12/10/155/26/16 Pilot/Controller Glossary B BACK-TAXI− A term used by air traffic controllers BLIND VELOCITY [ICAO]− The radial velocity of to taxi an aircraft on the runway opposite to the traffic a moving target such that the target is not seen on flow. The aircraft may be instructed to back-taxi to primary radars fitted with certain forms of fixed echo the beginning of the runway or at some point before suppression. reaching the runway end for the purpose of departure BLIND ZONE− or to exit the runway. (See BLIND SPOT.) BASE LEG− BLOCKED− Phraseology used to indicate that a (See TRAFFIC PATTERN.) radio transmission has been distorted or interrupted BEACON− due to multiple simultaneous radio transmissions. (See AERONAUTICAL BEACON.) BOTTOM ALTITUDE– In reference to published (See AIRPORT ROTATING BEACON.) altitude restrictions on a STAR or STAR runway (See AIRWAY BEACON.) transition, the lowest altitude authorized. (See MARKER BEACON.) BOUNDARY LIGHTS− (See NONDIRECTIONAL BEACON.) (See AIRPORT LIGHTING.) (See RADAR.) BRAKING ACTION (GOOD, MEDIUM, POOR, BEARING− The horizontal direction to or from any OR NIL)− A report of conditions on the airport point, usually measured clockwise from true north, movement area providing a pilot with a degree/qual- magnetic north, or some other reference point ity of braking that he/she might expect. Braking through 360 degrees. action is reported in terms of good, fair, poor, or nil. (See NONDIRECTIONAL BEACON.) Effective October 1, 2016, Braking Action will be categorized in the following terms: Good, Good to BELOW MINIMUMS− Weather conditions below Medium, Medium, Medium to Poor, Poor, and Nil. the minimums prescribed by regulation for the (See RUNWAY CONDITION READING.) particular action involved; e.g., landing minimums, takeoff minimums. BRAKING ACTION ADVISORIES− When tower controllers have received runway braking action BLAST FENCE− A barrier that is used to divert or reports which include the terms “fair,” “poor,” or dissipate jet or propeller blast. “nil,” or whenever weather conditions are conducive to deteriorating or rapidly changing runway braking BLAST PAD− A surface adjacent to the ends of a conditions, the tower will include on the ATIS runway provided to reduce the erosive effect of jet broadcast the statement, “Braking action advisories blast and propeller wash. are in effect” on the ATIS broadcast. During the time BLIND SPEED− The rate of departure or closing of braking action advisories are in effect, ATC will issue a target relative to the radar antenna at which the latest braking action report for the runway in use cancellation of the primary radar target by moving to each arriving and departing aircraft. Pilots should target indicator (MTI) circuits in the radar equipment be prepared for deteriorating braking conditions and causes a reduction or complete loss of signal. should request current runway condition information (See ICAO term BLIND VELOCITY.) if not volunteered by controllers. Pilots should also be prepared to provide a descriptive runway BLIND SPOT− An area from which radio condition report to controllers after landing. transmissions and/or radar echoes cannot be Effective October 1, 2016, the term “fair” will be received. The term is also used to describe portions replaced with “medium”. of the airport not visible from the control tower. BREAKOUT− A technique to direct aircraft out of BLIND TRANSMISSION− the approach stream. In the context of simultaneous (See TRANSMITTING IN THE BLIND.) (independent) parallel operations, a breakout is used PCG B−1 Pilot/Controller Glossary 12/10/155/26/16 to direct threatened aircraft away from a deviating BROADCAST [ICAO]− A transmission of informa- aircraft. tion relating to air navigation that is not addressed to BROADCAST− Transmission of information for a specific station or stations. which an acknowledgement is not expected. (See ICAO term BROADCAST.) PCG B−2.