4. Drag

Question 1

What is Drag?

Answer 1

The aeronautical term for the air resistance experienced by the aircraft as it moves relative to the air.

Question 2

What are the two types of drag?

Answer 2

Parasite Drag
Induced Drag

Question 3

What is Induced Drag?

Answer 3

The unavoidable by-product of lift and increases as the angle of attack increases.
Manifested as vortices at the trailing edge of the wing and especially at the wingtips.

Question 4

What is parasite drag?

Answer 4

(Aerodynamic of the AC)
This is not directly associated with development of lift.

Question 5

2 sub groups of Parasite drag and onwards?

Answer 5

PROFILE DRAG
- Skin Friction
- Form Drag
INTERFERENCE DRAG

Question 6

What is Interference Drag? (PD)

Answer 6

Interference drag occurs when a substantial change of airflow direction occurs over an airframe.

1. At the junction of aircraft surfaces, (e.g. where the wing joins the fuselage) air flow interference occurs. This disruption of flow creates additional drag.

Question 7

How to reduce Interference Drag? (PD)

Answer 7

Suitable filleting, fairings and streamlining can help to reduce this sort of drag on large components such as the tail, but even on engine pylons and aerials.

Question 8

What is Skin Friction? (PD) (Profile)

Answer 8

Results from the friction forces existing between an object and the air through which it is moving.

Question 9

What affects the magnitude of Skin Friction? (PD) (Profile)

Answer 9

1. The surface area of the aircraft. The whole surface area of the aircraft experiences skin friction drag as it moves through the air.
2. Whether the boundary layer airflow near the surface is laminar or turbulent.
   A turbulent boundary layer causes drag.
3. Roughness on a surface (including ice) will increase skin friction.
4. An increase in airspeed increases skin friction drag.
5. An increase in aerofoil thickness increases skin friction drag from the wing.

Question 10

What is Form Drag? (PD) (Profile)

Answer 10

Form drag results when the airflow separates from the surface of the aerofoil.
Eddies are formed and the streamlined (laminar) flow is disturbed.

Question 11

What is Induced Drag?

Answer 11

Induced drag is a byproduct of lift.

Question 12

What do winglets do?

Answer 12

Another means of reducing wing tip vortices is to
attach ‘winglets’ or ‘sharklets’ at the wing tips.