1 Principles Of Flight Flashcards
1
Q
What is the air density in an ISA?
A
1.225 kg/m^3
2
Q
What is the standard pressure in an ISA?
A
1013.25 hPa
3
Q
1 hPa = ? ft at low level
A
30 ft
4
Q
What occurs with temperature at the Tropopause
A
It remains constant
5
Q
What is the Tropopause height in an ISA?
A
36,090 ft
6
Q
What is the temp lapse rate in the troposphere?
A
-1.98C / 1000ft
7
Q
What occurs with density as height increases?
A
It decreases
8
Q
What factors affect density?
A
Pressure
Temp
Altitude
Water Vapour
9
Q
How is density affected by temperature?
A
As temperature increases density decreases
10
Q
What is Newton’s 1st Law?
A
Law of Inertia
A body remains in a state of rest or uniform motion unless acted on by an external force
11
Q
What is momentum?
A
Mass x Velocity
12
Q
What is Newton’s 2nd Law?
A
Law of Force
The rate of change of momentum (acceleration) experienced by a body of mass is proportional to the force applied to it
13
Q
What is Newton’s 3rd Law?
A
Law of Action/Reaction
For every action there is an equal and opposite reaction
14
Q
A gas in steady motion has what properties? (in term of energies)
A
Potential Energy
Heat Energy
Pressure Energy
Kinetic Energy
15
Q
Total Pressure = ? + ?
A
Static Pressure + Dynamic Pressure = Total Pressure
16
Q
Write Bernoulli’s Theorem
A
Total Pressure = P + (1/2 x ρ x V^2)
17
Q
In Bernoulli’s what is ρ?
A
Density
18
Q
What happens to pressure with an increase in velocity of a fluid?
A
Pressure decreases
19
Q
What is an Aerofoil?
A
Surface designed to generate lift from airflow over it’s surface.
20
Q
What is the Leading Edge Radius?
A
The shape of the leading edge.
21
Q
What is the Chord Line?
A
Infinite line through the leading and trailing edge of an aerofoil section.
22
Q
What is the Chord?
A
Distance between the leading and trailing edge of an aerofoil section
23
Q
What is the Camber?
A
The curvature of the aerofoil. (Upper surface camber/Lower surface camber)
24
Q
What is the Mean Camber Line?
A
A line equidistant from the upper and lower surfaces of an aerofoil.
25
What is the Angle of Incidence?
Angle between the chord line and the longitudinal fuselage datum.
26
What is the Relative Airflow (RAF)?
Direction of airflow that is remote from the aircraft/ unaffected by its presence. Also known as Freestream flow
27
What is the Angle of Attack (AoA)?
The angle between the chord line and the relative airflow.
28
Streamline is?
The path that a particle of air would/will take
29
Freestream Flow is?
A region of air where P, T and relative vel. are unaffected by the passage of an aerofoil
30
Define Aspect Ratio
AR = Span/Mean Chord or (Span^2)/Mean Chord
31
Describe a wing with High Aspect Ratio
Long and Thin (Glider)
32
Describe a wing with Low Aspect Ratio
Short and Stubby (F35)
33
What is Laminar Flow (steady flow)?
Steady flow lines with no mixing
34
What is Separated Flow?
Halfway between steady and unsteady flow
35
What is Turbulent Flow (unsteady flow)?
Large amount of mixing and not represented with streamlines
36
What 4 factors impact the pressure distribution on an aerofoil?
Shape of the aerofoil
Aerofoil attitude to RAF
Air Density
Velocity
37
True or False. Changing the AoA changes the Centre of Pressure?
True
38
Centre of Pressure is optimal at what AoA?
Normal
39
At a LOW AoA the Centre of Pressure moves to the .... of the aerofoil
Rear
40
At a HIGH AoA the Centre of Pressure moves to the .... of the aerofoil
Front
41
Lift acts perpendicular to what?
Relative Airflow
42
Drag acts perpendicular to what upwards force?
Lift
43
Combining Lift and Drag gives what?
Total Aerodynamic Reaction
44
What is the Lift equation and define each term?
L = C(L) 0.5 rho V^2 S
```
L=Lift
C(L)= Coefficient of Lift
rho=density
V=Free Stream Velocity
S= Wing Area
```
45
What is the Critical Angle of Attack?
15 or 16 deg
46
Coefficient of lift is made up of what 3 components?
AoA
Wing Planform
Wing Surface Condition
47
What happens to the critical AoA as the camber of the aerofoil increases?
Critical AoA reduces with increasing camber
48
Describe the C(L) vs AoA graph with changing cambers
The steepness of the performance line does not change but shifts to the left as camber is increased, with the max C(L) increasing slightly.
49
How does Aspect Ratio (AR) affect the C(L) vs AoA graph?
AR alters the gradient of the performance line. High AR steeper gradient, lower AR shallower gradient.
Lower AR tend to have higher critical AoA.
50
How does the planform affect the C(L) vs AoA graph?
Straight wing has a more gentle change of C(L) around critical angle.
Swept wing has a more abrupt change to the C(L) around the critical angle.
51
How does wing surface condition affect the C(L) vs AoA graph?
Smoother surface gives max performance.
As the surface roughens, the gradient of the performance curve remains the same but the critical angle is lower.
52
What factors affect lift?
RAF
AoA
Downwash. Increasing AoA will increase downwash Increase downwash will reduce the effective AoA. Reduced AoA tilts the lift component backwards therefore reducing lift.
53
What vector opposes thrust?
Drag
54
What are the 2 types of drag?
Zero Lift Drag (ZLD)
| Lift Dependant Drag (LDD)
55
What is the Drag equation?
D =C(D) x 0.5 x rho x V^2 x S
```
D=Drag
C(D)= Coefficient of Drag
rho=density
V=Free Stream Velocity
S= Wing Area
```
56
Zero Lift Drag is made up of what 3 components?
Surface Friction - Aero resistance from contact of RAF with surface of aircraft.
Form drag - The shape 'shown' to the airflow.
Interference - Caused by external tanks, pods, weapons etc
57
How can we reduce interference drag?
Better aero shapes, internal stowage
58
Lift dependant drag comprises of
Induced Drag
| Elements of Zero Lift Drag (ZLD)
59
Induced drag predominantly comes from what behaviour associated with spanwise flow?
Vortex formation
60
5 factors that effect vortex formation are:
```
Wing Planform
Aspect Ratio
Lift and Weight
Speed
AoA
```
61
How can we minimise Induced Drag?
```
Winglet
Tip Tank/Missile
Taper
High AR
Washout
Change of Aerofoil Section
```
62
What is the 'Taper' of a wing?
The changing of the chord between the base to the tip of the wing
63
What is washout?
The 'twist' of the wing along its length?
64
Zero Lift Drag (ZLD) ...... as speed increases.
increases
65
Zero Lift Drag (ZLD) is dominant at ..... speeds
higher
66
Lift Dependant Drag (LDD) ...... as speed increases.
decreases
67
Lift Dependant Drag (LDD) is dominant at ...... speeds
lower
68
Total drag is the combination of ...... + ......
Zero Lift Drag (ZLD)
+
Lift Dependant Drag (LDD)
69
What does V(IMD) stand for?
Velocity (Indicated Minimum Drag)
70
With respect to fuel, why is V(IMD) of interest?
Lowest fuel consumption required to overcome drag of aircraft.
71
Optimal lift/drag ratio occurs at about what velocity? (name of velocity)
V(IMD)
72
Max lift occurs at AoA of ....
16 deg
73
Min drag occurs at AoA of ....
2 deg
74
Most efficient lift/drag performance our aerofoil of interest occurs at .... (AoA)
4 deg
75
What is the lift/drag ratio defined as?
C(L) / C(D)
76
The LATERAL axis passes....
through the wings
77
The LONGITUDINAL axis passes....
along the length of the fuselage
78
The NORMAL axis passes...
vertically through the a/c
79
What action is performed around the LONG, LAT and NORMAL axis'
LONG - Roll
LAT - Pitch
NORMAL - Yaw
80
Name the 3 PRIMARY flight control surfaces
Elevator
Aileron
Rudder
81
What action do each of the the Primary Flight Control Surfaces control?
Elevator - Pitch
Aileron - Roll
Rudder - Yaw
82
A 'heavy' stick can make the a/c .... to control
Difficult
83
A 'light' stick may cause the a/c to be ..... easily.
Overstressed
84
Control movements should be ...... to the given a/c
Proportional
85
What PFCS is most responsive?
Aileron
86
What are the PRIMARY and further effects of the PFCS?
Elevator - (P) Pitch + (Furth) Height/Speed Interchange
Aileron - (P) Roll + (Furth) Yaw
Rudder - (P) Yaw + (Furth) Roll
87
Name the SECONDARY flight control surfaces
Flaps
Spoilers
Air Brakes
Trim Tabs
88
Flaps provide extra l... and d...
Lift and drag
89
What happens to the Lift vs Drag ratio when the form drag is increased?
The Lift vs Drag ratio will decrease.
90
With flaps extended. What happens to the critical angle?
Critical angle will decrease
91
Flaps have 3 effects. 2 increasing, 1 decreasing. What are these?
Increase Lift
Increase Drag
Decrease Lift/Drag ratio
92
What are the 2 types of trim surfaces?
Fixed Trim
| Trim Tabs
93
If you want to trim the nose up. What direction should the trim tabs in the elevator be pointing?
Upwards
94
Rate of climb is determined by what?
Airspeed
Angle of Climb
95
If we want to climb and maintain the same speed. We need to add ....
POWER
96
To maintain a climb at a given airspeed (more accurately EAS) ____ power is required than in level flight.
MORE
97
The angle of climb is determined by the amount of _____ left after ______ drag.
THRUST
OPPOSING
98
For a piston a/c, the max angle of climb speed will be just above what speed? Denoted as V(MU)
Unstick speed
99
The lowest calibrated airspeed at and above an a/c can safely lift off and continue take-off is .....
Unstick speed
V(MU)
100
At higher altitudes the "power available" curve of the engine is _____
LOWER
101
Glide descent is defined as ______ travel per altitude ____.
FORWARD travel per altitude LOST
102
When descending. To maintain airspeed, energy must be _____ to overcome drag.
EXPENDED
103
Endurance gliding is about ....
flying for as LONG (time) as possible.
104
Range gliding is about ....
flying as FAR as possible.
105
Max glide distance is achieved at .... lift/drag ratio.
OPTIMUM
106
A tailwind will ____ ground distance travelled while gliding.
DECREASE
107
A headwind will ____ ground distance travelled while gliding.
INCREASE
108
Weight does what to glide angle? (also impact on range vs endurance gliding)
- Not effect the gliding angle.
- Range gliding is unchanged in still air.
- Endurance gliding decreases with increased weight.
109
What control surface do we use to ROLL the aircraft?
Aileron
110
T or F? When turning, without other inputs you will lose altitude.
TRUE
The vertical lift component will be reduced in a turn.
111
To maintain altitude when turning you are required to increase lift by increasing what?
And what is the secondary effect of this?
Angle of Attack
Therefore will begin to introduce a centripetal force and therefore g.
112
Progressive increase in lift and loading in a turn can be continued until:
A/c stall when AoA reaches critical angle
g threshold of pilot is reached
g threshold of the a/c is reached
113
When making a level turn the _____ component of ____ must be equal to the ____ to maintain altitude.
VERTICAL component of LIFT
equal to
WEIGHT
114
When an a/c turns, lift acts towards the ____ of the turn as well as _____.
CENTRE of the turn as well as UPWARDS
115
In a level turn, if weight increases;
What is also required to increase?
What else will increase to maintain the same radius turn?
Vertical component of lift required to increase.
Therefore, the centripetal force will also increase ('g')
116
To achieve a max rate turn, the following should be satisfied...
- Wing loading (weight of a/c) to be as low as possible.
- Air as dense as possible.
- Max value of the product of C(L) and Angle of Bank.
117
In a minimum radius or max rate turn, thrust _____ the lift needed from the wing and can help ____ turn radius.
thrust REDUCES the lift needed
help IMPROVE/MINIMISE
118
Describe a standard rate turn
3 deg per second
180 in a minute
119
A clean a/c will always stall at the ____ AoA, regardless of weight
SAME AoA
120
Basic stall speed is denoted by ....
V(B)
121
In level flight and at low speeds, the AoA will be _____
HIGH
As the wing works 'hard' to maintain lift in the reduced airflow.
122
During the stalling process, describe what happens to the centre of pressure.
As the AoA increases towards the critical angle the CoP will move towards the leading edge.
When it passes the critical angle it will quickly move back towards the trailing edge.
123
At what point does the air over the wing become turbulent?
Transition Point
124
As speed reduces, what must the AoA do to keep lift constant?
The AoA must INCREASE.
125
Key factors that change stalling speed are:
- Changing weight
- Manoeuvring (Load factor(n))
- Configuration (changes in C(L)max)
- Power and slipstream
126
Changing the weight of the a/c impacts; the stall SPEED or stall ANGLE?
SPEED
127
If the weight is increased, the AoA required to maintain level flight ______ for the same speed.
INCREASES
128
Stability describes the motion of a body after __________________________
after AN EXTERNAL FORCE HAS BEEN REMOVED/APPLIED.
129
The two types of stability are:
Static - Immediate Reaction
Dynamic - Subsequent Reaction
130
What happens to a POSITIVELY Stable body?
A body returns to original position
131
What happens to a NEUTRALLY Stable body?
A body that takes up a new position
132
What happens to a NEGATIVELY Stable body?
A body continues to move away from original position
133
STATIC stability describes ...
The immediate reaction of the body after disturbance.
134
DYNAMIC stability describes ...
The subsequent reaction of the body after disturbance.
135
Factors that will affect the long term response of an a/c are:
```
Momentum (Vel x Mass)
Static stabilities (pitch, roll, yaw)
Angular velocities about the 3 axes
Angular momentum
Aerodynamic damping methods
```
136
Dynamic stability can be described in 5 ways. These are:
```
Negative Dynamic Stability
Negative Dynamic Stability (Divergence)
Neutral Dynamic Stability
Positive Dynamic Stability (Damped Phugoid)
Positive Dynamic Stability (Convergence)
```
137
What design features will enhance
| DIRECTIONAL STABILITY?
- Large Fin
- Long Moment Arm
Example: TORNADO
138
What design features will enhance
| LONGITUDINAL STABILITY?
- Long Horizontal Tailplane
- Long Moment Arm
Example: A400
139
What design features will enhance
| LATERAL STABILITY?
- Large Fin
- Dihedral
- Sweep Back
- High Wing
Example: C17
140
The range of an a/c is determined by
```
Airframe Consideration - Flaps, Gear etc
Temperature - Colder=More Dens + Increase engine efficiency
High Altitude
IAS vs Drag
IAS vs TAS
```
141
Considering range, V(IMD) is important because ...
It is the speed that provides the least amount of drag on the airframe.
142
In a turboprop maximum range is achieved at:
- Cruise Climb
- Max Continuous RPM
- IAS at V(IMD)
143
Lift Dependent Drag curves moves to the _____ when you lose weight
LEFT
144
In a turbojet a/c when flying for range we should:
- Fly at Max TAS/drag
- At low altitudes at 1.32xV(IMD)
- As weight reduces (burning fuel) a/c should cruise climb at constant mach
145
What RPM do we want to operate at in a TURBOPROP and TURBOJET?
TURBOPROP - Max CONTINUOUS
TURBOJET - OPTIMUM
146
TURBOJET engines are designed to operate in the _____ rpm band.
OPTIMUM rpm band
147
What speeds do we want to operate at in a TURBOPROP and TURBOJET?
TURBOPROP - V(IMD)
TURBOJET - 1.32xV(IMD)
148
What is a C of A?
Certificate of Airworthiness
149
The maximum permissible T/O weight is the least after considering:
- C of A limit
- WAT (Weight-Alt-Temp) limit for T/O and LANDING
- Field Length
- T/O net flight path
- En-route terrain clearance
150
Define Wing Loading
Weight/Area
151
Name 3 lift augmentation devices
Slats - delay stall until higher angle of attack
Flaps - increase lift by increasing the camber
Boundary layer control
152
Lift augmentation devices are used to increase ______ ______ ____________
MAX LIFT COEFFICIENT
153
The airflow caused by slats does what to the boundary layer?
RE-ENERGISES it
154
The use of slats does provides what?
- Improved control at low speeds
| - Augments lift
155
Flaps vary the ______ ____ of the wing section
CAMBER LINE
156
The GREATER the mean camber the _____ the lift capability of the wing.
GREATER
157
Name the 3 types of propeller
- Fixed Pitch
- Variable Pitch - Piston
- Variable Pitch - Gas turbine
158
TRUE or FALSE? - Propellers have washout?
TRUE - Propellers do have washout (twist) along their length
159
At what speed does drag increase significantly?
Near the speed of sound
160
The PREFECT propeller rotates _____ from the pilots perspective
CLOCKWISE
161
Propeller blade washout is used to _____ an ______ angle of attack along its length
MAINTAIN an EFFICIENT
162
____ Pitch is used to maintain maximum efficiency at LOW AIRSPEEDS
FINE Pitch
163
____ Pitch is used to maintain maximum efficiency at HIGHER AIRSPEEDS
COARSE Pitch
164
Define Windmilling
Loss of positive torque on the propellers
Propellers will spin due to air movement over their surface. Spinning the drive shaft and the gearbox
165
Propellers are _________ following engine failure, to prevent them inducing significant drag
FEATHERED
166
How can you increase the 'SOLIDITY' of the propeller
- Increase the number of blades
| - Increase the chord of each blade
167
Swing on take-off can be caused by:
- Slipstream effect
| - Torque Reaction
168
The slipstream effect of a CLOCKWISE rotating propeller (pilot's view) will induced asymmetric flow over the fin and rudder.
Resulting in the a/c yawing to the ____
LEFT
169
The torque reaction of a CLOCKWISE rotating propeller (pilot's view) will induce a counter torque on the a/c frame.
There will be an increased load on the ____ side undercarriage causing the a/c to swing ____ on travel down the runway during takeoff.
Increased load on LEFT undercarriage
Swing to the LEFT on travel
170
What does Vx represent?
Max angle climb speed
171
What does Vy represent?
Max rate climb
172
V(mu) is known as the ______ speed.
UNSTICK
173
What a/c will try and operate at OPTIMUM RPM?
Jet Engine A/C
174
What a/c will try and operate at MAX CONTINUOUS RPM?
TurboProp
175
Lowering slats does what to the critical angle?
INCREASES CRITICAL ANGLE
