A Alpha

abbreviated briefing - An updated weather briefing for pilots who need only a little additional weather data information to give them an accurate weather picture for their final flight planning.

absolute altitude - Actual height above the surface of the Earth, either land or water.

AC (Advisory Circular) - Statements that are issued by the National Weather Service for probable weather situations of inconvenience that do not carry the danger of warning criteria, but, if not observed, could lead to hazardous situations.

accelerate - To speed up. For example, when an airplane takes off it accelerates down the runway until enough lift is created by the air flowing over the wings so that it can fly.

accelerometer - (1) A device for sensing or measuring acceleration and converting it to an electric signal. (2) An inertial device for measuring acceleration, usually in three orthogonal axes (lateral X, longitudinal Y, and vertical Z); accelerometers usually consist of a mass, spring, and damper; accelerometers are usually included in inertial sensors, such as AHRS and INS.

Active FAST (aFAST) - Designed by NASA and the FAA, this is new software tool designed to help air traffic controllers manage aircraft more efficiently and reduce delays by up to 20 percent. The main function of FAST is to provide advisories to help controllers manage arriving aircraft and achieve an accurately spaced flow of traffic on final approach. FAST can accurately predict arrival times based on specific knowledge of the type of aircraft, weather conditions and airport landing procedure. FAST also advises the air traffic controllers how to accurately meet the schedule and assure the required aircraft separations for safety purposes. Active FAST provides advisories on speed and headings to the controller to assist in spacing the aircraft to meet the FAST-predicted arrival times.

ADF (Automatic Direction Finder) - Radio compass which gives a relative bearing to the non-directional radio beacon to which it is tuned.

ADS-B (Automatic Dependent Surveillance-Broadcast) - Technology currently being developed by NASA to be used along with the autonomous Airborne Information for Lateral Spacing (AILS) technology. This on-board equipment would automatically broadcast data to transceivers on the ground. The data would consist of airspeed, altitude and include whether the aircraft is turning, climbing or descending. The data would then appear on the controller's computer screen and also on a display screen within the cockpit. The cockpit display will allow the pilot to track other aircraft in the vicinity.

advection fog - A type of fog formed when warm, moist air moves
horizontally over a cold surface and the air is consequently cooled to below its dew point; this is found especially along a coastline where the temperature of land and the temperature of water markedly differ.

aerobatics - Flight that commonly involves barrel rolls, spins, and other high-performance maneuvers.

aerodynamics - (1) A field of fluid dynamics that studies how gases, including air, flow and how forces act upon objects moving through air. (2) A general term for the properties and performance of an airfoil or other body with respect to the forces acting upon it as it moves through air and other gaseous fluids.

aeronautical chart - A map used in air navigation containing all or part of the following: Topographical features, hazards and obstructions, navigation aids, navigation routes, designated airspace, and airports. Aeronautical charts are regularly revised to provide current information.

aeronautics - The study of flight and the science of designing, construction and operation of an aircraft.

aerosol - the suspension of very fine particles of a solid or droplets of a liquid in a gaseous medium. Fog, smoke, and volcanic dust are naturally occurring examples of aerosols.

affirmative - Aviation term for "yes"; to declare or confirm that something is true.

AFSS (Automated Flight Service Stations) - These are a network of 61 facilities across the United States operated by the United States Department of Transportation and the FAA. These stations are a part of the FAA air traffic system and are staffed by uniquely trained air traffic control specialists. The primary role of an AFSS is to provide weather briefing and flight planning services to pilots. AFSSs also coordinate VFR search and rescue services, provide orientation service to lost aircraft, maintain continuous weather broadcasts on selected Navigational Aids (NAVAIDs), and issue and cancel Notices To Airmen (NOTAMs). The general aviation community makes up the lion's share of traffic at these facilities; however, military and commercial pilots are also frequent customers.

AGL (Above Ground Level) - Height, usually in feet, above the surface of the earth.

ailerons - Control surfaces on the trailing edge of each wing that are used to make the aircraft roll. When flying straight and level, moving the control stick to the right will raise the aileron on the right wing and lower the aileron on the left wing. This will cause the aircraft to roll to the right.

AILS (Airborne Information for Lateral Spacing) - Technology developed by NASA and industry. This procedures-based concept uses existing or near-term flight-deck technology. AILS allows airplanes to safely land more closely together than is currently allowed in instrument conditions. An AILS display in the cockpits shows each pilot the nearby traffic.

air density - The density of the air in terms of mass per unit volume.

air mass - An extensive body of air in a horizontal plane having fairly uniform properties of temperature and moisture.

air pressure - (1) The force created by air pushing on a surface. (2) The weight of the atmosphere over a particular point, also called barometric pressure. Average air exerts approximately 14.7 pounds (6.8 kg) of force on every square inch (or 101,325 newtons on every square meter) at sea level.

air traffic controller - A person at an air traffic control tower or radar approach control facility who coordinates the safe, orderly and expeditious flow of air traffic within designated airspace.

air traffic management system - see TMS.

airborne - Supported only by aerodynamic forces; aloft or flying.

aircraft - A machine used for flying. Airplanes, helicopters, airships and jets are all aircraft.

airflow - The motion of air molecules as they flow around an object, such as a wing.

airfoil - An object with a special shape that is designed to produce lift efficiently when the object is moved through the air. For example, the cross-section of a wing is an airfoil.

airframe - The structure of an aircraft, as opposed to its engine and accessories, including the fuselage, wings, empennage, landing gear (minus tires), and engine mounts.

airliner - A passenger-carrying aircraft operated by an airline.

AIRMET (AIRman's METeorological information) - Inflight weather advisory concerning moderate icing, moderate turbulence, sustained winds of 30 knots or more at the surface and wide spread areas of ceilings of less than 1000 feet and/or visibility less than 3 miles.

airplane - An aircraft that uses the force of air on its wings (called lift) to fly.

airport - An area of land or water that is used or intended to be used for the landing and takeoff of aircraft, and includes its building and facilities if any.

airport capacity - The maximum number of aircraft operations that can be safely accomplished at an airport.

airport facility directory - A reference for determining detail data not found on aeronautical charts for a specific airport. Seven geographic areas of the United States, Puerto Rico and the Virgin Islands are each covered by a directory and updated every eight weeks.

airport identifier - A specific combination of four letters or a combination of letters and numbers, assigned by the FAA, to each airport as a recognition sign.

airspace - Space in the air above the surface of the earth or a particular portion of such space, usually defined by the boundaries of an area on the surface projected upward.

airspeed - The speed of an aircraft relative to its surrounding air mass. The unqualified term "airspeed" means one of the following: (1) Indicated airspeed - The speed shown on the aircraft airspeed indicator. (2) True airspeed - The airspeed of an aircraft relative to undisturbed air. Used primarily in flight planning and en route portion of flight. When used in pilot/controller communications, it is referred to as "true airspeed" and not shortened to "airspeed".

airstrip - A synonym for "runway".

airway - A path or a continuous designated space of air through which aircraft are directed to fly by air traffic control. Called a jetway at altitudes above 18,000 feet.

airworthy - The state of being capable of flight, usually referring to an airplane's mechanical condition.

Alpha - Designator for the letter "A" in the International Phonetic Alphabet.

altimeter - The instrument that indicates flight altitude (in feet), by sensing pressure changes.

altimetry - The science or practice of measuring altitudes, as with an altimeter.

altitude - Height expressed in units of distance above a reference plane, usually above mean sea level or above ground.

altocumulus - White or gray layers or patches of cloud, often with a waved appearance; cloud elements appear as rounded masses or rolls; composed liquid water droplets which may be supercooled; may contain ice crystals at subfreezing temperatures.

altostratus - An extended cloud formation of bluish or gray sheets or layers.

analyze - To take something apart so it can be examined and studied.

aneroid barometer - A barometer which operates on the principle of having changing atmospheric pressure bend a metallic surface which, in turn, moves a pointer across a scale graduated in units of pressure.

angle of attack - The angle of a wing to the oncoming airflow. A pilot pulls back on the control stick to raise the elevator. This causes the aircraft to pitch which increases the angle of attack.

antenna - An arrangement of wire, metal rods, etc. used in sending or receiving electromagnetic waves.

approach - The flight phase during which an aircraft has its landing gear extended and is descending and slowing its speed for landing.

approach controller - The air traffic control personnel responsible for all movement of incoming aircraft before arriving at the final approach fix.

arrival traffic - Incoming aircraft to an airport

ARTCC (Air Route Traffic Control Center) - A facility established to provide air traffic control service to aircraft operating on IFR flight plans within controlled airspace, principally during the en route phase of flight.

ARTCC controller - The air traffic control personnel responsible for all movement of aircraft along the en route portion of the flight between the departure controller and the approach controller.

ascend - To move upward in a flight vehicle, often directly upward in a near-vertical trajectory, as opposed to the more gradual trajectory of a climb.

ASDE (Automated Surface Detection Equipment) - A tool used by local controllers at an airport that displays all ground traffic movement even during inclement weather.

associate controller - A person who assists the radar controller.

ATA (Air Transportation Association) - Founded in 1936, it was the first, and today remains, the only trade organization for the principal U.S. airlines. The purpose of the ATA is to support and assist its members by promoting the air transport industry and the safety, cost effectiveness, and technological advancement of its operations; advocating common industry positions before state and local governments; conducting designated industry-wide programs; and assuring governmental and public understanding of all aspects of air transport.

ATC (Air Traffic Control) - A service operated by appropriate authority to monitor and regulate all air traffic departing and arriving in the United States, as well as all ground traffic within immediate airport boundaries.

ATCSCC ( Air Traffic Control System Command Center) - Operated by the FAA, the role of ATCSCC is to manage the flow of air traffic within the continental United States. The ATCSCC has been operational since 1994 and is located in one of the largest and most sophisticated facilities of its kind.

ATCT (Airport Traffic Control Tower) - A central operations facility in the terminal air traffic control system, consisting of a tower cab structure, including an associated IFR room if radar equipped, using air/ground communications and/or radar, visual signaling and other devices, to provide safe and expeditious movement of terminal air traffic. Also known as "Local Control" or the control tower at an airport.

ATIS (Automatic Terminal Information Service) - The continuous broadcast of recorded noncontrol information (such as weather and airport operations) in selected terminal areas. Its purpose is to improve controller effectiveness and to relieve frequency congestion by automating the repetitive transmission of essential but routine information.

atmosphere - The gaseous or air portion of the physical environment that encircles a planet. In the case of the Earth, it is held more or less near the surface by the earth's gravitational attraction. The divisions of the atmosphere include the troposphere, the stratosphere, the mesosphere, the ionosphere, and the exosphere.

atmospheric pressure - The amount of force exerted over a surface area, caused by the weight of air molecules above it. As elevation increases, fewer air molecules are present. Therefore, atmospheric pressure always decreases with increasing height. A column of air, 1 square inch in cross section, measured from sea level to the top of the atmosphere would weigh approximately 14.7 lb/in2. The standard value for atmospheric pressure at sea level is: 29.92 inches or 760 mm of mercury 1013.25 millibars (mb) or 101,325 pascals (pa).

attitude - The position of an aircraft as determined by the relationship between its axes and some reference object such as the horizon.

automated system - Performance of an operation by a mechanical or computerized method.

autonomously - self-governing or capable of being done without supervision or permission from superiors.

aviation - The operation of heavier-than-air aircraft also considered to be the design, development and manufacture of aircraft. There are three types of aviation: general, commercial and military.

Aviation Operation System - NASA research and technology on ground, satellite and aerospace vehicle systems and human operations to improve operational safety, efficiency and the capacity of aerospace vehicles operating in the air transportation system.

Aviation Systems Capacity Program - A NASA program whose goal is to provide enabling technologies to safely triple the nation's aviation system capacity, in all weather conditions, by the year 2007. Implementation of the program will be closely coordinated with the Federal Aviation Administration (FAA) and the aerospace industry.

avionics - a general term for the development and production of electrical and electronic equipment for use in aircraft, spacecraft, and missiles.

AVOSS (Aircraft VOrtex Spacing System) - Designed by NASA researchers, this system predicts aircraft wake turbulence on final approach, so airliners can be spaced more safely and efficiently. AVOSS determines how winds and other atmospheric conditions affect the wake vortex patterns of different types of aircraft. The system uses laser radar, or lidar technology, to confirm the accuracy of those forecasts. This information is processed by computers, which can then provide safe spacing criteria automatically.

axis - An imaginary line, through the center of gravity, around which an aircraft rotates. For example, an aircraft rolls around its longitudinal axis which is an imaginary line that runs through the center of the aircraft, from the nose to the tail.