Theory of Flight

Question 1

In what direction does lift act in relation to the relative airflow?

Answer 1

Lift acts perpendicular to relative airflow

Question 2

What is the coefficient of lift?

Answer 2

The angle of attack that an airfoil is meeting the relative wind and the camber of the airfoil of the wing. These two factors together are the ‘coefficient of lift’

Question 3

In what direction does drag act in relation to the relative airflow?

Answer 3

Drag acts parallel to the relative airflow.

Lift acts perpendicular to RA

Question 4

What is parasite drag?

Answer 4

Drag that is created by parts of the aircraft that do not contribute to lift. There are three types of parasite drag:

Form (literally the shape of the plane, smoother curves = less drag)
Skin (smoother skin = less drag)
Interferance (where to parts meet)

Question 5

Does induced drag increase or decrease with an increase in speed?

Answer 5

Induced drag decreases the faster you go.

Because going slower means you need a higher angle of attack to create more lift and more lift means more induced drag.

Question 6

In what direction does the air go once it goes over the top of the wing?

Answer 6

Its going to speed up and go in towards the root of the wing.

Under the wing it moves outward toward the wing tip

Question 7

What causes wing tip vortices?

Answer 7

Low pressure moving toward the root of the wing on top.

High pressure moving toward the wing tip on the bottom.

Like rolling a marker between your palms.

Question 8

Induced drag decreases the faster you go, but parasite drag ____ as you go faster.

Answer 8

increases

Question 9

Lift and weight must be ____ in order to maintain level flight.

Answer 9

Equal

Question 10

What does the M represent on this graph?

Answer 10

Glide speed. Speed where drag is at a minimum and lift is at a maximum.

Question 11

In what direction does thrust act in relation to the longitudinal axis?

Answer 11

Thrust is directed parrallel to the longitudinal aircraft and acts opposite to drag

Question 12

Thrust acts opposite to ____

Answer 12

drag

Question 13

What is the definition of equilibrium

Answer 13

A steady state of motion

Question 14

If thrust or drag becomes greater than the other, the state of equilibrium will be lost.

What happens if thrust is greater than drag?

Answer 14

The plane will accelerate

Question 15

Equilibrium is only broken when there is some form of?

Answer 15

acceleration or deceleration

Question 16

If a plane is in a constant climb or constant descent, it is considered to still be in a state of ___________

Answer 16

equilibrium

Question 17

When lift and weight are equal the aircraft will be in a steady state of equilibrium in cruise or…?

Answer 17

In a steady rate of climb or descent

Question 18

Once a climb or descent becomes stable it is in equilibrium. However as soon as you put pressure on the controls, what happens?

Answer 18

It will lose equilibrium but only briefly

Question 19

What is the difference between centrifugal and centripital force?

Answer 19

Centripital acts towards the inside of the circle
Centrifugal acts towards the outside of the circle

Question 20

In a turn an aircraft is not in a state of ________. Why?

Answer 20

Equilibrium. Because you are constantly changing your direction, which counts in physics as a type of accelleration. And an acceleration means thrust is greater than drag and equilibrium is only established when they are equal.

Question 21

What causes centripital force?
Other wording: What causes an airplane to turn?

Answer 21

The horizontal component of lift

Question 22

If the horizontal component of lift acts toward the inside of the turn (centripital force), what force opposes it?

Answer 22

Centrifugal force.

Question 23

What acts opposite to the verticle and horizontal components of lift?

Answer 23

Weight and centrifugal force
This is the load factor

Question 24

Why does the weight of the aircraft in a turn increase?

Answer 24

Because of the centrifugal force pulling it to the outside of the turn

Question 25

What is resultant lift and resultant load?

Answer 25

Resultant lift: Combo of Verticle and Horiontal components of lift

Resultant load: Combo of centrifugal force and weight

Question 26

Why does stall speed increase in a turn?

Answer 26

• In a turn the plane is not in equilibrium
• It will descend unless the angle of attack is increased to produce more lift
• Increasing the angle of attack increases the stall speed

Question 27

What is the only thing that can change the coefficient of lift?

Answer 27

Angle of attack