Bailout. To make a parachute jump.

Bank. To slant an airplane laterally.

Beacon. A device that guides an aircraft with light, radio, or radar beams.

Beam. A stream of radio or radar impulses or light rays used for aircraft guidance.

Blackout. Temporary loss of vision, sometimes followed by unconsciousness, in making a fast turn or pulling out of a dive when centrifugal forces decreases blood pressure in the head, resulting in insufficient oxygen. A redout results at the top of a dive when blood rushes to the head.

Blind flying. Flight with the use of instruments when the pilot cannot see out because of darkness or weather.

Boundary layer. A thin layer of air next to an airfoil, distinct from the main air flow, with flow characteristics resulting from friction. Its flow may be laminar (smooth) or turbulent (eddying).

Braking ellipses. A series of orbital approaches to the atmosphere of the earth or other planet to slow a spacecraft before landing.

C

Ceiling. 1. Maximum altitude an aircraft can attain. 2. Upper limit of flying visibility because of clouds.

Chord. The dimension between the leading and trailing edges of an airfoil section.

Clearance. Authorization for a flight to depart from an airfield or to fly a specified route.

Collective pitch control. The control in a helicopter for changing the pitch of all the main rotor blades simultaneously to regulate lift.

Condensation trail, or vapor trail. A visible trail of water droplets or ice crystals formed in the wake of highaltitude aircraft by disturbing supercooled air and by ejecting water vapor of the exhaust into cold air.

Control stick, or stick. A lever which controls movements of a plane by operating elevators and ailerons. Some aircraft have a wheel on a control column instead of a stick.

Convertiplane. An aircraft designed to fly vertically (like a helicopter) and horizontally (like a fixed-wing plane).

Crabbing. To point an aircraft partly into the wind to offset drift.

Crosswind landing gear. A landing gear with wheels that turn from side to side enabling the airplane to land in a shaky attitude.

Cruising speed. Speed at which a plane flies best under given conditions.

Cyclic pitch control. Helicopter control