the Aviation Dictionary

airmass - An extensive body of air having fairly
uniform properties of temperature and moisture within
a horizontal plane.
airmass thunderstorm - A "nonsevere" or "ordinary"
thunderstorm produced by local airmass instability.
May produce small hail, wind gusts less than 50 knots.
See also severe thunderstorm.
airmass wind shear -Wind shear that develops near the
ground at night under fair weather conditions in the
absence of strong fronts and/or strong surface pressure
gradients.
AIRMET - An advisory pertinent to aircraft with
limited capabilities, containing information on:
1. moderate icing,
2. moderate turbulence,
3. sustained surface winds of 30 knots or more,
4. ceilings less than 1,000 feet and/or visibility less
than 3 miles affecting 50 percent of the area at one
time, and
5. extensive mountain obscuration.
Issued only to amend the area forecast concerning
weather phenomena which are of operational interest to
all aircraft and potentially hazardous to aircraft having
limited capability because of lack of equipment,
instrumentation, or pilot qualifications. AIRMETs
concern weather of less severity than that covered by
SIGMETs or Convective SIGMETs.
air-oil separator - A device in the vent portion of the
lubrication system of a gas turbine engine that
separates any oil from the air before the air is vented
overboard.
airplane - An engine-driven, heavier-than-air, fixedwing
aircraft that is supported in flight by the dynamic
reaction of the air against its wings.
airplane checkouts - An instructional program
designed to familiarize and qualify a pilot to fly an
aircraft not previously familiar.
airport - An area of land or water, including any
associated buildings and facilities, used or intended to
be used for the landing and takeoff of aircraft.
airport advisory area - The area within 10 statute
miles of an airport where a flight service station is
located, but where there is no control tower in
operation.
airmass . airport lighting
airport elevation - The highest point of an airport's
usable runways measured in feet from mean sea level.
airport information aid - See airport information desk.
airport information desk - An airport unmanned
facility designed for pilot self-service briefing, flight
planning, and filing of flight plans.
airport lighting - Various lighting aids that can be
installed at an airport. Types of airport lighting include:
a. Approach Light System (ALS) - An airport
lighting facility which provides visual guidance to
landing aircraft by radiating light beams in a
directional pattern by which the pilot aligns the aircraft
with the extended centerline of the runway on his final
approach for landing. Condenser Discharge Sequential
Flashing LightsjSequenced Flashing Lights may be
installed in conjunction with the ALS at some airports.
Types of Approach Light Systems are:
1) ALSF- I. -Approach Light System with Sequenced
Flashing Lights in ILS Cat-I configuration.
2) ALSF-2. -Approach Light System with Sequenced
Flashing Lights in ILS Cat-I1 configuration. The
ALSF-2 may operate as an SSALR when weather
conditions permit.
3) SSALF - Simplified Short Approach Light System
with Sequenced Flashing Lights.
4) SSALR - Simplified Short Approach Light System
with Runway Alignment Indicator Lights.
5) ALSF - Medium Intensity Approach Light System
with Sequenced Flashing Lights.
6) MALSR - Medium Intensity Approach Light
System with Runway Alignment Indicator Lights.
7) LDIN - Lead-in-light system: Consists of one or
more series of flashing lights installed at or near
ground level that provides positive visual guidance
along an approach path, either curving or straight,
where special problems exist with hazardous terrain,
obstructions, or noise abatement procedures.
8) RAIL - Runway Alignment lndicator Lights
(Sequenced Flashing Lights which are installed only in
combination with other light systems).
9) ODALS - Ornni-directional Approach Lighting
System consists of seven omni-directional flashing
lights located in the approach area of a nonprecision
runway. Five lights are located on the runway
centerline extended with the first light located 300 feet
from the threshold and extending at equal intervals up
to 1,500 feet from the threshold. The other two lights
are located, one on each side of the runway threshold,
at a lateral distance of 40 feet from the runway edge, or
75 feet from the runway edge when installed on a
runway equipped with a VASI.
airport arrival rate (AAR) - A dynamic input
parameter specifying the number of arriving aircraft
which an airport or airspace can accept from the
ARTCC per hour. The AAR is used to calculate the
desired interval between successive arrival aircraft. b. Runway LightsRunway Edge Lights - Lights
having a prescribed angle of emission used to define
airport departure rate (ADR)- A dynamic parameter the lateral limits of a runway. Runway lights are
specifying the number of aircraft which can depart an uniformly spaced at intervals of approximately 200
airport and the airspace can accept per hour.
feet, and the intensity may be controlled or preset.
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