Glossary - B

Ballast.   A weight installed or carried in an aircraft to move the center of gravity to a location within its allowable limits.

Base.  In mathematics, used to refer to a particular mathematical object that is used as a building block. A base-a system is one that uses a as a new unit from which point counting starts again. (See decimal system.) In the mathematical expression an, read as “a to the nth power," a is the base.

Basic empty weight.   Standard empty weight plus optional equipment.

Bernoulli’s principle.   Equivalent to the principle of conservation of energy, this principle states that the static pressure of a fluid (liquid or gas) decreases at points where the velocity of the fluid increases, provided no energy is added to or taken away from the fluid.

Binary number system.   The binary number system is a number system that has only two digits, 0 (zero) and 1. Binary numbers are made from a series of zeros and ones. An example of an 8-bit binary number is 11010010. The prefix “bi" in the word binary is a Latin root for the word “two."

Block diagrams.   Used to show a simplified relationship of a more complex system of components.

Borescope.   A device that enables the inspector to see inside areas that could not otherwise be inspected without disassembly.

Boyle’s law.  States that the volume of an enclosed dry gas varies inversely with its absolute pressure, provided the temperature remains constant.

Break lines.  Line on a drawing indicating that a portion of the object is not shown on the drawing.

British thermal unit (Btu).  The amount of heat required to change the temperature of 1 pound of water by 1 degree Fahrenheit.

Buoyancy.  The upward force that any fluid exerts on a body submerged in it.

Buttock line (BL).  The longitudinal axis of the aircraft that serves as the reference location for positions to the left and right of center. The positions are usually dimensioned in inches.