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Aeronautical Laboratory > Module 6 - Drag Measurements > Flashcards

Module 6 - Drag Measurements Flashcards

1
Q

What are the four forces of flight?

A
  • lift
  • drag
  • thrust
  • weight
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2
Q

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

A

drag

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3
Q

forms of drag

A
  • total drag
  • parasite drag
  • induced drag
  • skin friction drag
  • form drag
  • interference drag
  • profile drag
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4
Q

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

A

parasite drag

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5
Q

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

A

induced drag

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6
Q

is the aerodynamic resistance due to the contact of moving air with the surface of an object

A

skin friction drag

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7
Q

factors that affect the type of flow in the boundary layer

A
  • flow quality
  • shape
  • texture
  • pressure gradient
  • Reynold’s number
  • heating of the fluid
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8
Q

a pressure gradient where the static pressure increases in the direction of the flow

A

adverse pressure gradient

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9
Q

A laminar layer cannot exist when pressure is rising in the _______________.

A

direction of the flow

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10
Q

On a curved surface, such as an airfoil, the transition point is usually ___________ the point of maximum thickness.

A

at, or near

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11
Q

Because of the adverse pressure gradient existing on a curved surface, such as an airfoil, the transition point will be ___________ than if the surface was flat.

A

further forward

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12
Q

is generated due to the aircraft’s shape and the airflow around it

A

form drag

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13
Q

When the air has to separate to move around a moving aircraft and its components, it eventually ______ after passing the body. How quickly and smoothly it does is representative of the _________ it creates, which creates additional force to overcome.

A

rejoins, resistance

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14
Q

How to reduce form drag?

A

delay the separation as close to the trailing edge as possible

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15
Q

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

A

streamlining

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16
Q

measure of streamlining

A

fitness ratio

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17
Q

formula for fitness ratio

A

fitness ratio = length/depth

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18
Q

an example of this would be the intersection created by the connection of the wing and the fuselage at the wing root

A

interference drag

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19
Q

The most interference drag is observed when two surfaces meet at _________________.

A

perpendicular angles

20
Q

What is used to reduce interference drag?

A

fairings

21
Q

factors affecting parasite drag

A
  • indicated airspeed
  • configuration
  • airframe contamination
22
Q

parasite drag varies with the square of the _________

A

indicated airspeed

23
Q

parasite drag varies directly in proportion to the frontal area presented to the airflow, also known as the _________________

A

Parasite Area

24
Q

contamination by ice, frost, snow, mud or slush will increase the ________________

A

parasite drag coefficient

25
Q

is an inherent component, a rather undesirable by-product of lift

A

induced drag

26
Q

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 ___________

A

induced drag

27
Q

factors affecting induced drag

A
  • size of the lift force
  • speed of the aircraft
  • aspect ratio of the wing
28
Q

lift must be equal to _______ in flight so induced drag will depend on the _______ of the aircraft

A

weight, weight

29
Q

induced drag will be _______ at higher aircraft weights

A

greater

30
Q

certain maneuvers require the lift force to be ________ than the aircraft weight

A

greater

31
Q

the relationship of lift to weight ratio is also known as the _________

A

load factor

32
Q

relationship of load factor and induced drag

A

directly proportional

33
Q

relationship of induced drag and speed of the aircraft

A

inversely proportional

34
Q

as speed increases, the downwash caused by the tip vortices become ________________, the rearward inclination of the lift is _____, and therefore induced drag is less

A

less significant, less

35
Q

relationship of induced drag and aspect ratio of the wing

A

inversely proportional

36
Q

factors to consider if one decides to continue the increase of the aspect ratio

A
  • excessive wing bending moments
  • reduced rate of roll
  • reduced ground clearance in roll during take-off and landing
37
Q

methods of reducing induced drag

A
  • wing-end plates
  • tip tanks
  • winglets
  • wing tip shape
38
Q

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

A

wing-end plates

39
Q

What type of drag do wing-end plates cause?

A

parasite drag

40
Q

fuel tanks placed at the wing tips will have a similar beneficial effect to an endplate, will reduce the induced drag

A

tip tanks

41
Q

Small vertical aerofoils which form part of the wing tip. Shaped and angled to the induced flow, they generate a small forward force.

A

winglets

42
Q

________ partly block the air flowing from the bottom to the top surface of the wing, reducing the strength of the tip vortex

A

winglets

43
Q

the _____________ 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

A

shape of the wingtip

44
Q

is the sum of an aircraft’s induced drag and parasite drag

A

total drag

45
Q

a number that aerodynamicists use to model all of the complex dependencies of shape, inclination, and flow conditions on aircraft drag

A

drag coefficient

Aeronautical Laboratory (4 decks)

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