forward
direction.
CENTER OF GRAVITY (CG)—
The point at which an airplane would
balance if it were possible to suspend
it at that point. It is the mass center of
the airplane, or the theoretical point at
which the entire weight of the airplane
is assumed to be concentrated. It may
be expressed in inches from the reference
datum, or in percent of mean
aerodynamic chord (MAC). The location
depends on the distribution of
weight in the airplane.
BUFFETING—The beating of an
aerodynamic structure or surface by
unsteady flow, gusts, etc.; the irregular
shaking or oscillation of a vehicle
component owing to turbulent air or
separated flow.
BUS BAR—An electrical power
distribution point to which several
circuits may be connected. It is often a
solid metal strip having a number of
terminals installed on it.
BUS TIE—A switch that connects
two or more bus bars. It is usually
used when one generator fails and
power is lost to its bus. By closing the
switch, the operating generator
powers both busses.
BYPASS AIR—The part of a
turbofan’s induction air that bypasses
the engine core.
BYPASS RATIO—The ratio of the
mass airflow in pounds per second
through the fan section of a turbofan
engine to the mass airflow that passes
through the gas generator portion of
the engine. Or, the ratio between fan
mass airflow (lb/sec.) and core engine
mass airflow (lb/sec.).
CABIN PRESSURIZATION—A
condition where pressurized air is
forced into the cabin simulating
pressure conditions at a much lower
altitude and increasing the aircraft
occupants comfort.
CALIBRATED AIRSPEED
(CAS)—Indicated airspeed corrected
for installation error and instrument
error. Although manufacturers attempt
to keep airspeed errors to a minimum,
it is not possible to eliminate all errors
throughout the airspeed operating
range. At certain airspeeds and with
certain flap settings, the installation
and instrument errors may total
several knots. This error is generally
greatest at low airspeeds. In the
cruising and higher airspeed ranges,
indicated airspeed and calibrated
airspeed are approximately the same.
Refer to the airspeed calibration chart
to correct for possible airspeed errors.
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CENTER-OF-GRAVITY
LIMITS—The specified forward and
aft points within which the CG must
be located during flight. These limits
are indicated on pertinent airplane
specifications.
CENTER-OF-GRAVITY
RANGE—The distance between the
forward and aft CG limits indicated on
pertinent airplane specifications.
CENTRIFUGAL
FLOW COMPRESSOR—
An impeller-shaped device that receives
air at its center and slings air outward at
high velocity into a diffuser for increased
pressure. Also referred to as a radial outflow
compressor.
CHORD LINE—An imaginary
straight line drawn through an airfoil
from the leading edge to the trailing
edge.
CIRCUIT BREAKER—
A circuit-protecting device that opens
the circuit in case of excess current
flow. A circuit breakers differs from a
fuse in that it can be reset without
having to be replaced.
CLEAR AIR TURBULENCE—
Turbulence not associated with any
visible moisture.
CLIMB GRADIENT—The ratio
between distance traveled and altitude
gained.
COCKPIT RESOURCE
MANAGEMENT—Techniques
designed to reduce pilot errors and
manage errors that do occur utilizing
cockpit human resources. The
assumption is that errors are going to
happen in a complex system with
error-prone humans.
COEFFICIENT OF LIFT—See
LIFT COEFFICIENT.
COFFIN CORNER—The flight
regime where any increase in airspeed
will induce high speed mach buffet
and any decrease in airspeed will
induce low speed mach buffet.
CONDITION LEVER—In a turbine
engine, a powerplant control that controls
the flow of fuel to the engine.
The condition lever sets the desired
engine r.p.m. within a narrow range
between that appropriate for ground
and flight operations.
CONFIGURATION—This is a
general term, which normally refers to
the position of the landing gear
and flaps.
CONSTANT SPEED
PROPELLER— A controllablepitch
propeller whose pitch is
automatically varied in flight by a
governor to maintain a constant r.p.m.
in spite of varying air loads.
CONTROL TOUCH—The ability to
sense the action of the airplane and its
probable actions in the immediate
future, with regard to attitude and
speed variations, by sensing and
evaluation of varying pressures and
resistance of the control surfaces
transmitted through the cockpit flight
controls.
CONTROLLABILITY—A measure
of the response of an aircraft relative
to the pilot’s flight control inputs.
CONTROLLABLE PITCH
PROPELLER—Apropeller in which
the blade angle can be changed during
flight by a control in the cockpit.
CONVENTIONAL LANDING
GEAR—Landing gear employing a
third rear-mounted wheel. These
airplanes are also sometimes referred
to as tailwheel airplanes.
COORDINATED FLIGHT—
Application of all appropriate flight
and power controls to prevent slipping
or skidding in any flight condition.
COORDINATION—The ability to
use the hands and feet together
subconsciously and in the proper
relationship to produce desired results
in the airplane.
CORE AIRFLOW—Air drawn into
the engine for the gas generator.
COMBUSTION CHAMBER—The
section of the engine into which fuel
is injected and burned.
COMMON TRAFFIC
ADVISORY FREQUENCY—The
common frequency used by airport
traffic to announce position reports in
the vicinity of the airport.
COMPLEX AIRCRAFT—
An aircraft with retractable landing
gear, flaps, and a controllable-pitch
propeller, or is turbine powered.
COMPRESSION RATIO—1. In a
reciprocating engine, the ratio of the
volume of an engine cylinder with the
piston at the bottom center to the
volume with the piston at top center.
2. In a turbine engine, the ratio of the
pressure of the air at the discharge to
the pressure of air at the inlet.
COMPRESSOR BLEED AIR—
See BLEED AIR.
COMPRESSOR BLEED
VALVES—See BLEED VALVE.
COMPRESSOR SECTION— The
section of a turbine engine that
increases the pressure and density of
the air flowing through the engine.
COMPRESSOR STALL—In gas
turbine engines, a condition in an
axial-flow compressor in which one
or more stages of rotor blades fail to
pass air smoothly to the succeeding
stages. Astall condition is caused by a
pressure ratio that is incompatible
with the engine r.p.m. Compressor
stall will be indicated by a rise in
exhaust temperature or r.p.m.
fluctuation, and if allowed to
continue, may result in flameout and
physical damage to the engine.
COMPRESSOR SURGE—Asevere
compressor stall across the entire
compressor that can result in severe
damage if not quickly corrected. This
condition occurs with a complete
stoppage of airflow or a reversal of
airflow.
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COWL FLAPS—Devices arranged
around certain air-cooled engine
cowlings which may be opened or
closed to regulate the flow of air
around the engine.
CRAB—A flight condition in which
the nose of the airplane is pointed into
the wind a sufficient amount to counteract
a crosswind and maintain a
desired track over the ground.
CRAZING—Small fractures in
aircraft windshields and windows
caused from being exposed to the
ultraviolet rays of the sun and
temperature extremes.
CRITICAL ALTITUDE—
The maximum altitude under standard
atmospheric conditions at which a
turbocharged engine can produce its
rated horsepower.
CRITICAL ANGLE
OF ATTACK—The angle of attack at
which a wing stalls regardless of
airspeed, flight attitude, or weight.
CRITICAL ENGINE—The engine
whose failure has the most adverse
effect on directional control.
CROSS CONTROLLED—
A condition where aileron deflection
is in the opposite direction of rudder
deflection.
CROSSFEED—Asystem that allows
either engine on a twin-engine
airplane to draw fuel from any fuel
tank.
CROSSWIND COMPONENT—
The wind component, measured in
knots, at 90° to the longitudinal axis
of the runway.
CURRENT LIMITER—A device
that limits the generator output to a
level within that rated by the
generator manufacturer.
DATUM (REFERENCE
DATUM)—An imaginary vertical
plane or line from which all
measurements of moment arm are
taken. The datum is established by the
manufacturer. Once the datum has
been selected, all moment arms and
parasite drag to compensate for the
additional induced drag caused by the
down aileron. This balancing of the
drag forces helps minimize adverse
yaw.
DIFFUSION—Reducing the velocity
of air causing the pressure to increase.
DIRECTIONAL STABILITY—
Stability about the vertical axis of an
aircraft, whereby an aircraft tends to
return, on its own, to flight aligned
with the relative wind when disturbed
from that equilibrium state. The
vertical tail is the primary contributor
to directional stability, causing an
airplane in flight to align with the
relative wind.
DITCHING—Emergency landing in
water.
DOWNWASH—
Air deflected perpendicular to the
motion of the airfoil.
DRAG—An aerodynamic force on a
body acting parallel and opposite to
the relative wind. The resistance of
the atmosphere to the relative motion
of an aircraft. Drag opposes thrust and
limits the speed of the airplane.
DRAG CURVE—
A visual representation of the amount
of drag of an aircraft at various
airspeeds.
DRIFT ANGLE—Angle between
heading and track.
DUCTED-FAN ENGINE—
An engine-propeller combination that
has the propeller enclosed in a radial
shroud. Enclosing the propeller
improves the efficiency of the
propeller.
DUTCH ROLL—A combination of
rolling and yawing oscillations that
normally occurs when the dihedral
effects of an aircraft are more
powerful than the directional stability.
Usually dynamically stable but
objectionable in an airplane because
of the oscillatory nature.
the location of CG range are measured
from this point.
DECOMPRESSION SICKNESS—
A condition where the low pressure at
high altitudes allows bubbles of
nitrogen to form in the blood and
joints causing severe pain. Also
known as the bends.
DEICER BOOTS—Inflatable rubber
boots attached to the leading edge of
an airfoil. They can be sequentially
inflated and deflated to break away ice
that has formed over their surface.
DEICING—Removing ice after it
has formed.
DELAMINATION—The separation
of layers.
DENSITY ALTITUDE—
This altitude is pressure altitude corrected
for variations from standard
temperature. When conditions are
standard, pressure altitude and density
altitude are the same. If the temperature
is above standard, the density altitude
is higher than pressure altitude. If
the temperature is below standard, the
density altitude is lower than pressure
altitude. This is an important altitude
because it is directly related to the
airplane’s performance.
DESIGNATED PILOT
EXAMINER (DPE)—An individual
designated by the FAA to administer
practical tests to pilot applicants.
DETONATION—
The sudden release of heat energy
from fuel in an aircraft engine caused
by the fuel-air mixture reaching its
critical pressure and temperature.
Detonation occurs as a violent
explosion rather than a smooth
burning process.
DEWPOINT—The temperature at
which air can hold no more water.
DIFFERENTIAL AILERONS—
Control surface rigged such that the
aileron moving up moves a greater
distance than the aileron moving
down. The up aileron produces extra
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DYNAMIC HYDROPLANING—A
condition that exists when landing on
a surface with standing water deeper
than the tread depth of the tires. When
the brakes are applied, there is a
possibility that the brake will lock up
and the tire will ride on the surface of
the water, much like a water ski.
When the tires are hydroplaning,
directional control and braking action
are virtually impossible. An effective
anti-skid system can minimize the
effects of hydroplaning.
DYNAMIC STABILITY—
The property of an aircraft that causes
it, when disturbed from straight-andlevel
flight, to develop forces or
moments that restore the original
condition of straight and level.
ELECTRICAL BUS—
See BUS BAR.
ELECTROHYDRAULIC—
Hydraulic control which is electrically
actuated.
ELEVATOR—
The horizontal, movable primary
control surface in the tail section, or
empennage, of an airplane. The
elevator is hinged to the trailing edge
of the fixed horizontal stabilizer.
EMERGENCY LOCATOR
TRANSMITTER—A small, selfcontained
radio transmitter that will
automatically, upon the impact of a
crash, transmit an emergency signal
on 121.5, 243.0, or 406.0 MHz.
EMPENNAGE—The section of the
airplane that consists of the vertical
stabilizer, the horizontal stabilizer,
and the associated control surfaces.
ENGINE PRESSURE RATIO
(EPR)—The ratio of turbine
discharge pressure divided by
compressor inlet pressure that is used
as an indication of the amount of
thrust being developed by a turbine
engine.
ENVIRONMENTAL SYSTEMS—
In an aircraft, the systems, including
the supplemental oxygen systems, air
conditioning systems, heaters, and
FIXED SHAFT TURBOPROP
ENGINE—A turboprop engine
where the gas producer spool is
directly connected to the output shaft.
FIXED-PITCH PROPELLERS—
Propellers with fixed blade angles.
Fixed-pitch propellers are designed as
climb propellers, cruise propellers, or
standard propellers.
FLAPS—Hinged portion of the
trailing edge between the ailerons and
fuselage. In some aircraft, ailerons
and flaps are interconnected to
produce full-span “flaperons.” In
either case, flaps change the lift and
drag on the wing.
FLAT PITCH—
A propeller configuration when the
blade chord is aligned with the direction
of rotation.
FLICKER VERTIGO—
A disorientating condition caused
from flickering light off the blades of
the propeller.
FLIGHT DIRECTOR—An automatic
flight control system in which
the commands needed to fly the airplane
are electronically computed and
displayed on a flight instrument. The
commands are followed by the human
pilot with manual control inputs or, in
the case of an autopilot system, sent to
servos that move the flight controls.
FLIGHT IDLE—Engine speed,
usually in the 70-80 percent range, for
minimum flight thrust.
FLOATING—A condition when
landing where the airplane does not
settle to the runway due to excessive
airspeed.
FORCE (F)—The energy applied to
an object that attempts to cause the
object to change its direction, speed,
or motion. In aerodynamics, it is
expressed as F, T (thrust), L (lift), W
(weight), or D (drag), usually in
pounds.
FORM DRAG—The part of parasite
drag on a body resulting from the
pressurization systems, which make it
possible for an occupant to function at
high altitude.
EQUILIBRIUM—A condition that
exists within a body when the sum of
the moments of all of the forces acting
on the body is equal to zero. In
aerodynamics, equilibrium is when all
opposing forces acting on an aircraft
are balanced (steady, unaccelerated
flight conditions).
EQUIVALENT SHAFT
HORSEPOWER (ESHP)—
A measurement of the total horsepower
of a turboprop engine, including
that provided by jet thrust.
EXHAUST GAS TEMPERATURE
(EGT)—The temperature of the
exhaust gases as they leave the
cylinders of a reciprocating engine or
the turbine section of a turbine engine.
EXHAUST MANIFOLD—The part
of the engine that collects exhaust
gases leaving the cylinders.
EXHAUST—The rear opening of a
turbine engine exhaust duct. The
nozzle acts as an orifice, the size of
which determines the density and
velocity of the gases as they emerge
from the engine.
FALSE HORIZON—An optical
illusion where the pilot confuses a row
of lights along a road or other straight
line as the horizon.
FALSE START—
See HUNG START.
FEATHERING PROPELLER
(FEATHERED)—A controllable
pitch propeller with a pitch range
sufficient to allow the blades to be
turned parallel to the line of flight to
reduce drag and prevent further
damage to an engine that has been
shut down after a malfunction.
FIXATION—
A psychological condition where the
pilot fixes attention on a single source
of information and ignores all
other sources.
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integrated effect of the static pressure
acting normal to its surface resolved
in the drag direction.
FORWARD SLIP—A slip in which
the airplane’s direction of motion continues
the same as before the slip was
begun. In a forward slip, the airplane’s
longitudinal axis is at an angle to its
flightpath.
FREE POWER TURBINE
ENGINE—A turboprop engine
where the gas producer spool is on a
separate shaft from the output shaft.
The free power turbine spins
independently of the gas producer and
drives the output shaft.
FRICTION DRAG—The part of
parasitic drag on a body resulting
from viscous shearing stresses over its
wetted surface.
FRISE-TYPE AILERON—Aileron
having the nose portion projecting
ahead of the hinge line. When the
trailing edge of the aileron moves up,
the nose projects below the wing’s
lower surface and produces some
parasite drag, decreasing the amount
of adverse yaw.
FUEL CONTROL UNIT—
The fuel-metering device used on a
turbine engine that meters the proper
quantity of fuel to be fed into the
burners of the engine. It integrates the
parameters of inlet air temperature,
compressor speed, compressor
discharge pressure, and exhaust gas
temperature with the position of the
cockpit power control lever.
FUEL EFFICIENCY—Defined as
the amount of fuel used to produce a
specific thrust or horsepower divided
by the total potential power contained
in the same amount of fuel.
FUEL HEATERS—A radiator-like
device which has fuel passing through
the core. A heat exchange occurs to
keep the fuel temperature above the
freezing point of water so that
entrained water does not form ice
crystals, which could block fuel flow.
FUEL INJECTION—
A fuel metering system used on some
aircraft reciprocating engines in
GO-AROUND—
Terminating a landing approach.
GOVERNING RANGE—The range
of pitch a propeller governor can
control during flight.
GOVERNOR—A control which
limits the maximum rotational speed
of a device.
GROSS WEIGHT—
The total weight of a fully loaded
aircraft including the fuel, oil, crew,
passengers, and cargo.
GROUND ADJUSTABLE TRIM
TAB—A metal trim tab on a control
surface that is not adjustable in flight.
Bent in one direction or another while
on the ground to apply trim forces to
the control surface.
GROUND EFFECT—A condition
of improved performance encountered
when an airplane is operating
very close to the ground. When an
airplane’s wing is under the influence
of ground effect, there is a reduction
in upwash, downwash, and wingtip
vortices. As a result of the reduced
wingtip vortices, induced drag is
reduced.
GROUND IDLE—Gas turbine
engine speed usually 60-70 percent of
the maximum r.p.m. range, used as a
minimum thrust setting for ground
operations.
GROUND LOOP—A sharp, uncontrolled
change of direction of an
airplane on the ground.
GROUND POWER UNIT (GPU)—
A type of small gas turbine whose
purpose is to provide electrical power,
and/or air pressure for starting aircraft
engines. Aground unit is connected to
the aircraft when needed. Similar to
an aircraft-installed auxiliary power
unit.
GROUNDSPEED (GS)—The actual
speed of the airplane over the ground.
It is true airspeed adjusted for
wind. Groundspeed decreases with a
headwind, and increases with
a tailwind.
which a constant flow of fuel is fed to
injection nozzles in the heads of all
cylinders just outside of the intake
valve. It differs from sequential fuel
injection in which a timed charge of
high-pressure fuel is sprayed directly
into the combustion chamber of the
cylinder.
FUEL LOAD—The expendable part
of the load of the airplane. It includes
only usable fuel, not fuel required to
fill the lines or that which remains
trapped in the tank sumps.
FUEL TANK SUMP—A sampling
port in the lowest part of the fuel tank
that the pilot can utilize to check for
contaminants in the fuel.
FUSELAGE—The section of the
airplane that consists of the cabin
and/or cockpit, containing seats for
the occupants and the controls for the
airplane.
GAS GENERATOR—The basic
power producing portion of a gas
turbine engine and excluding such
sections as the inlet duct, the
fan section, free power turbines,
and tailpipe. Each manufacturer
designates what is included as the gas
generator, but generally consists of
the compressor, diffuser, combustor,
and turbine.
GAS TURBINE ENGINE—A form
of heat engine in which burning fuel
adds energy to compressed air and
accelerates the air through the
remainder of the engine. Some of the
energy is extracted to turn the air
compressor, and the remainder
accelerates the air to produce thrust.
Some of this energy can be converted
into torque to drive a propeller or a
system of rotors for a helicopter.
GLIDE RATIO—The ratio between
distance traveled and altitude lost
during non-powered flight.
GLIDEPATH—The path of an
aircraft relative to the ground while
approaching a landing.
GLOBAL POSITION SYSTEM
(GPS)—A satellite-based radio positioning,
navigation, and time-transfer
system.
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GROUND TRACK—The aircraft’s
path over the ground when in flight.
GUST PENETRATION SPEED—
The speed that gives the greatest
margin between the high and low
mach speed buffets.
GYROSCOPIC PRECESSION—
An inherent quality of rotating bodies,
which causes an applied force to be
manifested 90º in the direction of
rotation from the point where the
force is applied.
HAND PROPPING—Starting an
engine by rotating the propeller by
hand.
HEADING—The direction in which
the nose of the aircraft is pointing
during flight.
HEADING BUG—A marker on the
heading indicator that can be rotated
to a specific heading for reference
purposes, or to command an autopilot
to fly that heading.
HEADING INDICATOR—
An instrument which senses airplane
movement and displays heading based
on a 360º azimuth, with the final zero
omitted. The heading indicator, also
called a directional gyro, is fundamentally
a mechanical instrument
designed to facilitate the use of the
magnetic compass. The heading indicator
is not affected by the forces that
make the magnetic compass difficult
to interpret.
HEADWIND COMPONENT—The
component of atmospheric winds that
acts opposite to the aircraft’s flightpath.
HIGH PERFORMANCE
AIRCRAFT—An aircraft with an
engine of more than 200 horsepower.
HORIZON—The line of sight
boundary between the earth and the
sky.
HORSEPOWER—
The term, originated by inventor
James Watt, means the amount of
work a horse could do in one second.
engine. Some igniters resemble spark
plugs, while others, called glow plugs,
have a coil of resistance wire that
glows red hot when electrical current
flows through the coil.
IMPACT ICE—Ice that forms on the
wings and control surfaces or on the
carburetor heat valve, the walls of the
air scoop, or the carburetor units
during flight. Impact ice collecting on
the metering elements of the
carburetor may upset fuel metering or
stop carburetor fuel flow.
INCLINOMETER—An instrument
consisting of a curved glass tube,
housing a glass ball, and damped with
a fluid similar to kerosene. It may be
used to indicate inclination, as a level,
or, as used in the turn indicators, to
show the relationship between gravity
and centrifugal force in a turn.
INDICATED AIRSPEED (IAS)—
The direct instrument reading
obtained from the airspeed indicator,
uncorrected for variations in atmospheric
density, installation error, or
instrument error. Manufacturers use
this airspeed as the basis for determining
airplane performance. Takeoff,
landing, and stall speeds listed in the
AFM or POH are indicated airspeeds
and do not normally vary with altitude
or temperature.
INDICATED ALTITUDE—
The altitude read directly from the
altimeter (uncorrected) when it is set
to the current altimeter setting.
INDUCED DRAG—That part of
total drag which is created by the
production of lift. Induced drag
increases with a decrease in airspeed.
INDUCTION MANIFOLD—The
part of the engine that distributes
intake air to the cylinders.
INERTIA—The opposition which a
body offers to a change of motion.
INITIAL CLIMB—This stage of the
climb begins when the airplane leaves
the ground, and a pitch attitude has
One horsepower equals 550
foot-pounds per second, or 33,000
foot-pounds per minute.
HOT START—In gas turbine
engines, a start which occurs with
normal engine rotation, but exhaust
temperature exceeds prescribed
limits. This is usually caused by an
excessively rich mixture in the
combustor. The fuel to the engine
must be terminated immediately to
prevent engine damage.
HUNG START—In gas turbine
engines, a condition of normal light
off but with r.p.m. remaining at some
low value rather than increasing to the
normal idle r.p.m. This is often the
result of insufficient power to the
engine from the starter. In the event of
a hung start, the engine should be shut
down.
HYDRAULICS—The branch of
science that deals with the
transmission of power by incompressible
fluids under pressure.
HYDROPLANING—A condition
that exists when landing on a surface
with standing water deeper than the
tread depth of the tires. When the
brakes are applied, there is a
possibility that the brake will lock up
and the tire will ride on the surface of
the water, much like a water ski.
When the tires are hydroplaning,
directional control and braking action
are virtually impossible. An effective
anti-skid system can minimize the
effects of hydroplaning.
HYPOXIA—A lack of sufficient
oxygen reaching the body tissues.
IFR (INSTRUMENT FLIGHT
RULES)—Rules that govern the
procedure for conducting flight in
weather conditions below VFR
weather minimums. The term “IFR”
also is used to define weather
conditions and the type of flight plan
under which an aircraft is operating.
IGNITER PLUGS—The electrical
device used to provide the spark for
starting combustion in a turbine
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been established to climb away from
the takeoff area.
INTEGRAL FUEL TANK—
A portion of the aircraft structure,
usually a wing, which is sealed off and
used as a fuel tank. When a wing is
used as an integral fuel tank, it is
called a “wet wing.”
INTERCOOLER—A device used to
reduce the temperature of the
compressed air before it enters the
fuel metering device. The resulting
cooler air has a higher density, which
permits the engine to be operated with
a higher power setting.
INTERNAL COMBUSTION
ENGINES—An engine that produces
power as a result of expanding hot
gases from the combustion of fuel and
air within the engine itself. A steam
engine where coal is burned to heat up
water inside the engine is an example
of an external combustion engine.
INTERSTAGE TURBINE
TEMPERATURE (ITT)—The temperature
of the gases between the high
pressure and low pressure turbines.
INVERTER—An electrical device
that changes DC to AC power.
ISA (INTERNATIONAL
STANDARD ATMOSPHERE)—
Standard atmospheric conditions
consisting of a temperature of 59°F
(15°C), and a barometric pressure of
29.92 in. Hg. (1013.2 mb) at sea level.
ISA values can be calculated for
various altitudes using a standard
lapse rate of approximately 2°C per
1,000 feet.
JET POWERED AIRPLANE—An
aircraft powered by a turbojet or
turbofan engine.
KINESTHESIA—The sensing of
movements by feel.
LATERAL AXIS—An imaginary
line passing through the center of
gravity of an airplane and extending
across the airplane from wingtip
to wingtip.
the coefficient of drag for any given
angle of attack.
LIFT-OFF—The act of becoming
airborne as a result of the wings
lifting the airplane off the ground, or
the pilot rotating the nose up,
increasing the angle of attack to start a
climb.
LIMIT LOAD FACTOR—Amount
of stress, or load factor, that an aircraft
can withstand before structural
damage or failure occurs.
LOAD FACTOR—The ratio of the
load supported by the airplane’s wings
to the actual weight of the aircraft and
its contents. Also referred to as
G-loading.
LONGITUDINAL AXIS—
An imaginary line through an aircraft
from nose to tail, passing through its
center of gravity. The longitudinal
axis is also called the roll axis of the
aircraft. Movement of the ailerons
rotates an airplane about its
longitudinal axis.
LONGITUDINAL STABILITY
(PITCHING)—Stability about the
lateral axis. A desirable characteristic
of an airplane whereby it tends to
return to its trimmed angle of attack
after displacement.
MACH—Speed relative to the speed
of sound. Mach 1 is the speed of
sound.
MACH BUFFET—
Airflow separation behind a
shock-wave pressure barrier caused
by airflow over flight surfaces
exceeding the speed of sound.
MACH COMPENSATING
DEVICE—A device to alert the pilot
of inadvertent excursions beyond its
certified maximum operating speed.
MACH CRITICAL—The MACH
speed at which some portion of the
airflow over the wing first equals
MACH 1.0. This is also the speed at
which a shock wave first appears on
the airplane.
LATERAL STABILITY
(ROLLING)—The stability about the
longitudinal axis of an aircraft.
Rolling stability or the ability of an
airplane to return to level flight due to
a disturbance that causes one of the
wings to drop.
LEAD-ACID BATTERY—
A commonly used secondary cell
having lead as its negative plate and
lead peroxide as its positive plate.
Sulfuric acid and water serve as the
electrolyte.
LEADING EDGE DEVICES—
High lift devices which are found on
the leading edge of the airfoil. The
most common types are fixed slots,
movable slats, and leading edge flaps.
LEADING EDGE—The part of an
airfoil that meets the airflow first.
LEADING EDGE FLAP—
A portion of the leading edge of an
airplane wing that folds downward to
increase the camber, lift, and drag of
the wing. The leading-edge flaps are
extended for takeoffs and landings to
increase the amount of aerodynamic
lift that is produced at any given
airspeed.
LICENSED EMPTY WEIGHT—
The empty weight that consists of the
airframe, engine(s), unusable fuel,
and undrainable oil plus standard and
optional equipment as specified in the
equipment list. Some manufacturers
used this term prior to GAMA
standardization.
LIFT—One of the four main forces
acting on an aircraft. On a fixed-wing
aircraft, an upward force created by
the effect of airflow as it passes over
and under the wing.
LIFT COEFFICIENT— A coefficient
representing the lift of a given
airfoil. Lift coefficient is obtained by
dividing the lift by the free-stream
dynamic pressure and the representative
area under consideration.
LIFT/DRAG RATIO—
The efficiency of an airfoil section. It
is the ratio of the coefficient of lift to
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MACH TUCK—Acondition that can
occur when operating a swept-wing
airplane in the transonic speed range.
A shock wave could form in the root
portion of the wing and cause the
air behind it to separate. This
shock-induced separation causes the
center of pressure to move aft. This,
combined with the increasing amount
of nose down force at higher speeds to
maintain left flight, causes the nose to
“tuck.” If not corrected, the airplane
could enter a steep, sometimes
unrecoverable dive.
MAGNETIC COMPASS—A device
for determining direction measured
from magnetic north.
MAIN GEAR—The wheels of an
aircraft’s landing gear that supports
the major part of the aircraft’s weight.
MANEUVERABILITY—Ability of
an aircraft to change directions along
a flightpath and withstand the stresses
imposed upon it.
MANEUVERING SPEED (VA) —
The maximum speed where full,
abrupt control movement can be used
without overstressing the airframe.
MANIFOLD PRESSURE (MP)—
The absolute pressure of the fuel/air
mixture within the intake manifold,
usually indicated in inches of
mercury.
MAXIMUM ALLOWABLE
TAKEOFF POWER—The maximum
power an engine is allowed to
develop for a limited period of time;
usually about one minute.
MAXIMUM LANDING
WEIGHT—The greatest weight that
an airplane normally is allowed to
have at landing.
MAXIMUM RAMP WEIGHT—
The total weight of a loaded aircraft,
including all fuel. It is greater than the
takeoff weight due to the fuel that will
be burned during the taxi and runup
operations. Ramp weight may also be
referred to as taxi weight.
allows air to continue flowing over the
top of the wing and delays airflow
separation.
MUSHING—A flight condition
caused by slow speed where the
control surfaces are marginally
effective.
N1, N2, N3—Spool speed expressed in
percent rpm. N1 on a turboprop is the
gas producer speed. N1 on a turbofan
or turbojet engine is the fan speed or
low pressure spool speed. N2 is the
high pressure spool speed on engine
with 2 spools and medium pressure
spool on engines with 3 spools with
N3 being the high pressure spool.
NACELLE—
Astreamlined enclosure on an aircraft
in which an engine is mounted.
On multiengine propeller-driven
airplanes, the nacelle is normally
mounted on the leading edge of the
wing.
NEGATIVE STATIC
STABILITY—The initial tendency
of an aircraft to continue away from
the original state of equilibrium after
being disturbed.
NEGATIVE TORQUE SENSING
(NTS)— A system in a turboprop
engine that prevents the engine from
being driven by the propeller. The
NTS increases the blade angle when
the propellers try to drive the engine.
NEUTRAL STATIC
STABILITY—The initial tendency
of an aircraft to remain in a new
condition after its equilibrium has
been disturbed.
NICKEL-CADMIUM BATTERY
(NICAD)— A battery made up of
alkaline secondary cells. The positive
plates are nickel hydroxide, the
negative plates are cadmium
hydroxide, and potassium hydroxide
is used as the electrolyte.
NORMAL CATEGORY—
An airplane that has a seating
configuration, excluding pilot seats,
MAXIMUM TAKEOFF
WEIGHT—The maximum allowable
weight for takeoff.
MAXIMUM WEIGHT—
The maximum authorized weight of
the aircraft and all of its equipment as
specified in the Type Certificate Data
Sheets (TCDS) for the aircraft.
MAXIMUM ZERO FUEL
WEIGHT (GAMA)—The maximum
weight, exclusive of usable fuel.
MINIMUM CONTROLLABLE
AIRSPEED—An airspeed at which
any further increase in angle of attack,
increase in load factor, or reduction in
power, would result in an immediate
stall.
MINIMUM DRAG SPEED
(L/DMAX)—The point on the total
drag curve where the lift-to-drag ratio
is the greatest. At this speed, total drag
is minimized.
MIXTURE—The ratio of fuel to air
entering the engine’s cylinders.
MMO—Maximum operating speed
expressed in terms of a decimal of
mach speed.
MOMENT ARM—The distance
from a datum to the applied force.
MOMENT INDEX (OR INDEX)—
A moment divided by a constant such
as 100, 1,000, or 10,000. The purpose
of using a moment index is to simplify
weight and balance computations of
airplanes where heavy items and long
arms result in large, unmanageable
numbers.
MOMENT—The product of the
weight of an item multiplied by its
arm. Moments are expressed in
pound-inches (lb-in). Total moment is
the weight of the airplane multiplied
by the distance between the datum and
the CG.
MOVABLE SLAT—A movable
auxiliary airfoil on the leading edge of
a wing. It is closed in normal flight but
extends at high angles of attack. This
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G-11
of nine or less, a maximum
certificated takeoff weight of 12,500
pounds or less, and intended for
nonacrobatic operation.
NORMALIZING
(TURBONORMALIZING)—
A turbocharger that maintains sea
level pressure in the induction manifold
at altitude.
OCTANE—The rating system of
aviation gasoline with regard to its
antidetonating qualities.
OVERBOOST—A condition in
which a reciprocating engine has
exceeded the maximum manifold
pressure allowed by the manufacturer.
Can cause damage to engine
components.
OVERSPEED—A condition in
which an engine has produced more
r.p.m. than the manufacturer
recommends, or a condition in which
the actual engine speed is higher than
the desired engine speed as set on the
propeller control.
OVERTEMP—A condition in which
a device has reached a temperature
above that approved by the
manufacturer or any exhaust
temperature that exceeds the
maximum allowable for a given operating
condition or time limit. Can
cause internal damage to an engine.
OVERTORQUE—A condition in
which an engine has produced more
torque (power) than the manufacturer
recommends, or a condition in a
turboprop or turboshaft engine where
the engine power has exceeded the
maximum allowable for a given
operating condition or time limit. Can
cause internal damage to an engine.
PARASITE DRAG—That part of
total drag created by the design or
shape of airplane parts. Parasite drag
increases with an increase in airspeed.
PAYLOAD (GAMA)—The weight
of occupants, cargo, and baggage.
P-FACTOR—A tendency for an
aircraft to yaw to the left due to the
for scheduling fuel flow to the
combustion chambers of a turbine
engine.
POWER—Implies work rate or units
of work per unit of time, and as such,
it is a function of the speed at which
the force is developed. The term
“power required” is generally
associated with reciprocating engines.
POWERPLANT—
A complete engine and propeller
combination with accessories.
PRACTICAL SLIP LIMIT—The
maximum slip an aircraft is capable of
performing due to rudder travel limits.
PRECESSION—The tilting or
turning of a gyro in response to
deflective forces causing slow drifting
and erroneous indications in
gyroscopic instruments.
PREIGNITION—Ignition occurring
in the cylinder before the time of
normal ignition. Preignition is often
caused by a local hot spot in the
combustion chamber igniting the
fuel/air mixture.
PRESSURE ALTITUDE—
The altitude indicated when the
altimeter setting window (barometric
scale) is adjusted to 29.92. This is the
altitude above the standard datum
plane, which is a theoretical plane
where air pressure (corrected to 15ºC)
equals 29.92 in. Hg. Pressure altitude
is used to compute density altitude,
true altitude, true airspeed, and other
performance data.
PROFILE DRAG—The total of the
skin friction drag and form drag for a
two-dimensional airfoil section.
PROPELLER BLADE ANGLE—
The angle between the propeller chord
and the propeller plane of rotation.
PROPELLER LEVER—
The control on a free power turbine
turboprop that controls propeller
speed and the selection for propeller
feathering.
PROPELLER SLIPSTREAM—
The volume of air accelerated behind
a propeller producing thrust.
descending propeller blade on the
right producing more thrust than the
ascending blade on the left. This
occurs when the aircraft’s
longitudinal axis is in a climbing
attitude in relation to the relative
wind. The P-factor would be to the
right if the aircraft had a counterclockwise
rotating propeller.
PILOT’S OPERATING
HANDBOOK (POH)—A document
developed by the airplane
manufacturer and contains the FAAapproved
Airplane Flight Manual
(AFM) information.
PISTON ENGINE—A reciprocating
engine.
PITCH—The rotation of an airplane
about its lateral axis, or on a propeller,
the blade angle as measured from
plane of rotation.
PIVOTAL ALTITUDE—A specific
altitude at which, when an airplane
turns at a given groundspeed, a projecting
of the sighting reference line
to a selected point on the ground will
appear to pivot on that point.
PNEUMATIC SYSTEMS—
The power system in an aircraft used
for operating such items as landing
gear, brakes, and wing flaps with
compressed air as the operating fluid.
PORPOISING—
Oscillating around the lateral axis of
the aircraft during landing.
POSITION LIGHTS—Lights on an
aircraft consisting of a red light on the
left wing, a green light on the right
wing, and a white light on the tail.
CFRs require that these lights be
displayed in flight from sunset to
sunrise.
POSITIVE STATIC STABILITY—
The initial tendency to return to a state
of equilibrium when disturbed from
that state.
POWER DISTRIBUTION BUS—
See BUS BAR.
POWER LEVER—The cockpit
lever connected to the fuel control unit
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PROPELLER
SYNCHRONIZATION—
A condition in which all of
the propellers have their pitch
automatically adjusted to maintain a
constant r.p.m. among all of the
engines of a multiengine aircraft.
PROPELLER—A device for
propelling an aircraft that, when
rotated, produces by its action on
the air, a thrust approximately
perpendicular to its plane of rotation.
It includes the control components
normally supplied by its
manufacturer.
RAMP WEIGHT—The total weight
of the aircraft while on the ramp. It
differs from takeoff weight by the
weight of the fuel that will be
consumed in taxiing to the point of
takeoff.
RATE OF TURN—The rate in
degrees/second of a turn.
RECIPROCATING ENGINE—An
engine that converts the heat energy
from burning fuel into the
reciprocating movement of the pistons.
This movement is converted into
a rotary motion by the connecting rods
and crankshaft.
REDUCTION GEAR—The gear
arrangement in an aircraft engine that
allows the engine to turn at a faster
speed than the propeller.
REGION OF REVERSE
COMMAND—Flight regime in
which flight at a higher airspeed
requires a lower power setting and a
lower airspeed requires a higher
power setting in order to maintain
altitude.
REGISTRATION
CERTIFICATE—A State and Federal
certificate that documents
aircraft ownership.
RELATIVE WIND—The direction
of the airflow with respect to the wing.
If a wing moves forward horizontally,
the relative wind moves backward
horizontally. Relative wind is parallel
to and opposite the flightpath of
the airplane.
alignment guidance during takeoff
and landings. The centerline consists
of a line of uniformly spaced stripes
and gaps.
RUNWAY EDGE LIGHTS—
Runway edge lights are used to
outline the edges of runways during
periods of darkness or restricted
visibility conditions. These light
systems are classified according to the
intensity or brightness they are
capable of producing: they are the
High Intensity Runway Lights
(HIRL), Medium Intensity Runway
Lights (MIRL), and the Low Intensity
Runway Lights (LIRL). The HIRL
and MIRL systems have variable
intensity controls, whereas the LIRLs
normally have one intensity setting.
RUNWAY END IDENTIFIER
LIGHTS (REIL)—One component
of the runway lighting system. These
lights are installed at many airfields
to provide rapid and positive
identification of the approach end of a
particular runway.
RUNWAY INCURSION—
Any occurrence at an airport
involving an aircraft, vehicle, person,
or object on the ground that creates a
collision hazard or results in loss of
separation with an aircraft taking off,
intending to takeoff, landing, or
intending to land.
RUNWAY THRESHOLD
MARKINGS—Runway threshold
markings come in two configurations.
They either consist of eight
longitudinal stripes of uniform
dimensions disposed symmetrically
about the runway centerline, or the
number of stripes is related to the
runway width. A threshold marking
helps identify the beginning of the
runway that is available for landing.
In some instances, the landing
threshold may be displaced.
SAFETY (SQUAT) SWITCH—An
electrical switch mounted on one of
the landing gear struts. It is used to
sense when the weight of the aircraft
is on the wheels.
SCAN—A procedure used by the
pilot to visually identify all resources
of information in flight.
REVERSE THRUST—A condition
where jet thrust is directed forward
during landing to increase the rate of
deceleration.
REVERSING PROPELLER—
A propeller system with a pitch
change mechanism that includes full
reversing capability. When the pilot
moves the throttle controls to reverse,
the blade angle changes to a pitch
angle and produces a reverse thrust,
which slows the airplane down during
a landing.
ROLL—The motion of the aircraft
about the longitudinal axis. It is
controlled by the ailerons.
ROUNDOUT (FLARE)—
Apitch-up during landing approach to
reduce rate of descent and forward
speed prior to touchdown.
RUDDER—The movable primary
control surface mounted on the
trailing edge of the vertical fin of an
airplane. Movement of the rudder
rotates the airplane about its vertical
axis.
RUDDERVATOR—Apair of control
surfaces on the tail of an aircraft
arranged in the form of a V. These
surfaces, when moved together by the
control wheel, serve as elevators, and
when moved differentially by the
rudder pedals, serve as a rudder.
RUNWAY CENTERLINE
LIGHTS—Runway centerline lights
are installed on some precision
approach runways to facilitate landing
under adverse visibility conditions.
They are located along the runway
centerline and are spaced at 50-foot
intervals. When viewed from the
landing threshold, the runway
centerline lights are white until the
last 3,000 feet of the runway. The
white lights begin to alternate with red
for the next 2,000 feet, and for the last
1,000 feet of the runway, all centerline
lights are red.
RUNWAY CENTERLINE
MARKINGS—
The runway centerline identifies the
center of the runway and provides
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G-13
SEA LEVEL—A reference height
used to determine standard
atmospheric conditions and altitude
measurements.
SEGMENTED CIRCLE—A visual
ground based structure to provide
traffic pattern information.
SERVICE CEILING—
The maximum density altitude where
the best rate-of-climb airspeed will
produce a 100 feet-per-minute climb
at maximum weight while in a clean
configuration with maximum continuous
power.
SERVO TAB—An auxiliary control
mounted on a primary control surface,
which automatically moves in the
direction opposite the primary control
to provide an aerodynamic assist in
the movement of the control.
SHAFT HORSE POWER (SHP)—
Turboshaft engines are rated in shaft
horsepower and calculated by use of
a dynamometer device. Shaft
horsepower is exhaust thrust
converted to a rotating shaft.
SHOCK WAVES—A compression
wave formed when a body moves
through the air at a speed greater than
the speed of sound.
SIDESLIP—A slip in which the
airplane’s longitudinal axis remains
parallel to the original flightpath, but the
airplane no longer flies straight ahead.
Instead, the horizontal component of
wing lift forces the airplane to move
sideways toward the low wing.
SINGLE ENGINE ABSOLUTE
CEILING—The altitude that a twinengine
airplane can no longer climb
with one engine inoperative.
SINGLE ENGINE SERVICE
CEILING—The altitude that a twinengine
airplane can no longer climb at
a rate greater then 50 f.p.m. with one
engine inoperative.
SKID—A condition where the tail of
the airplane follows a path outside the
path of the nose during a turn.
SPLIT SHAFT
TURBINE ENGINE—See FREE
POWER TURBINE ENGINE.
SPOILERS—High-drag devices that
can be raised into the air flowing over
an airfoil, reducing lift and increasing
drag. Spoilers are used for roll control
on some aircraft. Deploying spoilers
on both wings at the same time allows
the aircraft to descend without gaining
speed. Spoilers are also used to
shorten the ground roll after landing.
SPOOL—A shaft in a turbine engine
which drives one or more
compressors with the power derived
from one or more turbines.
STABILATOR—A single-piece horizontal
tail surface on an airplane that
pivots around a central hinge point. A
stabilator serves the purposes of both
the horizontal stabilizer and
the elevator.
STABILITY—The inherent quality
of an airplane to correct for conditions
that may disturb its equilibrium, and
to return or to continue on the original
flightpath. It is primarily an airplane
design characteristic.
STABILIZED APPROACH—A
landing approach in which the pilot
establishes and maintains a constant
angle glidepath towards a predetermined
point on the landing runway. It
is based on the pilot’s judgment of
certain visual cues, and depends on
the maintenance of a constant final
descent airspeed and configuration.
STALL—A rapid decrease in lift
caused by the separation of airflow
from the wing’s surface brought on by
exceeding the critical angle of attack.
A stall can occur at any pitch attitude
or airspeed.
STALL STRIPS—Aspoiler attached
to the inboard leading edge of some
wings to cause the center section of
the wing to stall before the tips. This
assures lateral control throughout the
stall.
SLIP—An intentional maneuver to
decrease airspeed or increase rate of
descent, and to compensate for a
crosswind on landing. A slip can also
be unintentional when the pilot fails
to maintain the aircraft in coordinated
flight.
SPECIFIC FUEL
CONSUMPTION—
Number of pounds of fuel consumed
in 1 hour to produce 1 HP.
SPEED—The distance traveled in a
given time.
SPEED BRAKES—A control
system that extends from the airplane
structure into the airstream to
produce drag and slow the airplane.
SPEED INSTABILITY—
A condition in the region of reverse
command where a disturbance that
causes the airspeed to decrease causes
total drag to increase, which in turn,
causes the airspeed to decrease
further.
SPEED SENSE—The ability to
sense instantly and react to any
reasonable variation of airspeed.
SPIN—An aggravated stall that
results in what is termed an “autorotation”
wherein the airplane follows a
downward corkscrew path. As the airplane
rotates around the vertical axis,
the rising wing is less stalled than the
descending wing creating a rolling,
yawing, and pitching motion.
SPIRAL INSTABILITY—
A condition that exists when the static
directional stability of the airplane is
very strong as compared to the effect
of its dihedral in maintaining lateral
equilibrium.
SPIRALING SLIPSTREAM—The
slipstream of a propeller-driven
airplane rotates around the airplane.
This slipstream strikes the left side of
the vertical fin, causing the airplane to
yaw slightly. Vertical stabilizer offset
is sometimes used by aircraft designers
to counteract this tendency.
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G-14
STANDARD ATMOSPHERE—
At sea level, the standard atmosphere
consists of a barometric pressure of
29.92 inches of mercury (in. Hg.) or
1013.2 millibars, and a temperature of
15°C (59°F). Pressure and temperature
normally decrease as altitude
increases. The standard lapse rate in
the lower atmosphere for each 1,000
feet of altitude is approximately 1 in.
Hg. and 2°C (3.5°F). For example, the
standard pressure and temperature at
3,000 feet mean sea level (MSL) is
26.92 in. Hg. (29.92 - 3) and 9°C
(15°C - 6°C).
STANDARD DAY—
See STANDARD ATMOSPHERE.
STANDARD EMPTY WEIGHT
(GAMA)—This weight consists of
the airframe, engines, and all items of
operating equipment that have fixed
locations and are permanently
installed in the airplane; including
fixed ballast, hydraulic fluid, unusable
fuel, and full engine oil.
STANDARD WEIGHTS—These
have been established for numerous
items involved in weight and balance
computations. These weights should
not be used if actual weights are
available.
STANDARD-RATE TURN—A turn
at the rate of 3º per second which
enables the airplane to complete a
360º turn in 2 minutes.
STARTER/GENERATOR—
A combined unit used on turbine
engines. The device acts as a starter
for rotating the engine, and after
running, internal circuits are shifted to
convert the device into a generator.
STATIC STABILITY—The initial
tendency an aircraft displays when
disturbed from a state of equilibrium.
STATION—A location in the
airplane that is identified by a number
designating its distance in inches from
the datum. The datum is, therefore,
identified as station zero. An item
located at station +50 would have an
arm of 50 inches.
TAXIWAY LIGHTS—
Omnidirectional lights that outline the
edges of the taxiway and are blue in
color.
TAXIWAY TURNOFF LIGHTS—
Flush lights which emit a steady green
color.
TETRAHEDRON—
A large, triangular-shaped, kite-like
object installed near the runway.
Tetrahedrons are mounted on a pivot
and are free to swing with the wind to
show the pilot the direction of the
wind as an aid in takeoffs and
landings.
THROTTLE—The valve in a
carburetor or fuel control unit that
determines the amount of fuel-air
mixture that is fed to the engine.
THRUST LINE—An imaginary line
passing through the center of the
propeller hub, perpendicular to the
plane of the propeller rotation.
THRUST REVERSERS—Devices
which redirect the flow of jet exhaust
to reverse the direction of thrust.
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.
TIMING—The application of
muscular coordination at the proper
instant to make flight, and all
maneuvers incident thereto, a constant
smooth process.
TIRE CORD—Woven metal wire
laminated into the tire to provide extra
strength. A tire showing any cord
must be replaced prior to any further
flight.
TORQUE METER—An indicator
used on some large reciprocating
engines or on turboprop engines to
indicate the amount of torque the
engine is producing.
STICK PULLER—A device that
applies aft pressure on the control
column when the airplane is approaching
the maximum operating speed.
STICK PUSHER—A device that
applies an abrupt and large forward
force on the control column when the
airplane is nearing an angle of attack
where a stall could occur.
STICK SHAKER—An artificial
stall warning device that vibrates the
control column.
STRESS RISERS—
A scratch, groove, rivet hole, forging
defect or other structural discontinuity
that causes a concentration of stress.
SUBSONIC—Speed below the speed
of sound.
SUPERCHARGER—An engine- or
exhaust-driven air compressor used to
provide additional pressure to the
induction air so the engine can
produce additional power.
SUPERSONIC—Speed above the
speed of sound.
SUPPLEMENTAL TYPE
CERTIFICATE (STC)—
A certificate authorizing an alteration
to an airframe, engine, or component
that has been granted an Approved
Type Certificate.
SWEPT WING—A wing planform
in which the tips of the wing are
farther back than the wing root.
TAILWHEEL AIRCRAFT—
SEE CONVENTIONAL LANDING
GEAR.
TAKEOFF ROLL
(GROUND ROLL)—The total
distance required for an aircraft to
become airborne.
TARGET REVERSER—A thrust
reverser in a jet engine in which
clamshell doors swivel from the
stowed position at the engine tailpipe
to block all of the outflow and redirect
some component of the thrust
forward.
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G-15
TORQUE SENSOR—
See TORQUE METER.
TORQUE—1.Aresistance 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.
TOTAL DRAG—The sum of the
parasite and induced drag.
TOUCHDOWN ZONE LIGHTS—
Two rows of transverse light bars
disposed symmetrically about the
runway centerline in the runway
touchdown zone.
TRACK—The actual path made over
the ground in flight.
TRAILING EDGE—The portion of
the airfoil where the airflow over the
upper surface rejoins the lower
surface airflow.
TRANSITION LINER—
The portion of the combustor that
directs the gases into the turbine
plenum.
TRANSONIC—At the speed of
sound.
TRANSPONDER—The airborne
portion of the secondary surveillance
radar system. The transponder emits a
reply when queried by a radar facility.
TRICYCLE GEAR—Landing gear
employing a third wheel located on
the nose of the aircraft.
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.
TRIPLE SPOOL ENGINE—
Usually a turbofan engine design
where the fan is the N1 compressor,
followed by the N2 intermediate
compressor, and the N3 high pressure
compressor, all of which rotate on
separate shafts at different speeds.
TURBINE SECTION—The section
of the engine that converts high
pressure high temperature gas into
rotational energy.
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 turbojet
engine in which additional propulsive
thrust is gained by extending a portion
of the compressor or turbine blades
outside the inner engine case. The
extended blades propel bypass air
along the engine axis but between the
inner and outer casing. The air is not
combusted but does provide additional
thrust.
TURBOJET ENGINE—A jet
engine incorporating a turbine-driven
air compressor to take in and compress
air for the combustion of fuel,
the gases of combustion being used
both to rotate the turbine and create a
thrust producing jet.
TURBOPROP ENGINE—Aturbine
engine that drives a propeller through
a reduction gearing arrangement.
Most of the energy in the exhaust
gases is converted into torque, rather
than its acceleration being used to
propel the aircraft.
TURBULENCE—An occurrence in
which a flow of fluid is unsteady.
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.
TURN-AND-SLIP INDICATOR—
Aflight 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.
TROPOPAUSE—The boundary
layer between the troposphere and the
mesosphere 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 (TAS)—
Calibrated airspeed corrected for altitude
and nonstandard temperature.
Because air density decreases with an
increase in altitude, an airplane has to
be flown faster at higher altitudes to
cause the same pressure difference
between pitot impact pressure and
static pressure. Therefore, for a given
calibrated airspeed, true airspeed
increases as altitude increases; or for a
given true airspeed, calibrated airspeed
decreases as altitude increases.
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.
T-TAIL—An aircraft with the
horizontal stabilizer mounted on the
top of the vertical stabilizer, forming
a T.
TURBINE BLADES—The portion
of the turbine assembly that absorbs
the energy of the expanding gases and
converts it into rotational energy.
TURBINE OUTLET
TEMPERATURE (TOT)—
The temperature of the gases as they
exit the turbine section.
TURBINE PLENUM—The portion
of the combustor where the gases are
collected to be evenly distributed to
the turbine blades.
TURBINE ROTORS—The portion
of the turbine assembly that mounts to
the shaft and holds the turbine blades
in place.
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G-16
TURNING ERROR—One of the
errors inherent in a magnetic compass
caused by the dip compensating
weight. It shows up only on turns to or
from northerly headings in the
Northern Hemisphere and southerly
headings in the Southern Hemisphere.
Turning error causes the compass to
lead turns to the north or south and lag
turns away from the north or south.
ULTIMATE 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.
UNFEATHERING
ACCUMULATOR—Tanks that hold
oil under pressure which can be used
to unfeather a propeller.
UNICOM—
A nongovernment air/ground radio
communication station which may
provide airport information at public
use airports where there is no tower or
FSS.
UNUSABLE FUEL—Fuel that
cannot be consumed by the engine.
This fuel is considered part of the
empty weight of the aircraft.
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.
UTILITY CATEGORY—
An airplane that has a seating
configuration, excluding pilot seats,
of nine or less, a maximum
certificated takeoff weight of 12,500
pounds or less, and intended for
limited acrobatic operation.
V-BARS—The flight director
displays on the attitude indicator that
provide control guidance to the pilot.
V-SPEEDS—Designated speeds for a
specific flight condition.
VFE—The maximum speed with the
flaps extended. The upper limit of the
white arc.
VFO—The maximum speed that the
flaps can be extended or retracted.
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.
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.
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 FLIGHT
RULES (VFR)—
Code of Federal Regulations that govern
the procedures for conducting
flight under visual conditions.
VLE—Landing gear extended speed.
The maximum speed at which an
airplane can be safely flown with the
landing gear extended.
VLOF—Lift-off speed. The speed at
which the aircraft departs the runway
during takeoff.
VLO—Landing gear operating speed.
The maximum speed for extending or
retracting the landing gear if using an
airplane equipped with retractable
landing gear.
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.
VA—The design maneuvering speed.
This is the “rough air” speed and the
maximum speed for abrupt
maneuvers. If during flight, rough air
or severe turbulence is encountered,
reduce the airspeed to maneuvering
speed or less to minimize stress on the
airplane structure. It is important to
consider weight when referencing this
speed. For example, VA may be 100
knots when an airplane is heavily
loaded, but only 90 knots when the
load is light.
VECTOR—A force vector is a
graphic representation of a force and
shows both the magnitude and
direction of the force.
VELOCITY—The speed or rate of
movement in a certain direction.
VERTICAL AXIS—An imaginary
line passing vertically through the
center of gravity of an aircraft. The
vertical axis is called the z-axis or the
yaw axis.
VERTICAL CARD COMPASS—
Amagnetic 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)—
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.
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G-17
VMC—Minimum control airspeed.
This is the minimum flight speed at
which a twin-engine airplane can be
satisfactorily controlled when an
engine suddenly becomes inoperative
and the remaining engine is at takeoff
power.
VMD—Minimum drag speed.
VMO—Maximum operating speed
expressed in knots.
VNE—Never-exceed speed. Operating
above this speed is prohibited since it
may result in damage or structural
failure. The red line on the airspeed
indicator.
VNO—Maximum structural cruising
speed. Do not exceed this speed
except in smooth air. The upper limit
of the green arc.
VP—Minimum dynamic hydroplaning
speed. The minimum speed
required to start dynamic
hydroplaning.
VR—Rotation speed. The speed that
the pilot begins rotating the aircraft
prior to lift-off.
VS0—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—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.
VSSE—Safe, intentional one-engine
inoperative speed. The minimum
speed to intentionally render the
critical engine inoperative.
V-TAIL—A design which utilizes
two slanted tail surfaces to perform
equal to the mass of the body times
the local value of gravitational
acceleration. One of the four main
forces acting on an aircraft.
Equivalent to the actual weight of the
aircraft. It acts downward through the
aircraft’s center of gravity toward the
center of the Earth. Weight opposes
lift.
WEIGHT AND BALANCE—The
aircraft is said to be in weight and
balance when the gross weight of the
aircraft is under the max gross weight,
and the center of gravity is within
limits and will remain in limits for the
duration of the flight.
WHEELBARROWING—
A condition caused when forward
yoke or stick pressure during takeoff
or landing causes the aircraft to ride
on the nosewheel alone.
WIND CORRECTION ANGLE—
Correction applied to the course to
establish a heading so that track will
coincide with course.
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.
WINDMILLING—When the air
moving through a propeller creates
the rotational energy.
WINDSOCK—A truncated cloth
cone open at both ends and mounted
on a freewheeling pivot that indicates
the direction from which the wind is
blowing.
WING—Airfoil attached to each side
of the fuselage and are the main
lifting surfaces that support the
airplane in flight.
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.
VXSE—Best angle of climb speed with
one engine inoperative. The airspeed
at which an airplane gains the greatest
amount of altitude in a given distance
in a light, twin-engine airplane
following an engine failure.
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, twinengine
airplane following an engine
failure.
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.
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.
WEATHERVANE—The tendency of
the aircraft to turn into the relative
wind.
WEIGHT—A measure of the
heaviness of an object. The force by
which a body is attracted toward the
center of the Earth (or another
celestial body) by gravity. Weight is
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G-18
WING AREA—The total surface of
the wing (square feet), which includes
control surfaces and may include
wing area covered by the fuselage
(main body of the airplane), and
engine nacelles.
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. It is also referred to as
ZERO FUEL WEIGHT—
The weight of the aircraft to include
all useful load except fuel.
ZERO SIDESLIP—Amaneuver in a
twin-engine airplane with one engine
inoperative that involves a small
amount of bank and slightly
uncoordinated flight to align the
fuselage with the direction of travel
and minimize drag.
ZERO THRUST
(SIMULATED FEATHER)—
An engine configuration with a low
power setting that simulates a
propeller feathered condition.