A

Ablation. The melting, erosion, evaporation, or vaporization of nose cone materials of vehicles entering a planetary atmosphere at high speeds.

Aerodynamics. The science that studies the motion of air and other gases and the forces that act on bodies moving through them.

Aeronautics. The science or art of operating both lighter-than-air and heavier-than-air craft.

Aerospace. The earth's atmosphere and the space above it, in which aircraft, missiles, and spacecraft fly.

Afterburner. An auxiliary combustion chamber at the rear of a jet engine into which additional fuel is injected and burned, utilizing unburned oxygen in the exhaust gases to increase thrust.

Aileron. A movable control surface, usually on the trailing edge of a wing, used to control the rolling of an airplane.

Airfoil. A surface designed to obtain a reaction from air, such as a, wing for lift, fin for stability, elevator for control, and propeller blade for thrust.

Airspeed. Speed of an aircraft relative to the air in contrast to ground speed, or its speed relative to the ground.

Airway. A designated air route equipped with navigational aids.

Angle of attack. The angle formed by the chord of an airfoil and the line of air flow, or relative wind.

Angle of incidence. Angle made by the chord of an airfoil and the longitudinal axis of the aircraft; that is, the angle at which the airfoil is attached to the airplane.

Area rule. A method of aircraft design for minimizing drag. The cross-sectional area, of transonic aircraft is distributed to resemble that of an ideal body of minimum drag by lengthening the nose, adding a, tail blister, or indenting the fuselage in a Coke-bottle shape.

Aspect ratio of airfoil wing. Ratio of span of a wing to its mean chord.

Attitude. The position of an aircraft or spacecraft as determined by the relationship of its axes to some reference line, plane, or system of reference axes.

Automatic direction finder (ADF). A radio compass that automatically indicates the direction of the station to which it is tuned.

Automatic pilot, or autopilot. A device that maintains an aircraft in straight and level flight on a set course.

Aviation. The art or practice of designing, developing, manufacturing, or operating heavier than-air craft.

Axis. A line passing through an airplane about which it may revolve. An airplane has three mutually lateral, from wing tip to wing tip, measuring pitch; and vertical, from back to belly, measuring yaw.

B

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

D

Dead reckoning. Calculation of position using earlier known position, elasped time, speed, heading, and wind.

Deicer. Device for removing ice from wings, propeller, or control surfaces.

Dihedral. Upward (positive) or downward (negative) inclination of a wing or stabilizer from the horizontal.

Drag. Resistance to the passage of an airplane through the air.

E

Ejection seat. A seat designed to be catapulted with its occupant high-speed aircraft in an emergency

Elevator. A control surface hinged to a horizontal stabilizer for rotating an aircraft about its lateral axis

Empennage, or tail assembly. Horizontal and vertical stabilizers and control surfaces at rear of an aircraft

F

Feather. 1. To turn a propeller balade edgewise into the airflow to minimize resistance. 2. To change a blade angle or a rotor blade or rotating wing

Flap. A movable control surface at rear of wing for increasing lift or drag in takeoff or landing.

Flight plan. A detailed statement about a proposed flight submitted to Air Traffic Control prior to takeoff, including point of departure and destination, flight route, altitude, and airspeed.

Free fall. The drop of a parshutist before opening his parachute.

Fuselage. The main body of an airplane.

G

G-force. A force exerted by gravity or by reaction to acceleration or deceleration when direction is changed. Measured in g's, or multiples of force of gravity.

Glide path. The line of flight of aircraft in controlled descent.

Ground controlled approach (GCI) An instrument landing system, used during poor visibility in which a ground operator observes a plane's position and direction on a radarscope and directs the pilot by radio.

Ground loop. A violent turn while moving on the ground.

Gull wing. A wing which slants upward from its roots and then flattens out or angles upward. An inverted gull wing slants downward and then straightens out or slants upward.

H

Heat barrier. See Thermal barrier.

Helicopter. An aircraft capable of both vertical and horizontal flight, which derives both lift and thrust from rotating wings power-driven about a vertical axis.

High-wing monoplane. An airplane whose wing is mounted at, near, or above the top of the fuselage. A parasol monoplane has its wing mounted above the fuselage on struts.

I

Icing. Atmospheric moisture freezing on the surfaces of an aircraft.

Instrument flight rules (IFR). Traffic and procedure rules governing flight under instrument conditions.

Instrument flying. Navigating and controlling an aircraft solely by the use of instruments.

Instrument Landing System (ILS). Radio system for guiding aircraft in landing during poor visibility. Directional radio transmitters indicate direction of runway and angle of glide path, and radio marker beacons establish position along approach path.

J

Jet. See Turbofan; Turbojet

Jet stream. 1. Narrow band of highspeed wind in upper troposphere or in stratosphere moving west to east. 2. Stream of combustion products expelled from a reaction engine.

K

L

Lift. Aerodynamic force which acts on an airfoil perpendicular to the relative wind and is usually exerted upward, opposing force of gravity.

Loop. Maneuver in which an airplane makes a circular path in the vertical plane, with its lateral axis horizontal

Low·wing monoplane. An airplane whose wing is mounted at or near the bottom of the fuselage.

M

Mach number. A number expressing the ratio of the speed of a moving body or of air to the speed of sound, with Mach 1.0 equal to the speed of sound.

Mid-wing monoplane. An airplane whose wing is mounted halfway between the top and bottom of the fuselage.

Mush. To settle or to gain little or no altitude while flying with the airplane's nose held high.

N

Nacelle. A housing on an aircraft for engines, personnel, or equipment.

Nose cone. The shield that fits over, or is, the nose of an aerospace vehicle; constructed to resist the high temperatures generated by friction with air particles.

O

Omnidirectional range or omnirange. A radio navigation system that gives bearings in all directions from a transmitter.

P

Pilotage. Navigation by visual reference to check points and by comparing landmarks with symbols on a chart.

Pilot chute. A small parachute which pulls out the main parachute from a pack.

Pitch. The up-and-down, or vertical, movement of an aircraft about its lateral axis.

Pilot-static tubes. A device, consisting of a pilot tube and a static tube, that measures impact and static pressures. The pressure difference registers airspeed in an air-speed indicator. The static pressure may operate an altimeter or similar instruments.

Pressurize. To maintain normal pressure in a cabin at high altitudes.

Q

R

Radius of action, or radius. The distance an airplane can fly and return to it's starting point.

Range. Maximum distance an aircraft can fly from takeoff until its fuel supply is exhausted.

Reaction engine. An engine, such as a. jet or rocket type, which derives thrust by its reaction to a substance ejected rearward.

Reciprocating engine. An engine which develops thrust by back-and-forth motion of pistons in cylinders to rotate a crankshaft.

Reduction gear. A gear assembly used to run a propeller or a rotor at a slower rate than the engine.

Relative wind. Flow of air with reference to an object passing through it.

Rendezvous. The meeting in flight of two or more aerospace vehicles at a planned time and place; also, the point in aerospace where the meeting occurs.

Rev, or rev up. To revolve or to increase the revolutions per minute of an engine.

Reversible-pitch propeller. A propeller whose blade angle can be changed to give reverse thrust for braking the airplane in landing.

Rocket. An engine which derives thrust from expulsion of hot gases and car- ries an oxidiser, making it independ- ent of atmosphere for combustion.

Roger. 1. A code word meaning "message received and understood." 2. An expression of agreement meaning "O. K." or "all right."

Roll. Rotation of an airplane about its longitudinal axis.

Run, or run up. To increase engine speed while the aircraft is standing still to check or to warm up the engine.

S

Sideslip. 1. To slide sideways and downward along the lateral axis with wings sharply banked. 2. In a turn, a sidewise movement toward the inside of a turn. A skid is a slide sideways away from the center of the turn.

Solo. Flying alone.

Sonic. Pertaining to speed of sound.

Sonic barrier, or sound barrier. Large increase in drag when approaching the speed of sound.

Space platform or station. A large habitable satellite for scientific and military uses.

Span. The dimension of an airfoil from tip to tip.

Spar. The principal longitudinal member in a wing or other airfoil.

Spin. A maneuver, controlled or uncontrolled, in which an airplane dives and spirals at the same time.

Stability. Ability of an aircraft to return to level flight.

Stabilizer. An airfoil which keeps an aircraft steady in flight; includes horizontal member of the tail assembly.

Stall. A condition which occurs when an airplane flies at insufficient airspeed and with the nose too high, creating an excessive angle of attack on the wings and resulting in a loss of lift.

Strut. A rigid member that bears compression loads, such as between longerons in a fuselage or in a landing gear.

Subsonic. Less than speed of sound.

Supercharger. A pump or compressor for forcing air into a reciprocating engine for high altitude flights.

Supersonic. Greater than speed of sound.

Sweepback. The backward slant of a wing or other airfoil.

T

Tab. A small airfoil hinged to a control surface and used to move the larger surface or to trim or balance the plane. May be a balancing tab, servo tab, or trim tab. Taxi. To move an airplane over ground or water under its own power.

Thermal barrier, or heat barrier. Zone of speed at which friction heat generated by passage of an object through air endangers its operation.

Three·point landing. A landing in which the tail skid or tail or nose wheel of an airplane and its two main wheels touch ground at the same instant.

Torque. A force which produces twisting, such as rolling of an airplane in reaction to the rotating propeller or turning of a helicopter fuselage because of the revolving rotor.

Transonic. The transitional speed between subsonic and supersonic.

Turbofan. A jet engine of the bypass, or ducted-fan, type in which part of the air taken in at the front by a compressor or fan bypasses the combustion chamber to give extra, thrust; one type has a fan at the rear.

Turbojet. A jet engine with a turbine- driven compressor that takes in and compresses air for combustion of fuel, producing hot exhaust gases that rotate the turbine and create a jet steam for thrust.

Turboprop, or prop let. A jet engine whose exhaust gases drive a turbine- connected propeller and also produce thrust.

U

V

Visual night rules (VFR). Rules for minimum altitudes and limits of visibility to govern contact flight by visual reference to the ground.

W

Worm-up. Running an engine to heat it to operating temperature.

Wind sock. A cloth cone pivoted on a pole to show wind direction.

Wind tee. A pivoted T-shaped device that indicates wind direction.

Wing loading. Cross weight of loaded airplane divided by the wing area.

X

Y

Yaw. Movement about vertical axis.

Z

Zoom. A brief, steep climb.