Aviation Dictionary
Browse 880+ aviation terms, acronyms, and definitions used by pilots, mechanics, and aviation professionals.
0-9(1 terms)
A(104 terms)
A.C.
Alternating current
Absolute accuracy
The ability to determine present position in space independently, and is most often used by pilots
Absolute altitude
The actual distance between an aircraft and the terrain over which it is flying
Absolute pressure
Pressure measured from the reference of zero pressure, or a vacuum
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
Acceleration error
A magnetic compass error apparent when the aircraft accelerates while flying on an easterly or westerly heading, causing the compass card to rotate toward North
Accelerometer
A part of an inertial navigation system (INS) that accurately measures the force of acceleration in one direction
ADC
See air data computer
ADF
See automatic direction finder
ADI
See attitude director indicator
Adiabatic cooling
A process of cooling the air through expansion. For example, as air moves up slope it expands with the reduction of atmospheric pressure and cools as it expands
Adiabatic heating
A process of heating dry air through compression. For example, as air moves down a slope it is compressed, which results in an increase in temperature
Adjustable stabilizer
A stabilizer that can be adjusted in flight to trim the airplane, thereby allowing the airplane to fly hands-off at any given airspeed
Adjustable-pitch propeller
A propeller with blades whose pitch can be adjusted on the ground with the engine not running, but which cannot be adjusted in flight. Also referred to as a ground adjustable propeller. Sometimes also used to refer to constant-speed propellers that are adjustable in flight
ADM
See aeronautical decision-making
ADS-B
See automatic dependent surveillance-broadcast
Advection fog
Fog resulting from the movement of warm, humid air over a cold surface
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
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
Aeronautical chart
A map used in air navigation containing all or part of the following: topographic features, hazards and obstructions, navigation aids, navigation routes, designated airspace, and airports
Aeronautical decision-making (ADM)
A systematic approach to the mental process used by pilots to consistently determine the best course of action in response to a given set of circumstances
Agonic line
An irregular imaginary line across the surface of the Earth along which the magnetic and geographic poles are in alignment, and along which there is no magnetic variation
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 data computer (ADC)
An aircraft computer that receives and processes pitot pressure, static pressure, and temperature to calculate very precise altitude, indicated airspeed, true airspeed, and air temperature
Air mass
An extensive body of air having fairly uniform properties of temperature and moisture
Air route surveillance radar (ARSR)
Air route traffic control center (ARTCC) radar used primarily to detect and display an aircraft's position while en route between terminal areas
Air route traffic control center (ARTCC)
Provides ATC service to aircraft operating on IFR flight plans within controlled airspace and principally during the en route phase of flight
Air traffic control radar beacon system (ATCRBS)
Sometimes called secondary surveillance radar (SSR), which utilizes a transponder in the aircraft. The ground equipment is an interrogating unit, in which the beacon antenna is mounted so it rotates with the surveillance antenna. The interrogating unit transmits a coded pulse sequence that actuates the aircraft transponder. The transponder answers the coded sequence by transmitting a preselected coded sequence back to the ground equipment, providing a strong return signal and positive aircraft identification, as well as other special data
Aircraft
A device that is used, or intended to be used, for flight
Aircraft altitude
The actual height above sea level at which the aircraft is flying
Aircraft approach category
A performance grouping of aircraft based on a speed of 1.3 times the stall speed in the landing configuration at maximum gross landing weight
Airfoil
Any surface, such as a wing, propeller, rudder, or even a trim tab, which provides aerodynamic force when it interacts with a moving stream of air
AIRMET
Inflight weather advisory issued as an amendment to the area forecast, concerning weather phenomena of operational interest to all aircraft and that is potentially hazardous to aircraft with limited capability due to lack of equipment, instrumentation, or pilot qualifications
Airplane
An engine-driven, fixed-wing aircraft heavier than air that is supported in flight by the dynamic reaction of air against its wings
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 diagram
The section of an instrument approach procedure chart that shows a detailed diagram of the airport. This diagram includes surface features and airport configuration information
Airport surface detection equipment (ASDE)
Radar equipment specifically designed to detect all principal features and traffic on the surface of an airport, presenting the entire image on the control tower console; used to augment visual observation by tower personnel of aircraft and/or vehicular movements on runways and taxiways
Airport surveillance radar (ASR)
Approach control radar used to detect and display an aircraft's position in the terminal area
Airport surveillance radar approach
An instrument approach in which ATC issues instructions for pilot compliance based on aircraft position in relation to the final approach course and the distance from the end of the runway as displayed on the controller's radar scope
Airport/Facility Directory (A/FD)
See Chart Supplement U.S.
Airspeed
Rate of the aircraft's progress through the air
Airspeed indicator
A differential pressure gauge that measures the dynamic pressure of the air through which the aircraft is flying. Displays the craft's airspeed, typically in knots, to the pilot
Airway
An airway is based on a centerline that extends from one navigation aid or intersection to another navigation aid (or through several navigation aids or intersections); used to establish a known route for en route procedures between terminal areas
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) are to be complied with within the required time limit, and the fact of compliance, the date of compliance, and the method of compliance are recorded in the aircraft's maintenance records
Alert area
An area in which there is a high volume of pilot training or an unusual type of aeronautical activity
Almanac data
Information the global positioning system (GPS) receiver can obtain from one satellite which describes the approximate orbital positioning of all satellites in the constellation. This information is necessary for the GPS receiver to know what satellites to look for in the sky at a given time
ALS
See approach lighting system
Alternate airport
An airport designated in an IFR flight plan, providing a suitable destination if a landing at the intended airport becomes inadvisable
Alternate static source valve
A valve in the instrument static air system that supplies reference air pressure to the altimeter, airspeed indicator, and vertical speed indicator if the normal static pickup should become clogged or iced over
Altimeter
A flight instrument that indicates altitude by sensing pressure changes
Altimeter setting
Station pressure (the barometric pressure at the location the reading is taken) which has been corrected for the height of the station above sea level
Altitude engine
A reciprocating aircraft engine having a rated takeoff power that is producible from sea level to an established higher altitude
Ambient pressure
The pressure in the area immediately surrounding the aircraft
Ambient temperature
The temperature in the area immediately surrounding the aircraft
AME
See aviation medical examiner
Amendment status
The circulation date and revision number of an instrument approach procedure, printed above the procedure identification
Ammeter
An instrument installed in series with an electrical load used to measure the amount of current flowing through the load
Aneroid
The sensitive component in an altimeter or barometer that measures the absolute pressure of the air. It is a sealed, flat capsule made of thin disks of corrugated metal soldered together and evacuated by pumping all of the air out of it
Aneroid barometer
An instrument that measures the absolute pressure of the atmosphere by balancing the weight of the air above it against the spring action of the aneroid
Angle of attack
The angle at which relative wind meets an airfoil. It is the angle that is formed by the chord of the airfoil and the direction of the relative wind or between the chord line and the flight path. The angle of attack changes during a flight as the pilot changes the direction of the aircraft and is related to the amount of lift being produced
Angle of incidence
The acute angle formed between the chord line of an airfoil and the longitudinal axis of the aircraft on which it is mounted
Anhedral
A downward slant from root to tip of an aircraft's wing or horizontal tail surface
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&P technician holding an Inspection Authorization can conduct an annual inspection
Anti-ice
Preventing the accumulation of ice on an aircraft structure via a system designed for that purpose
Antiservo tab
An adjustable tab attached to the trailing edge of a stabilator that moves in the same direction as the primary control. It is used to make the stabilator less sensitive
Approach lighting system (ALS)
Provides lights that will penetrate the atmosphere far enough from touchdown to give directional, distance, and glidepath information for safe transition from instrument to visual flight
Area chart
Part of the low-altitude en route chart series, this chart furnishes terminal data at a larger scale for congested areas
Area forecast (FA)
A report that gives a picture of clouds, general weather conditions, and visual meteorological conditions (VMC) expected over a large area encompassing several states
Area navigation (RNAV)
Allows a pilot to fly a selected course to a predetermined point without the need to overfly ground-based navigation facilities, by using waypoints
Arm
See moment arm
ARSR
See air route surveillance radar
ARTCC
See air route traffic control center
ASDE
See airport surface detection equipment
ASOS
See Automated Surface Observing System
Aspect ratio
Span of a wing divided by its average chord
ASR
See airport surveillance radar
Asymmetric thrust
Also known as P-factor. A tendency for an aircraft to yaw to the left due to the 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
ATC
Air Traffic Control
ATCRBS
See air traffic control radar beacon system
ATIS
See automatic terminal information service
Atmospheric propagation delay
A bending of the electromagnetic (EM) wave from the satellite that creates an error in the GPS system
Attitude
A personal motivational predisposition to respond to persons, situations, or events in a given manner that can, nevertheless, be changed or modified through training as sort of a mental shortcut to decision-making
Attitude and heading reference system (AHRS)
A system composed of three-axis sensors that provide heading, attitude, and yaw information for aircraft. AHRS are designed to replace traditional mechanical gyroscopic flight instruments and provide superior reliability and accuracy
Attitude director indicator (ADI)
An aircraft attitude indicator that incorporates flight command bars to provide pitch and roll commands
Attitude indicator
The foundation for all instrument flight, this instrument reflects the airplane's attitude in relation to the horizon
Attitude instrument flying
Controlling the aircraft by reference to the instruments rather than by outside visual cues
Attitude management
The ability to recognize hazardous attitudes in oneself and the willingness to modify them as necessary through the application of an appropriate antidote thought
Autokinesis
Nighttime visual illusion that a stationary light is moving, which becomes apparent after several seconds of staring at the light
Automated Surface Observing System (ASOS)
Weather reporting system which provides surface observations every minute via digitized voice broadcasts and printed reports
Automated Weather Observing System (AWOS)
Automated weather reporting system consisting of various sensors, a processor, a computer-generated voice subsystem, and a transmitter to broadcast weather data
Automatic dependent surveillance-broadcast (ADS-B)
A function on an aircraft or vehicle that periodically broadcasts its state vector (i.e., horizontal and vertical position, horizontal and vertical velocity) and other information
Automatic direction finder (ADF)
Electronic navigation equipment that operates in the low- and medium-frequency bands. Used in conjunction with the ground-based nondirectional beacon (NDB), the instrument displays the number of degrees clockwise from the nose of the aircraft to the station being received
Automatic terminal information service (ATIS)
The continuous broadcast of recorded non-control information in selected terminal areas. Its purpose is to improve controller effectiveness and relieve frequency congestion by automating repetitive transmission of essential but routine information
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
Aviation medical examiner (AME)
A physician with training in aviation medicine designated by the Civil Aerospace Medical Institute (CAMI)
Aviation Routine Weather Report (METAR)
Observation of current surface weather reported in a standard international format
AWOS
See Automated Weather Observing System
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 rotates. The three axes pass through the center of gravity at 90circ angles to each other. The axis from nose to tail is the longitudinal axis (pitch), the axis that passes from wingtip to wingtip is the lateral axis (roll), and the axis that passes vertically through the center of gravity is the vertical axis (yaw)
Axial flow compressor
A type 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
Azimuth card
A card that may be set, gyroscopically controlled, or driven by a remote compass
B(10 terms)
Back course (BC)
The reciprocal of the localizer course for an ILS. When flying a back-course approach, an aircraft approaches the instrument runway from the end at which the localizer antennas are installed
Balance 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
Baro-aiding
A method of augmenting the GPS integrity solution by using a nonsatellite input source. To ensure that baro-aiding is available, the current altimeter setting must be entered as described in the operating manual
Barometric scale
A scale on the dial of an altimeter to which the pilot sets the barometric pressure level from which the altitude shown by the pointers is measured
Basic empty weight (GAMA)
Basic empty weight includes the standard empty weight plus optional and special equipment that has been installed
BC
See back course
Bernoulli's Principle
A principle that explains how the pressure of a moving fluid varies with its speed of motion. An increase in the speed of movement causes a decrease in the fluid's pressure
Biplanes
Airplanes with two sets of wings
Block altitude
A block of altitudes assigned by ATC to allow altitude deviations; for example, "Maintain block altitude 9 to 11 thousand"
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
C(78 terms)
Cabin altitude
Cabin pressure in terms of equivalent altitude above sea level
Cage
The black markings on the ball instrument indicating its neutral position
Calibrated
The instrument indication compared with a standard value to determine the accuracy of the instrument
Calibrated airspeed
The speed at which the aircraft is moving through the air, found by correcting IAS for instrument and position errors
Calibrated orifice
A hole of specific diameter used to delay the pressure change in the case of a vertical speed indicator
Camber
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
Canard
A horizontal surface mounted ahead of the main wing to provide longitudinal stability and control. It may be a fixed, movable, or variable geometry surface, with or without control surfaces
Canard configuration
A configuration in which the span of the forward wings is substantially less than that of the main wing
Cantilever
A wing designed to carry loads without external struts
CAS
Calibrated airspeed
CDI
Course deviation indicator
Ceiling
The height above the earth's surface of the lowest layer of clouds, which is reported as broken or overcast, or the vertical visibility into an obscuration
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 percentage of mean aerodynamic chord (MAC). The location depends on the distribution of weight in the airplane
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
Center of pressure
A point along the wing chord line where lift is considered to be concentrated. For this reason, the center of pressure is commonly referred to as the center of lift
Centrifugal flow compressor
An impeller-shaped device that receives air at its center and slings the air outward at high velocity into a diffuser for increased pressure. Also referred to as a radial outflow compressor
Centrifugal force
An outward force that opposes centripetal force, resulting from the effect of inertia during a turn
Centripetal force
A center-seeking force directed inward toward the center of rotation created by the horizontal component of lift in turning flight
CFR 14 CFR
See Title 14 of the Code of Federal Regulations
CG
See center of gravity
Changeover point (COP)
A point along the route or airway segment between two adjacent navigation facilities or waypoints where changeover in navigation guidance should occur
Chart Supplement U.S.
(formerly Airport/Facility Directory). An FAA publication containing information on all airports, communications, and NAVAIDs
Checklist
A tool that is used as a human factors aid in aviation safety. It is a systematic and sequential list of all operations that must be performed to properly accomplish a task
Chord line
An imaginary straight line drawn through an airfoil from the leading edge to the trailing edge
Circling approach
A maneuver initiated by the pilot to align the aircraft with a runway for landing when a straight-in landing from an instrument approach is not possible or is not desirable
Class A airspace
Airspace from 18,000 feet MSL up to and including FL 600, including the airspace overlying the waters within 12 NM of the coast of the 48 contiguous states and Alaska; and designated international airspace beyond 12 NM of the coast of the 48 contiguous states and Alaska within areas of domestic radio navigational signal or ATC radar coverage, and within which domestic procedures are applied
Class B airspace
Airspace from the surface to 10,000 feet MSL surrounding the nation's busiest airports in terms of IFR operations or passenger numbers. The configuration of each Class B airspace is individually tailored and consists of a surface area and two or more layers, and is designed to contain all published instrument procedures once an aircraft enters the airspace. For all aircraft, an ATC clearance is required to operate in the area, and aircraft so cleared receive separation services within the airspace
Class C airspace
Airspace from the surface to 4,000 feet above the airport elevation (charted in MSL) surrounding those airports having an operational control tower, serviced by radar approach control, and having a certain number of IFR operations or passenger numbers. Although the configuration of each Class C airspace area is individually tailored, the airspace usually consists of a 5 NM radius core surface area that extends from the surface up to 4,000 feet above the airport elevation, and a 10 NM radius shelf area that extends from 1,200 feet to 4,000 feet above the airport elevation
Class D airspace
Airspace from the surface to 2,500 feet above the airport elevation (charted in MSL) 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 is normally designed to contain the procedures
Class E airspace
Airspace that is not Class A, Class B, Class C, or Class D, and is controlled airspace
Class G airspace
Airspace that is uncontrolled, except when associated with a temporary control tower, and has not been designated as Class A, Class B, Class C, Class D, or Class E airspace
Clean configuration
A configuration in which all flight control surfaces have been placed to create minimum drag. In most aircraft this means flaps and gear retracted
Clear ice
Glossy, clear, or translucent ice formed by the relatively slow freezing of large, supercooled water droplets
Clearance
ATC permission for an aircraft to proceed under specified traffic conditions within controlled airspace, for the purpose of providing separation between known aircraft
Clearance delivery
Control tower position responsible for transmitting departure clearances to IFR flights
Clearance limit
The fix, point, or location to which an aircraft is cleared when issued an air traffic clearance
Clearance on request
An IFR clearance not yet received after filing a flight plan
Clearance void time
Used by ATC, the time at which the departure clearance is automatically canceled if takeoff has not been made. The pilot must obtain a new clearance or cancel the IFR flight plan if not off by the specified time
Coefficient of lift (CL)
The ratio between lift pressure and dynamic pressure
Cold front
The boundary between two air masses where cold air is replacing warm air
Compass course
A true course corrected for variation and deviation errors
Compass locator
A low-power, low- or medium-frequency (L/MF) radio beacon installed at the site of the outer or middle marker of an ILS
Compass rose
A small circle graduated in 360circ increments, to show direction expressed in degrees
Complex aircraft
An aircraft with retractable landing gear, flaps, and a controllable-pitch propeller
Compressor pressure ratio
The ratio of compressor discharge pressure to compressor inlet pressure
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. A stall condition is caused by a pressure ratio that is incompatible with the engine rpm. Compressor stall will be indicated by a rise in exhaust temperature or rpm fluctuation, and if allowed to continue, may result in flameout and physical damage to the engine
Computer navigation fix
A point used to define a navigation track for an airborne computer system such as GPS or FMS
Concentric rings
Dashed-line circles depicted in the plan view of IAP charts, outside of the reference circle, that show en route and feeder facilities
Condensation
A change of state of water from a gas (water vapor) to a liquid
Condensation nuclei
Small particles of solid matter in the air on which water vapor condenses
Cone of confusion
A cone-shaped volume of airspace directly above a VOR station where no signal is received, causing the CDI to fluctuate
Configuration
This is a general term, which normally refers to the position of the landing gear and flaps
Constant-speed propeller
A controllable-pitch propeller whose pitch is automatically varied in flight by a governor to maintain a constant rpm in spite of varying air loads
Continuous flow oxygen system
System that supplies a constant supply of pure oxygen to a rebreather bag that dilutes the pure oxygen with exhaled gases and thus supplies a healthy mix of oxygen and ambient air to the mask. Primarily used in passenger cabins of commercial airliners
Control and performance
A method of attitude instrument flying in which one instrument is used for making attitude changes, and the other instruments are used to monitor the progress of the change
Control display unit
A display interfaced with the master computer, providing the pilot with a single control point for all navigations systems, thereby reducing the number of required flight deck panels
Control pressures
The amount of physical exertion on the control column necessary to achieve the desired attitude
Controllability
A measure of the response of an aircraft relative to the pilot's flight control inputs
Controllable-pitch propeller (CPP)
A type of propeller with blades that can be rotated around their long axis to change their pitch. If the pitch can be set to negative values, the reversible propeller can also create reverse thrust for braking or reversing without the need of changing the direction of shaft revolutions
Controlled airspace
An airspace of defined dimensions within which ATC service is provided to IFR and VFR flights in accordance with the airspace classification. It includes Class A, Class B, Class C, Class D, and Class E airspace
Convective SIGMET
Weather advisory concerning convective weather significant to the safety of all aircraft, including thunderstorms, hail, and tornadoes
Convective weather
Unstable, rising air found in cumiliform clouds
Conventional landing gear
Landing gear employing a third rear-mounted wheel. These airplanes are also sometimes referred to as tailwheel airplanes
Coordinated flight
Flight with a minimum disturbance of the forces maintaining equilibrium, established via effective control use
COP
See changeover point
Coriolis illusion
The illusion of rotation or movement in an entirely different axis, caused by an abrupt head movement, while in a prolonged constant-rate turn that has ceased to stimulate the brain's motion sensing system
Coupled ailerons and rudder
Rudder and ailerons are connected with interconnected springs in order to counteract adverse yaw. Can be overridden if it becomes necessary to slip the aircraft
Course
The intended direction of flight in the horizontal plane measured in degrees from north
Cowl flaps
Shutter-like devices arranged around certain air-cooled engine cowlings, which may be opened or closed to regulate the flow of air around the engine
Crew resource management (CRM)
The application of team management concepts in the flight deck environment. It was initially known as cockpit resource management, but as CRM programs evolved to include cabin crews, maintenance personnel, and others, the phrase "crew resource management" was adopted. This includes single pilots, as in most general aviation aircraft. Pilots of small aircraft, as well as crews of larger aircraft, must make effective use of all available resources; human resources, hardware, and information. A current definition includes all groups routinely working with the flight crew who are involved in decisions required to operate a flight safely. These groups include, but are not limited to pilots, dispatchers, cabin crewmembers, maintenance personnel, and air traffic controllers. CRM is one way of addressing the challenge of optimizing the human/machine interface and accompanying interpersonal activities
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 areas
Areas where disturbances to the ILS localizer and glideslope courses may occur when surface vehicles or aircraft operate near the localizer or glideslope antennas
CRM
See crew resource management
Cross-check
The first fundamental skill of instrument flight, also known as "scan," the continuous and logical observation of instruments for attitude and performance information
Cruise clearance
An ATC clearance issued to allow a pilot to conduct flight at any altitude from the minimum IFR altitude up to and including the altitude specified in the clearance. Also authorizes a pilot to proceed to and make an approach at the destination airport
Current induction
An electrical current being induced into, or generated in, any conductor that is crossed by lines of flux from any magnet
D(45 terms)
D.C.
Direct current
DA
See decision altitude
Dark adaptation
Physical and chemical adjustments of the eye that make vision possible in relative darkness
Datum (Reference Datum)
An imaginary vertical plane or line from which all measurements of arm are taken. The datum is established by the manufacturer. Once the datum has been selected, all moment arms and the location of CG range are measured from this point
Dead reckoning
Navigation of an airplane solely by means of computations based on airspeed, course, heading, wind direction and speed, groundspeed, and elapsed time
Deceleration error
A magnetic compass error that occurs when the aircraft decelerates while flying on an easterly or westerly heading, causing the compass card to rotate toward South
Decision altitude (DA)
A specified altitude in the precision approach, charted in feet MSL, at which a missed approach must be initiated if the required visual reference to continue the approach has not been established
Decision height (DH)
A specified altitude in the precision approach, charted in height above threshold elevation, at which a decision must be made either to continue the approach or to execute a missed approach
Deice
The act of removing ice accumulation from an aircraft structure
Delta
A Greek letter expressed by the symbol Delta to indicate a change of values. As an example, ACG indicates a change (or movement) of the CG
Density altitude
Pressure altitude corrected for nonstandard temperature. Density altitude is used in computing the performance of an aircraft and its engines
Departure procedure (DP)
Preplanned IFR ATC departure, published for pilot use, in textual and graphic format
Deposition
The direct transformation of a gas to a solid state, in which the liquid state is bypassed. Some sources use sublimation to describe this process instead of deposition
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
Deviation
A magnetic compass error caused by local magnetic fields within the aircraft. Deviation error is different on each heading
Dew
Moisture that has condensed from water vapor. Usually found on cooler objects near the ground, such as grass, as the near-surface layer of air cools faster than the layers of air above it
Dewpoint
The temperature at which air reaches a state where it can hold no more water
DGPS
Differential global positioning system
DH
See decision height
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 parasite drag to compensate for the additional induced drag caused by the down aileron. This balancing of the drag forces helps minimize adverse yaw
Differential Global Positioning System (DGPS)
A system that improves the accuracy of Global Navigation Satellite Systems (GNSS) by measuring changes in variables to provide satellite positioning corrections
Differential pressure
A difference between two pressures. The measurement of airspeed is an example of the use of differential pressure
Dihedral
The positive acute angle between the lateral axis of an airplane and a line through the center of a wing or horizontal stabilizer. Dihedral contributes to the lateral stability of an airplane
Diluter-demand oxygen system
An oxygen system that delivers oxygen mixed or diluted with air in order to maintain a constant oxygen partial pressure as the altitude changes
Direct indication
The true and instantaneous reflection of aircraft pitch-and-bank attitude by the miniature aircraft, relative to the horizon bar of the attitude indicator
Direct User Access Terminal System (DUATS)
A system that provides current FAA weather and flight plan filing services to certified civil pilots, via personal computer, modem, or telephone access to the system. Pilots can request specific types of weather briefings and other pertinent data for planned flights
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
Distance circle
See reference circle
Distance measuring equipment (DME)
A pulse-type electronic navigation system that shows the pilot, by an instrument-panel indication, the number of nautical miles between the aircraft and a ground station or waypoint
DME
See distance measuring equipment
DME arc
A flight track that is a constant distance from the station or waypoint
DOD
Department of Defense
Doghouse
A turn-and-slip indicator dial mark in the shape of a doghouse
Domestic Reduced Vertical Separation Minimum (DRVSM)
Additional flight levels between FL 290 and FL 410 to provide operational, traffic, and airspace efficiency
Double gimbal
A type of mount used for the gyro in an attitude instrument. The axes of the two gimbals are at right angles to the spin axis of the gyro, allowing free motion in two planes around the gyro
DP
See departure procedure
Drag
The net aerodynamic force parallel to the relative wind, usually the sum of two components: induced drag and parasite drag
Drag curve
The curve created when plotting induced drag and parasite drag
Drift angle
Angle between heading and track
DRVSM
See Domestic Reduced Vertical Separation Minimum
DUATS
See direct user access terminal system
Duplex
Transmitting on one frequency and receiving on a separate frequency
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
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-and-level flight, to develop forces or moments that restore the original condition of straight and level
E(25 terms)
Eddy current damping
The decreased amplitude of oscillations by the interaction of magnetic fields. In the case of a vertical card magnetic compass, flux from the oscillating permanent magnet produces eddy currents in a damping disk or cup. The magnetic flux produced by the eddy currents opposes the flux from the permanent magnet and decreases the oscillations
Eddy currents
Current induced in a metal cup or disc when it is crossed by lines of flux from a moving magnet
EFC
See expect-further-clearance
EFD
See electronic flight display
EGT
See exhaust gas temperature
Electronic flight display (EFD)
For the purpose of standardization, any flight instrument display that uses LCD or other image-producing system (cathode ray tube (CRT), etc.)
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
Elevator illusion
The sensation of being in a climb or descent, caused by the kind of abrupt vertical accelerations that result from up- or downdrafts
EM wave
Electromagnetic wave
Emergency
A distress or urgent condition
Empennage
The section of the airplane that consists of the vertical stabilizer, the horizontal stabilizer, and the associated control surfaces
Emphasis error
The result of giving too much attention to a particular instrument during the cross-check, instead of relying on a combination of instruments necessary for attitude and performance information
Empty-field myopia
Induced nearsightedness that is associated with flying at night, in instrument meteorological conditions and/or reduced visibility. With nothing to focus on, the eyes automatically focus on a point just slightly ahead of the airplane
En route facilities ring
Depicted in the plan view of IAP charts, a circle which designates NAVAIDs, fixes, and intersections that are part of the en route low altitude airway structure
En route high-altitude charts
Aeronautical charts for en route instrument navigation at or above 18,000 feet MSL
En route low-altitude charts
Aeronautical charts for en route IFR navigation below 18,000 feet MSL
Encoding altimeter
A special type of pressure altimeter used to send a signal to the air traffic controller on the ground showing the pressure altitude the aircraft is flying
Engine pressure ratio (EPR)
The ratio of turbine discharge pressure divided by compressor inlet pressure, which is used as an indication of the amount of thrust being developed by a turbine engine
EPR
See engine pressure ratio
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 airspeed
Airspeed equivalent to CAS in standard atmosphere at sea level. As the airspeed and pressure altitude increase, the CAS becomes higher than it should be, and a correction for compression must be subtracted from the CAS
Evaporation
The transformation of a liquid to a gaseous state, such as the change of water to water vapor
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
Expect-further-clearance (EFC)
The time a pilot can expect to receive clearance beyond a clearance limit
Explosive decompression
A change in cabin pressure faster than the lungs can decompress. Lung damage is possible
F(35 terms)
FA
See area forecast
FAA
Federal Aviation Administration
FAF
See final approach fix
False horizon
Inaccurate visual information for aligning the aircraft, caused by various natural and geometric formations that disorient the pilot from the actual horizon
FDI
See flight director indicator
Federal airways
Class E airspace areas that extend upward from 1,200 feet to, but not including, 18,000 feet MSL, unless otherwise specified
Feeder facilities
Used by ATC to direct aircraft to intervening fixes between the en route structure and the initial approach fix
Final approach
Part of an instrument approach procedure in which alignment and descent for landing are accomplished
Final approach fix (FAF)
The fix from which the IFR final approach to an airport is executed, and which identifies the beginning of the final approach segment. An FAF is designated on government charts by a Maltese cross symbol for nonprecision approaches, and a lightning bolt symbol for precision approaches
Fixating
Staring at a single instrument, thereby interrupting the cross-check process
Fixed slot
A fixed, nozzle shaped opening near the leading edge of a wing that ducts air onto the top surface of the wing. Its purpose is to increase lift at higher angles of attack
Fixed-pitch propellers
Propellers with fixed blade angles. Fixed-pitch propellers are designed as climb propellers, cruise propellers, or standard propellers
FL
See flight level
Flameout
A condition in the operation of a gas turbine engine in which the fire in the engine goes out due to either too much or too little fuel sprayed into the combustors
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
Flight configurations
Adjusting the aircraft control surfaces (including flaps and landing gear) in a manner that will achieve a specified attitude
Flight director indicator (FDI)
One of the major components of a flight director system, it provides steering commands that the pilot (or the autopilot, if coupled) follows
Flight level (FL)
A measure of altitude (in hundreds of feet) used by aircraft flying above 18,000 feet with the altimeter set at 29.92 "Hg
Flight management system (FMS)
Provides pilot and crew with highly accurate and automatic long-range navigation capability, blending available inputs from long- and short-range sensors
Flight path
The line, course, or track along which an aircraft is flying or is intended to be flown
Flight patterns
Basic maneuvers, flown by reference to the instruments rather than outside visual cues, for the purpose of practicing basic attitude flying. The patterns simulate maneuvers encountered on instrument flights such as holding patterns, procedure turns, and approaches
Flight strips
Paper strips containing instrument flight information, used by ATC when processing flight plans
Floor load limit
The maximum weight the floor can sustain per square inch/foot as provided by the manufacturer
FMS
See flight management system
FOD
See foreign object damage
Fog
Cloud consisting of numerous minute water droplets and based at the surface; droplets are small enough to be suspended in the earth's atmosphere indefinitely. (Unlike drizzle, it does not fall to the surface. Fog differs from a cloud only in that a cloud is not based at the surface, and is distinguished from haze by its wetness and gray color.)
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
Foreign object damage (FOD)
Damage to a gas turbine engine caused by some object being sucked into the engine while it is running. Debris from runways or taxiways can cause foreign object damage during ground operations, and the ingestion of ice and birds can cause FOD in flight
Form drag
The drag created because of the shape of a component or the aircraft
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
Front
The boundary between two different air masses
Frost
Ice crystal deposits formed by sublimation when temperature and dewpoint are below freezing
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
Fundamental skills
Pilot skills of instrument cross-check, instrument interpretation, and aircraft control
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
G(22 terms)
GAMA
General Aviation Manufacturers Association
Gimbal ring
A type of support that allows an object, such as a gyroscope, to remain in an upright condition when its base is tilted
Glideslope (GS)
Part of the ILS that projects a radio beam upward at an angle of approximately 3circ from the approach end of an instrument runway. The glideslope provides vertical guidance to aircraft on the final approach course for the aircraft to follow when making an ILS approach along the localizer path
Glideslope intercept altitude
The minimum altitude of an intermediate approach segment prescribed for a precision approach that ensures obstacle clearance
Global landing system (GLS)
An instrument approach with lateral and vertical guidance with integrity limits (similar to barometric vertical navigation (BARO VNAV)
Global navigation satellite system (GNSS)
Satellite navigation system that provides autonomous geospatial positioning with global coverage. It allows small electronic receivers to determine their location (longitude, latitude, and altitude) to within a few meters using time signals transmitted along a line of sight by radio from satellites
Global positioning system (GPS)
Navigation system that uses satellite rather than ground-based transmitters for location information
GLS
See global landing system
GNSS
See global navigation satellite system
Goniometer
As used in radio frequency (RF) antenna systems, a direction-sensing device consisting of two fixed loops of wire oriented 90circ from each other, which separately sense received signal strength and send those signals to two rotors (also oriented 90circ) in the sealed direction-indicating instrument. The rotors are attached to the direction-indicating needle of the instrument and rotated by a small motor until minimum magnetic field is sensed near the rotors
GPS
See global positioning system
GPS Approach Overlay Program
An authorization for pilots to use GPS avionics under IFR for flying designated existing nonprecision instrument approach procedures, with the exception of LOC, LDA, and SDF procedures
GPWS
See ground proximity warning system
Graveyard spiral
The illusion of the cessation of a turn while still in a prolonged, coordinated, constant rate turn, which can lead a disoriented pilot to a loss of control of the aircraft
Great circle route
The shortest distance across the surface of a sphere (the Earth) between two points on the surface
Ground adjustable trim tab
Non-movable metal trim tab on a control surface. Bent in one direction or another while on the ground to apply trim forces to the control surface
Ground effect
The condition of slightly increased air pressure below an airplane wing or helicopter rotor system that increases the amount of lift produced. It exists within approximately one wing span or one rotor diameter from the ground. It results from a reduction in upwash, downwash, and wingtip vortices, and provides a corresponding decrease in induced drag
Ground proximity warning system (GPWS)
A system designed to determine an aircraft's clearance above the Earth and provides limited predictability about aircraft position relative to rising terrain
Groundspeed
Speed over the ground, either closing speed to the station or waypoint, or speed over the ground in whatever direction the aircraft is going at the moment, depending upon the navigation system used
GS
See glideslope
GWPS
See ground proximity warning system
Gyroscopic precession
An inherent quality of rotating bodies, which causes an applied force to be manifested 90circ in the direction of rotation from the point where the force is applied
H(32 terms)
HAA
See height above airport
HAL
See height above landing
HAT
See height above touchdown elevation
Hazardous attitudes
Five aeronautical decision-making attitudes that may contribute to poor pilot judgment: anti-authority, impulsivity, invulnerability, machismo, and resignation
Hazardous Inflight Weather Advisory Service (HIWAS)
An en route FSS service providing continuously updated automated of hazardous weather within 150 nautical miles of selected VORs, available only in the conterminous 48 states
Head-up display (HUD)
A special type of flight viewing screen that allows the pilot to watch the flight instruments and other data while looking through the windshield of the aircraft for other traffic, the approach lights, or the runway
Heading
The direction in which the nose of the aircraft is pointing during flight
Heading indicator
An instrument which senses airplane movement and displays heading based on a 360circ azimuth, with the final zero omitted. The heading indicator, also called a directional gyro (DG), 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
Headwork
Required to accomplish a conscious, rational thought process when making decisions. Good decision-making involves risk identification and assessment, information processing, and problem solving
Height above airport (HAA)
The height of the MDA above the published airport elevation
Height above landing (HAL)
The height above a designated helicopter landing area used for helicopter instrument approach procedures
Height above touchdown elevation (HAT)
The DA/DH or MDA above the highest runway elevation in the touchdown zone (first 3,000 feet of the runway)
HF
High frequency
Hg
Abbreviation for mercury, from the Latin hydrargyrum
High performance aircraft
An aircraft with an engine of more than 200 horsepower
Histotoxic hypoxia
The inability of cells to effectively use oxygen. Plenty of oxygen is being transported to the cells that need it, but they are unable to use it
HIWAS
See Hazardous Inflight Weather Advisory Service
Holding
A predetermined maneuver that keeps aircraft within a specified airspace while awaiting further clearance from ATC
Holding pattern
A racetrack pattern, involving two turns and two legs, used to keep an aircraft within a prescribed airspace with respect to a geographic fix. A standard pattern uses right turns; nonstandard patterns use left turns
Homing
Flying the aircraft on any heading required to keep the needle pointing to the 0circ relative bearing position
Horizontal situation indicator (HSI)
A flight navigation instrument that combines the heading indicator with a CDI, in order to provide the pilot with better situational awareness of location with respect to the courseline
Horsepower
The term, originated by inventor James Watt, means the amount of work a horse could do in one second. 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
HSI
See horizontal situation indicator
HUD
See head-up display
Human factors
A multidisciplinary field encompassing the behavioral and social sciences, engineering, and physiology, to consider the variables that influence individual and crew performance for the purpose of optimizing human performance and reducing errors
Hung start
In gas turbine engines, a condition of normal light off but with rpm remaining at some low value rather than increasing to the normal idle rpm. 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
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
Hypemic hypoxia
A type of hypoxia that is a result of oxygen deficiency in the blood, rather than a lack of inhaled oxygen. It can be caused by a variety of factors. Hypemic means "not enough blood"
Hyperventilation
Occurs when an individual is experiencing emotional stress, fright, or pain, and the breathing rate and depth increase, although the carbon dioxide level in the blood is already at a reduced level. The result is an excessive loss of carbon dioxide from the body, which can lead to unconsciousness due to the respiratory system's overriding mechanism to regain control of breathing
Hypoxia
A state of oxygen deficiency in the body sufficient to impair functions of the brain and other organs
Hypoxic hypoxia
This type of hypoxia is a result of insufficient oxygen available to the lungs. A decrease of oxygen molecules at sufficient pressure can lead to hypoxic hypoxia
I(36 terms)
IAF
See initial approach fix
IAP
See instrument approach procedures
IAS
See indicated airspeed
ICAO
See International Civil Aviation Organization
Ident
Air Traffic Control request for a pilot to push the button on the transponder to identify return on the controller's scope
IFR
See instrument flight rules
ILS
See instrument landing system
ILS categories
Categories of instrument approach procedures allowed at airports equipped with instrument landing systems: Category I (200ft height, 1,800ft RVR); Category II (100ft height, 1,200ft RVR); Category IIIA (no DH, 700ft RVR); Category IIIB (no DH, 150ft RVR); Category IIIC (no DH, no RVR minimum)
IMC
See instrument meteorological conditions
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)
Shown on the dial of the instrument airspeed indicator on an aircraft. Indicated airspeed (IAS) is the airspeed indicator reading uncorrected for instrument, position, and other errors. Indicated airspeed means the speed of an aircraft as shown on its pitot static airspeed indicator calibrated to reflect standard atmosphere adiabatic compressible flow at sea level uncorrected for airspeed system errors. Calibrated airspeed (CAS) is IAS corrected for instrument errors, position error (due to incorrect pressure at the static port) and installation errors
Indicated altitude
The altitude read directly from the altimeter (uncorrected) when it is set to the current altimeter setting
Indirect indication
A reflection of aircraft pitch-and-bank attitude by instruments other than the attitude indicator
Induced drag
Drag caused by the same factors that produce lift; its amount varies inversely with airspeed. As airspeed decreases, the angle of attack must increase, in turn increasing induced drag
Induction icing
A type of ice in the induction system that reduces the amount of air available for combustion. The most commonly found induction icing is carburetor icing
Inertial navigation system (INS)
A computer-based navigation system that tracks the movement of an aircraft via signals produced by onboard accelerometers. The initial location of the aircraft is entered into the computer, and all subsequent movement of the aircraft is sensed and used to keep the position updated. An INS does not require any inputs from outside signals
Initial approach fix (IAF)
The fix depicted on IAP charts where the instrument approach procedure (IAP) begins unless otherwise authorized by ATC
Inoperative components
Higher minimums are prescribed when the specified visual aids are not functioning; this information is listed in the Inoperative Components Table found in the United States Terminal Procedures Publications
INS
See inertial navigation system
Instantaneous vertical speed indicator (IVSI)
Assists in interpretation by instantaneously indicating the rate of climb or descent at a given moment with little or no lag as displayed in a vertical speed indicator (VSI)
Instrument approach procedures (IAP)
A series of predetermined maneuvers for the orderly transfer of an aircraft under IFR from the beginning of the initial approach to a landing or to a point from which a landing may be made visually
Instrument flight rules (IFR)
Rules and regulations established by the Federal Aviation Administration to govern flight under conditions in which flight by outside visual reference is not safe. IFR flight depends upon flying by reference to instruments in the flight deck, and navigation is accomplished by reference to electronic signals
Instrument landing system (ILS)
An electronic system that provides both horizontal and vertical guidance to a specific runway, used to execute a precision instrument approach procedure
Instrument meteorological conditions (IMC)
Meteorological conditions expressed in terms of visibility, distance from clouds, and ceiling less than the minimums specified for visual meteorological conditions, requiring operations to be conducted under IFR
Instrument takeoff
Using the instruments rather than outside visual cues to maintain runway heading and execute a safe takeoff
Intercooler
A device used to reduce the temperatures 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
Interference drag
Drag generated by the collision of airstreams creating eddy currents, turbulence, or restrictions to smooth flow
International Civil Aviation Organization (ICAO)
The United Nations agency for developing the principles and techniques of international air navigation, and fostering planning and development of international civil air transport
International standard atmosphere (IAS)
A model of standard variation of pressure and temperature
Interpolation
The estimation of an intermediate value of a quantity that falls between marked values in a series
Inversion
An increase in temperature with altitude
Inversion illusion
The feeling that the aircraft is tumbling backwards, caused by an abrupt change from climb to straight-and-level flight while in situations lacking visual reference
Inverter
A solid-state electronic device that converts D.C. into A.C. current of the proper voltage and frequency to operate A.C. gyro instruments
Isobars
Lines which connect points of equal barometric pressure
Isogonic lines
Lines drawn across aeronautical charts to connect points having the same magnetic variation
IVSI
See instantaneous vertical speed indicator
J(3 terms)
Jet route
A route designated to serve flight operations from 18,000 feet MSL up to and including FL 450
Jet stream
A high-velocity narrow stream of winds, usually found near the upper limit of the troposphere, which flows generally from west to east
Judgment
The mental process of recognizing and analyzing all pertinent information in a particular situation, a rational evaluation of alternative actions in response to it, and a timely decision on which action to take
K(3 terms)
L(35 terms)
L/MF
See low or medium frequency
LAAS
See local area augmentation system
Lag
The delay that occurs before an instrument needle attains a stable indication
Land as soon as possible
Land without delay at the nearest suitable area, such as an open field, at which a safe approach and landing is assured
Land as soon as practical
The landing site and duration of flight are at the discretion of the pilot. Extended flight beyond the nearest approved landing area is not recommended
Land breeze
A coastal breeze flowing from land to sea caused by temperature differences when the sea surface is warmer than the adjacent land. The land breeze usually occurs at night and alternates with the sea breeze that blows in the opposite direction by day
Land immediately
The urgency of the landing is paramount. The primary consideration is to ensure the survival of the occupants. Landing in trees, water, or other unsafe areas should be considered only as a last resort
Lateral axis
An imaginary line passing through the center of gravity of an airplane and extending across the airplane from wingtip to wingtip
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
Latitude
Measurement north or south of the equator in degrees, minutes, and seconds. Lines of latitude are also referred to as parallels
LDA
See localizer-type directional aid
Lead radial
The radial at which the turn from the DME arc to the inbound course is started
Leading edge
The part of an airfoil that meets the airflow first
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 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
Leans, the
A physical sensation caused by an abrupt correction of a banked attitude entered too slowly to stimulate the motion sensing system in the inner ear. The abrupt correction can create the illusion of banking in the opposite direction
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
Lift
A component of the total aerodynamic force on an airfoil and acts perpendicular to the relative wind
Limit load factor
Amount of stress, or load factor, that an aircraft can withstand before structural damage or failure occurs
Lines of flux
Invisible lines of magnetic force passing between the poles of a magnet
LMM
See locator middle marker
Load factor
The ratio of a specified load to the total weight of the aircraft. The specified load is expressed in terms of any of the following: aerodynamic forces, inertial forces, or ground or water reactions
Loadmeter
A type of ammeter installed between the generator output and the main bus in an aircraft electrical system
LOC
See localizer
Local area augmentation system (LAAS)
A differential global positioning system (DGPS) that improves the accuracy of the system by determining position error from the GPS satellites, then transmitting the error, or corrective factors, to the airborne GPS receiver
Localizer (LOC)
The portion of an ILS that gives left/right guidance information down the centerline of the instrument runway for final approach
Localizer-type directional aid (LDA)
A NAVAID used for nonprecision instrument approaches with utility and accuracy comparable to a localizer but which is not a part of a complete ILS and is not aligned with the runway
Locator middle marker (LMM)
Nondirectional radio beacon (NDB) compass locator, collocated with a middle marker (MM)
Locator outer marker (LOM)
NDB compass locator, collocated with an outer marker (OM)
LOM
See locator outer marker
Longitude
Measurement east or west of the Prime Meridian in degrees, minutes, and seconds. The Prime Meridian is 0circ longitude and runs through Greenwich, England. Lines of longitude are also referred to as meridians
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
Low or medium frequency
A frequency range between 190 and 535 kHz with the medium frequency above 300 kHz. Generally associated with nondirectional beacons transmitting a continuous carrier with either a 400 or 1,020 Hz modulation
Lubber line
The reference line used in a magnetic compass or heading indicator
M(75 terms)
MAA
See maximum authorized altitude
MAC
See mean aerodynamic chord
Mach meter
The instrument that displays the ratio of the speed of sound to the true airspeed an aircraft is flying
Mach number
The ratio of the true airspeed of the aircraft to the speed of sound in the same atmospheric conditions
Magnetic bearing (MB)
The direction to or from a radio transmitting station measured relative to magnetic north
Magnetic compass
A device for determining direction measured from magnetic north
Magnetic dip
A vertical attraction between a compass needle and the magnetic poles. The closer the aircraft is to a pole, the more severe the effect
Magnetic heading (MH)
The direction an aircraft is pointed with respect to magnetic north
Magneto
A self-contained, engine-driven unit that supplies electrical current to the spark plugs; completely independent of the airplane's electrical system
Magnus effect
Lifting force produced when a rotating cylinder produces a pressure differential. This is the same effect that makes a baseball curve or a golf ball slice
Mandatory altitude
An altitude depicted on an instrument approach chart with the altitude value both underscored and overscored. Aircraft are required to maintain altitude at the depicted value
Mandatory block altitude
An altitude depicted on an instrument approach chart with two underscored and overscored altitude values between which aircraft are required to maintain altitude
Maneuverability
Ability of an aircraft to change directions along a flight path and withstand the stresses imposed upon it
Maneuvering speed (VA)
The design maneuvering speed. Operating at or below design maneuvering speed does not provide structural protection against multiple full control inputs in one axis or full control inputs in more than one axis at the same time
Manifold absolute pressure
The absolute pressure of the fuel/air mixture within the intake manifold, usually indicated in inches of mercury
MAP
See missed approach point
Margin identification
The top and bottom areas on an instrument approach chart that depict information about the procedure, including airport location and procedure identification
Marker beacon
A low-powered transmitter that directs its signal upward in a small, fan-shaped pattern. Used along the flight path when approaching an airport for landing, marker beacons indicate both aurally and visually when the aircraft is directly over the facility
Mass
The amount of matter in a body
Maximum altitude
An altitude depicted on an instrument approach chart with overscored altitude value at which or below aircraft are required to maintain altitude
Maximum authorized altitude (MAA)
A published altitude representing the maximum usable altitude or flight level for an airspace structure or route segment
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
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
MB
See magnetic bearing
MCA
See minimum crossing altitude
MDA
See minimum descent altitude
MEA
See minimum en route altitude
Mean aerodynamic chord (MAC)
The average distance from the leading edge to the trailing edge of the wing
Mean sea level
The average height of the surface of the sea at a particular location for all stages of the tide over a 19-year period
MEL
See minimum equipment list
Meridians
Lines of longitude
Mesophere
A layer of the atmosphere directly above the stratosphere
METAR
See Aviation Routine Weather Report
MFD
See multi-function display
MH
See magnetic heading
MHz
Megahertz
Microburts
A strong downdraft which normally occurs over horizontal distances of 1 NM or less and vertical distances of less than 1,000 feet. In spite of its small horizontal scale, an intense microburst could induce windspeeds greater than 100 knots and downdrafts as strong as 6,000 feet per minute
Microwave landing system (MLS)
A precision instrument approach system operating in the microwave spectrum which normally consists of an azimuth station, elevation station, and precision distance measuring equipment
Mileage breakdown
A fix indicating a course change that appears on the chart as an "x" at a break between two segments of a federal airway
Military operations area (MOA)
Airspace established for the purpose of separating certain military training activities from IFR traffic
Military training route (MTR)
Airspace of defined vertical and lateral dimensions established for the conduct of military training at airspeeds in excess of 250 knots indicated airspeed (KIAS)
Minimum altitude
An altitude depicted on an instrument approach chart with the altitude value underscored. Aircraft are required to maintain altitude at or above the depicted value
Minimum crossing altitude (MCA)
The lowest allowed altitude at certain fixes an aircraft must cross when proceeding in the direction of a higher minimum en route altitude (MEA)
Minimum descent altitude (MDA)
The lowest altitude (in feet MSL) to which descent is authorized on final approach, or during circle-to-land maneuvering in execution of a nonprecision approach
Minimum drag
The point on the total drag curve where the lift-to-drag ratio is the greatest. At this speed, total drag is minimized
Minimum en route altitude (MEA)
The lowest published altitude between radio fixes that ensures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes
Minimum equipment list (MEL)
A list developed for larger aircraft that outlines equipment that can be inoperative for various types of flight including IFR and icing conditions. This list is based on the master minimum equipment list (MMEL) developed by the FAA and must be approved by the FAA for use. It is specific to an individual aircraft make and model
Minimum obstruction clearance altitude (MOCA)
The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments, which meets obstacle clearance requirements for the entire route segment and which ensures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR
Minimum reception altitude (MRA)
The lowest altitude at which an airway intersection can be determined
Minimum safe altitude (MSA)
The minimum altitude depicted on approach charts which provides at least 1,000 feet of obstacle clearance for emergency use within a specified distance from the listed navigation facility
Minimum vectoring altitude (MVA)
An IFR altitude lower than the minimum en route altitude (MEA) that provides terrain and obstacle clearance
Minimums section
The area on an IAP chart that displays the lowest altitude and visibility requirements for the approach
Missed approach
A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing
Missed approach point (MAP)
A point prescribed in each instrument approach at which a missed approach procedure shall be executed if the required visual reference has not been established
Mixed ice
A mixture of clear ice and rime ice
MLS
See microwave landing system
MM
Middle marker
MOA
See military operations area
MOCA
See minimum obstruction clearance altitude
Mode C
Altitude reporting transponder mode
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
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
Monocoque
A shell-like fuselage design in which the stressed outer skin is used to support the majority of imposed stresses. Monocoque fuselage design may include bulkheads but not stringers
Monoplanes
Airplanes with a single set of wings
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 allows air to continue flowing over the top of the wing and delays airflow separation
MRA
See minimum reception altitude
MSA
See minimum safe altitude
MSL
See mean sea level
MTR
See military training route
Multi-function display (MFD)
Small screen (CRT or LCD) in an aircraft that can be used to display information to the pilot in numerous configurable ways. Often an MFD will be used in concert with a primary flight display
MVA
See minimum vectoring altitude
N(28 terms)
N1
Rotational speed of the low pressure compressor in a turbine engine
N2
Rotational speed of the high pressure compressor in a turbine engine
Nacelle
A streamlined 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
NACG
See National Aeronautical Charting Group
NAS
See National Airspace System
National Aeronautical Charting Group (NACG)
A Federal agency operating under the FAA, responsible for publishing charts such as the terminal procedures and en route charts
National Airspace System (NAS)
The common network of United States airspace-air navigation facilities, equipment and services, airports or landing areas; aeronautical charts, information and services; rules, regulations and procedures, technical information; and manpower and material
National Route Program (NRP)
A set of rules and procedures designed to increase the flexibility of user flight planning within published guidelines
National Security Area (NSA)
Areas consisting of airspace of defined vertical and lateral dimensions established at locations where there is a requirement for increased security and safety of ground facilities. Pilots are requested to voluntarily avoid flying through the depicted NSA. When it is necessary to provide a greater level of security and safety, flight in NSAs may be temporarily prohibited
National Transportation Safety Board (NTSB)
A United States Government independent organization responsible for investigations of accidents involving aviation, highways, waterways, pipelines, and railroads in the United States. NTSB is charged by congress to investigate every civil aviation accident in the United States
NAV/COM
Navigation and communication radio
NAVAID
Navigational aid
NDB
See nondirectional radio beacon
Negative static stability
The initial tendency of an aircraft to continue away from the original state of equilibrium after being disturbed
Neutral static stability
The initial tendency of an aircraft to remain in a new condition after its equilibrium has been disturbed
NM
Nautical mile
No procedure turn (NoPT)
Term used with the appropriate course and altitude to denote that the procedure turn is not required
No-gyro approach
A radar approach that may be used in case of a malfunctioning gyro-compass or directional gyro. Instead of providing the pilot with headings to be flown, the controller observes the radar track and issues control instructions "turn right/left" or "stop turn," as appropriate
NOAA
National Oceanic and Atmospheric Administration
Nondirectional radio beacon (NDB)
A ground-based radio transmitter that transmits radio energy in all directions
Nonprecision approach
A standard instrument approach procedure in which only horizontal guidance is provided
NoPT
See no procedure turn
NOTAM
See Notice to Airmen
Notice to Airmen (NOTAM)
A notice filed with an aviation authority to alert aircraft pilots of any hazards en route or at a specific location. The authority in turn provides means of disseminating relevant NOTAMs to pilots
NRP
See National Route Program
NSA
See National Security Area
NTSB
See National Transportation Safety Board
NWS
National Weather Service
O(14 terms)
Obstacle departure procedures (ODP)
A preplanned instrument flight rule (IFR) departure procedure printed for pilot use in textual or graphic form to provide obstruction clearance via the least onerous route from the terminal area to the appropriate en route structure. ODPs are recommended for obstruction clearance and may be flown without ATC clearance unless an alternate departure procedure (SID or radar vector) has been specifically assigned by ATC
Obstruction lights
Lights that can be found both on and off an airport to identify obstructions
Occluded front
A frontal occlusion occurs when a fast-moving cold front catches up with a slow moving warm front. The difference in temperature within each frontal system is a major factor in determining whether a cold or warm front occlusion occurs
ODP
See obstacle departure procedures
OM
Outer marker
Omission error
The failure to anticipate significant instrument indications following attitude changes; for example, concentrating on pitch control while forgetting about heading or roll information, resulting in erratic control of heading and bank
Optical illusion
A misleading visual image. For the purpose of this handbook, the term refers to the brain's misinterpretation of features on the ground associated with landing, which causes a pilot to misread the spatial relationships between the aircraft and the runway
Orientation
Awareness of the position of the aircraft and of oneself in relation to a specific reference point
Otolith organ
An inner ear organ that detects linear acceleration and gravity orientation
Outer marker
A marker beacon at or near the glideslope intercept altitude of an ILS approach. It is normally located four to seven miles from the runway threshold on the extended centerline of the runway
Outside air temperature (OAT)
The measured or indicated air temperature (IAT) corrected for compression and friction heating. Also referred to as true air temperature
Overboost
A condition in which a reciprocating engine has exceeded the maximum manifold pressure allowed by the manufacturer. Can cause damage to engine components
Overcontrolling
Using more movement in the control column than is necessary to achieve the desired pitch-and-bank condition
Overpower
To use more power than required for the purpose of achieving a faster rate of airspeed change
P(50 terms)
P-factor
A tendency for an aircraft to yaw to the left due to the 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
P-static
See precipitation static
PAPI
See precision approach path indicator
PAR
See precision approach radar
Parallels
Lines of latitude
Parasite drag
Drag caused by the friction of air moving over the aircraft structure; its amount varies directly with the airspeed
Payload (GAMA)
The weight of occupants, cargo, and baggage
Personality
The embodiment of personal traits and characteristics of an individual that are set at a very early age and extremely resistant to change
PFD
See primary flight display
Phugoid oscillations
Long-period oscillations of an aircraft around its lateral axis. It is a slow change in pitch accompanied by equally slow changes in airspeed. Angle of attack remains constant, and the pilot often corrects for phugoid oscillations without even being aware of them
PIC
See pilot in command
Pilot in command (PIC)
The pilot responsible for the operation and safety of an aircraft
Pilot report (PIREP)
Report of meteorological phenomena encountered by aircraft
Pilot's Operating Handbook/Airplane Flight Manual (POH/AFM)
FAA-approved documents published by the airframe manufacturer that list the operating conditions for a particular model of aircraft
Pilotage
Navigation by visual reference to landmarks
PIREP
See pilot report
Pitot pressure
Ram air pressure used to measure airspeed
Pitot-static head
A combination pickup used to sample pitot pressure and static air pressure
Plan view
The overhead view of an approach procedure on an instrument approach chart. The plan view depicts the routes that guide the pilot from the en route segments to the IAF
Planform
The shape or form of a wing as viewed from above. It may be long and tapered, short and rectangular, or various other shapes
Pneumatic
Operation by the use of compressed air
POH/AFM
See Pilot's Operating Handbook/Airplane Flight Manual
Point-in-space approach
A type of helicopter instrument approach procedure to a missed approach point more than 2,600 feet from an associated helicopter landing area
Poor judgment chain
A series of mistakes that may lead to an accident or incident. Two basic principles generally associated with the creation of a poor judgment chain are: (1) one bad decision often leads to another; and (2) as a string of bad decisions grows, it reduces the number of subsequent alternatives for continued safe flight. ADM is intended to break the poor judgment chain before it can cause an accident or incident
Position error
Error in the indication of the altimeter, ASI, and VSI caused by the air at the static system entrance not being absolutely still
Position report
A report over a known location as transmitted by an aircraft to ATC
Positive static stability
The initial tendency to return to a state of equilibrium when disturbed from that state
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
Precession
The characteristic of a gyroscope that causes an applied force to be felt, not at the point of application, but 90circ from that point in the direction of rotation
Precipitation
Any or all forms of water particles (rain, sleet, hail, or snow) that fall from the atmosphere and reach the surface
Precipitation static (P-static)
A form of radio interference caused by rain, snow, or dust particles hitting the antenna and inducing a small radio-frequency voltage into it
Precision approach
A standard instrument approach procedure in which both vertical and horizontal guidance is provided
Precision approach path indicator (PAPI)
A system of lights similar to the VASI, but consisting of one row of lights in two- or four-light systems. A pilot on the correct glideslope will see two white lights and two red lights
Precision approach radar (PAR)
A type of radar used at an airport to guide an aircraft through the final stages of landing, providing horizontal and vertical guidance. The radar operator directs the pilot to change heading or adjust the descent rate to keep the aircraft on a path that allows it to touch down at the correct spot on the runway
Precision runway monitor (PRM)
System allows simultaneous, independent instrument flight rules (IFR) approaches at airports with closely spaced parallel runways
Preferred IFR routes
Routes established in the major terminal and en route environments to increase system efficiency and capacity. IFR clearances are issued based on these routes, listed in the Chart Supplement U.S. except when severe weather avoidance procedures or other factors dictate otherwise
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
Altitude above the standard 29.92 "Hg plane
Pressure demand oxygen system
A demand oxygen system that supplies 100 percent oxygen at sufficient pressure above the altitude where normal breathing is adequate. Also referred to as a pressure breathing system
Prevailing visibility
The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle (which is not necessarily continuous)
Preventive maintenance
Simple or minor preservative operations and the replacement of small standard parts not involving complex assembly operation as listed in 14 CFR part 43, appendix A. Certificated pilots may perform preventive maintenance on any aircraft owned or operated by them provided the aircraft is not used in air carrier service
Primary and supporting
A method of attitude instrument flying using the instrument that provides the most direct indication of attitude and performance
Primary flight display (PFD)
A display that provides increased situational awareness to the pilot by replacing the traditional six instruments used for instrument flight with an easy-to-scan display that provides key relevant indications
PRM
See precision runway monitor
Procedure turn
A maneuver prescribed when it is necessary to reverse direction to establish an aircraft on the intermediate approach segment or final approach course
Profile view
Side view of an IAP chart illustrating the vertical approach path altitudes, headings, distances, and fixes
Prohibited area
Designated airspace within which flight of aircraft is prohibited
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
Propeller/rotor modulation error
Certain propeller rpm settings or helicopter rotor speeds can cause the VOR course deviation indicator (CDI) to fluctuate as much as pm6circ. Slight changes to the rpm setting will normally smooth out this roughness
R(58 terms)
Rabbit, the
High-intensity flasher system installed at many large airports. The flashers consist of a series of brilliant blue-white bursts of light flashing in sequence along the approach lights, giving the effect of a ball of light traveling toward the runway
Radar
A system that uses electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects. The term RADAR was coined in 1941 as an acronym for Radio Detection and Ranging
Radar approach
The controller provides vectors while monitoring the progress of the flight with radar, guiding the pilot through the descent to the airport/heliport or to a specific runway
Radar services
Radar is a method whereby radio waves are transmitted into the air and are then received when reflected by an object. Range is determined by measuring the time it takes (at speed of light) for the radio wave to return. Direction is determined by position of the rotating antenna
Radar summary chart
A weather product derived from the national radar network that graphically displays a summary of radar weather reports
Radar weather report (SD)
A report issued by radar stations at 35 minutes after the hour. Provides information on type, intensity, and location of echo tops of precipitation
Radials
The courses oriented from a station
Radio frequency (RF)
A term that refers to alternating current (AC) having characteristics such that, if the current is input to antenna, an electromagnetic (EM) field is generated suitable for wireless broadcasting and/or communications
Radio magnetic indicator (RMI)
An electronic navigation instrument that combines a magnetic compass with an ADF or VOR. The card of the RMI acts as a gyro-stabilized magnetic compass
Radio or radar altimeter
An electronic altimeter that determines the height of an aircraft above the terrain by measuring the time needed for a pulse of radio-frequency energy to travel from the aircraft to the ground and return
Radio wave
An electromagnetic (EM) wave with frequency characteristics useful for radio transmission
Radiosonde
A weather instrument typically carried by balloon that observes and reports meteorological conditions from the upper atmosphere
RAIM
See receiver autonomous integrity monitoring
RAM recovery
The increase in thrust as a result of ram air pressures and density on the front of the engine caused by air velocity
Random RNAV routes
Direct routes between waypoints defined in terms of latitude/longitude coordinates, degree-distance fixes, or offsets from established routes
Ranging signals
Transmitted from the GPS satellite, signals allowing the aircraft's receiver to determine range (distance) from each satellite
Rapid decompression
The almost instantaneous loss of cabin pressure in aircraft with a pressurized cockpit or cabin
RB
See relative bearing
RBI
See relative bearing indicator
RCO
See remote communications outlet
Receiver autonomous integrity monitoring (RAIM)
A system used to verify usability of received GPS signals and warns the pilot of any malfunction. Required for IFR-certified GPS units
Receiver-transmitter (RT)
A system that receives and transmits a signal and an indicator
Recommended altitude
An altitude depicted on an instrument approach chart with the altitude value neither underscored nor overscored. The depicted value is an advisory value
Reduced vertical separation minimum (RVSM)
Reduces vertical separation between flight levels (FL) 290 and 410 from 2,000 feet to 1,000 feet
Reference circle
(also, distance circle). The circle depicted in the plan view of an IAP chart that typically has a 10 NM radius, within which chart the elements are drawn to scale
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
Regions of command
Refers to the relationship between speed and the power required to maintain or change that speed in flight
REIL
See runway end identifier lights
Relative bearing (RB)
The angular difference between the aircraft heading and the direction to the station, measured clockwise from the nose of the aircraft
Relative bearing indicator (RBI)
Also known as the fixed-card ADF, zero is always indicated at the top of the instrument and the needle indicates the relative bearing to the station
Relative humidity
The ratio of existing amount of water vapor in the air to the maximum amount that could exist at that temperature
Relative wind
Direction of the airflow produced by an object moving through the air. Flows in a direction parallel with and opposite to the direction of flight
Remote communications outlet (RCO)
An unmanned communications facility that is remotely controlled by air traffic personnel
Required navigation performance (RNP)
A specified level of accuracy defined by a lateral area of confined airspace in which an RNP-certified aircraft operates
Restricted area
Airspace designated under 14 CFR part 73 within which the flight of aircraft, while not wholly prohibited, is subject to restriction
Reverse sensing
The VOR needle appearing to indicate the reverse of normal operation
RF
Radio frequency
Rhodopsin
The photosensitive pigments that initiate the visual response in the rods of the eye
Rigging
The final adjustment and alignment of an aircraft and its flight control system that provides proper aerodynamic characteristics
Rigidity
The characteristic of a gyroscope that prevents its axis of rotation tilting as the Earth rotates
Rigidity in space
The principle that a wheel with a heavily weighted rim spinning rapidly will remain in a fixed position in the plane in which it is spinning
Rime ice
Rough, milky, opaque ice formed by the instantaneous freezing of small supercooled water droplets
Risk
The future impact of a hazard that is not eliminated or controlled
Risk elements
Four fundamental risk elements: the pilot, the aircraft, the environment, and the type of operation
Risk management
Part of the decision-making process which relies on situational awareness, problem recognition, and good judgment to reduce risks
RMI
See radio magnetic indicator
RNAV
See area navigation
RNP
See required navigation performance
RT
See receiver-transmitter
Rudder
The movable primary control surface mounted on the trailing edge of the vertical fin. Movement of the rudder rotates the airplane about its vertical axis
Ruddervator
A pair of control surfaces on the tail of an aircraft arranged in the form of a V. Serve as both elevators and rudder
Runway centerline lights
Runway lighting which consists of flush centerline lights spaced at 50-foot intervals beginning 75 feet from the landing threshold
Runway edge lights
Used to outline the edges of runways at night or during low visibility conditions
Runway end identifier lights (REIL)
A pair of synchronized flashing lights located on each side of the runway threshold
Runway visibility value (RVV)
The visibility determined for a particular runway by a transmissometer
Runway visual range (RVR)
The instrumentally derived horizontal distance a pilot should be able to see down the runway from the approach end
RVR
See runway visual range
RVV
See runway visibility value
S(75 terms)
SA
See selective availability
Satellite ephemeris data
Data broadcast by the GPS satellite containing accurate orbital data, atmospheric propagation data, and clock error data
Scan
The first fundamental skill of instrument flight, also known as "cross-check;" the continuous and logical observation of instruments
SDF
See simplified directional facility
Sea breeze
A coastal breeze blowing from sea to land caused by the temperature difference when the land surface is warmer than the sea surface
Sea level engine
A reciprocating aircraft engine having a rated takeoff power that is producible only at sea level
Sectional aeronautical charts
Designed for visual navigation of slow- or medium-speed aircraft. Portrays relief and features visual check points
Selective availability (SA)
A satellite technology permitting the Department of Defense (DOD) to create a significant clock and ephemeris error for national security
Semicircular canal
An inner ear organ that detects angular acceleration of the body
Semimonocoque
A fuselage design that includes a substructure of bulkheads and/or formers, along with stringers, to support flight loads
Sensitive altimeter
A form of multipointer pneumatic altimeter with an adjustable barometric scale
Service ceiling
The maximum density altitude where the best rate-of-climb airspeed will produce a 100-feet-per-minute climb
Servo
A motor or other form of actuator which receives a small signal and exerts a large force to accomplish work
Servo tab
An auxiliary control mounted on a primary control surface, which automatically moves in the direction opposite the primary control to provide assist
SIDS
See standard instrument departure procedures
SIGMET
Significant Meteorological information. A weather advisory concerning potentially hazardous en route weather phenomena
Signal-to-noise ratio
An indication of signal strength received compared to background noise
Significant weather prognostic
Presents four panels showing forecast significant weather
Simplex
Transmission and reception on the same frequency
Simplified directional facility (SDF)
A NAVAID used for nonprecision instrument approaches. Similar to an ILS localizer but may be offset and wider
Single-pilot resource management (SRM)
The ability for a pilot to manage all resources effectively to ensure a successful flight
Situational awareness
Pilot knowledge of where the aircraft is in regard to location, ATC, weather, regulations, and aircraft status
Skidding turn
An uncoordinated turn in which the rate of turn is too great for the angle of bank
Skills and procedures
Procedural, psychomotor, and perceptual skills used to control a specific aircraft or its systems
Skin friction drag
Drag generated between air molecules and the solid surface of the aircraft
Slant range
The horizontal distance from the aircraft antenna to the ground station due to line-of-sight DME transmission
Slaved compass
A system whereby the heading gyro is continuously corrected to agreement with a remotely located magnetic sensing device
Slipping turn
An uncoordinated turn in which the aircraft is banked too much for the rate of turn
Small airplane
An airplane of 12,500 pounds or less maximum certificated takeoff weight
Somatogravic illusion
The misperception of being in a nose-up or nose-down attitude caused by rapid acceleration or deceleration
Spatial disorientation
State of confusion due to misleading sensory information resulting in lack of awareness of aircraft position
Special flight permit
Issued to an aircraft that does not meet airworthiness requirements but is capable of safe flight (e.g., ferry permit)
Special fuel consumption
Amount of fuel in pounds per hour consumed per brake horsepower or per pound of thrust
Special use airspace
Airspace subject to restrictions (prohibited, restricted, warning, military operations, and alert areas)
Speed
The distance traveled in a given time
Spin
An aggravated stall that results in an airplane descending in a helical path
Spiral instability
Condition where static directional stability is very strong compared to dihedral effect
Spiraling slipstream
Propeller slipstream strikes the left side of the vertical fin, causing the aircraft to yaw slightly
Spoilers
High-drag devices raised into the airflow to reduce lift and increase drag
SRM
See single-pilot resource management
SSR
See secondary surveillance radar
SSV
See standard service volume
St. Elmo's Fire
A corona discharge which lights up the aircraft surface areas where maximum static discharge occurs
Stabilator
A single-piece horizontal tail surface that pivots around a central hinge point
Stability
Inherent quality of an airplane to correct for conditions that disturb its equilibrium
Stagnant hypoxia
Hypoxia resulting when oxygen-rich blood in the lungs is not moving to tissues
Stall
Rapid decrease in lift caused by separation of airflow from the wing's surface when critical angle of attack is exceeded
Standard atmosphere
At sea level: 29.92 "Hg (1013.2 mb) and 15circC (59 °F). Standard lapse rate: ~1 "Hg and 2circC per 1,000 feet
Standard empty weight (GAMA)
Weight of airframe, engines, fixed equipment, unusable fuel, and full engine oil
Standard holding pattern
A holding pattern in which all turns are made to the right
Standard instrument departure procedures (SIDS)
Published procedures to expedite clearance delivery and transition between takeoff and en route
Standard rate turn
3circ per second for low/medium-speed aircraft; 1 rac12circ per second for high-speed aircraft
Standard service volume (SSV)
Defines the limits of the volume of airspace which the VOR serves
Standard terminal arrival route (STAR)
Preplanned IFR ATC arrival procedure published for pilot use
Standard weights
Weights established for numerous items in weight and balance computations
STAR
See standard terminal arrival route
Static longitudinal stability
Aerodynamic pitching moments required to return aircraft to equilibrium angle of attack
Static pressure
Pressure of air that is still, measured perpendicular to the aircraft surface
Static stability
Initial tendency an aircraft displays when disturbed from equilibrium
Station
Location in airplane identified by distance in inches from the datum
Stationary front
A front moving at a speed of less than 5 knots
Steep turns
Instrument flight: any turn > standard rate; Visual flight: any bank > 45circ
Stepdown fix
The point after which additional descent is permitted within an IAP segment
Strapdown system
INS where accelerometers and gyros are permanently aligned with the three aircraft axes
Stratoshere
Layer of atmosphere above the tropopause to approximately 160,000 feet
Stress
The body's response to demands placed upon it
Stress management
Analysis of flight stress and application of coping mechanisms
Structural icing
Accumulation of ice on the exterior of the aircraft
Sublimation
Process by which a solid is changed to a gas without going through liquid state
Suction relief valve
Maintains correct low pressure inside vacuum instrument cases
Supercharger
Engine- or exhaust-driven compressor providing additional pressure to induction air
Supercooled water droplets
Water droplets cooled below freezing point but still in liquid state
Surface analysis chart
Depicts current surface weather including pressure areas, fronts, and local conditions
Synchro
Device used to transmit indications of angular movement between locations
Synthetic vision
Realistic display depiction of aircraft in relation to terrain and flight path
T(68 terms)
T-tail
Horizontal stabilizer mounted on top of vertical stabilizer
TAA
See terminal arrival area
TACAN
See tactical air navigation
Tactical air navigation (TACAN)
Military navigation system providing both distance and direction
Takeoff decision speed (V1)
Calibrated airspeed at which pilot is assumed to have made decision to continue or discontinue takeoff after engine failure
Takeoff distance
Distance required to complete all-engines takeoff to 35-foot height
Takeoff safety speed (V2)
Airspeed obtained after lift-off at which one-engine-inoperative climb performance can be achieved
TAWS
See terrain awareness and warning system
Taxiway lights
Omnidirectional blue lights outlining taxiway edges
Taxiway turnoff lights
Flush green lights on the runway
TCAS
See traffic alert collision avoidance system
TCH
See threshold crossing height
TDZE
See touchdown zone elevation
TEC
See Tower En Route Control
Technique
The manner in which procedures are executed
Telephone information briefing service (TIBS)
FSS automated telephone recordings of weather and route information
Temporary flight restriction (TFR)
Flight restriction imposed for safety, disaster relief, sightseeing congestion, or public figure protection
Tension
Maintaining an excessively strong grip on control column, often causing overcontrol
Terminal aerodrome forecast (TAF)
Weather report for 5 statute mile radius around an airport
Terminal arrival area (TAA)
Transition method for aircraft with FMS/GPS; contains a "T" structure
Terminal instrument approach procedure (TERP)
Standardized methods for designing instrument flight procedures
Terminal radar service areas (TRSA)
Areas where participating pilots can receive additional radar separation services
TERP
See terminal instrument approach procedure
Terrain awareness and warning system (TAWS)
Time-based system using GPS and a database to predict terrain hazards
TFR
See temporary flight restriction
Thermosphere
Atmosphere layer beginning above mesosphere that fades into space
Threshold crossing height (TCH)
Theoretical height of glideslope antenna over runway threshold
Thrust
Force imparting a change in mass velocity, measured in pounds
Thrust (aerodynamic force)
Forward force produced by propeller, fan, or jet engine
Thrust line
Imaginary line through center of propeller hub
Time and speed table
Chart table identifying distance FAF to MAP and required transit time
Timed turn
Turn using clock and turn coordinator to change heading in given time
TIS
See traffic information service
Title 14 of the Code of Federal Regulations (14 CFR)
Federal aviation regulations governing aircraft, airways, and airmen
Torque
Resistance to turning or twisting; tendency of aircraft to roll opposite engine/propeller rotation
Torquemeter
Measures reaction between propeller reduction gears and engine case
Total drag
Sum of parasite drag and induced drag
Touchdown zone elevation (TDZE)
Highest elevation in first 3,000 feet of landing surface
Touchdown zone lights
Two rows of transverse light bars in runway touchdown zone
Tower En Route Control (TEC)
IFR control between adjacent approach facilities to expedite traffic
TPP
See United States Terminal Procedures Publication
Track
The actual path made over the ground in flight
Tracking
Flying heading to maintain desired track regardless of crosswind
Traffic Alert Collision Avoidance System (TCAS)
Airborne system independent of ground ATC, serving as "last line of defense" against collisions
Traffic information service (TIS)
Ground-based service informing flight deck of nearby traffic via data link
Trailing edge
Portion of airfoil where upper and lower airflow rejoins
Transcribed Weather Broadcast (TWEB)
FSS automated broadcast of meteorological data in Alaska
Transponder
Airborne portion of the ATC radar beacon system
Transponder code
One of 4,096 four-digit codes assigned by ATC
Trend
Immediate indication of direction of aircraft movement
Tricycle gear
Landing gear employing a third wheel on the nose
Trim
Adjusting aerodynamic forces so aircraft maintains attitude without input
Trim tab
Small hinged portion of control surface adjusted during flight to balance forces
Tropopause
Boundary layer between troposphere and stratosphere
Troposphere
Atmosphere layer surface to 20,000-60,000 feet
True airspeed
Actual airspeed corrected for pressure altitude and temperature
True altitude
Vertical distance above sea level
Truss
Fuselage design using supporting structural members to resist deformation
Turbine discharge pressure
Total pressure at discharge of low-pressure turbine
Turbine engine
Engine consisting of air compressor, combustion section, and turbine
Turbocharger
Exhaust-driven air compressor increasing induction air pressure
Turbofan engine
Turbojet with secondary diverted airflow around combustion chamber
Turbojet engine
Turbine engine producing thrust entirely by accelerating air through the engine
Turboprop engine
Turbine engine driving a propeller through reduction gearing
Turboshaft engine
Gas turbine engine delivering power through a shaft to non-propeller hardware
Turn coordinator
Rate gyro sensing both roll and yaw
Turn-and-slip indicator
Indicates rate of yaw and relationship between gravity and centrifugal force
TWEB
See Transcribed Weather Broadcast
U(10 terms)
UHF
See ultra-high frequency
Ulitimate load factor
Load causing physical breakdown in aircraft component strength test
Ultra-high frequency (UHF)
Range of electromagnetic frequencies between 300 MHz and 3,000 MHz
Uncaging
Unlocking gyroscopic instrument gimbals
Uncontrolled airspace
Class G airspace where ATC has no authority
Underpower
Using less power than required for faster airspeed change
United States Terminal Procedures Publication (TPP)
Regional FAA booklets including DPs, STARS, and IAPs
Unusual attitude
Unintentional, unanticipated, or extreme aircraft attitude
Useful load
Weight of pilot, passengers, fuel, and oil (Basic Empty Weight subtracted from Max Gross Weight)
User-defined waypoints
Waypoint data input/editable by user in GPS database
V(47 terms)
V1
See takeoff decision speed
V2
See takeoff safety speed
VA
See maneuvering speed
VFE
Maximum speed with flaps extended
VLE
Maximum speed with landing gear extended
VLO
Maximum speed for landing gear extension/retraction
VMC
Minimum control airspeed (engine inoperative/takeoff power)
VNE
Never-exceed speed (red line on airspeed indicator)
VNO
Maximum structural cruising speed
VS0
Stalling speed in landing configuration (lower limit of white arc)
VS1
Stalling speed in specified/clean configuration (lower limit of green arc)
VX
Best angle-of-climb speed
VY
Best rate-of-climb speed
VYSE
Best rate-of-climb speed with one engine inoperative
V-G diagram
Chart relating velocity to load factor
V-tail
Slanted tail surfaces serving as both horizontal/vertical stabilizers
Vapor lock
Disruption of fuel delivery when liquid fuel changes to gas in the system
Variation
Compass error due to difference in magnetic and geographic north poles
VASI
See visual approach slope indicator
VDP
See visual descent point
Vector
Graphic representation of force showing magnitude and direction
Vectoring
Navigational guidance by assigning headings
VEF
Calibrated airspeed at which critical engine is assumed to fail
Velocity
Speed or rate of movement in certain direction
Venturi tube
Tube producing suction for gyro instruments
Vertical axis
Imaginary line passing vertically through center of gravity (yaw axis)
Vertical card compass
Magnetic compass using eddy current damping to present heading
Vertical speed indicator (VSI)
Rate-of-pressure change instrument indicating constant pressure deviation
Vertical stability
Stability about vertical axis (yawing/directional stability)
Very-high frequency (VHF)
Radio frequencies between 30 and 300 MHz
Very-high frequency omnidirectional range (VOR)
Navigation identifying radial from station measured from magnetic north
Vestibule
Central cavity of the bony labyrinth of the ear
VFR
See visual flight rules
VFR on top
ATC authorization for IFR aircraft in VFR conditions at VFR altitude
VFR over the top
VFR operation in VFR conditions on top of an undercast
VFR terminal area chart
1:250,000 scale chart depicting Class B airspace
Victor airways
Airways based on centerline between VOR/VORTAC facilities
Visual approach slope indicator (VASI)
Light aid for descent guidance; red over white is correct glideslope
Visual descent point (VDP)
Point from which normal descent from MDA to runway can begin if visible
Visual flight rules (VFR)
FAA rules governing flight using visual references
Visual meteorological conditions (VMC)
Visibility, cloud distance, and ceiling meeting/exceeding VFR minimums
VMC
See visual meteorological conditions
VOR
See very-high frequency omnidirectional range
VOR test facility (VOT)
Emits test signal to check VOR receiver accuracy
VORTAC
VOR and TACAN components at one site
VOT
See VOR test facility
VSI
See vertical speed indicator
W(24 terms)
WAAS
See wide area augmentation system
Wake turbulence
Wingtip vortices created when airplane generates lift
Warm front
Boundary when warm air flows over colder air, causing low ceilings/rain
Warning area
Hazards to non-participating aircraft; may include military exercises
WARP
See weather and radar processing
Waste gate
Controllable valve in turbocharger tailpipe
Waypoint
Geographical location used for route definition
WCA
See wind correction angle
Weather and radar processor (WARP)
Strategic weather info device in National Airspace System
Weather depiction chart
Surface conditions derived from METAR
Weight
Force exerted by aircraft from gravity
Wide area augmentation system (WAAS)
DGPS improving accuracy by determining/transmitting position error
Wind correction angle (WCA)
Angle necessary to keep aircraft tracking over desired track
Wind direction indicators
Wind sock, wind tee, or tetrahedron
Wind shear
Sudden shift in windspeed or direction
Winds and temperature aloft forecast (FB)
Twice daily forecast for contiguous U.S.
Wing area
Total wing surface including control surfaces and fuselage coverage
Wing root
Part of wing closest to fuselage, bearing highest bending forces
Wing span
Maximum distance from wingtip to wingtip
Wing twist
Design feature to improve aileron effectiveness near stall
Wings
Main lifting surfaces attached to fuselage
Wingtip vortices
Rapidly rotating air spilling over wings (wake turbulence)
Work
Measurement of force used to produce movement
World Aeronautical Charts (WAC)
Standard 1:1,000,000 scale navigation charts