Aero Dynamics

Front 1

Bernoulis’ principle

Back 1

Bernoulli’s principle states that as the velocity of a fluid increases, its pressure decreases.

When air flows along the upper wing surface, it travels faster than the airflow along the lower wing surface.

Therefore, the pressure above the wing is less than it is below the wing. This generates a lift force over the upper curved surface of a wing.

Front 2

Airfoil, Relative wind, AOA, Angle of incidence

Back 2

An airfoil is any surface, such as a wing, that provides aerodynamic force when it interacts with a moving stream of air.

Relative wind is the airflow which is parallel to and opposite the flight path of the airplane.

Angle of attack is the angle between the chord line of the airfoil and the direction of the relative wind.

Angle of incidence refers to the angle between the wing chord line and a line parallel to the longitudinal axis of the airplane.

Front 3

Parasite drag, Type

Back 3

Parasite drag is caused by any aircraft surface that deflects the smooth airflow around the airplane.

Parasite drag increases with the airspeed.

Form drag results from the turbulent wake caused by the separation airflow from the surface of a structure.

Interference drag occurs when the airflow around one part of the airplane interacts with the airflow around an adjacent part.

Skin friction drag is caused by the roughness of the airplane’s surfaces.

Front 4

Induced drag

Back 4

Induced drag is generated by the airflow circulation around the wing as it creates lift.

Induced drag is inversely proportional to the airspeed.

Front 5

Lift to drag ratio

Back 5

The low point on the total drag curve shows the airspeed at which drag is at its minimum.

This point where the lift to drag ratio is greatest, is referred to L/D max.

At this speed, the total capacity of airplane is most favorable.

Front 6

Ground Effect

Back 6

Ground effect is the result of the interference of the ground surface with the airflow patterns about an airplane, decreasing induced drag.

An airplane is affected by ground effect when it is within the length of the airplane’s wingspan above the ground.

Ground effect may cause an airplane to float on landings or permit it to become airborne with insufficient airspeed to stay in flight above the area of ground effect.

Front 7

Longitudinal stability

Back 7

The center of lift is a point where lift is considered to be concentrated.

The location of CG, CL determines the longitudinal stability.

Front 8

Longitudinal stability

Back 8

The center of lift is a point where lift is considered to be concentrated.

The location of CG, CL determines the longitudinal stability.

Front 9

Horizontal stabilizer

Back 9

The tail down force aids in longitudinal stability.

Airplanes normally pitch down when power is reduced. Because the downwash on the elevators from the propeller slipstream is reduced and elevator effectiveness is reduced.

Airplanes with the thrustline below the CG produce pitching moment. Increasing the thrust increases the pitching moment.

Front 10

Lateral stability

Back 10

Dihedral is upward angle of the wings with respect to the horizontal. When an airplane enters an uncoordinated roll, AOA and lift increases on low wing compared to the high wing. This tends to roll aircraft back toward a level flight attitude.

Sweepback means that wings are angled backward from the wing root to the wingtip. During a sideslip, the lowered wing becomes more perpendicular to the airflow, increasing lift and drag. Sweepback also aids in directional stability.

Lateral stability is also provided by the vertical fin and side area of the fuselage reacting to the airflow much like the keel of a ship.

Front 11

Directional Stability

Back 11

The primary contributor to directional stability is the vertical tail. It causes an airplane to act much like a weather vane.

Front 12

Dutch roll

Spiral instability

Back 12

A Dutch roll is a combination of rolling and yawing oscillations that occurs when the dihedral effects of an aircraft are more powerful than the directional stability.

Spiral instability occurs when airplanes have stronger directional stability than lateral stability. If the right wingtip moves down, it continues to move down the rolling the plane to the right.

Front 13

Left turning tendency

Back 13

1) Torque effect : The clockwise action of a spinning propeller causes a torque reaction, which tends to rotate the airplane counterclockwise about its longitudinal axis.

2) Gyroscopic precession : is the resultant action when a force is applied to the rim of a rotating disc. The reaction to a force applied to a gyro acts in the direction of rotation 90 degrees ahead of the point where force is applied.

3) P factor : Propeller blade descending on the right produces more thrust than the ascending blade on the left.

4) Spiraling slipstream : As the slipstream produced by the propeller rotation wraps around the fuselage, it strikes the left side of the vertical fin. It causes the tail of the airplane to move to the right, and the nose to yaw left about its vertical axis.

Front 14

Adverse Yaw

Back 14

Adverse Yaw is the natural tendency for an aircraft to yaw in the opposite direction of a roll.

Adverse yaw occurs when an airplane banks its wings for a turn. The increased lift of the raised wing makes an increased drag, which causes the airplane to yaw toward the side of the raised wing.

Front 15

Overbanking tendency

Back 15

As you enter a turn, outside wing travels faster than the inside wing, it produces more lift and the airplane tends to roll beyond the desired bank angle.

Front 16

Overbanking tendency

Back 16

As you enter a turn, outside wing travels faster than the inside wing, it produces more lift and the airplane tends to roll beyond the desired bank angle.

Front 17

Rate of turn

Radius of turn

Back 17

When airspeed is held constant, a larger angle of bank will result in a smaller turn radius and a greater turn rate.

When angle of bank is held constant, a slower airspeed will result in a smaller turn radius and greater turn rate.

Front 18

Load Factor

Back 18

Load factor is the ratio of the road supported by the airplane’s wings to the actual weight of the aircraft.