Axes of an aircraft.  Three imaginary lines that pass through  an aircraft’s center of gravity. The axes can be considered as  imaginary axles around which the aircraft turns. The three  axes pass through the center of gravity at 90° angles to each  other. The axis from nose to tail is the longitudinal axis, the  axis that passes from wingtip to wingtip is the lateral axis, and  the axis that passes vertically through the center of gravity  is the vertical axis.  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.  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.  Axial flow compressor.  A type of compressor used in a  turbine engine in which the airflow through the compressor  is essentially linear. An axial-flow compressor is made up of  several stages of alternate rotors and stators. The compressor  ratio is determined by the decrease in area of the succeeding  stages.  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.  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.  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.  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.  Ballast.  Removable or permanently installed weight in an  aircraft used to bring the center of gravity into the allowable  range.  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.).  Balloon.  The result of a too aggressive flare during landing  causing the aircraft to climb.  Basic empty weight (GAMA).  Basic empty weight  includes the standard empty weight plus optional and special  equipment that has been installed.  Best angle of climb (V$_{X}$).  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 (V$_{Y}$).  The speed at which the aircraft will  produce the most gain in altitude in the least amount of time.  Blade face.  The flat portion of a propeller blade, resembling  the bottom portion of an airfoil.  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.  Calibrated airspeed (CAS).  Indicated airspeed corrected  for installation error and instrument error. Although  manufacturers attempt to keep airspeed errors to a minimum,  it is not possible to eliminate all errors throughout the  airspeed operating range. At certain airspeeds and with  certain flap settings, the installation and instrument errors  may total several knots. This error is generally greatest at  low airspeeds. In the cruising and higher airspeed ranges,  indicated airspeed and calibrated airspeed are approximately  the same. Refer to the airspeed calibration chart to correct  for possible airspeed errors.  Cabin pressurization.  A condition where pressurized air is  forced into the cabin simulating pressure conditions at a much  lower altitude and increasing the aircraft occupants comfort.  G-3 C B Balked landing.  A go-around. 