Aerodynamics

The branch of physical science concerned with the reactions caused by the relative motion between a solid body and the surrounding air.

Astronautics

The art and science of designing, building, and operating manned or unmanned space objects.

Aileron

A control surface on fixed-wing aircraft, usually mounted on the aft edge of wings, that controls roll, and is controlled by the wheel; Symbols: delta sub A; Typical units: rad, deg;

Airfoil

Section of a wing, rudder, aileron, or rotorblade used for testing reactions from the air through which it moves.

Angle of Attack

The difference between pitch and the air-referenced flight path angle; the angle between the aircraft center line and the airspeed vector in the vertical plane, positive when the nose is up; Symbols: alpha; Typical units: rad, deg;

Bernoulli's Equation

In fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.

Boundary Layer

The layer of air immediately adjacent to the surface of an airfoil. Its flow, rather than being laminar, is essentially random, or circulatory, and produces a great deal of aerodynamic drag.

Camber

It is the asymmetry between the top and the bottom curves of an airfoil in cross-section

Center of Gravity

The point within something at which gravity can be considered to act; in uniform gravity it is equal to the center of mass

Center of Pressure

The point on a body where the total sum of the aerodynamic pressure field acts, causing a force and no momentum about that point.

Chord

The imaginary straight line joining the trailing edge and the center of curvature of the leading edge of the cross-section of an airfoil

Chord Line

The straight line drawn from a point on the top to a point on the base

Climb

Ascent, an upward slope or grade

Cruising Flight

To travel at a constant speed or at a speed providing maximum operating efficiency for a sustained period

Drag

Force of air against aircraft acting in opposite direction of the airspeed vector projected into horizontal plane

Drag Coefficient

The ratio of the drag on a body moving through air to the product of the velocity and the surface area of the body

Elevator

A control surface on fixed-wing aircraft, usually mounted on the aft edge of stabilizers, that controls pitch, and is controlled by the yoke

Energy

Any source of usable power

Glide Angle

The proper path for an airplane approaching a landing strip

Glide ratio

The ratio of the forward distance traveled to the vertical distance an aircraft descends when gliding without any power

Leading Edge

Forward edge of an airfoil

Lift

Force, created primarily by wings (fixed wing) or by rotors (rotary wing), acting in opposite direction of gravity fector

Lift Coefficient

A dimensionless coefficient that relates the lift generated by an airfoil

Lift to Drag Ratio

The amount of lift generated by a wing or vehicle, divided by the drag it creates by moving through the air

Mach Number

Ratio of airspeed to the local speed of sound (Mach 1 is the speed of sound under current atmospheric condition)

Mass

The property of a body that causes it to have weight in a gravitational field

Mean Camber Line

A plot of points that lie halfway between the upper and lower surfaces of the wing or airfoil cross section

Momentum

The product of a body's mass and its velocity

Pitch

The angle of a rotor measured in the plane of rotation

Pitot Static Tube

Measuring instrument consisting of a combined Pitot tube and static tube that measures total and static pressure; used in aircraft to measure airspeed

Roll

Bank Angle

Rudder

A control surface on fixed-wing aircraft, usually mounted at aft ending of the fuselage sticking up (like a dorsal fin), that controls yaw (heading), and is controlled by the pedals;

Slug

A unit of mass associated with Imperial units. It is a mass that accelerates by 1ft/second squared when a force of one pound-force (lbf) is exerted on it. Therefore a slug has a mass of 32.17405 pound-mass or 14.5939 kg.

Steady Descent

Going down at a constant rate

Streamline

To shape an object so that it creates less drag and moves smoothly and easily through the air. Airfoils are streamlined, as is the fuselage

Thrust

A force created by the engines that pushes an aircraft through the air

Weight

The force of gravity acting on an object. The weight force pulls an aircraft toward the Earth and must be overcome by a combination of lift and thrust.

Wing Area

In general, a greater wing area means better low-speed maneuverability and lower takeoff and landing speeds.

Wing Stall

The point at which a plane loses airspeed and stalls

Wing Tip

The part of the wing that is most distant from the fuselage of a fixed-wing aircraft

Yaw