Aerodynamic Terms

Question 1

Chord line

Answer 1

An imaginary straight line from the leading to the trailing edge of an airfoil. Lowering flaps changes the chord line

Question 2

Relative wind

Answer 2

The wind felt by an airfoil. It is parallel to and travels the opposite direction of the flight path of the airfoil.

Question 3

Angle of attack

Answer 3

Angle between the chord line and the relative wind

Question 4

Angle of incidence

Answer 4

Angle that the wing is attached to the fuselage

Question 5

Does the angle of attack that an airfoil stalls at change?

Answer 5

The indicated airspeed at which stalls occur is determined by weight and load factor, but the stall angle of attack is the same

Question 6

Lateral axis

Answer 6

Imaginary line from wingtip to wingtip

Question 7

Pitch

Answer 7

Rotation around the lateral axis. Controlled by the elevators.

Question 8

Longitudinal Axis

Answer 8

Imaginary line from the nose to the tail

Question 9

Roll

Answer 9

Rotation around the longitudinal axis. Controlled by the ailerons

Question 10

Vertical axis

Answer 10

Imaginary line extending through the intersection of the lateral and longitudinal axes.

Question 11

Yaw

Answer 11

Rotation about the vertical axis. Controlled by the rudder.

Question 12

Center of gravity

Answer 12

Imaginary point where all the weight is concentrated and plane would balance if it were suspended. The 3 axes intersect here.

Question 13

What are the 4 aerodynamic forces

Answer 13

Weight, lift, drag, and thrust

Question 14

Bernoulli’s principle

Answer 14

As the velocity of a fluid increases, it’s pressure decreases

Question 15

Lift

Answer 15

The result of a pressure difference between the top and bottom of the wing. Factors include: angle of attack, wing area and shape, air velocity, and air density.

Question 16

Thrust

Answer 16

The forward force produced by the propeller

Question 17

Drag

Answer 17

Rearward force which resists the forward movement of an airplane through the air. There is parasite drag and induced drag

Question 18

Parasite drag

Answer 18

Resistance by any part of the plane that doesn’t produce lift, like the antennae and landing gear

Question 19

Induced drag

Answer 19

As lift is developed, the high pressure air beneath the wing causes vortices all along the trailing edge of the wings. Increases as airspeed decreases

Question 20

Unaccelerated (straight and level) flight

Answer 20

The four aerodynamic forces are in equilibrium. Lift=weight, Thrust=drag

Question 21

What determines the longitudinal stability of an airplane

Answer 21

The location of the CG with respect tot he CL(center of lift).

Question 22

3 effects of forward CG

Answer 22

1-increased longitudinal stability
2-lower cruise speed. Higher AoA to create more lift, more induced drag
3-higher stall speed.

Question 23

4 effects of aft CG

Answer 23

1- decreased longitudinal stability
2- higher cruise speed
3- lower stall speed
4- poor stall/spin recovery

Question 24

Why does a plane lose altitude on a turn?

Answer 24

A portion of the vertical lift is diverted to a horizontal lift component. So, this will happen unless you increase the AoA or airspeed.

Question 25

What can increase the load factor on the airplane?

Answer 25

Overloading the plane, too steep an angle of bank, turbulence and abrupt movement of the controls.

Question 26

What is a stall?

Answer 26

At an AoA of approximately 18-20, turbulence over the upper wing decreases lift so drastically that flight can’t be maintained.

Question 27

Critical Angle of Attack

Answer 27

The angle at which a stall occurs. An airplane can stall at any airspeed or any attitude, but will always stall at the same critical AoA.

Question 28

When will an aircraft spin?

Answer 28

Only after a stall, and for as long as the outside wing continues to provide more lift than the inside wing.

Question 29

What wing is stalled in a spin

Answer 29

Both wings are stalled, but one is stalled more than the other.

Question 30

What does extending flaps on landing do?

Answer 30

Increases lift and drag, allowing a steeper approach without an increase in airspeed.

Question 31

What is ground effect

Answer 31

Occurs when flying one wingspan or less above the surface, and the airflow is modified and can cause an airplane to become airborne before takeoff speed or float on approach.

Question 32

When are maximum vortexes created?

Answer 32

When an aircraft is heavy, clean, and slow. Land beyond the previous plane and takeoff before.