Aeronautical Terms beginning with L

Landing Distance Available (LDA)

ICAO defines LDA as the length of runway, which is declared available and suitable for the ground run of an aeroplane landing.


Lateral Navigation (LNAV)

Azimuth navigation, without positive vertical guidance. This type of navigation is associated with nonprecision approach procedures or en route.


Local Area Augmentation System (LAAS)

LAAS further increases the accuracy of GPS and improves signal integrity warnings.


Localizer Performance with Vertical Guidance (LPV)

LPV is one of the four lines of approach minimums found on an RNAV (GPS) approach chart. Lateral guidance accuracy is equivalent to a localizer. The HAT is published as a DA since it uses an electronic glide path that is not dependent on any ground equipment or barometric aiding and may be as low as 200 feet and 1/2 SM visibility depending on the airport terrain and infrastructure. WAAS avionics approved for LPV is required. Baro-VNAV is not authorized to fly the LPV line of minimums on a RNAV (GPS) procedure since it uses an internally generated descent path that is subject to cold temperature effects and incorrect altimeter settings.


Loss of Separation

An occurrence or operation that results in less than prescribed separation between aircraft, or between an aircraft and a vehicle, pedestrian, or object.


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.


Lead-Acid Battery

A commonly used secondary cell having lead as its negative plate and lead peroxide as its positive plate. Sulfuric acid and water serve as the electrolyte.


Leading Edge

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.


Licensed Empty Weight

The empty weight that consists of the airframe, engine(s), unusable fuel, and undrainable oil plus standard and optional equipment as specified in the equipment list. Some manufacturers used this term prior to GAMA standardization.


Lift

One of the four main forces acting on an aircraft. On a fixed-wing aircraft, an upward force created by the effect of airflow as it passes over and under the wing.


Lift Coefficient

A coefficient representing the lift of a given airfoil. Lift coefficient is obtained by dividing the lift by the free-stream dynamic pressure and the representative area under consideration.


Lift-Off

The act of becoming airborne as a result of the wings lifting the airplane off the ground, or the pilot rotating the nose up, increasing the angle of attack to start a climb.


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.


Limit Load Factor

Amount of stress, or load factor, that an aircraft can withstand before structural damage or failure occurs.


Load Factor

The ratio of the load supported by the airplane’s wings to the actual weight of the aircraft and its contents. Also referred to as G-loading.


Longitudinal Axis

An imaginary line through an aircraft from nose to tail, passing through its center of gravity. The longitudinal axis is also called the roll axis of the aircraft. Movement of the ailerons rotates an airplane about its longitudinal axis.


Longitudinal Stability (Pitching)

Stability about the lateral axis. A desirable characteristic of an airplane whereby it tends to return to its trimmed angle of attack after displacement.


Lag

The delay that occurs before an instrument needle attains a stable indication.


Land as soon as possible

ATC instruction to pilot. 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

ATC instruction to pilot. 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 immediately

ATC instruction to pilot. 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.


Lead radial

The radial at which the turn from the DME arc to the inbound course is started.


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.


Lift

A component of the total aerodynamic force on an airfoil and acts perpendicular to the relative wind.


Lines of flux

Invisible lines of magnetic force passing between the poles of a magnet.


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.


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. Some LDAs are equipped with a glide slope.


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).


Long range navigation (LORAN)

[Decommissioned in 2010] 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 to 1950 kHz frequency band. LORAN C and D operate in the 100 to 110 kHz frequency band.


Low or medium frequency

A frequency range between 190-535 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.


Lack of common experience

In communication, a difficulty which arises because words have different meanings for the source and the receiver of information due to their differing backgrounds.


Lead-off question

In the guided discussion method, a question used by an instructor to open up an area for discussion and get the discussion started.


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 significant period of time before once again increasing.


Learning style

Preferred way(s) by which people learn. Common learning styles include visual, auditory, and kinesthetic, or tactile (hands on). Learning skills can be loosely grouped into physical and cognitive styles.


Learning theory

A body of principles advocated by psychologists and educators to explain how people acquire skills, knowledge, and attitudes.


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.


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.


Link

On a website, an external web location that can be accessed by merely clicking on words identifying the new site. They are usually identified by a different color type, underlining, or a button (picture or icon) indicating access to a new site.


Long-term memory

The portion of the brain that stores information that has been determined to be of sufficient value to be retained. In order for it to be retained in longterm memory, it must have been processed or coded in the working memory.


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.


Large aircraft

Aircraft of more than 12,500 pounds, maximum certificated takeoff weight.


Light-sport aircraft

An aircraft, other than a helicopter or powered-lift that, since its original certification, has continued to meet the following:
(1) A maximum takeoff weight of not more than—
(i) 1,320 pounds (600 kilograms) for aircraft not intended for operation on water; or
(ii) 1,430 pounds (650 kilograms) for an aircraft intended for operation on water.
(2) A maximum airspeed in level flight with maximum continuous power (Vh) of not more than 120 knots CAS under standard atmospheric conditions at sea level.
(3) A maximum never-exceed speed (Vne) of not more than 120 knots CAS for a glider.
(4) A maximum stalling speed or minimum steady flight speed without the use of lift-enhancing devices (Vs1) of not more than 45 knots CAS at the aircraft’s maximum certificated takeoff weight and most critical center of gravity.
(5) A maximum seating capacity of no more than two persons, including the pilot.
(6) A single, reciprocating engine, if powered.
(7) A fixed or ground-adjustable propeller if a powered aircraft other than a powered glider.
(8) A fixed or feathering propeller system if a powered glider.
(9) A fixed-pitch, semi-rigid, teetering, two-blade rotor system, if a gyroplane.
(10) A non-pressurized cabin, if equipped with a cabin.
(11) Fixed landing gear, except for an aircraft intended for operation on water or a glider.
(12) Fixed or retractable landing gear, or a hull, for an aircraft intended for operation on water.
(13) Fixed or retractable landing gear for a glider.


Lighter-than-air aircraft

Aircraft that can rise and remain suspended by using contained gas weighing less than the air that is displaced by the gas.


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, inertia forces, or ground or water reactions.


Long-range communication system (LRCS)

A system that uses satellite relay, data link, high frequency, or another approved communication system which extends beyond line of sight.


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.


Landing Weight

The takeoff weight of an aircraft less the fuel burned and/or dumped en route.


Large Aircraft

An aircraft of more than 12,500 pounds, maximum certificated takeoff weight. As defined in 14 CFR part 1.


Lateral Balance

Balance around the roll, or longitudinal, axis.


Lateral Offset Moment

The moment, in lb-in, of a force that tends to rotate a helicopter about its longitudinal axis. The lateral offset moment is the product of the weight of the object and its distance from butt line zero. Lateral offset moments that tend to rotate the aircraft clockwise are positive, and those that tend to rotate it counterclockwise are negative.


Load Cell

A component in an electronic weighing system that is placed between the jack and the jack pad on the aircraft. The load cell contains strain gauges whose resistance changes with the weight on the cell.


Load Factor

The ratio of the maximum load an aircraft can sustain to the total weight of the aircraft. Normal category aircraft must have a load factor of a least 3.8, Utility category aircraft 4.4, and acrobatic category aircraft, 6.0.


Loading Graph

A graph of load weight and load moment indexes. Diagonal lines for each item relate the weight to the moment index without having to use mathematics.


Loading Schedule

A method for calculating and documenting aircraft weight and balance prior to taxiing, to ensure the aircraft will remain within all required weight and balance limitations throughout the flight.


Longitudinal Axis

An imaginary line through an aircraft from nose to tail, passing through its center of gravity.


Longitudinal Balance

Balance around the pitch, or lateral, axis.


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.


Lapse rate

The rate of decrease of an atmospheric variable with height; commonly refers to decrease of temperature with height.


Latent heat

The amount of heat absorbed (converted to kinetic energy) during the processes of change of liquid water to water vapor, ice to water vapor, or ice to liquid water; or the amount released during the reverse processes. Four basic classifications are: latent heat of condensation, latent heat of fusion, latent heat of sublimation, and latent heat of vaporization.


Latent heat of condensation

Heat released during change of water vapor to water.


Latent heat of fusion

Heat released during change of water to ice or the amount absorbed in change of ice to water.


Latent heat of sublimation

Heat released during change of water vapor to ice or the amount absorbed in the change of ice to water vapor.


Latent heat of vaporization

Heat absorbed in the change of water to water vapor; the negative of latent heat of condensation.


Layer

In reference to sky cover, clouds or other obscuring phenomena whose bases are approximately at the same level. The layer may be continuous or composed of detached elements. The term “layer” does not imply that a clear space exists between the layers or that the clouds or obscuring phenomena composing them are of the same type.


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 called mountain wave or standing wave.


Lenticular cloud (or lenticularis)

A species of cloud whose elements have the form of more or less isolated, generally smooth lenses or almonds. These clouds appear most often in formations of orographic origin, the result of lee waves, in which case they remain nearly stationary with respect to the terrain (standing cloud), but they also occur in regions without marked orography.


Level of free convection (abbreviated LFC)

The level at which a parcel of air lifted dry-adiabatically until saturated and moist-adiabatically thereafter would become warmer than its surroundings in a conditionally unstable atmosphere.


Lifting condensation level (abbreviated LCL)

The level at which a parcel of unsaturated air lifted dry-adiabatically would become saturated. Compare level of free convection and convective condensation level.


Lightning

Generally, any and all forms of visible electrical discharge produced by a thunderstorm.


Lithometeor

The general term for dry particles suspended in the atmosphere such as dust, haze, smoke, and sand.


Low

An area of low barometric pressure, with its attendant system of winds. Also called a barometric depression or cyclone.


Lag

The delay that occurs before an instrument needle attains a stable indication.


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 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 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.


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. Some manufacturers used this term prior to GAMA standardization.


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.


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.


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. Some LDAs are equipped with a glideslope.


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).


Longitude

Measurement east or west of the Prime Meridian in degrees, minutes, and seconds. The Prime Meridian is 0° 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.


Long range navigation (LORAN)

[Decommissioned in 2010] 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.


LORAN-C

[Decommissioned in 2010] A radio navigation system that utilizes 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.


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.


Lubberline

The reference line used in a magnetic compass or heading indicator.


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