Terminology Used In Aerospace Industries

Pressure: Pressure is the normal force per unit area exerted on a surface due to time rate change of momentum of gas molecules.

 

Density: Density of a substance (including gas) is the mass of that substance per unit volume.

 

Temperature: Temperature is a measure of average kinetic energy of particles in the gas. If KE represents kinetic energy of particles then the temperature is given by KE = 1.5 x k x T where k is the Boltzmann constant which is equal to 1.38 x 10 ^-23  J/k.

 

Flow Velocity: The flow velocity at any point in the flowing gas is the velocity of an infinitesimally small fluid element as it sweeps through that point.

 

 

Specific Volume: Volume of substance for per unit mass or volume per unit mass. It is also defined as reciprocal of density.

 

Fuselage: The fuselage is the center body where the most of usable volume of airplane is found. It carries people, baggage, other payloads instruments and anything else that designer puts there.

 

Wings: The wings are the main lift producing components of the airplane. Left and right wings are so identical that as you see them from inside the airplane facing forward. The internal volume of wings can be used for such items as fuels tanks and storage of main landing gear.

 

Stabilizer: There are two stabilizers on the aircraft normally vertical and horizontal stabilizer. The horizontal and vertical stabilizers are sized so as to provide the necessary stability for the airplane in flight. Sometime these stabilizers are called vertical and stabilizer fins.

 

Ailerons: Ailerons are the control surfaces that control the rolling motion of the airplane around the fuselage. These are hinged at the wings just before wing tips.

 

Elevators: Elevators are the control surface that control the nose up and down or pitching motion. These are hinged at the rear of horizontal stabilizer.

 

Rudder: The rudder is a control surface that can turn the nose of the airplane to right or left (called yawing).

 

Nacelle: When the engines are mounted from the wings, they are usually housed in shroud called nacelle. 

 

Standard Atmosphere: Standard atmosphere is the reference atmosphere only and doesn’t predict the actual atmospheric properties. Standard atmosphere is defined in order to relate flight tests, wind tunnel results and general airplane design and performance to a common reference. 

 

Airfoil: The cross section obtained by intersection of the wing with the perpendicular is called airfoil.

 

Mean camber line: It is the locus of points halfway between upper and lower surfaces as measured perpendicular to mean camber line itself.

 

Leading and Trailing Edge: The most forward and rearward points of the mean camber lines are leading edge and trailing edge.

 

Chord line: The straight line connecting leading and trailing edge is called chord line and distance is simply called chord.

 

Camber: Camber is the maximum distance between mean camber line and chord line and distance is measured perpendicular to the chord line. 

 

Free Stream Velocity: It is the velocity of air for upstream of the airfoil and the direction of free stream velocity is defined as relative wind.

 

Angle of Attack (AoA): The angle between the relative wind and chord line is the angle of attack of airfoil.

 

Aerodynamic force: The pressure and shear stress distribution over the wing surface creates the aerodynamic force.

 

Drag: The drag is defined as the component of the aerodynamics force parallel to relative wind.

 

Lift: The lift L is defined as the component of the aerodynamic force perpendicular to the relative wind.

 

Moment: In addition to lift and drag, aerodynamic force also creates moment which in turn tends to rotate the wings.

 

Aerodynamic center: If you go in depth you will see moment about any point varies with angle of attack but there exists a point on the airfoil where moment doesn’t vary with the angle of attack. This point about which moment is independent of angle of attack is called aerodynamic center. And the location is found experimentally.

 

Zero-lift angle of attack: It is defined as the value of angle of attack when lift is zero is called zero lift angle of attack. 

 

Stall: It is an aerodynamic phenomenon which is of critical importance in airplane design. Experimentally it is found that lift increases with increase in angle of attack but at certain point further increase in angle of attack cause abrupt loss of lift and the phenomena is called stall.