NIFE Aerodynamics - Unit 1

General Gas Law

Sets the relationship between three properties of air: pressure (P), density (ρ), and temperature (T).

P=ρRT (R is a constant for any given gas)

Trimmed Flight

Exists when the sum of all moments around the center of gravity is equal to zero.

Temperature vs Altitude

Decreases linearly with an increase in altitude at a rate of 2 deg C per 1000 ft until approximately 36,000 ft. After 36,000 ft, the temperature is constant (isothermal)

Humidity vs Air density

As humidity increases, air density decreases

Steady Airflow

Exists if at every point in the airflow static pressure, density, temperature, and velocity remain constant over time.

Continuity equation

A1V1=A2V2

Vector

A quantity that has magnitude and direction. Resultant vector may be divided into separate components.

Density (rho)

Mass per unit volume

Moment

A rotational force around a point or axis

Equilibrium Flight

Exists when the sum of all forces and the sum of all moments around the center of gravity are equal to zero.

Bernoulli's Equation

Total pressure (Pt) equals static pressure (Ps) plus dynamic pressure (q)

Pt=Ps+q

q=(1/2)ρ(V^2)

Order of Airspeeds

Indicated Airspeed (IAS)

Calibrated Airspeed (CAS)

Equivalent Airspeed (EAS)

True Airspeed (TAS)

Ground Speed

Remember "ICE-TG"

Indicated Airspeed (IAS)

Airspeed read directly from the airspeed indicator

Calibrated Airspeed (CAS)

Indicated airspeed corrected for instrument error.

Equivalent Airspeed (EAS)

The true airspeed at sea level on a standard day that produces the same dynamic pressure as the actual flight condition.

Found by correcting calibrated airspeed for compressibility error

True Airspeed (TAS)

Actual speed you are moving through the air

Ground Speed (GS)

True Airspeed corrected for winds; actual speed of airplane over the ground.

Mean chamber line

line drawn halfway between the upper and lower surfaces of a wing.

Chord

precise measurement between the leading and trailing edges measured along the chordline

Camber

maximum distance between the mean camber line and the chord line measured perpendicular to the chord line

Types of camber

Positive - Mean chord is above the chordline

Zero - Symmetric airfoil or flat plate

Negative - Mean chord is below the chordline

Wingspan (b)

The length of a wing, measured from wingtip to wingtip.

Wing Area (S)

Apparent surface area of a wing from wingtip to wingtip; S=bc

Chordwise Flow

Air flowing at right angles to the leading edge of an airfoil.

Spanwise Flow

Airflow that travels along the span of the wing, parallel to the leading edge.

Pitch Attitude

The angle between an airplane's longitudinal axis and the horizon.

Flight Path

The path described by its center of gravity as it moves through an air mass.

Relative wind

the flow of air which moves opposite the flight path of an airplane

Angle of Attack

The angle formed by the wing chord line and the relative wind.

Angle of incidence

The angle between the airplane's longitudinal axis and the chordline of the wing.

Airplane Three-Axis Reference System

Longitudinal axis - passes from the nose to the tail of the airplane

Lateral axis - passes from wingtip to wingtip

Vertical Axis - passes vertically through the center of gravity

Center of Gravtiy

The point at which all weight is considered to be concentrated and about which all forces and moments are measured

Aerodynamic Center

The point along the chordline around which all changes in the aerodynamic force take place.

Two forces considered aerodynamic forces

Lift and Drag

Pressure distribution around an airfoil

Factors in the lift equation that affect lift production

L = (1/2)ρ(V^2)SCL

Density (ρ)

Velocity (V)

Surface Area (S)

Compressibility

Aspect ratio (AR)

Viscosity (μ)

Angle of attack (α)

Camber

Factors affecting coefficient of lift

Shape of the airfoil

Angle of attack (α)

CL_max

Maximum value for the coefficient of lift

Coefficient of lift vs angle of attack

As angle of attack increases, the coefficient of lift increases.

Any increase in angle of attack beyond CL_max AOA causes a decrease in the coefficient of lift

How flaps affect coefficient of lift

Flaps change the chamber of the airfoil.

Extending flaps adds positive chamber, decreasing the zero-lift AOA