Aeronautical Terms beginning with B
B-RNAV
European Basic Rnav
Back course (BC)
The reciprocal of the localizer course for an ILS. When flying a back-course approach, an aircraft approaches the instrument runway from the end at which the localizer antennas are installed.
Back Side Of The Power Curve
Flight regime in which flight at a higher airspeed requires a lower power setting and a lower airspeed requires a higher power setting in order to maintain altitude.
Back-Taxi
A term used by air traffic controllers to taxi an aircraft on the runway opposite to the traffic flow. The aircraft may be instructed to back-taxi to the beginning of the runway or at some point before reaching the runway end for the purpose of departure or to exit the runway.
Backing
Shifting of the wind in a counterclockwise direction with respect to either space or time; opposite of veering. Commonly used by meteorologists to refer to a cyclonic shift (counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere).
Backscatter
Pertaining to radar, the energy reflected or scattered by a target; an echo.
Balance tab
An auxiliary control mounted on a primary control surface, which automatically moves in the direction opposite the primary control to provide an aerodynamic assist in the movement of the control. Sometimes referred to as a servo tab.
Balanced Laterally
Balanced in such a way that the wings tend to remain level.
Balked Landing
A go-around.
Ballast
A weight installed or carried in an aircraft to move the center of gravity to a location within its allowable limits.
Balloon
The result of a too aggressive flare during landing causing the aircraft to climb.
Balloon
A lighter-than-air aircraft that is not engine driven, and that sustains flight through the use of either gas buoyancy or an airborne heater.
Banner cloud (also called cloud banner)
A banner-like cloud streaming off from a mountain peak.
Baro-aiding
A method of augmenting the GPS integrity solution by using a non-satellite input source. To ensure that baro-aiding is available, the current altimeter setting must be entered as described in the operating manual.
Baro-aiding
A method of augmenting the GPS integrity solution by using a nonsatellite input source. To ensure that baro-aiding is available, the current altimeter setting must be entered as described in the operating manual.
Baro-VNAV
Barometric Vertical Navigation
Barograph
A continuous-recording barometer.
Barometer
An instrument for measuring the pressure of the atmosphere; the two principle types are mercurial and aneroid.
Barometric altimeter
Also called a pressure altimeter. An aneroid barometer with a scale graduated in altitude instead of pressure using standard atmospheric pressure-height relationships; shows indicated altitude (not necessarily true altitude); may be set to measure altitude (indicated) from any arbitrarily chosen level.
Barometric pressure
Same as atmospheric pressure—the pressure exerted by the atmosphere as a consequence of gravitational attraction exerted upon the “column” of air lying directly above the point in question.
Barometric scale
A scale on the dial of an altimeter to which the pilot sets the barometric pressure level from which the altitude shown by the pointers is measured.
Barometric scale
A scale on the dial of an altimeter to which the pilot sets the barometric pressure level from which the altitude shown by the pointers is measured.
Barometric tendency
The change of barometric pressure within a specified period of time. In aviation weather observation, routinely determined periodically, usually for a 3-hour period.
Base Leg
A flight path at right angles to the landing runway off its approach end. The base leg normally extends from the downwind leg to the intersection of the extended runway centerline.
Basic Empty Weight
(GAMA) Standard empty weight plus optional equipment.
Basic Empty Weight (GAMA)
Basic empty weight includes the standard empty weight plus optional and special equipment that has been installed.
Basic empty weight (GAMA)
Basic empty weight includes the standard empty weight plus optional and special equipment that has been installed.
Basic need
A perception factor that describes a person’s ability to maintain and enhance the organized self.
Basic Operating Index
The moment of the airplane at its basic operating weight divided by the appropriate reduction factor.
Basic Operating Weight (BOW)
The empty weight of the aircraft plus the weight of the required crew, their baggage and other standard item such as meals and potable water.
Basic Radar Service
These services are provided for VFR aircraft by all commissioned terminal radar facilities. Basic radar service includes safety alerts, traffic advisories, limited radar vectoring when requested by the pilot, and sequencing at locations where procedures have been established for this purpose and/or when covered by a letter of agreement. The purpose of this service is to adjust the flow of arriving IFR and VFR aircraft into the traffic pattern in a safe and orderly manner and to provide traffic advisories to departing VFR aircraft.
BC
Back Course.
Beacon
Aeronautical Beacon.
Beam resolution
The ability of radar to distinguish between targets at approximately the same range but at different azimuths.
Bearing
The horizontal direction to or from any point, usually measured clockwise from true north, magnetic north, or some other reference point through 360 degrees.
Beaufort scale
A scale of wind speeds.
BECMG
Becoming group
Behaviorism
Theory of learning that stresses the importance of having a particular form of behavior reinforced by someone other than the student to shape or control what is learned.
Below Minimums
Weather conditions below the minimums prescribed by regulation for the particular action involved; e.g., landing minimums, takeoff minimums.
Bernoulli’s Principle
A principle that explains how the pressure of a moving fluid varies with its speed of motion. An increase in the speed of movement causes a decrease in the fluid’s pressure.
Best Angle Of Climb (Vx)
The speed at which the aircraft will produce the most gain in altitude in a given distance.
Best Glide
The airspeed in which the aircraft glides the furthest for the least altitude lost when in non-powered flight.
Best Rate Of Climb (Vy)
The speed at which the aircraft will produce the most gain in altitude in the least amount of time.
Bilge Area
The lowest part of an aircraft structure in which water and contaminants collect.
Biplanes
Airplanes with two sets of wings.
Black blizzard
Same as dust storm—an unusual, frequently severe weather condition characterized by strong winds and dust-filled air over an extensive area.
Blade Face
The flat portion of a propeller blade, resembling the bottom portion of an airfoil.
Blast Fence
A barrier that is used to divert or dissipate jet or propeller blast.
Blast Pad
A surface adjacent to the ends of a runway provided to reduce the erosive effect of jet blast and propeller wash.
Bleed Air
Compressed air tapped from the compressor stages of a turbine engine by use of ducts and tubing. Bleed air can be used for deice, anti-ice, cabin pressurization, heating, and cooling systems.
Bleed Valve
In a turbine engine, a flapper valve, a popoff valve, or a bleed band designed to bleed off a portion of the compressor air to the atmosphere. Used to maintain blade angle of attack and provide stall-free engine acceleration and deceleration.
Blind Spot
An area from which radio transmissions and/or radar echoes cannot be received. The term is also used to describe portions of the airport not visible from the control tower.
Blind Transmission
A transmission from one station to other stations in circumstances where two-way communication cannot be established, but where it is believed that the called stations may be able to receive the transmission.
Blind Zone
Blind Spot. An area from which radio transmissions and/or radar echoes cannot be received. The term is also used to describe portions of the airport not visible from the control tower.
Blizzard
A severe weather condition characterized by low temperatures and strong winds bearing a great amount of snow, either falling or picked up from the ground.
Block altitude
A block of altitudes assigned by ATC to allow altitude deviations; for example, Maintain block altitude 9 to 11 thousand.
Blocked
Phraseology used to indicate that a radio transmission has been distorted or interrupted due to multiple simultaneous radio transmissions.
Blowing dust
A type of lithometeor composed of dust particles picked up locally from the surface and blown about in clouds or sheets.
Blowing sand
A type of lithometeor composed of sand picked up locally from the surface and blown about in clouds or sheets.
Blowing snow
A type of hydrometeor composed of snow picked up from the surface by the wind and carried to a height of 6 feet or more.
Blowing spray
A type of hydrometeor composed of water particles picked up by the wind from the surface of a large body of water.
Boost Pump
An electrically driven fuel pump, usually of the centrifugal type, located in one of the fuel tanks. It is used to provide fuel to the engine for starting and providing fuel pressure in the event of failure of the engine driven pump. It also pressurizes the fuel lines to prevent vapor lock.
Boundary Lights
Lights defining the perimeter of an airport or landing area.
Brake horsepower
The power delivered at the propeller shaft (main drive or main output) of an aircraft engine.
Braking Action (Good, Fair, Poor, Or Nil)
A report of conditions on the airport movement area providing a pilot with a degree/quality of braking that he/she might expect. Braking action is reported in terms of good, fair, poor, or nil.
Braking Action Advisories
When tower controllers have received runway braking action reports which include the terms “fair,” “poor,” or “nil,” or whenever weather conditions are conducive to deteriorating or rapidly changing runway braking conditions, the tower will include on the ATIS broadcast the statement, “Braking action advisories are in effect” on the ATIS broadcast. During the time braking action advisories are in effect, ATC will issue the latest braking action report for the runway in use to each arriving and departing aircraft. Pilots should be prepared for deteriorating braking conditions and should request current runway condition information if not volunteered by controllers. Pilots should also be prepared to provide a descriptive runway condition report to controllers after landing.
Branching
A programming technique which allows users of interactive video, multimedia courseware, or online training to choose from several courses of action in moving from one sequence to another.
Breakout
A technique to direct aircraft out of the approach stream. In the context of close parallel operations, a breakout is used to direct threatened aircraft away from a deviating aircraft.
Briefing
An oral presentation where the speaker presents a concise array of facts without inclusion of extensive supporting material.
Bright band
In radar meteorology, a narrow, intense echo on the range-height indicator scope resulting from water-covered ice particles of high reflectivity at the melting level.
BRITE
Bright Radar Indicator Tower Equipment
Broadcast
Transmission of information for which an acknowledgement is not expected.
Buffeting
The beating of an aerodynamic structure or surface by unsteady flow, gusts, etc.; the irregular shaking or oscillation of a vehicle component owing to turbulent air or separated flow.
Building block concept
Concept of learning that new knowledge and skills are best based on a solid foundation of previous experience and/or old learning. As knowledge and skills increase, the base expands, supporting further learning.
Bus Bar
An electrical power distribution point to which several circuits may be connected. It is often a solid metal strip having a number of terminals installed on it.
Bus Tie
A switch that connects two or more bus bars. It is usually used when one generator fails and power is lost to its bus. By closing the switch, the operating generator powers both busses.
Butt (or buttock) Line Zero
A line through the symmetrical center of an aircraft from nose to tail. It serves as the datum for measuring the arms used to determine the lateral CG. Lateral moments that cause the aircraft to rotate clockwise are positive (+) , and those that cause it to rotate counterclockwise are negative (-).
Buys Ballot’s law
If an observer in the Northern Hemisphere stands with his back to the wind, lower pressure is to his left.
Bypass Air
The part of a turbofan’s induction air that bypasses the engine core.
Bypass Ratio
The ratio of the mass airflow in pounds per second through the fan section of a turbofan engine to the mass airflow that passes through the gas generator portion of the engine. Or, the ratio between fan mass airflow (lb/sec.) and core engine mass airflow (lb/sec.).
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