8.3 theory of flight Flashcards
1
Q
wat are the 4 fundamental forces?
A
lift
weight
thrust
drag
2
Q
what is glide ratio?
A
ratio of distance forward to the distance downwards
3
Q
what does glide scope vary with?
A
decreasing airspeed and fundamental forces
4
Q
will glide scope change if fundamental forces remain the same?
A
the glide ratio will remain constant
5
Q
the max value of the glide ratio is relative to what?
A
lift and drag ratio
6
Q
what is the glide ratio the sum off?
A
forward speed divided by the sink speed
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
8
Q
what does the sum of all upward components of forces equal what?
A
equals the sum of all downwards components of forces
9
Q
what does the sum of all forward components of forces equal?
A
the sum of all backwards components of forces
10
Q
lift is equal to what?
A
weight
sum of vertical force is 0
no climb or decent
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
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
13
Q
what are moments caused by?
A
forces on a lever not acting through the point of rotation
14
Q
what does lift on the wing carry?
A
weight of aircraft and downwards acting stabilizer
15
Q
anti clockwise rotation equals what?
A
clockwise rotation
16
Q
what does lift produce?
A
L1 to produce a anticlockwise rotation and forward force
17
Q
what must L1 be balanced by?
A
a clockwise rotation giving upwards force to ensure equilibrium is maintained
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
19
Q
how can a pitching moment of a wing be measured?
A
direct measurement on a balance or by pressure plotting
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
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
22
Q
what happens when an aircraft enters climb?
A
weight acting parallel to the drag line which slows it further
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
24
Q
what does aircraft performance result from?
A
combination of aircraft powerplant and characteristics
25
aircraft characteristics define what?
power and thrust requirements for various conditions of flight
26
what does the red, blue, green curve represent in total drag diagram?
red = induced drag
blue = parasite drag
green = total drag
27
what does a aircraft require to fly?
mechanical energy
28
what are the two forms of mechanical energy?
kinetic - energy of speed
potential - stored energy
29
what formula summarizes energy relationships?
KE = 1/2 * m * a
PE = m * g * h
30
what is thrust measured in?
pounds or newtons
31
when does positive climb performance occur?
when an aircraft gains PE by increasing altitude
32
the combination of what factors contributes t positive climb performance?
aircraft climb using excess power
aircraft climb by converting airspeed to altitude
33
what does an increase in altitude also does what?
increase the power required to decrease the power available climb performance diminished with altitude
34
what is range performance?
ability of an aircraft to convert fuel energy into flying distance
35
rang performance appears in what forms?
take max flying distance from given fuel load
to fly at specified distance with minimum fuel used
36
if max specific range is desired what must flight conditions provide?
flight conditions must provide max speed pre fuel flow
37
the values of specific range versus speed are affected by what variables?
aircraft gross weight
altitude
external aerodynamic configuration of the aircraft
38
when an aircraft flies at a constant altitude with its wings level what happens?
lift is equal to the weight of the aircraft
39
what happens when an aircraft banks?
lift acts inwards toward center of turn and upwards
40
an aircraft requires what to make a turn?
sidewards force
41
the force of lift is divided into what?
vertical ad horizontal components at right angles to each other
42
what is the vertical component of a turn?
weight
43
what is the horizonal component of a turn?
force that pulls the aircraft from straight path into a turn
44
what is centrifugal force?
equal and opposite reaction of aircraft to change the direction and act as equal and opposite to the horizontal component of lift
45
for an aircraft to turn it must be what?
banked
46
what must happen to ensure the aircraft maintains its altitude during turn?
lift must be equal to the resultant of centrifugal force and weight
47
what is the risk of increasing AOA to maintain the vertical component of lift?
could reach critical AOA so risk of accelerated stall
48
what must compensate for added lift if airspeed was increased during a turn what must happen?
AOA must decrease or increase bank angle to maintain constant altitude
49
what happens in a slipping turn?
aircraft is not turning at the rate appropriate to the bank being used since yaw is outside the turn path
50
when the aircraft is banked to much the horizonal component is grater than what?
grater than centrifugal force
51
equilibrium is what during a turn?
horizontal lift and centrifugal force is re established by decreasing the bank or increasing the turn or both
52
what does a skidding turn result from?
excess centrifugal force over the horizontal over horizontal lift component
53
maximum load factor at given bank angle what is the ratio?
ratio of lift to weight
54
load factor is given in what ratio?
in grams
55
load factor is a representation of what?
the load of the aircraft structure compared to the relative acceleration of gravity in straight and level flight
56
what is the max load factor given as?
limit load factors
57
what load id an aircraft designed to handle for safety?
limit load factor
58
the load factor is the resultant of what?
resultant force or lift in a turn divided by the weight
59
load factor can also be described as what?
g load
60
the load factor is related to the max bank angle why?
for structural strength of the aircraft and passenger comfort
61
the higher the speed what is the rate of turn?
the slower the rate of turn
62
what is a stall?
aerodynamic loss of lift that occurs when an airfoil exeats critical angle of attack and smooth flow over the wing breaks
63
where can stall occur?
at any sir speed or any altitude
64
once stall has occurred what must happen?
reduce AOA below original stalling angle to restore lift
65
what are the characteristics of a stall?
loss of lift
pitch down
roll or yaw to one side
66
how easy is it to recover a stall with a nose pitch down moment in a stable aircraft?
easy by lowering pitch altitude
67
how easy is it to recover a stall with a nose pitching down moment on a unstable aircraft?
hard as it can go in to a spin which can be impossible to recover from
68
where are stalls common?
at low speeds
69
where is the more room to recover from a stall in flight?
during landing and takeoff
70
the graph of load factor can be plotted against what?
against indicated airspeed
71
what is the flight envelope diagram known as?
V n diagrams
72
each flight envelope is an illustration of what?
aircrafts gross weight
configuration of flaps and landing gear
applicable altitude
73
in the V n diagram what are the different stages?
normal operating range
caution range
structural damage
structural failure
74
what are structural limits?
positive and negative G allowed limits of the aircraft
75
what are structural limits also refereed to?
acceleration limits or limit loads factors
76
what will numerous over stresses cause?
shorten the service life of the aircraft
77
what do aeroelastic limits define?
the max operating speeds
above this structural damage or failure can occur
78
what is the aeroelastic limit frequently referred to as?
redline airspeeds
79
what does ultimate structural limits define?
operating strength limits of the aircraft
80
ultimate structural loads are outside what?
outside normal operating envelope
81
what is the usual aircraft designee rule for ultimate structural limits?
150% of the structural limit
82
what do plain flaps do?
change wing curvature when extended increasing flow serrating at the trailing edge creating larger drag
83
what is the maximum angle of attack of plain flaps?
12 degrease
84
what increase in lift does plain flaps give?
50% - 55% of increase in lift
85
what increase in lift for single slotted flap?
65% - 70% at 16 degrease AOA
86
what is the increase in lift for multi slotted flap?
70% at 18 degrease
87
what does splatted flap produce?
higher level of lift
88
what do split flaps produce?
a nose pitching down moment with 60% - 65% increase in lift at 14 degrease
89
what s the most common type of flaps on aircraft?
fowler flaps
90
what do fowler flaps allow pilots to do?
to change settings for take off and landing
91
what do fowler flaps increase?
wing area when extended witch can help generate lift
92
what do fowler flaps produce?
nose down pitching moment with a 95% increase in lift at 15 degrease of angle of attack
93
flaps create a change in what?
in pressure
94
what flaps create the most pressure change?
slotted flaps
95
what flaps create the smallest pressure change?
plain wing
96
what happens when flaps are lowered?
lift is increased and is to proportional increase in drag
97
what do leading edge flaps lower?
staling speeds
98
what happens when the leading edge and not the trailing edge is dropped?
increase in stalling angle and level flight stalling altitude
99
leading edge flaps can be licked with what?
airspeed measuring systems so they droop when the speeds fall below the minimum
100
what do Kruger flaps increases?
increase wings camber to generate more lift
101
wat type of wings are Kruger flaps installed on?
on swept wings
102
slotted Kruger flaps have similar aerodynamic performance to slotted flaps but what is different?
they have a different deployment method
103
what do leading edge flaps increase?
the Cl
104
what do leading edge cuffs increase?
CL-max and the camber of the wing
105
wat devices are cuffs?
aerodynamic devices
106
where do leading edge cuffs extend?
down and forward
107
108
fixed nature of leading edge cuffs extract a penalty in what?
maximum cruise airspeed
recent advances have reduced this penalty
109
what do slats prevent?
flow separation by suppling more energy to the boundary layer
110
what happens when the slat is deployed?
an increase in the camber of the wing
110
what is a slot?
fixed aerodynamic feature of the wing
reduces stall speeds and performance at low handling speeds
111
define a slot?
a spanwise gap in each wing allowing air to flow bellow the upper surface
112
what happens with slots at low AOA?
airflow through the slot is insufficient and contributes to drag
113
a leading edge slot can do what?
increase maximum coefficient of lift o an airfoil by 40%
114
what is a vortex gyrator?
metal projection on the wings surface
115
what are the shapes of vortex generators?
rectangular
arofoil shape
116
what do vortex generators do when placed correctly?
improve performance and controllability on the aircraft at low speeds and in climb at high AOA
117
what is the adverse pressure gradient?
air moves from low pressure to high pressure
118
high pressure losses energy until what?
until the airflow separates from the wing
119
wat air is not affected by skin friction?
air above the boundary layer
120
wat do vortex generators act like and what do they create?
act like mini wing tip vortices so spiral the free stream airflow
121
wat do vortex generators enable the wing to do?
enable wing tip to operate at higher AOA
122
wat are winglets?
small structs at the aircrafts wing
123
what do winglets do?
creates vortices at wing tip witch creates a lot of drag and turbulence
124
what is the simplest way to reduce induced drag?
increase the wing span
125
wat does increasing the wing span do?
generates more lift and thrust
126
what is the down side of a longer wing span?
weight penalty
fuel efficiency losses
127
wat is the solution t the problem on increasing the wingspan?
adding winglets which ensures the vortex of induced drag which is torn apart and distributed vertically
128
winglets generate lift in what direction?
perpendicular to relative wind
129
when a lift vector is drawn from the winglet the lift vector points where?
forward a little
130
what are the benefits of installing winglets on aircraft?
reduced fuel consumption
increased range
improved performance
lower emissions
