Aero 2: Stalls & Drag

Question 1

Total Drag

Answer 1

The sum of parasite drag and induced drag

Question 2

Parasite Drag

Answer 2

All drag not associated with the production of lift.

Question 3

Form Drag

Answer 3

Drag resulting from the airflow separation over a surface and the low pressure wake created

Is a component of Parasite Drag

Question 4

Friction Drag

Answer 4

Drag arising from friction forces at the surface of an aircraft, due to the viscosity of the air

Is a component of Parasite Drag

Question 5

Induced Drag

Answer 5

That portion of total drag resulting from the production of lift

Question 6

Boundary Layer

Answer 6

The layer of airflow over the surface of an airfoil, which shows local airflow retardation caused by viscosity

Question 7

Stall

Answer 7

A condition of flight in which an increase in AOA will result in a decrease in the coefficient of lift

Question 8

Spin

Answer 8

An asymmetrical aggravated stall resulting in autorotation

Question 9

Drag

Answer 9

The component of the aerodynamic force that is parallel to relative wind and acts in the same direction

Question 10

What factors affect induced drag?

Answer 10

Lift
Weight
Air density
Velocity
Wing span

Question 11

How can induced drag be minimized?

Answer 11

(1) Increasing density, velocity, or wingspan

(2) Install devices to impede airflow around the wingtip (spanwise airflow) such as winglets, missile rails, and wingtip tanks

Question 12

L/Dᴍᴀx

Answer 12

The greatest ratio of lift to drag

Question 13

L/Dᴍᴀx AOA

Answer 13

The most efficient AOA for that airfoil

Also known as max range

Question 14

How does velocity change total drag?

Answer 14

As airspeed decreases to stalling speed, total drag increases due to induced drag increase.

As airspeed increases to terminal airspeed/velocity, total drag increases due to parasite drag increase.

Question 15

On the total drag curve, which type of drag dominates at lower airspeeds?

Answer 15

Induced drag

Question 16

On the total drag curve, which type of drag dominates at higher airspeeds?

Answer 16

Parasite drag

Question 17

How can form drag be reduced?

Answer 17

By creating a more streamlined object

Form drag is easier to reduce than friction drag

Question 18

How can friction drag be reduced?

Answer 18

(1) By using a glossy, flat finish on plane surfaces

(2) By removing protruding heads, any surface roughness, and irregularities

Question 19

What types of flow are present with the boundary layer?

Answer 19

Laminar flow and turbulent flow

Question 20

Laminar flow

Answer 20

Boundary layer airflow that is smooth/ unbroken (creates little friction)

Question 21

Turbulent flow

Answer 21

Boundary layer airflow characterized by turbulent, unsteady airflow (creates more friction)

Question 22

Which boundary airflow sticks to the boundary layer? Which does not?

Answer 22

Turbulent airflow sticks to the boundary layer. Laminar airflow separates from the boundary layer easily.

Question 23

What is the difference between speeds for a power-on stall and a power-off stall?

Answer 23

Power-off stall speeds are higher because the engines are at idle

Higher stall speed means it’s easier to stall at a high speed (not good)

Question 24

What must be present for an aircraft to spin?

Answer 24

(1) Aircraft must be stalled

(2) Yaw present

Question 25

What is the relationship between the wings during a spin?

Answer 25

The inside wing is more stalled than the outside wing (due to higher AOA).

This causes the inside wing to have more drag than the outside wing.

Question 26

How do you recover from a spin?

Answer 26

(1) Correct the stall by reducing excessive AOA

(2) Correct the yaw input by applying opposite rudder

PARE Procedure

Question 27

What causes induced drag?

Answer 27

It is caused by air downwash that is created from wingtip vortices from spanwise airflow over the wings

Question 28

Induced Drag Formula

Answer 28

Di = kL² / (ρV²b²)

Question 29

How thick is the boundary layer?

Answer 29

About 1mm thick

Question 30

Stall Equation

Answer 30

Vₛ= sqrt(2W/ρSCₗₘₐₓ)