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Mod 8 basic aerodynamics > 8.3 theory of flight > Flashcards

8.3 theory of flight Flashcards

1
Q

wat are the 4 fundamental forces?

A

lift
weight
thrust
drag

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2
Q

what is glide ratio?

A

ratio of distance forward to the distance downwards

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3
Q

what does glide scope vary with?

A

decreasing airspeed and fundamental forces

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4
Q

will glide scope change if fundamental forces remain the same?

A

the glide ratio will remain constant

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5
Q

the max value of the glide ratio is relative to what?

A

lift and drag ratio

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6
Q

what is the glide ratio the sum off?

A

forward speed divided by the sink speed

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7
Q

what must a heavier aircraft do to ensure it has the same glide scope as a lighter aircraft?

A

higher airspeed is required

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8
Q

what does the sum of all upward components of forces equal what?

A

equals the sum of all downwards components of forces

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9
Q

what does the sum of all forward components of forces equal?

A

the sum of all backwards components of forces

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10
Q

lift is equal to what?

A

weight
sum of vertical force is 0
no climb or decent

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11
Q

power plant is set so thrust is equal to what?

A

to drag
sum of horizontal forces is 0
no change in acceleration

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12
Q

what is the clockwise moments acting on an aircraft are equal to what?

A

the anticlockwise moment acting on an aircraft
sum of moment of 0
no rotation

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13
Q

what are moments caused by?

A

forces on a lever not acting through the point of rotation

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14
Q

what does lift on the wing carry?

A

weight of aircraft and downwards acting stabilizer

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15
Q

anti clockwise rotation equals what?

A

clockwise rotation

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16
Q

what does lift produce?

A

L1 to produce a anticlockwise rotation and forward force

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17
Q

what must L1 be balanced by?

A

a clockwise rotation giving upwards force to ensure equilibrium is maintained

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18
Q

what is the wing pitching moment a product of?

A

lift and distance between center of gravity and center of pressure of the wing

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19
Q

how can a pitching moment of a wing be measured?

A

direct measurement on a balance or by pressure plotting

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20
Q

if pitching moments are measured at various points along the cord for 7 values what will we find?

A

at one particular point the centrifugal moment will be constant

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21
Q

what are the ways of considering the effects of changing angle of attack on the pitching moment on an airfoil?

A

change in lift through CP
changes in aerodynamic center

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22
Q

what happens when an aircraft enters climb?

A

weight acting parallel to the drag line which slows it further

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23
Q

what are the primary factors affecting performance?

A

take off and landing distance
rate of climb
ceiling
payload
range
speed
maneuverability
stability
fuel economy

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24
Q

what does aircraft performance result from?

A

combination of aircraft powerplant and characteristics

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25
Q

aircraft characteristics define what?

A

power and thrust requirements for various conditions of flight

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26
Q

what does the red, blue, green curve represent in total drag diagram?

A

red = induced drag
blue = parasite drag
green = total drag

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27
Q

what does a aircraft require to fly?

A

mechanical energy

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28
Q

what are the two forms of mechanical energy?

A

kinetic - energy of speed
potential - stored energy

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29
Q

what formula summarizes energy relationships?

A

KE = 1/2 * m * a
PE = m * g * h

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30
Q

what is thrust measured in?

A

pounds or newtons

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31
Q

when does positive climb performance occur?

A

when an aircraft gains PE by increasing altitude

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32
Q

the combination of what factors contributes t positive climb performance?

A

aircraft climb using excess power
aircraft climb by converting airspeed to altitude

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33
Q

what does an increase in altitude also does what?

A

increase the power required to decrease the power available climb performance diminished with altitude

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34
Q

what is range performance?

A

ability of an aircraft to convert fuel energy into flying distance

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35
Q

rang performance appears in what forms?

A

take max flying distance from given fuel load
to fly at specified distance with minimum fuel used

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36
Q

if max specific range is desired what must flight conditions provide?

A

flight conditions must provide max speed pre fuel flow

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37
Q

the values of specific range versus speed are affected by what variables?

A

aircraft gross weight
altitude
external aerodynamic configuration of the aircraft

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38
Q

when an aircraft flies at a constant altitude with its wings level what happens?

A

lift is equal to the weight of the aircraft

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39
Q

what happens when an aircraft banks?

A

lift acts inwards toward center of turn and upwards

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40
Q

an aircraft requires what to make a turn?

A

sidewards force

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41
Q

the force of lift is divided into what?

A

vertical ad horizontal components at right angles to each other

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42
Q

what is the vertical component of a turn?

A

weight

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43
Q

what is the horizonal component of a turn?

A

force that pulls the aircraft from straight path into a turn

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44
Q

what is centrifugal force?

A

equal and opposite reaction of aircraft to change the direction and act as equal and opposite to the horizontal component of lift

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45
Q

for an aircraft to turn it must be what?

A

banked

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46
Q

what must happen to ensure the aircraft maintains its altitude during turn?

A

lift must be equal to the resultant of centrifugal force and weight

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47
Q

what is the risk of increasing AOA to maintain the vertical component of lift?

A

could reach critical AOA so risk of accelerated stall

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48
Q

what must compensate for added lift if airspeed was increased during a turn what must happen?

A

AOA must decrease or increase bank angle to maintain constant altitude

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49
Q

what happens in a slipping turn?

A

aircraft is not turning at the rate appropriate to the bank being used since yaw is outside the turn path

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50
Q

when the aircraft is banked to much the horizonal component is grater than what?

A

grater than centrifugal force

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51
Q

equilibrium is what during a turn?

A

horizontal lift and centrifugal force is re established by decreasing the bank or increasing the turn or both

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52
Q

what does a skidding turn result from?

A

excess centrifugal force over the horizontal over horizontal lift component

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53
Q

maximum load factor at given bank angle what is the ratio?

A

ratio of lift to weight

54
Q

load factor is given in what ratio?

A

in grams

55
Q

load factor is a representation of what?

A

the load of the aircraft structure compared to the relative acceleration of gravity in straight and level flight

56
Q

what is the max load factor given as?

A

limit load factors

57
Q

what load id an aircraft designed to handle for safety?

A

limit load factor

58
Q

the load factor is the resultant of what?

A

resultant force or lift in a turn divided by the weight

59
Q

load factor can also be described as what?

A

g load

60
Q

the load factor is related to the max bank angle why?

A

for structural strength of the aircraft and passenger comfort

61
Q

the higher the speed what is the rate of turn?

A

the slower the rate of turn

62
Q

what is a stall?

A

aerodynamic loss of lift that occurs when an airfoil exeats critical angle of attack and smooth flow over the wing breaks

63
Q

where can stall occur?

A

at any sir speed or any altitude

64
Q

once stall has occurred what must happen?

A

reduce AOA below original stalling angle to restore lift

65
Q

what are the characteristics of a stall?

A

loss of lift
pitch down
roll or yaw to one side

66
Q

how easy is it to recover a stall with a nose pitch down moment in a stable aircraft?

A

easy by lowering pitch altitude

67
Q

how easy is it to recover a stall with a nose pitching down moment on a unstable aircraft?

A

hard as it can go in to a spin which can be impossible to recover from

68
Q

where are stalls common?

A

at low speeds

69
Q

where is the more room to recover from a stall in flight?

A

during landing and takeoff

70
Q

the graph of load factor can be plotted against what?

A

against indicated airspeed

71
Q

what is the flight envelope diagram known as?

A

V n diagrams

72
Q

each flight envelope is an illustration of what?

A

aircrafts gross weight
configuration of flaps and landing gear
applicable altitude

73
Q

in the V n diagram what are the different stages?

A

normal operating range
caution range
structural damage
structural failure

74
Q

what are structural limits?

A

positive and negative G allowed limits of the aircraft

75
Q

what are structural limits also refereed to?

A

acceleration limits or limit loads factors

76
Q

what will numerous over stresses cause?

A

shorten the service life of the aircraft

77
Q

what do aeroelastic limits define?

A

the max operating speeds
above this structural damage or failure can occur

78
Q

what is the aeroelastic limit frequently referred to as?

A

redline airspeeds

79
Q

what does ultimate structural limits define?

A

operating strength limits of the aircraft

80
Q

ultimate structural loads are outside what?

A

outside normal operating envelope

81
Q

what is the usual aircraft designee rule for ultimate structural limits?

A

150% of the structural limit

82
Q

what do plain flaps do?

A

change wing curvature when extended increasing flow serrating at the trailing edge creating larger drag

83
Q

what is the maximum angle of attack of plain flaps?

A

12 degrease

84
Q

what increase in lift does plain flaps give?

A

50% - 55% of increase in lift

85
Q

what increase in lift for single slotted flap?

A

65% - 70% at 16 degrease AOA

86
Q

what is the increase in lift for multi slotted flap?

A

70% at 18 degrease

87
Q

what does splatted flap produce?

A

higher level of lift

88
Q

what do split flaps produce?

A

a nose pitching down moment with 60% - 65% increase in lift at 14 degrease

89
Q

what s the most common type of flaps on aircraft?

A

fowler flaps

90
Q

what do fowler flaps allow pilots to do?

A

to change settings for take off and landing

91
Q

what do fowler flaps increase?

A

wing area when extended witch can help generate lift

92
Q

what do fowler flaps produce?

A

nose down pitching moment with a 95% increase in lift at 15 degrease of angle of attack

93
Q

flaps create a change in what?

A

in pressure

94
Q

what flaps create the most pressure change?

A

slotted flaps

95
Q

what flaps create the smallest pressure change?

A

plain wing

96
Q

what happens when flaps are lowered?

A

lift is increased and is to proportional increase in drag

97
Q

what do leading edge flaps lower?

A

staling speeds

98
Q

what happens when the leading edge and not the trailing edge is dropped?

A

increase in stalling angle and level flight stalling altitude

99
Q

leading edge flaps can be licked with what?

A

airspeed measuring systems so they droop when the speeds fall below the minimum

100
Q

what do Kruger flaps increases?

A

increase wings camber to generate more lift

101
Q

wat type of wings are Kruger flaps installed on?

A

on swept wings

102
Q

slotted Kruger flaps have similar aerodynamic performance to slotted flaps but what is different?

A

they have a different deployment method

103
Q

what do leading edge flaps increase?

A

the Cl

104
Q

what do leading edge cuffs increase?

A

CL-max and the camber of the wing

105
Q

wat devices are cuffs?

A

aerodynamic devices

106
Q

where do leading edge cuffs extend?

A

down and forward

107
Q
A
108
Q

fixed nature of leading edge cuffs extract a penalty in what?

A

maximum cruise airspeed
recent advances have reduced this penalty

109
Q

what do slats prevent?

A

flow separation by suppling more energy to the boundary layer

110
Q

what happens when the slat is deployed?

A

an increase in the camber of the wing

110
Q

what is a slot?

A

fixed aerodynamic feature of the wing
reduces stall speeds and performance at low handling speeds

111
Q

define a slot?

A

a spanwise gap in each wing allowing air to flow bellow the upper surface

112
Q

what happens with slots at low AOA?

A

airflow through the slot is insufficient and contributes to drag

113
Q

a leading edge slot can do what?

A

increase maximum coefficient of lift o an airfoil by 40%

114
Q

what is a vortex gyrator?

A

metal projection on the wings surface

115
Q

what are the shapes of vortex generators?

A

rectangular
arofoil shape

116
Q

what do vortex generators do when placed correctly?

A

improve performance and controllability on the aircraft at low speeds and in climb at high AOA

117
Q

what is the adverse pressure gradient?

A

air moves from low pressure to high pressure

118
Q

high pressure losses energy until what?

A

until the airflow separates from the wing

119
Q

wat air is not affected by skin friction?

A

air above the boundary layer

120
Q

wat do vortex generators act like and what do they create?

A

act like mini wing tip vortices so spiral the free stream airflow

121
Q

wat do vortex generators enable the wing to do?

A

enable wing tip to operate at higher AOA

122
Q

wat are winglets?

A

small structs at the aircrafts wing

123
Q

what do winglets do?

A

creates vortices at wing tip witch creates a lot of drag and turbulence

124
Q

what is the simplest way to reduce induced drag?

A

increase the wing span

125
Q

wat does increasing the wing span do?

A

generates more lift and thrust

126
Q

what is the down side of a longer wing span?

A

weight penalty
fuel efficiency losses

127
Q

wat is the solution t the problem on increasing the wingspan?

A

adding winglets which ensures the vortex of induced drag which is torn apart and distributed vertically

128
Q

winglets generate lift in what direction?

A

perpendicular to relative wind

129
Q

when a lift vector is drawn from the winglet the lift vector points where?

A

forward a little

130
Q

what are the benefits of installing winglets on aircraft?

A

reduced fuel consumption
increased range
improved performance
lower emissions

Mod 8 basic aerodynamics (4 decks)

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