4/20/23 

Pilot/Controller Glossary 

B 

B4UFLY

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 A free downloadable application, which allows operators to check airspace and local advisories 

before flying. 

BACK-TAXI

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 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. 
BASE LEG

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(See TRAFFIC PATTERN.) 

BEACON

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(See AERONAUTICAL BEACON.) 
(See AIRPORT ROTATING BEACON.) 
(See AIRWAY BEACON.) 
(See MARKER BEACON.) 
(See NONDIRECTIONAL BEACON.) 
(See RADAR.) 

BEARING

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 The horizontal direction to or from any point, usually measured clockwise from true north, 

magnetic north, or some other reference point through 360 degrees. 

(See NONDIRECTIONAL BEACON.) 

BELOW MINIMUMS

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Weather conditions below the minimums prescribed by regulation for the particular 

action involved; e.g., landing minimums, takeoff minimums. 
BEYOND VISUAL LINE OF SIGHT (BVLOS)

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 The operation of a UAS beyond the visual capability of the 

flight crew members (i.e., remote pilot in command [RPIC], the person manipulating the controls, and visual 

observer [VO]), if used to see the aircraft with vision unaided by any device other than corrective lenses, 

spectacles, and contact lenses. 
BLAST FENCE

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 A barrier that is used to divert or dissipate jet or propeller blast. 

BLAST PAD

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 A surface adjacent to the ends of a runway provided to reduce the erosive effect of jet blast and 

propeller wash. 
BLIND SPEED

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 The rate of departure or closing of a target relative to the radar antenna at which cancellation 

of the primary radar target by moving target indicator (MTI) circuits in the radar equipment causes a reduction 

or complete loss of signal. 

(See ICAO term BLIND VELOCITY.) 

BLIND SPOT

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 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

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(See TRANSMITTING IN THE BLIND.) 

BLIND VELOCITY [ICAO]

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 The radial velocity of a moving target such that the target is not seen on primary 

radars fitted with certain forms of fixed echo suppression. 
BLIND ZONE

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(See BLIND SPOT.) 

BLOCKED

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Phraseology used to indicate that a radio transmission has been distorted or interrupted due to 

multiple simultaneous radio transmissions. 
BOTTOM ALTITUDE– In reference to published altitude restrictions on a STAR or STAR runway transition, 

the lowest altitude authorized. 

PCG B

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