Aerodynamics of Flight

Question 1

The Four forces of Flight

Answer 1

Lift, Weight, Thrust and Drag

Question 2

Drag

Answer 2

The net aerodynamic force parallel to the relative wind, usually the sum of two components: Induced drag and parasite drag

Question 3

Induced drag

Answer 3

The byproduct of lift. Drag caused by the same factors that produce lift; its amount varies inversely with airspeed.
As airspeed decreases, the AOA must increase, in turn increasing induced drag.

Question 4

Parasite Drag

Answer 4

Drag caused by the friction of air moving over the aircraft structure; its amount varies directly with the airspeed.

Question 5

Axes of Flight

Answer 5

Longitudinal axis, Lateral axis and Vertical axis

Question 6

Longitudinal Axis

Answer 6

Imaginary line through an aircraft from the nose to tail, passing through its center of gravity. Also called the “Roll axis” of the aircraft. Movement of the ailerons rotates an airplane about its longitudinal axis.

Question 7

Lateral Axis

Answer 7

Imaginary line passing through the center of gravity of an airplane and extending across the airplane from wingtip to wingtip.

Question 8

Vertical axis

Answer 8

Imaginary line passing vertically through the center of gravity of an aircraft. The vertical axis is called the z-axis or the “yaw axis”.

Question 9

Stability

Answer 9

The characteristic of an airplane in flight to correct for conditions that may disturb its equilibrium, and to return or to continue on the original flight path.

Question 10

Static stability

Answer 10

The initial tendency an aircraft displays when disturbed from a state of equilibrium.

Question 11

Dynamic stability

Answer 11

How an aircraft responds over time to disturbance.

Question 12

Longitudinal stability (Pitching)

Answer 12

Stability about the lateral axis. A desirable characteristic of an airplane whereby it tends to return to its trimmed AOA after displacement.

Question 13

Directional stability (yaw)

Answer 13

Stability about the vertical axis of an aircraft, whereby an aircraft tends to return, on its own, to flight aligned with the relative wind when disturbed from that equilibrium state.

Question 14

Lateral stability (roll)

Answer 14

The stability about the longitudinal axis of an aircraft. Rolling stability or the ability of an airplane to return to level flight due to a disturbance that causes one of the wings to drop.

Question 15

Lift

Answer 15

A component of the total aerodynamic force on an airfoil and acts perpendicular to the relative wind.

Question 16

Weight

Answer 16

The force exerted by an aircraft from the pull of the gravity.

Question 17

Thrust

Answer 17

The forward aerodynamic force produced by a propeller, fan, or turbojet engine as it forces a mass of air to the rear, behind the aircraft, and propels the airplane through the air.

Question 18

Angle of Attack

Answer 18

The angle at which relative wind meets an airfoil. It’s the angle that is formed by the chord of the airfoil and the direction of the relative wind or between the chord line and the flight path.

Question 19

Stalls

Answer 19

A rapid decrease in lift caused by the separation of airflow from the wing’s surface, brought on by exceeding the critical angle of attack. A stall can occur at any pitch attitude or airspeed.

Question 20

Spins

Answer 20

An aggravated stall that results in an airplane descending in a helical, or corkscrew path.

Question 21

Adverse Yaw

Answer 21

A condition of flight in which the nose of an airplane tends to. yaw toward the outside of the turn. This is caused by the higher induced drag on the outside wing, which is also producing more lift. Induced drag is a by-product of the lift associated with the outside wing.

Question 22

Ground Effect

Answer 22

The condition of slightly increased air pressure below an airplane wing that increases the amount of lift produced. It exists within approximately one wing span fro the ground. It results from a reduction in upwash, downwash, and wingtip vortices, and provides a corresponding decrease in induced drag.

Question 23

Load Factor

Answer 23

The ratio of a specified load to the total weight of the aircraft. Measured in G’s.

Question 24

Positive load factor

Question 25

Negative load factor

Question 26

Maneuvering speed (Va)

Answer 26

Maneuvering speed (VA) is the maximum speed at which an aircraft can make abrupt or full movements of a single control without damaging the aircraft’s structure. It’s an airspeed limit that’s determined by the aircraft’s designer and published by the manufacturer.