PT2 CHP5 Basic Aerodynamics

Question 1

What is the upward force that opposes weight?

Answer 1

Lift

Question 2

What is the downward force that opposes lift?

Answer 2

weight

Question 3

What is the forward force that opposes drag?

Answer 3

thrust

Question 4

What is the rearward force that opposes thrust?

Answer 4

drag

Question 5

In unaccelerated, level flight, describe the balance of all four forces

Answer 5

they are all equal
Lift = Weight
Thrust = Drag

Question 6

What is weight?

Answer 6

• The result of gravity
• Applied at the Center of Gravity (CG)
• Always pointed towards the center of the Earth, opposite of Lift
• If the weight of the aircraft exceeds the maximum allowable weight, the airfoil won’t be able to generate enough lift to counteract the weight
• Will change throughout the flight due to fuel being burned

Question 7

What is the Center of Gravity?

Answer 7

the point at which, if a string was attached, the object would be in equilibrium

Question 8

What is Lift?

Answer 8

• The upward force produced by the wing (airfoil) on a fixed wing aircraft
• It is applied at the center of pressure (also called center of lift)
• Lift will always be perpendicular to the relative wind

Question 9

The lift vector is always perpendicular to what?

Answer 9

the relative wind (parallel to the path of the aircraft, not the nose)

Question 10

What part of the of airfoil does the air hit first and last?

Answer 10

The air hits the leading edge first then the trailing edge last

Question 11

The line drawn through the leading edge and the training edge is know as what?

Answer 11

Chord line

Question 12

What is the angle of attack?

Answer 12

The angle between the chord line and the relative wind

Question 13

If lift is generated, what else is generated?

Answer 13

drag

Question 14

What is the simplified lift equation?

Answer 14

L = V * α
V = velocity
α = angle of attack

Question 15

What is the full lift equation?

Answer 15

L = (CL * ρ * V² * S)/2
CL = coefficient of lift
ρ = air density
V = velocity
S = surface area of the wing

Question 16

What is the breakdown of each variable for the full lift equation?
(CL * ρ * V² * S)/2

Answer 16

CL = coefficient of lift
ρ = air density
V = velocity
S = surface area of the wing

Question 17

What are the two principles that create lift?

Answer 17

• Newton’s 3rd law
• Bernoulli’s principle

Question 18

What is Newton’s 3rd law?

Answer 18

For every action, there is an equal and opposite reaction
(the propeller moves air backward, and causes the airplane to move forward)

Question 19

What is Bernoulli’s principle

Answer 19

As air moves through a venturi, the speed increases in the middle, which decreases pressure
- Lower pressure above the wing
- Higher pressure below the wing
* Pressure wants to move from high to low*

Question 20

What is thrust?

Answer 20

• Created by the propeller that is attached to the motor
• ## The propeller is an airfoil that generates horizontal lift

Question 21

What is the blade angle?

Answer 21

• Blade angle is measured between the chord line and plane of rotation
• Angle of attack is measured between the chord line and the relative wind
• If the aircraft is not moving forward, the blade angle equals the angle of attack
• As the aircraft moves forward, the relative wind changes
• As a result, the angle of attack changes as well

Question 22

What is drag?

Answer 22

• Opposes thrust generated
• During unaccelerated flight, thrust = drag

Question 23

What are the types of drag?

Answer 23

• Parasite drag
• (Lift) Induced drag

Question 24

What is Parasite drag?

Answer 24

• The byproduct of flying through the air
• Increases as speed increases

Question 25

What are the three types of parasite drag?

Answer 25

- Form drag - Interference drag - Skin friction drag

Question 26

What is form drag?

Answer 26

- Based on the shape of the object (airplane)

Question 27

What is the type of drag that is based on the shape of the object?

Answer 27

form drag

Question 28

What is interference drag?

Answer 28

- Occurs at surfaces with sharp angles - Varied currents meet and interact

Question 29

What is the type of drag that is occurs at surfaces with sharp and varied angles when they meet and interact?

Answer 29

interference drag

Question 30

What is skin friction drag?

Answer 30

aerodynamic resistance due to the contact of moving air with the aircraft surface

Question 31

The aerodynamic resistance due to the contact of moving air with the aircraft surface is which type of drag?

Answer 31

skin friction drag

Question 32

The byproduct of flying through the air is which type of drag?

Answer 32

parasite drag

Question 33

What is (lift) induced drag?

Answer 33

- Generated as soon as lift is created - Increases as speed decreases - Greater angle of attack = greater induced drag

Question 34

What type of drag is created as soon as lift is created, when speed decreases, and with a greater angle of a attack this drag increases as well?

Answer 34

Induced drag

Question 35

Describe the relationship between drag and airspeed for parasite and induced drags.

Answer 35

- Parasite drag: increase as the speed increase - Induced drag: increased at slower airspeed, reduces at higher airspeeds - Parasite and induced drag added up equals total drag; in the middle is where the least amount of drag is created (Vglide)

Question 36

Describe the relationship between Coefficient of drag or lift and angle of attack.

Answer 36

- The coefficient of drag increases as the angle of attack increases - The coefficient of lift increases to a certain point as the angle of attack increases - The point that the coefficient of lift decreases at a certain angle of attack is when the critical angle of attack has been reached and the airplane begins to stall - The coefficients of drag and lift added up equal a curve that signify at which point is the best angle of attack for the best ratio of lift and drag

Question 37

What are wingtip vortices?

Answer 37

- Created due to the difference of pressure below the wing (high pressure) and above the wing (low pressure) - Due to pressure wanting to go from high to low, the high pressure moves upward to the low pressure, then outward at the wingtips - the size of the aircraft will affect the size of the wingtip vortices

Question 38

Wingtip vortices are greatest for which types of aircraft?

Answer 38

- Heavy: generating more lift = more wingtip vortices - Clean: no flaps used (flaps allow aircraft to generate more lift while flying at slower speeds, if no flaps are used, then the aircraft will need to fly faster, which will create more lift and result in more wingtip vortices) - Slow: will have a higher angle of attack, which will create more lift, which will create more wingtip vortices

Question 39

Why does an aircraft in a clean configuration create wingtip vortices?

Answer 39

- No flaps are used - Flaps allow aircraft to generate more lift while flying at slower speeds - If no flaps are used, then the aircraft will need to fly faster, which will create more lift and result in more wingtip vortices

Question 40

Why does an aircraft in a heavy configuration create wingtip vortices?

Answer 40

- More lift is being generated, which will result in more wingtip vortices

Question 41

Why does an aircraft in a slow configuration create wingtip vortices?

Answer 41

- Will have a higher angle of attack - Will create more lift - Will create more wingtip vortices

Question 42

When wingtip vortices are generated, where do they go?

Answer 42

They will "fall"/sink under the aircraft's flight path

Question 43

In order to avoid the area/path where the wingtip vortices will fall/sink under, how do you maneuver the aircraft when on takeoff?

Answer 43

- Fly above the other (larger) aircraft - Wait several minutes to pass

Question 44

In order to avoid the area/path where the wingtip vortices will fall/sink under, how do you maneuver the aircraft when on landing?

Answer 44

- Touchdown before the path where the other (larger) aircraft took off

Question 45

When a large aircraft generates large wingtip vortices and there is wind, what do you need to consider?

Answer 45

The wind can push the wingtip vortices over into the other runway where the smaller airplane is trying to takeoff/land

Question 46

What is ground effect?

Answer 46

The result of the interference of the surface of the Earth with the airflow patterns about and airplane

Question 47

The result of the interference of the surface of the Earth with the airflow patterns about and airplane is known as what?

Answer 47

ground effect

Question 48

When is ground effect most prevalent?

Answer 48

At an altitude that is less than the length of the wingspan above the ground

Question 49

Describe the sensation of ground effect and why it occurs?

Answer 49

The aircraft will feel as if it's floating at an altitude that is less than the length of the wingspan due to less lift but more induced drag

Question 50

How will ground effect affect an aircraft when on takeoff?

Answer 50

The aircraft become airborne before the proper takeoff speed

Question 51

How will ground effect affect an aircraft when on landing?

Answer 51

The aircraft will float on landing

Question 52

What is one maneuver that ground effect can be used?

Answer 52

Soft field landing, get to the speed to be in ground effect until enough airspeed is gained and then full take off