Alpha
Bismillah
Charlie Delta
Echo
Foxtrot
Golf
Hotel
insaallah Juliett
Kilo
Lima
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November
Oscar
Piaggio Quebec Romeo
Sierra Turks Uniform
Victory Water X-ray
Yankee Zulu Main Page
lag 1
LAG 1labyrinth air seal
The thin sheet metal rims on turbine blades, either rotating or stationary, that control air leakage from the gas path to the inner portions of the engine. Same as knife edge air seal.labyrinth oil seal A main bearing oil seal. It is configured with thread-type grooves that allow gas path air to leak inward to the bearing sump and keep oil mist from escaping. Unlike the carbon seal, which rides on a surface, the labyrinth oil seal has a small clearance between its sealing lands and the rotating shaft.
lacing cord A strong cotton, linen, or synthetic fiber cord used to rib stitch fabric covering to an aircraft structure. Also referred to as rib-stitching cord.
lack of common experience In communication, a difficulty that arises because words have different meanings for the source and the receiver of information due to their differing backgrounds.
lacquer The pigments dissolved in a volatile base (solvents, plasticizers, and thinners) in preparation for spraying as a liquid. Cures to a durable surface when the solvent evaporates.
lag 1. A delay in time. 2. To fall behind.
lagging current An occurrence in an AC inductive reactance circuit whereby changes in the voltage occur before changes in the current. Current, therefore, lags the voltage.
lagging material An insulating material wrapped around aircraft plumbing to prevent the unwanted loss of heat to the outside air.
LAHSO An acronym for Land and Hold Short Operation. These operations include landing and holding short of an intersecting runway, a taxiway, a predetermined point, or an approach/departure flightpath.
LAHSO-dry Land and hold short operations on runways that are dry.
LAHSO-wet Land and hold short operations on runways that are wet (but not contaminated).
laminar Arranged in or consisting of thin layers.
laminar flow The nonturbulent flow of air or viscous fluid over a surface.
laminate A structure made by bonding together two or more layers of material with resin. It contains no core material.
laminate ply In composites, one fabric-resin or fiber-resin layer that is bonded to adjacent layers in the curing process.
laminated Composed of thin layers of material firmly bonded or united together.
laminated core The core of a coil, transformer, or other electrical device consisting of a stack of thin, soft iron sheets insulated from each other by a film oxide or varnish. Laminated cores are used to minimize eddy currents.
laminated plastic material A reinforced plastic resin made up of layers of material such as cloth, paper, or wood bonded with plastic resin to form complex shapes or to produce a material with high strength for its weight.
laminated structure An element or part of an aircraft made up of layers of material bonded together to form complex shapes or to produce a material with high strength for its weight.
laminated wood Layers of wood bonded together to make a stronger material.
lampblack The black soot from incompletely burned carbonaceous materials used for making generator brushes. Lampblack is used as a pigment when mixed with rubber for making tires.
land and hold short operations (LAHSO) Operations that include simultaneous takeoffs and landings and/or simultaneous landings when a landing aircraft is able and is instructed by the controller to hold-short of the intersecting runway/taxiway or designated hold-short point. Pilots are expected to promptly inform the controller if the hold short clearance cannot be accepted.
land breeze A coastal breeze blowing from land to sea, caused by temperature difference when the sea surface is warmer than the adjacent land. Therefore, it usually blows at night and alternates with a sea breeze, which blows in the opposite direction by day.
land plane An airplane designed to operate from the surface of land using wheeled landing gear rather than pontoons or skis for landing on water or snow.
lander A space vehicle designed for landing on a celestial body.
landing area Any locality either on land, water, or structures, including airports/heliports and intermediate landing fields, used or intended to be used, for the landing and takeoff of aircraft whether or not facilities are provided for the shelter, servicing, or for receiving or discharging passengers or cargo.
landing area [ICAO] That part of the movement area intended for the landing and takeoff of aircraft.
landing direction indicator A device that visually indicates the direction in which landings and takeoffs should be made.
landing distance available The length of runway declared available and suitable for the ground run of an aeroplane landing.
landing flaps A secondary control surface that increases the overall wing area or changes the camber of the wing. The increased wing area permits a lower landing speed. Increased camber increases the lift and allows lower landing speeds and shorter landing distances.
landing gear The wheels, floats, skis, and all of the attachments that support an airplane when it is resting on a landing surface.
landing gear door warning system A group of components that warn of an unsafe landing gear door condition by the use of a horn, indicators, or red warning lights. Used on aircraft with retractable landing gear.
landing gear extended speed The maximum speed at which an aircraft can be safely flown with the landing gear extended.
landing gear operating speed The maximum speed at which the landing gear can be safely extended or retracted.
landing gear position indicating system A group of components that shows the position of the landing gear though the use of lights or instruments. Used on aircraft with retractable landing gear.
landing gear warning system A group of components incorporated on all retractable gear aircraft to warn of an unsafe landing gear condition. The pilot is warned of an unsafe condition by a warning light and aural device. The horn blows and the light comes on when one or more throttles are retarded and the landing gear is in any position other than down and locked.
landing lights The high-intensity lights located on the wing or fuselage used to illuminate the runway for landing and taking off at night. These lights also make an aircraft more visible to other aircraft during the day.
landing minimums The minimum visibility prescribed for landing a civil aircraft while using an instrument approach procedure. The minimum applies with other limitations set forth in FAR 91 with respect to the Minimum Descent Altitude (MDA) or Decision Height (DH) prescribed in the instrument approach procedures as follows:
a. Straight-in landing minimums A statement of MDA and visibility, or DH and visibility, required for straight-in landing on a specified runway, or
b. Circling minimums A statement of MDA and visibility required for the circle-to-land maneuver.
NOTE: Descent below the established MDA or DH is not authorized during an approach unless the aircraft is in a position from which a normal approach to the runway of intended landing can be made and adequate visual reference to required visual cues is maintained.
landing roll The distance from the point of touchdown to the point where the aircraft can be brought to a stop or exit the runway.
landing sequence The order in which aircraft are positioned for landing.
landing weight The weight of the aircraft at touchdown. Often limited by the manufacturer to less than takeoff weight for structural reasons.
landing wires The streamlined wires attached to the upper wing above the fuselage and extending to near the outboard end of the lower wing in a biplane. These wires brace the wings against the forces that affect the wings during landing. These forces are opposite those encountered during flight.
lap belt A seat belt or safety belt that crosses a person s lap while seated in an aircraft.
lap joint A joint in a sheet metal structure where the edge of one sheet overlaps the other. Welding, riveting, or bolting fastens the lap joints together.
lap winding A method of manufacturing the armature of a DC generator by connecting the ends of each coil wound on the armature to the next adjacent commutator segment with the coils lapping over each other.
lapping To rub two surfaces together with a very fine abrasive between them in order to produce an extremely close fit.
lapping compound An abrasive paste used to polish surfaces.
laps The surface defects in sheet metal caused by the folding over of fins or sharp corners into the surface of the material. Occurs during the rolling process.
lapse rate The rate of decrease of an atmospheric variable with altitude; commonly refers to a decrease of temperature or pressure with altitude.
lapse rate The rate of decrease of an atmospheric variable with height; commonly refers to decrease of temperature with height.
large aircraft Aircraft of more than 12,500 pounds, maximum certificated takeoff weight.
large calorie (Cal.) A unit of heat energy. It is the amount of heat energy necessary to raise the temperature of 1 kg of water 1 C.
large scale integration A
method of fabricating integrated circuit (IC) chips to
place multiple transistors or logic circuits on one
small IC. Large scale integration was an early version
that placed hundreds of logic circuits
LASER
Laserlaser A device that emits coherent light (light that vibrates in phase) used in many applications, from CD players to powerful metal cutting devices. Acronym for Light Amplification by Stimulated Emission of Radiation.
laser beam welding The use of laser beam heat for welding engine parts. Currently used to weld titanium fan blades, which could not be welded by conventional methods.
laser memory A method of storing billions of bits of digital information on a disk such as a CD or DVD.
laser printer A printer that prints a high quality copy of the information being processed by a computer.
last assigned altitude The last altitude/flight level assigned by ATC and acknowledged by the pilot.
last chance filter The final filter located just before the spray nozzle of a turbine lubrication system. Used to prevent foreign matter from clogging the spray nozzle.
latch A fastening device used to hold a door closed.
latching relay An electrically operated relay that, once energized, holds the contacts in the energized position by a mechanical latch and can only be released by some mechanical means.
late timing On a reciprocating engine, the condition where the timing is late (retarded). That is, the ignition occurs very near top dead center (TDC) on the compression stroke or even after TDC. Late timing is an inefficient fuel condition and the causes the engine to develop less than optimum power.
latent heat The amount of heat required to change the state of a material without changing its temperature (eg., The amount of heat absorbed or released during a change of state from ice to water.)
latent heat of condensation The amount of heat given off when a substance changes from a vapor to a liquid without changing its temperature.
latent heat of evaporation The amount of heat absorbed by a substance when it changes from a liquid to a vapor without changing its temperature.
latent heat of fusion The amount of heat that must be removed from a substance to change it from a liquid to a solid without changing its temperature.
latent heat of vaporization The amount of heat that must be absorbed by a liquid to change it into a vapor without changing its temperature.
lateral The span of an airplane from wingtip to wingtip.
lateral axis An imaginary straight line drawn perpendicularly (laterally) across the fuselage and through the center of gravity. Pitch movement occurs around the lateral axis, and is controlled by the elevator.
lateral navigation (LNAV) A function of area navigation (RNAV) equipment that calculates, displays, and provides lateral guidance to a profile or path.
lateral separation The lateral spacing of aircraft at the same altitude by requiring operation on different routes or in different geographical locations.
lateral stability 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.
lateral vibration An unwanted lateral or side-to-side movement in a helicopter. The cause of lateral vibration is normally an unbalanced main rotor.
lathe A wood or metal-working tool in which the material is turned about its longitudinal axis and cutting tools are fed into its outer circumference in order to change its shape.
latitude Measurement north or south of the equator in degrees, minutes, and seconds. Lines of latitude are also referred to as parallels.
launch The release of an aircraft or rocket for flight.
launching pad A specially designed platform from which rockets can be fired to launch them.
law of conservation of energy The law that states that the internal energy of an isolated system remains constant; only forms of energy can be changed.
lay of a control cable The twist of the strands of a wire cable.
layer 1. A single thickness. 2. In reference to sky cover, clouds or other obscuring phenomena whose bases are approximately at the same level. The layer can be continuous or composed of detached elements.
layout A drawing, pattern, or format of a piece of sheet metal in which the locations for all of the bends and drilled holes are indicated.
lay-up In composites, reinforcing material that is placed in position in the mold.
L-band radar An airborne radar.
LC circuit A circuit network containing inductance and capacitance.
LCR electrical circuit An AC circuit that has inductance (L), capacitance (C), and resistance (R). The total opposition to the flow of current in an LCR circuit is the vector sum of resistance and the difference between inductive and capacitive reactances.
L/Dmax The maximum ratio between total lift (L) and total drag (D). This point provides the best glide speed. Any deviation from the best glide speed increases drag and reduces the distance of the glide.
lead A heavy, pliant, silvery metallic element with a symbol of Pb and an atomic weight of 82.
lead and lag In rotorcraft, the fore (lead) and aft (lag) movement of the rotor blade in the plane of rotation.
lead of screw thread The distance a nut will move forward on a screw if it is turned one revolution.
lead-acid battery A commonly used secondary cell having lead as its negative plate and lead peroxide as its positive plate. Sulfuric acid and water serve as the electrolyte.
leading current An AC electrical circuit in which the current that flows in the circuit has more capacitive reactance than it has inductive reactance.
leading edge The foremost edge of an airfoil section.
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.
leading edge mean aerodynamic chord (LEMAC) The leading edge of the mean aerodynamic chord often used as a location or reference for many aerodynamic measurements in aircraft operations and designs.
lead-lag hinge A hinge at the root of a helicopter rotor blade with its axis perpendicular to the plane of rotation. Also referred to as the alpha, drag, or hunting hinge.
lead-off question A question used by an instructor to open up an area for discussion. The purpose is to get the discussion started.
leaf brake A bending tool used to form straight bends in sheet metal. The material is clamped in the tool, and a heavy leaf folds the metal back over a radius block to form the desired bend. Also referred to as a cornice brake.
leaf spring assembly A series of flat springs hinged at one end and arched in the center. When a load is applied to the center of the arch it is absorbed as the spring alternately straightens out and returns to its arched shape.
leakage 1. The breakdown of the dielectric strength of an insulator that allows current to pass through it. 2. An amount of a liquid or gas that leaks into or out of something.
leakage current The amount of current that flows from the battery terminals to the battery case through any moisture or contamination on top of the battery.
leakage
leakage flux The magnetic flux that does not follow a direct path between the poles of a magnet and which does not provide any useful work.
lean blow out A condition in jet engine fuel combustion during which the fuel supply is decreased to maintain or reduce engine speed. During this condition the burning can be so slow that the flame is carried out of the combustion chamber and extinguished.
lean flame out A condition of turbine engine operation in which the fire goes out in the engine because the fuel-air mixture is too lean to support combustion.
lean mixture A fuel-air mixture in which there is an excess amount of air in the mixture.
learning A change in behavior as a result of experience.
learning plateau A learning phenomenon where progress appears to cease or slow down for a time before once again increasing.
learning style The concept that how a person learns is dependent on that person s background and personality, as well as the instructional methods used.
least significant bit A bit in a binary number that has the lowest value. It is the bit on the far right of a binary number.
least significant digit A digit in a decimal number that is the least meaningful for accuracy. It is the digit on the far right of a decimal number.
Leclanche cell battery A name for a common carbon-zinc cell flashlight battery.
lecture method An educational presentation usually delivered by an instructor to a group of students with the use of instructional aids and training devices. Lectures are useful for the presentation of new material, summarizing ideas, and showing relationships between theory and practice.
lee side The downwind side of a mountain range, building, island, etc.
lee wave Any stationary wave disturbance caused by a barrier in a fluid flow. In the atmosphere when sufficient moisture is present, this wave will be evidenced by lenticular clouds to the lee of mountain barriers. Also referred to as a mountain wave or standing wave.
lee wave region The upper layer of a two-layer lee-wave system where smooth wave flow dominates and microscale turbulence occasionally occurs.
lee wave system A system marked by two distinct layers. The upper layer is the lee wave region, which begins just above mountain to level, and the lower layer is the lower turbulent zone.
left brain A concept that each hemisphere of the brain processes information differently. People with left-brain dominance are more verbal, analytical, and objective.
left-hand rule 1. The left-hand generator rule: The fingers of the left hand are arranged in such a way that the thumb, first finger, and second finger point 90 to each other. If the thumb points in the direction of movement of the conductor, the first finger will point in the direction of the lines of flux (north to south), and the second finger will point in the direction of the induced voltage (back voltage, from positive to negative). 2. The direction of magnetic flux: If the fingers of the left hand encircle a conductor in the direction of the lines of magnetic flux, the thumb will point in the direction of electron flow. 3. The polarity of an electromagnet: If the coil of an electromagnet is grasped in such a way that the fingers encircle the coil in the same way the electrons are flowing, the thumb will point to the north pole of the electromagnet that is formed by the coil.
left-hand thread A thread that winds in a counterclockwise direction. All left-hand threads are designated LH.
leg 1. One side of a formed angle. 2. One portion of a trip made with dead reckoning navigation (the distance between turn points.) 3. The portion of a trip between stops.
legs of a right triangle The sides of a right triangle joined by the right angle (90 ).
LEMAC The leading edge of the mean aerodynamic chord. Often used as a reference location for aerodynamic measurements in aircraft operations and designs.
lenticular cloud A cloud shaped like a lens that forms on the downwind side of a mountain. It usually indicates severe air turbulence and should be avoided. They can extend the entire length of the mountain range producing the wave and are called wave clouds or lennies by glider pilots.
Lenz s law The law of induced current that says the current induced in a conductor will produce a magnetic field that opposes the field producing the original current.
lesson plan An organized outline for a single instructional period. It is a necessary guide for the instructor in that it tells what to do, in what order to do it, and what procedure to use in teaching the material of a lesson.
letter of authorization (LOA) A letter from the FAA authorizing use of a Minimum Equipment List (MEL) for a specific airplane. The letter and the MEL together are considered a supplemental type certificate.
level 1. The horizontal condition of a body: A flat horizontal surface of an object is level when no part of the object is higher than another. 2. A spirit or bubble level: An indicating device that has a curved glass tube filled with a slightly colored liquid, except for a small air bubble. The tube is mounted in a housing so when it is place in a parallel position to the ground the bubble will move to the center of the tube indicating a level condition.
leveling lugs The points on an aircraft on which a level can be placed for leveling the aircraft.
leveling means A method of checking an aircraft for level flight attitude as specified by the aircraft manufacturer. This can be longitudinal, lateral, and/or both.
leveling scale A scale built into the aircraft for checking the leveling of the aircraft in conjunction with a plumb bob.
lever 1. A device such as a bar used for prying. 2. A flat bar pivoting on a fulcrum.
Leyden jar A primitive capacitor. In effect, an apparatus for storing an electric charge on the inside foil lining of a glass jar.
L-filter An inductor-input filter consisting of an inductor and a capacitor used to smooth the ripple from the output of a rectifier.
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.
life-limited part A part with a specified number of operating hours or operating cycles before it must be removed for overhaul.
life-support systems The oxygen and pressurization systems in an aircraft that make it possible for the occupants to function at high altitudes.
lift One of the four main forces acting on an aircraft. On a fixed-wing aircraft, an upward force created by the effect of airflow as it passes over and under the wing.
lift fan A turbofan engine with an exhaust duct that can be pointed down to provide upward thrust for vertical or short takeoff. Used in VSTOL (Vertical/Short Takeoff and Land) aircraft.
lift wires The biplane wing support wires installed between the wings of a biplane to hold the wings in alignment against the forces of lift. Lift wires extend from the inboard end of the lower wing to the interplane struts on the upper wing.
lift-drag ratio The efficiency of an airfoil section. It is the ratio of the coefficient of lift to the coefficient of drag for any given angle of attack.
lifted index The common approach to the evaluation of potential instability requirement for thunderstorm formation. It is the difference between the observed 500 mb temperature and the temperature the parcel of air would have if lifted from the boundary layer to the 500 mb level.
lifting body A wingless aircraft developed by NASA where lift is created by the shape of the craft itself.
light The electromagnetic radiations of a frequency range visible to the human eye.
light aircraft An aircraft having a total gross weight of 12,500 lbs. or less. See also light plane.
light emitting diode (LED) A semiconductor diode that emits light when current flows through it.
light ends The products of petroleum that boil off first in the process of fractional distillation.
light gun A handheld directional light signaling device that emits a brilliant narrow beam of white, green, or red light as selected by the tower controller. The color and type of light transmitted can be used to approve or disapprove anticipated pilot actions where radio communication is not available. The light gun is used for controlling traffic operating in the vicinity of the airport and on the airport movement area.
light plane An aircraft having a total gross weight of 12,500 lbs. or less. Light plane is also used as a colloquial term to mean a small, single-engine airplane.
light sport aircraft An aircraft, other than a helicopter or powered-lift that, since its original certificate, has continued to meet the following:
1. A maximum takeoff weight of not more than 660 pounds (300 kilograms) for lighter-than-air aircraft; 1,320 pounds (600 kilograms) for aircraft not intended for operation on water; or 1,430 pounds (650 kilograms) for an aircraft intended for operation on water.
2. A maximum airspeed in level light, with maximum continuous power (VH), of not more than 120 knots CAS under standard atmospheric conditions at sea level.
light year The distance light travels in one year. Unit of measurement in astronomy equal to 5.88 X 1012 miles.
light-activated silicon control rectifier In electronics, a semiconductor device that conducts when exposed to light.
lighted airport An airport where runway and obstruction lighting is available.
lightening hole A hole cut in a structural part to decrease weight. Strength is often maintained by flanging the area around the hole.
lighter-than-air aircraft An aircraft that can rise and remain suspended by using contained gas weighing less than the air that is displaced by the gas.
lightning An immense discharge of static electricity in response to the build-up of electrical potential between cloud and ground, between clouds, within a single cloud, or between a cloud and the surrounding air.
light-up The point at which combustion occurs in a turbine engine as indicated by an exhaust temperature rise on the cockpit indicator.
lime grease A grease made up of oil and calcium hydroxide. It does not emulsify in water and is highly resistant to washout in wet environments.
limit load The maximum load, expressed as multiples of positive and negative G (force of gravity), that an aircraft can sustain before structural damage becomes possible. The load limit varies from aircraft to aircraft.
limit switch A switch designed to stop an actuator at the limit of its movement.
limiter A stage in a frequency modulated receiver that limits the amplitude of the signal and thus removes static.
limits The bounds of travel or size allowed for a component.
limits of size The applicable maximum and minimum dimensions of a part.
Lindberg fire detection system A continuous-element-type fire detector consisting of a stainless steel tube containing a discrete element that has been processed to absorb gas in proportion to the operating temperature. As the temperature rises, gas is released, causing the pressure in the stainless steel tube to increase to the operating temperature set point. This closes a switch that actuates the warning light and bell.
line loss The voltage loss in a conductor. The amount of loss is related to its length.
line maintenance The inspection and repairs accomplished on the flight line as opposed to shop maintenance.
line of sight radio reception The clear path between the transmitting and receiving antennas of high-frequency radio signals.
line voltage The main power line voltage that operates a system.
line voltage regulator The device used to stabilize the line voltage by sensing and regulating the voltage demands supplied to a piece of electrical or electronic equipment.
linear accelerometer A device that measures acceleration of a body in a straight line.
linear actuator An actuator that changes hydraulic or pneumatic pressure into linear motion.
linear amplification In electronics, an amplifier in which the change in output is proportional to the change in input.
linear control In electronics, a control device in which the change in output is proportional to the amount the control s adjustment is changed.
linear integrated circuit In electronics, an integrated circuit (IC) in which the change in output is proportional to the change in input.
linear movement A movement or progression in which the output or result is directly proportional to the input.
linear operation The operation in which the output of a device is directly proportional to its input. If the input increases by 10 percent, the output will also be increased by 10 percent.
linear resistance curve The characteristic illustrated by a load when any increase or decrease in the voltage across the load results in a proportional change in the current through the load.
linen A fabric made from flax that was a favorite covering material for truss-type airplanes. In the United States, it has been almost totally replaced by grade-A cotton and synthetic fiber.
lines of flux The lines of magnetic force connecting the poles of a magnet.
link 1. A short connecting rod used for transmitting power and/or force. 2. On the Internet, an identifier indicating connection with another similarly identified element. Links are usually identified by a different color of text, underlining, or button and can be accessed merely by clicking on them with a mouse. The mouse pointer also will usually change from an arrow to a hand when it hovers over a link.
link rod An articulated rod that connects the pistons in a radial engine to the master rod. There is one less articulated rod than there are cylinders in each row of cylinders in a radial engine since one piston is attached to the master rod.
linseed oil A solvent used in some aircraft finishes. Also used to coat the inside of steel tubing to prevent rusting. Linseed oil is obtained from flaxseed.
liquid A fluid that assumes the shape of the container in which it is held.
liquid air A slightly bluish, transparent liquid that has been changed into a liquid by lowering its temperature to -312 F (-191 C, 81 Kelvin). It is used chiefly as a refrigerant.
liquid crystal A liquid whose reflectivity varies according to the voltage applied to it.
liquid crystal display A constantly activated display that consists of segments of a liquid crystal. Uses very low current levels, making it more suitable for displays than light emitting diodes (LED s).
liquid lock A condition that occurs in reciprocating engines that have the cylinders below the crankcase. Oil leaks past the piston rings and fills the cylinder. The engine cannot be rotated without damage. Also referred to as a hydraulic lock.
liquid nitrogen Nitrogen that has been changed into its liquid state by lowering its temperature to -195 C (78 Kelvin) or lower.
liquid oxygen (LOX) Oxygen that has been changed into its liquid state by lowering its temperature to -113 C (160 Kelvin) or lower.
liquid-cooled A device or machine that is cooled by the use of liquid.
liquid-cooled engine A reciprocating engine that uses a mixture of water and ethylene glycol to remove excess heat. This mixture flows around the cylinders in jackets and absorbs the heat created by the combustion in the cylinders. This heat is released to the outside air through a radiator.
listening Hearing your students talk and listening to what they are saying are two different things. Instructors can use a variety of techniques or tools to become better listeners, including do not interrupt, do not judge, think before answering, be close enough to hear, watch nonverbal behavior, be aware of biases, look for underlying feelings, concentrate, avoid rehearsing answers while listening, do not insist on the last word.
liter A metric unit of volume (1.0567 qt.) used for gaseous or liquid measurement.
lithium An alkaline-metal element with a symbol of Li and an atomic number of 3. The lightest metallic element known.
lithium cell One of a family of chemical cell types incorporating lithium in one pole.
lithium grease A water-resistant, low operating temperature grease made of lithium salts and fatty acids.
lithometeor In meteorology, dry particles suspended in the atmosphere such as dust, smoke, and haze.
lithosphere The Earth s most outer area consisting of the Earth s crust and the upper mantle. The lithosphere extends downward toward the center of the Earth approximately 50 to 60 miles.
litmus paper An indicator paper that changes color when it comes in contact with an acid or an alkali. It turns red when wet with an acid, and blue when wet with an alkali.
live center A lathe component with a sharp-pointed center that fits into the headstock of a lathe and turns with it. Used to locate the exact center of the headstock.
load An energy-absorbing or energy-using device of any sort connected to a current.
load bank A heavy-duty resistor used to discharge a storage battery.
load cell An electronic weighing system component that contains the strain gauges. It is placed between an aircraft jack pad and the jack to measure the weight of the aircraft load.
load chart A chart used for weight and balance purposes that specifies the location and distribution of weights. It aids the pilot in determining the loaded center of gravity condition.
load, electrical Any apparatus that uses electrical power to perform a function such as operating a motor.
load factor The ratio of the load supported by the airplane s wings to the actual weight of the aircraft and its contents. Also referred to as G-loading.
load manifest An itemized list of weights and moments of a particular load taken on a specific flight. Used by FAR Part 121 and 135 operators.
loading graph A method of computing the loaded weight and center of gravity of an aircraft.
loading schedule A document showing where cargo should be stowed and in what weights at specified locations.
loadmeter A current measuring instrument calibrated in terms of the percentage of the total rated current of the power source.
lobes The eccentric portions of a cam or camshaft.
LOC mode The operating position of an automatic pilot when it is receiving its signals from the localizer portion of an instrument landing system.
local action The formation of tiny chemical cells in one or both of the poles of a chemical cell (battery) due to impurities in the material. Local action can result in the exhausting of the service capacity of a cell or corrosion of the pole pieces.
local airport advisory (LAA) A service provided by flight service stations or the military at airports not serviced by an operating control tower. This service consists of providing information to arriving and departing aircraft concerning wind direction and speed, favored runway, altimeter setting, pertinent known traffic, pertinent known field conditions, airport taxi routes and traffic patterns, and authorized instrument approach procedures. This information is advisory in nature and does not constitute an ATC clearance.
local Mach number In aerodynamics, the speed of air flow (Mach number) at a specified location. Because of the aerodynamic shape of an aircraft, the speed of airflow at any point can be greater than the air speed of the aircraft as a whole.
local oscillator The internal oscillator section of a superhetrodyne circuit.
local traffic Aircraft operating in the traffic pattern or within sight of the tower, or aircraft known to be departing or arriving from flight in local practice areas, or aircraft executing practice instrument approaches at the airport.
localizer The component of an ILS that provides course guidance to the runway.
localizer course [ICAO] The locus of points, in any given horizontal plane, at which the DDM (difference in depth of modulation) is zero.
localizer offset An angular offset of the localizer from the runway extended centerline in a direction away from the no transgression zone (NTZ) that increases the normal operating zone (NOZ) width. An offset requires a 50 foot increase in DH and is not authorized for CAT II and CAT III approaches.
localizer performance with vertical guidance (LPV)
An instrument approach that takes advantage of WAAS to provide electronic lateral and vertical guidance.
localizer type directional aid A NAVAID used for nonprecision instrument approaches with utility and accuracy comparable to a localizer but that is not a part of a complete ILS and is not aligned with the runway.
localizer usable distance The maximum distance from the localizer transmitter at a specified altitude, as verified by flight inspection, at which reliable course information is continuously received.
locator An L/MF NDB used as an aid to final approach. NOTE: A locator usually has an average radius of rated coverage of between 18.5 and 46.3 km (10 and 25 NM)
lock tabs A washer with tabs that are bent to prevent a nut from loosening.
locked-rotor current The amount of current flowing through the windings of an electric motor when the motor is prevented from turning. This is the highest current draw of the motor since once the motor starts rotating, counter electromotive force (CEMF) is generated in the windings that opposes voltage and, in turn, current flow through the windings.
lockout debooster A hydraulic component that decreases the pressure applied to aircraft brakes. Its lockout function shuts off all flow of fluid to the brake in the event of a rupture of the brake line below the debooster.
lockring A horseshoe-shaped ring that snaps into a groove on a shaft in order to hold the shaft in position.
lockstitch A modified seine knot used to lock the stitches when hand sewing aircraft fabric. The baseball stitch is used for sewing and it is locked with the seine knot every eight to ten stitches to prevent loosening.
locktab A mechanical lock used to prevent a nut from coming loose. Its appearance is similar to a washer but with notches cut from the periphery. When a locktab is placed under a nut on the shaft of a bolt, one or more of the external locking tabs are bent up against the flats of the nut to keep it from backing off and becoming loose.
lockwire A stainless steel, brass, or galvanized steel wire used to exert a pulling motion on the head of screws or bolts to prevent them from loosening. Also referred to as safetywire.
lockwiring A method of tying two or more screws or bolts together by twisting lockwire between them in such a way that tension is held on the head of each fastener in the direction of tightening.
lodestone A natural rock having magnetic characteristics.
log A journal containing a record of activities. Pilots keep a log of their flight time, and ground crews keep logs on the mechanical operating components of the aircraft, airframe, engine, propeller, and rotor to show the amount of time in service, and to record all the maintenance that has been completed on each device.
logarithm The exponent that indicates the power to which a number is raised to produce a given number. For 52 = 25, the logarithm of 25 to the base 5 is 2.
logarithmic or audio taper potentiometer A volume control potentiometer whose resistance decreases (volume increases) logarithmically as the control shaft is rotated in a clockwise direction.
logbooks, mechanical The journals containing records of the total operating time, repairs, alterations or inspections performed, and all AD notes complied with. A mechanical logbook should be kept for the airframe, for each engine, and for each propeller.
logic Valid reasoning through facts and actuality.
logic circuit A circuit designed to operate according to the fundamental laws of logic.
logic flowchart A flowchart that resembles a pert chart, which graphically shows the flow of information through a computer program, and the decisions that must be made at various points. Boxes show information, a diamond shaped figure is a logical decision point, and a parallelogram is a point where data is either put into or taken out of the program.
logic functions Statements of logic conditions used in digital computers. Usually associated with logic gates such as AND, OR, NOT, NAND, NOR, and exclusive OR. See also AND, OR, NOT, NAND, NOR, and exclusive OR.
logic gate See logic functions.
logic one In logic functions, the ON, YES, or TRUE choices that correspond to a binary 1.
logic state The state or condition (logic one or zero) of a digital electronic conductor.
logic zero In logic functions, the OFF, NO, or FALSE choices that correspond to a binary 0.
logical one A YES or a TRUE condition in digital electronics. It is produced by a closed switch or the presence of a voltage.
logical zero A NO or a FALSE condition in digital electronics. It is produced by an open switch or the absence of a voltage.
long duct turbofan A design that ducts the cold stream to the rear of the engine and to the atmosphere. The cold and hot streams mix on some engines.
long range navigation (LORAN) An electronic navigational system by which lines of position are determined by measuring the difference in the time of reception of synchronized pulse signals from fixed transmitters
long waves In meteorology, the wave-like structure in the contour and westerly wind patterns in the mid- and upper troposphere. Marked by long, (5,000 miles) slow moving wave troughs located frequently along the east coasts of both Asia and North America.
longeron The main longitudinal strength-carrying member of an aircraft fuselage or engine nacelle.
longitude Measurement east or west of the Prime Meridian in degrees, minutes, and seconds. The Prime Meridian is 0 degrees longitude and runs through Greenwich, England. Lines of longitude are also referred to as meridians.
longitudinal Of or pertaining to length.
longitudinal axis The axis of an airplane that extends through the fuselage from the nose to the tail, passing through the center of gravity. Longitudinal axis is also referred to as the roll axis, which is controlled by the movement of the ailerons.
longitudinal separation The longitudinal spacing of aircraft at the same altitude by a minimum distance expressed in units of time or miles.
longitudinal stability Stability about the lateral axis. A desirable characteristic of an airplane whereby it tends to return to its trimmed angle of attack after displacement.
longitudinal wave A wave in which the particles vibrate in the same direction as the wave as a whole is moving..
long-range communication system (LRCS) A system that uses satellite relay, data link, high frequency, or another approved communication system that extends beyond line of sight.
long-range navigation (LORAN) A radio navigation system that utilizes the master and slave stations transmitting timed pulses. The time difference in reception of pulses from several stations establishes a hyperbolic line of position, which can be identified on a loran chart. A fix in position is obtained by utilizing signals from two or more stations.
long-range navigation system (LRNS) An electronic navigation unit that is approved for use under instrument flight rules as a primary means of navigation, and has at least one source of navigational input, such as inertial navigation system, global positioning system, Omega/ very low frequency, or Loran C.
long-term memory The portion of the brain that stores information which has been determined to be of sufficient value to be retained. In order for it to be retained in long-term memory, it must have been processed or coded in the working memory.
long-wire antenna A radio energy antenna with a length greater than one-half the wavelength of the frequency of the energy being transmitted or received.
loom A tubular flexible insulating material used for wire protection.
loop 1. A control circuit consisting of a sensor, a controller, an actuator, a controller unit, and a follow-up or feedback to the sensor. Also, any closed electronic circuit including a feedback signal that is compared with the reference signal to maintain a desired condition. 2. A flight maneuver executed in such a manner that the airplane follows a closed 360 circle in a vertical plane.
loop antenna A highly directional sensitive antenna wound in the form of a coil used to find the direction between the loop and the station transmitting the received signal.
loopstick antenna An antenna with a large number of turns of wire wound on a powdered iron (ferrite) rod to increase the radio signal the coil receives. Loopsticks are particularly useful in small portable radio receivers.
LORAN An electronic navigational system by which hyperbolic lines of position are determined by measuring the difference in the time of reception of synchronized pulse signals from two fixed transmitters. Loran A operates in the 1750-1950 kHz frequency band. Loran C and D operate in the 100-110 kHz frequency band.
lost communications Loss of the ability to communicate by radio. Aircraft are sometimes referred to as NORDO (No Radio). Standard pilot procedures are specified in FAR 91. Radar controllers issue procedures for pilots to follow in the event of lost communications during a radar approach when weather reports indicate that an aircraft will likely encounter IFR weather conditions during the approach.
louver An opening with fixed or movable slanted slats. Also spelled louvre.
low In meteorology, an area of low barometric pressure, with its attendant system of winds. Also referred to as a cyclone.
low altitude airway structure The network of airways serving aircraft operations up to but not including 18,000 feet MSL.
low altitude airway structure / federal airways (USA) The network of airways serving aircraft operations up to but not including 18,000 feet MSL.
low altitude alert, check your altitude immediately A safety alert issued by ATC to aircraft under their control if ATC is aware the aircraft is at an altitude which, in the controller s judgment, places the aircraft in unsafe proximity to terrain/obstructions.
low altitude alert system An automated function of the TPX-42 that alerts the controller when a Mode C transponder-equipped aircraft on an IFR flight plan is below a predetermined minimum safe altitude. If requested by the pilot, LAAS monitoring is also available to VFR Mode C transponder-equipped aircraft.
low approach An approach over an airport or runway following an instrument approach or a VFR approach including the go-around maneuver where the pilot intentionally does not make contact with the runway.
low blower The lower speed setting of a two-speed internal supercharger.
low bypass turbofan An engine with a one-to-one bypass ratio. Approximately the same air mass flows across the fan as across the core engine.
low frequency (LF) The frequency band between 30 and 300 kHz.
low IFR (LIFR) Weather characterized by ceilings lower than 500 feet AGL and/or visibility less than one statute mile.
low pitch, high RPM setting The setting of a controllable-pitch propeller that allows the engine to produce its highest RPM with the propeller at its lowest pitch.
low pressure turbine The turbine rotor that drives the low pressure compressor in a dual or triple spool axial flow gas turbine engine.
lower turbulent zone The portion of the lee wave system, starting at ground level extending to just above the mountaintop, and marked by turbulence.
low-frequency radio waves Radio waves of frequency lower than the bottom of the commercial AM broadcast radio band.
low-lead 100-octane aviation gasoline (100 LL) Gasoline that contains a maximum of 2 ml. of tetraethyl lead per gallon. Normal 100-octane avgas is allowed to contain 4.6 ml. of tetraethyl lead per gallon.
low-level wind shear Wind shear below 2,000 feet AGL along the final approach path or along the takeoff and initial climb out path.
low-level wind shear alert system (LLWAS) A system installed at many large airports that continually monitors surface winds at remote sites on the airport. A computer evaluates the wind differences from the remote sites to determine if a wind shear problem exists.
low-pass filter A filter circuit designed to pass low-frequency signals and attenuate high-frequency signals.
low-pressure compressor The front section of a dual compressor gas turbine engine Also referred to as the N1 compressor or low-speed compressor.
low-pressure compressor gas turbine engine The front section of a dual compressor driven by the last stages of the turbine. Also referred to as the N1 compressor or low-speed compressor.
low-pressure oxygen system A gaseous oxygen system formerly used in military aircraft in which the oxygen is stored under pressures of approximately 450 PSI.
low-tension ignition system A magneto system used for reciprocating engine airplanes that fly at high altitudes. It consists of a rotating magnet, a cam, breaker points, a condenser, a coil with only the primary winding, and a carbon brush-type distributor. The primary current is directed through the distributor to a coil for each individual spark plug. These coils have a primary and a secondary winding that generate the high voltage at the spark plug.
low-tension magneto An ignition system used for reciprocating engine airplanes that fly at high altitudes. It consists of a rotating magnet, a cam, breaker points, condenser, a coil with only the primary winding, and a carbon brush-type distributor. The primary current is directed through the distributor to a coil for each individual spark plug. These coils have a primary and a secondary winding that generate the high voltage at the spark plug.
low-voltage ignition system A main ignition system used on turbine engines with a voltage output in the range of approximately 1,000 to 5,000 volts delivered to the igniter plug.
low-wing airplane An airplane having one main supporting aerodynamic surface flush with the bottom of the fuselage.
lubber line The reference line on a magnetic compass or directional gyro that represents the heading of a ship or aircraft.
lubricant A natural or artificial substance used to reduce friction, heat, and wear between moving parts. It also can be used to prevent corrosion on metallic surfaces.
lubricating The process of applying a lubricant.
Lucite A transparent, thermoplastic resin used for windshields and side windows of small aircraft. A trademark of the DuPont company.
lug A projection from a structural member used as an attachment point.
luminance The intensity of light emitted or scattered from a surface area in a given direction.
luminescence The emission of light from essentially nonthermal sources such as phosphorescence.
luminous paint A paint that glows in the dark. Used for marking aircraft instrument dials and pointers.
lye An alkaline solution consisting of potassium hydroxide or sodium hydroxide.