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PHAK Glossary — L

35 terms, every entry under this letter, no curation. Definitions reproduced verbatim from the Pilot's Handbook of Aeronautical Knowledge glossary, FAA-H-8083-25C (July 2023).

Download the PDF — the same 35 terms as a two-column printable sheet.

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LAAS

See local area augmentation system.

The FAA’s definition of 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.

In the glossary: l

Lag

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

In the glossary: l

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.

In the glossary: l

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.

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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.

In the glossary: l

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.

In the glossary: l

Lateral axis

An imaginary line passing through the center of gravity of an airplane and extending across the airplane from wingtip to wingtip.

In the glossary: l

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.

In the glossary: l

Latitude

Measurement north or south of the equator in degrees, minutes, and seconds. Lines of latitude are also referred to as parallels.

In the glossary: l

LDA

See localizer-type directional aid.

The FAA’s definition of 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.

In the glossary: l

Lead radial

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

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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.

In the glossary: l

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.

In the glossary: l

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.

In the glossary: l

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.

In the glossary: l

Lift

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

In the glossary: l

Limit load factor

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

In the glossary: l

Lines of flux

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

In the glossary: l

L/MF

See low or medium frequency.

The FAA’s definition of 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.

In the glossary: l

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.

In the glossary: l

Loadmeter

A type of ammeter installed between the generator output and the main bus in an aircraft electrical system.

In the glossary: l

LOC

See localizer.

The FAA’s definition of Localizer (LOC)

The portion of an ILS that gives left/right guidance information down the centerline of the instrument runway for final approach.

In the glossary: l

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.

In the glossary: l

Localizer (LOC)

The portion of an ILS that gives left/right guidance information down the centerline of the instrument runway for final approach.

In the glossary: l

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.

In the glossary: l

Locator middle marker (LMM)

Nondirectional radio beacon (NDB) compass locator, collocated with a middle marker (MM).

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Locator outer marker (LOM)

NDB compass locator, collocated with an outer marker (OM).

In the glossary: l

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.

In the glossary: l

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.

In the glossary: l

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.

In the glossary: l

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.

In the glossary: l

Lubber line

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

In the glossary: l

Source. Definitions: Pilot's Handbook of Aeronautical Knowledge glossary, FAA-H-8083-25C (July 2023), reproduced verbatim from https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak. A United States Government work. Selection: none — every entry under this letter, no curation. Check the current publication before you rely on any of it.