AEROLAB DRAG

Question 1

As an aircraft moves/travel through air, every part of it that is exposed to the airflow produces a different type of resistance to the forward motion which constitute to the ____________.

Answer 1

Total Drag

Question 2

2 forms of drag

Answer 2

Parasite and Induced

Question 3

is comprised of all the forces
that work to slow an aircraft’s
movement which includes
resistance of air moving over
aircraft’s surface.

Answer 3

Parasite drag

Question 4

is an inevitable
consequence of lift and is
produced by the passage
of an airfoil through the air.

Answer 4

Induced drag

Question 5

types of parasite drag

Answer 5

Skin friction, Form drag, interference drag

Question 6

skin friction and form drag are also called?

Answer 6

profile drag

Question 7

Type of drag is the aerodynamic resistance due to the contact of moving air
with the surface of an object, and in this particular case that object would be an
aircraft. Every surface, no matter how apparently smooth, has a rough, ragged
surface when observed under a microscope.

Answer 7

Skin Friction Drag

Question 8

Factors that affect the flow in the boundary layer

Answer 8

Flow Quality
Shape
Texture
Pressure Gradient
Reynolds Number
Heating of the fluid

Question 9

A laminar layer cannot exist when pressure is rising in the direction of the flow. On a curved surface, such as an airfoil, the transition point is usually at, or near to the point of maximum thickness. Because of the _________________ existing on a curved surface the transition point will be further forward than if the surface was flat.

Answer 9

Adverse Pressure Gradient

Question 10

This is generated due to the aircraft’s shape and the airflow around
it. When the air has to separate to move around a moving aircraft
and its components, it eventually rejoins after passing the body.
How quickly and smoothly it rejoins is representative of the
resistance it creates, which creates additional force to overcome.

Answer 10

Form Drag

Question 11

To reduce form drag, it is necessary to delay the separation as close to the trailing edge as possible.

___________ increases the ratio between the length and depth of the body, reducing the curvature
of the surfaces and thus the adverse pressure gradient.

Answer 11

Streamlining

Question 12

___________ is the measure of streamlining.

Answer 12

Fitness ratio

Question 13

Formula of Fitness Ratio

Answer 13

f = length / depth

Question 14

An example of this would be the intersection created by the connection of the wing and the fuselage at the wing root. The most _____________ is observed when two surfaces meet at perpendicular angles. Fairings are used to reduce this tendency.

Answer 14

interference drag

Question 15

Factors affecting Parasite Drag

Answer 15

IAS
Configuration
Airframe Contamination

Question 16

Once again, ________ is an inherent component, a rather undesirable by-product
of lift. Wing tip vortices modify upwash and downwash in the vicinity of the wing
which produces a rearward component to the lift vector known as the “__________________”.

Answer 16

Induced drag

Question 17

Factors Affecting Induced Drag

Answer 17

Size of the lift force, speed of the aircraft, aspect ratio of the wing

Question 18

Lift must be equal to weight in flight so induced drag will depend on the weight of the aircraft. Induced drag will be greater at higher aircraft weights. Certain maneuvers require the lift force to be ___________. This relationship of lift to weight ratio is also known as the
Load Factor.

Answer 18

greater than the aircraft weight

Question 19

Induced drag decreased with increasing speed. This is because as speed __________ the downwash caused by the tip vortices becomes less significant, the rearward inclination of the lift is less, and therefore induced drag is less.

Answer 19

increases

Question 20

The tip vortices of a high
aspect ratio wing affect a
smaller proportion of the span
so the overall change in
downwash will be _____, giving a
smaller rearward tilt to the lift
force. Induced drag therefore
decreases as aspect ratio
increases (for a given lift
force).

Answer 20

less

Question 21

Factors to consider if one decides to continue the increase of AR

Answer 21

Excessive wing bending moments
Reduced rate of roll
Reduced ground clearance in roll during TO and L

Question 22

Methods of Reducing Induced Drag

Answer 22

Wing end plates
Tip Tanks
Winglets
Wing tip shape

Question 23

• A flat plate placed at the wing tip will
  restrict the tip vortices and have a
  similar effect to an increased aspect
  ratio, but without the extra bending
  loads.
• However, the plate itself will cause
  parasite drag, and at a higher speeds
  there may be no overall

Answer 23

Wing end-plates

Question 24

• Fuel tanks placed at the wing
  tips will have a similar
  beneficial effect to an end
  plate, will reduce the induced
  drag.

Answer 24

Tip tanks

Question 25

• Small vertical aerofoils which
  form part of the wing tip. Shaped
  and angled to the induced flow,
  they generate a small forward
  force.
• Winglets partly block the air
  flowing from the bottom to the
  top surface of the wing, reducing
  the strength of the tip vortex.

Answer 25

Winglets

Question 26

• The shape of the wing
  tip can affect the
  strength of the tip
  vortices, and designs
  such as turned down or
  turned up wing tips
  have been used to
  reduce induced drag.

Answer 26

Wing tip shape