Subsonic aerodynamics Flashcards
1
Q
The lift and drag forces, acting on an airfoil cross section depend on the ___ around the aerofoil cross section
A
pressure distribution
2
Q
Hvað gerist í “convergent tube with an incrompressible sub-sonic airflow” fyrir static pressure, dynamic pressure og total pressure?
A
Static pressure minnkar
dynamic pressure increases
total pressure það sama
3
Q
Hver er formúla dynamic pressure?
A
1/2 hró * v^2
4
Q
Hvaða eining er notuð til að mæla thickness of aerofoil ?
A
% chord
5
Q
Aspect ratio of a wing is the ratio between..
A
wingspan squared and wing area
6
Q
Dihedral of the wing is the angle between the ___ and the horizontal with the aeroplane in an unbanked, level condition.
A
wing plane
7
Q
Angle of attack is the angle between the __ vector and __ axis.
A
speed, longitudinal
8
Q
Pressure constant and temperature increases, what happens to density?
A
decreases
9
Q
Hvað gerist fyrir hlutfall IAS vs TAS með minnkandi flughæð?
A
mismunur á milli IAS og TAS minnkar með lækkun flughæðar. (Veit að TAS eykst í flughæð og því er þetta væntanlega öfugt í lækkun flugs - EAK).
10
Q
Hvað kallast “the angle between the 0.25 chord line of the wing and the lateral axis”?
A
dihedral of the wing
11
Q
Hvað kallast þetta?: Aircraft weight / wing area
A
wing loading
12
Q
Lift acts at right angles to the ___ ____.
A
relative airflow
13
Q
Thickness to chord ratio: __ thickness of aerofoil section to chord.
A
max
14
Q
Taper ratio is the tip chord to ___ ___.
A
root chord
15
Q
What is the unit of measurement for power?
a) N/m
b) N m/s
A
b) N m/s
16
Q
The __ of an object depends on the acceleration due to gravity.
A
weight
17
Q
kg*(m/s)^2 er í SI-unit system þekkt sem __.
A
Newton
18
Q
Hvað gerist fyrir static- og dynamic pressure í flöskuhálsinum?
A
static pressure drops, dynamic pressure increases (og total pressure er sá sami).
19
Q
Bergnoulli lögmálið segir: The sum of ___ energy and ___ energy is constant
A
pressure, dynamic
20
Q
The SI system unit of measurement for weight is the __.
A
Newton.
21
Q
The (subsonic) static pressure increases/decreases in a flow in a tube when the diameter decreases.
A
decreases
Það er þá væntanlega dynamic pressure sem increases.
22
Q
Subsonic incompressible airflow through a venturi, the dynamic pressure in the throat is higher/lower than in the undisturbed airflow.
A
higher
23
Q
What is the SI unit used for power?
A
W
24
Q
What is the unit of wing loading?
A
N/m^2
25
What is the unit of dynamic pressure (q)?
N/m^2
26
Hvaða mælieining er notuð fyrir "rate of doing work"?
Watt (power)
27
Kinetic energy er mælt í..
joules
28
Hvað færðu ef þú segir mass(kg) * velocity(ms)
momentum
29
Hvaða formúla er þetta? Pstat + 1/2 rho * TAS^2 = Constant
Bernoulli
30
Hvernig er þríhyrningurinn með weight, mass og acceleration, hvað er efst?
weight
31
A line connecting the leading and trailing edge midway between the upper and lower surface of an aerofoil is called the __ line.
camber
32
Hvað heitir SI eining "work"?
J
33
What is the unit measurement for Power?
a) P
b) J/s
c) N/m
b) J/s
34
Hvernig breytist samspil IAS og TAS undir sjávarmáli í ISA aðstæðum?
TAS verður lægri.
35
Units of measurement of pressure is
a) psi
b) kg/m^3
a) psi
36
Hvað er rétt:
a) Drag is acting in the direction of relative wind (airflow) and lift is perpendicular to the relative wind (airflow).
b) Drag is acting in the direction of the longitudinal axis and lift is perpendicular to the longitudinal axis.
a) Drag is acting in the direction of relative wind (airflow) and lift is perpendicular to the relative wind (airflow).
37
If density is kept constant, the dynamic pressure increases proportionately with ____.
the square of the velocity.
| Formúlan er dynamic pressure = 1/2 hró * V^2
38
Hvað heitir "the ratio between the wingspan and the mean geometric chord"?
aspect ratio
39
Hvernig væri þríhyrningurinn úr þessum (hvað væri efst)? Wingspan, mean geometric chord, wing area.
wing area væri efst, þ.e. wing area = wingspan * mean geometric chord.
40
A wing would be __ if the quarter chord line was inclined backwards from the lateral axis.
swept back
41
A wing is said to be ___ if the chord at the wing tip is less than the chord at the root.
tapered.
42
Hvaða SI mælieining er notuð fyrir mass?
kg
43
Hvaða SI mælieining er notuð fyrir weight?
N
44
what is the unit measurement for density?
kg/m^3
45
"In a streamlined flow of fluid, the sum of all energies is constant" þetta á sér rætur að rekja til hvaða kenningar?
Bernoulli
46
If humidity increases, what happens to density?
Density decreases
47
Is weight a force?
yes
48
Hvað er SI unit of pressure?
N / m^2
49
Largest distance between ___ line and camber line is called the camber of an aerofoil section.
chord
50
Hvað er annað orð yfir geometric washout?
wing twist
51
Geometric washout þýðir að the tip of the wing has higher/lower AoA than the root.
lower
52
Hvað kallast force: "Component of the total aerodynamic force, perpendicular to the undisturbed flow"?
lift
53
Profile drag is proportional to relative velocity of air/square of relative velocity of air and ___ coefficient.
square of relative velocity of air and drag coefficient.
54
Hvað gerist fyrir centre of pressure og magnitude of total lift ef þú eykur hraða?
CP moves aft
| Total lift remains constant
55
When AoA decreases, what happens to the point of lowest static pressure? (Assuming no flow seperation)
It moves aft
56
The point where aerodynamic force acts on a wing is called the ___.
centre of pressure, CG
57
Where is Cl/Cd angle typically maximum? _°.
4°
58
Hvað gerist fyrir stagnation point ef AoA increases? (assuming no flow seperation)
stagnation point moves down
59
Total drag (two dimensional) comprises ___ drag and ___ drag.
pressure, skin friction
60
Hvernig er static pressure at stagnation point?
Static pressure reaches a maximum value
61
The aerodynamic centre of the wing is where pitching moment coefficient does not vary with ___.
the angle of attack.
62
The point where the aerodynamic force is applied is called..
the center of pressure
63
The point where the single resultant aerodynamic force acts on an aerofoil is called the..
Centre of pressure
64
With a decrease in AoA, the stagnation point moves..
up/forward (mátt segja bæði held ég).
65
Hvað gerist fyrir location of aerodynamic center of an airfoil section með breytingum á angle of attack?
Ekkert, independent of angle of attack.
66
With increasing downwash, lift generated by the airfoil ___.
increases.
67
Þú ert með positively cambered airfoil í straight and level flight, what happens when speed decreases to a) centre of pressure and b) magnitude of total lift force
a) centre of pressure moves forward
b) magnitude of total lift force remains constant (þar sem þú ert í straight and level flight þá hlýtur magnitude of lift að vera það sama).
68
Profile drag is proportional to __ density and the square of the relative __ of the air.
air, velocity
69
Hvað gerist fyrir center of pressure of a symmetrical aerofoil section (no flow seperation or compressibility effects) ef þú eykur AoA
ekkert, independent of AoA
70
At __ Cl/Cd you will find minimum drag
maximum
71
hró segir til um..
density
72
An aerofoil polar is: a graph of the relation between the lift coefficient and the drag coefficient/angle of attack.
drag coefficient
73
Coefficient of lift is a function of:
| a) density b) pressure c) altitude d) camber of the airflow section e) angle of attack of the airflow section
d) camber of the airflow section
| e) angle of attack of the airflow section
74
Í polvar curve graph getur þú lesið maximum __ coefficient
lift
75
which part of the airplane has the greatest effect on induced drag?
a) wing root junction b) wing tip c) landing gear
b) wing tip
76
Total drag is the sum of __ drag and __ drag.
parasite, induced
77
Spoilers; Hvað gerist fyrir Cd og Cl ef þú beitir spoilers með
a) Constant angle of attack
b) constant speed and load factor
Constant AoA: Cd increases, Cl decreases
| Constant speed and load factor: Cd increases Cl unaffected
78
Hvað gerist við notkun á speed brakes?
Airplane decelerates, ROD increases, lift decreases and drag increases
79
Hvað gerist fyrir minimum drag speed við notkun speed brakes?
reduces
80
Hvað gerist við stall speed við notkun spoilers?
Increases
81
Spoiler surfaces on top of a wing
a) Are for use in landing only for reduction in speed
b) May be used as speed brakes in flight
b) May be used as speed brakes in flight
82
When roll spoilers are extended the part of the wing on which they are mounted experiences a reduction in lift, which generates the desired ___ moment. There is a local increase in drag which suppresses __ __.
rolling, adverse yaw
83
Which boundary layer, when considering its velocity profile perpendicular to the flow, has the greatest change in velocity close to the surface?
a) Turbulent boundary layer
b) The boundary layer in transition between turbulent and laminar.
a) Turbulent boundary layer
84
A turbulent boundary layer produces more __ drag than a laminar one.
friction
85
A laminar boundary layer turns into a turbulent one at the __ point.
transition
86
Er þetta lýsing á laminar eða turbulent layer?: "No velocity components exist normal to the surface"
Laminar
87
The boundary layer is considered to be turbulent between the transition and ___ points.
seperation
88
The turbulent boundary layer has the greatest/least change in velocity close to the surface.
greatest
89
Which resists positive pressure gradient better, laminar or turbulent layer?
Turbulent, it resists positive pressure gradient, has less tendency to separate from the surface.
90
What effect does ageing of an aeroplane have on the boundary layer condition?
The transition point moves forward and a larger part is turbulent
91
To what part of the take-off is icing most detrimental?
rotation
92
What does icing do to the critical angle of attack?
decreases it
93
The drag due to an ageing airframe is identified as
a) Parasite drag
b) Form drag
a) Parasite drag
| það er nú stundum talað um skin friction drag.
94
Ice which is present on leading edges on wings may increase landing distances up to _to_%
40-50%
95
The most important problem of ice accretion on a transport aeroplane during flight is:
a) Increase in drag
b) Blockage of the control surfaces
c) Reduction in CLmax
d) Increase in weight
c) Reduction in CLmax
96
Hvaða formúlu notar þú til að finna Vs eftir því sem load factor breytist?
Vs = Vs1g * sqrt (load factor)
97
Hvaða formúlu notar þú þegar þú ætlar að finna stall speed í X° turn?
Vx = Vs1g * sqrt(1/cos(x))
98
Straight wing, hvað gerist fyrir CP við það að AoA er aukið og fer yfir critical angle of attack
CP moves back.
| Þegar straight wing stallar færist CP back.
99
Swept back wing: CP moves ___ as angle of attack approaches and exceeds the critical angle of attack.
forward.
| Þegar swept wing vængur stalar færist CP foward.
100
A sweep back wing has a pitch down/up effect in stall due to the ___ stalling first
Pitch up, wing tip
101
CP reaches it's most forward point
a) at the stalling angle
b) just below the stalling angle
b) just below the stalling angle
102
Hvað gerist fyrir stagnation point á swept back wing going beyond the critical angle of attack?
stagnation point moves rearward.
103
Stall speeds/control speeds are determined with the CG at the forward limit.
Stall speeds. Control speeds are determined with the CG at the aft limit.
104
Stall speed increases/decreases when during a manoeuvre the aeroplane nose is suddenly pushed firmly downards.
decreases.
105
A negative tail tail stall causes an uncontrollable pitch _ moment.
down
106
Hver er formúla load factor?
Load factor = lift/weight
107
The minimum speed at which lift equals weight is
| a) Vso b) Vs1 c) Vs1g
c) Vs1g
108
During a steady wings level climb, load factor is more/equal/less than one?
Less than one.
| Skýring var að thrust væri að compenseita og því væri véli að ná að klífa.
109
Increase of wing loading will increase/decrease the stall speeds.
increase
110
Í steady wings level horizontal flight þá er load factor hver?
einn
111
Hvað kallast the phenomenon which could happen when sudden reduction in the downward aerodynamic force on the tailplane, happens?
Negative tail stall
112
Hvað færðu ef þú segir mass * acceleration due to gravity?
weight (force)
113
A stall that occurs while the aircraft is experiencing a load factor higher than 1g is called ___.
An accelerated stall
114
Hvað gerist fyrir CP vængs ef þú stallar á swept back væng?
Það færist fram.
115
Hvað gerist fyrir CP vængs ef þú stallar á straight wing?
CP færist aftur
116
When loking at the airflow over the wing, from the wing surface and up, the air is:
a) accelerated to the transition point
b) decelerated to the transition point
c) accelerated to the seperation point
a) accelerated to the transition point
117
Does stall speed (IAS) vary with weight?
Yes
118
Ef þú stallar á conventional low speed aerofoil at low subsonic speeds, flow seperation normally starts on the upper surface near the ___ edge.
trailing
119
Hvað gerist fyrir critical angle of attack ef þú breytir weight? En ef þú færir CG fram/aftur?
Critical angle breytist ekki. Það eykst ef þú færir CG aftur held ég.
120
Hvað virkjar stick pusher?
of hátt angle of attack
121
When pulling out of a dive the angle of attack __.
increases
122
Getur stall hraði breyst í turbulence?
já
123
hvað veldur pitch up tendency í swept wing airplanes at low airspeed?
wingtip stall
124
Is a stick shaker system fitted to an aeroplane to resolve deep stall problems?
No
125
Lowering flaps sometimes produces a pitch moment change due to movement of..
the center of pressure
126
When the load factor is more than 1, __ is more than ___.
lift, weight.
127
Þú færð gefinn stall hraða og svo load factorinn 1.5. Hvernig reiknar þú nýjan stall hraða miðað við þennan load factor?
gamli stall hraðinn * sqrt(1.5)
128
A stall warning vane on an aircraft wing is fitted
a) on or at the leading edge
b) just below the leading edge
b) just below the leading edge
129
The main purpose of a boundary layer fence on a swept wing is to:
a) improve the low speed handling characteristics
b) improve the lift coefficient of the trailing edge flaps
a) improve the low speed handling characteristics
130
Vs1 is:
a) stall speed in the clean configuration
b) The stall speed or the minimum steady flight speed obtained in a specific configuration
b) The stall speed or the minimum steady flight speed obtained in a specific configuration
131
In a steady horizontal turn, the stall speed increases with the square root of __ ___.
load factor
132
At 5000 ft vs sea level, the IAS will be higher or lower? How about TAS?
IAS will be the same speed at high altitude but TAS will be higher.
133
Airflow separation is characterised by
a) increased velocity on the surface of the body
b) airflow reversal on the surface of the body
b) airflow reversal on the surface of the body
134
Stall speed increases when pulling out of a ___.
dive
135
The sensor of a stall warning system can be activated by a change in the location of the ___ point.
stagnation
136
Hvað gerist fyrir critical angle of attack ef aspect ratio increases?
decreases
137
Hvað gerist fyrir stalling angle of a wing í beygju?
breytist ekki
138
The pitch up tendency of an aeroplane with swept back wings during a stall is caused by the forward/aft movement of the CG/CP
forward movement of centre of pressure (CP).
139
Hvað gerist fyrir stall speed (IAS) ef CG moves forward?
Eykst
140
Hvað gerist fyrir stall speed (IAS) ef þú lendir í icing conditions?
eykst
141
Hver er munurinn á Krueger flaps og slats?
a) Deploying a slat will increase critical angle of attack, deploying a Krueger flap does not.
b) Deploying a slat will form a slot, delploying a Krueger flap does not.
b) Deploying a slat will form a slot, delploying a Krueger flap does not.
142
As stagnation point moves downward, the flapper switch moves..
upward
143
Hvað er notað til að reduce spanwise airflow over swept wings?
Wing fence
144
Hvað gerir fixed spoiler on a leading edge root?
Ensures the root of the wing stalls before the tip.
145
Hvað gerist fyrir stall speed (IAS) at higher altitudes?
Initially remains constant but increases at higher altitudes.
146
Critical angle of attack is dependent on:
a) design of the wing
b) aircraft mass
a) design of the wing
147
On a forward CG airplane the Vs is lower/same/higher and the stalling angle is lower/same/higher
```
Vs higher (auðveldara að stalla framhlaðinni vél en létt að koma sér úr stallinu)
Stalling angle er bara það sama (held að það sé bara alltaf eins).
```
148
Ef þú lendir í spinni (spinnar t.d. til left), eru vængirnir stallaðir? Báðir? Hvor?
Both wings are stalled.
| Recovery úr spin: Ailerons neutral.
149
A super stall is most probable with
a) T-tails
b) Swept wings
b) Swept wings
150
Boundary layer is created by a layer on the wing in which the stream velocity is higher/lower than the free stream velocity.
lower
151
The purpose of a leading edge droop is? to increase ___, and delay separation of the airflow when trailing edge flaps are lowered
wing camber
152
When flaps are lowered the stalling angle of attack of the wing ___. Clmax ___.
decreases, increases
153
If the flaps are lowered in flight, with the airspeed kept constant, to maintain level flight the angle of attack..
must be decreased.
| Hugsaðu þér bara þegar þú setur niður flapa og hún balloonar þá upp, verður að setja stýrin fram svo hún ballooni ekki.
154
When flaps are lowered the spanwise flow on the upper surface of the wing?
b. increase towards the tip
c. increases towards the root
c. increases towards the root
155
Lowering flaps sometimes produces a pitch moment change due to movement of..
the center of pressure
156
When a leading edge slot is opened, the stalling speed will?
a. increase
b. decrease
c. remain the same
b. decrease
157
Which type of flap would give the greatest change in pitching moment?
a. Split
b. Plain
c. Fowler
d. Plain slotted
c. Fowler
158
The correct definition of Vs1 is
a) the stall speed in the clean configuration
b) the stall speed or the minimum steady flight speed obtained in a specific configuration
b) the stall speed or the minimum steady flight speed obtained in a specific configuration
159
During a steady horizontal turn, the stall speed increases with the __ __ of the load factor.
square root
160
An automatic leading edge slat is operated by:
a) Aerodynamic forces acting on the leading edge.
b) Changes in the dynamic pressure acting on the stagnation point
a) Aerodynamic forces acting on the leading edge.
