Module 11.1 Theory of flight Flashcards
1
Q
What are the 3 primary axes in flight?
A
- Longitudinal
- Lateral
- Vertical
2
Q
What are the 3 movements about the axes?
A
- Roll
- Pitch
- Yaw
3
Q
What movement is about the vertical axis?
A
Yaw
4
Q
What movement is about the lateral axis?
A
Pitch
5
Q
What are the primary flight controls?
A
- Rudder
- Aileron
- Elevator
6
Q
What happens when the aileron deflects upwards?
A
Decrease in lift
7
Q
What is the equation for dynamic energy?
A
= 1/2 x Density x Velocity Squared
8
Q
What occurs to the outboard aileron at high speeds?
A
Locked
9
Q
What aileron is used at high speeds?
A
Inboard aileron
10
Q
What is the purpose of roll/flight spoilers on an up-going aileron of a rolling aircraft?
A
Supplement aileron control by reducing lift
11
Q
What is the differential operation of flight spoilers linked to?
A
Aileron control system
12
Q
Roll spoilers have two purposes what are they?
A
- Execute accurate turn
- Reduce need for large aileron deflection at high speeds
13
Q
Why is the elevator at the position furthest away from the C of G?
A
Greater leverage
14
Q
What are stabilators?
A
Dual purpose control surface
15
Q
Where are stabilators used?
A
High speed military aircraft
16
Q
When a shockwave forms on the hinge line of an elevator the control surface is ineffective what is the solution to this?
A
Stabilators
17
Q
THS is also known as what?
A
Variable incidence stabilisers
18
Q
THS are only used for what purpose?
A
Pitch trimming
19
Q
What is the advantage of the THS?
A
Reduced drag due to reduced requirement for elevator deflection
20
Q
What does the trim angle account for?
A
- Weight distribution
- Fuel consumption
- Flap and engine settings
21
Q
Which way is the trim wheel movement for nose down?
A
Spin wheels forward
22
Q
What are Canards?
A
Flight control system forward of the wings
23
Q
How Canard config influence the flight control system?
A
- Lift and trim
- Pitch control
- Stability
- Stall prevention
- High A of A manouvuers
- Control redundancy
24
Q
What is the purpose of a rudder limiter?
A
Limits rudder movement at high speeds
25
What is side slip?
Yaw in the direction of the roll movement
26
Elevons are a combination of what controls?
Elevators and ailerons
27
Ruddervators are a combination of what controls?
Rudder and elevator
28
What is adverse yaw?
Yaw in the opposite direction to roll
29
How is adverse yaw prevented?
- Aileron differential
- Frise aileron
- Spoilers
30
Frise ailerons increase drag how?
Has a leading edge that protrudes into airflow
31
What direction is roll in adverse roll?
Opposite to yaw
32
What do slots do?
Do not increase lift but they energise the boundary layer to delay separation
33
What is the disadvantage of slots?
Fair amount of drag
34
What is the main difference of slots and slats?
Slats are moveable
35
What does a slat produce?
Lift due to camber increase
36
Flap extension has what effect on the nose?
Pitch it down
37
Which flaps produce the least lift increase?
Plain flaps
38
What are the leading edge droops designed to improve?
Improve airflow over wings at high A of A
39
What do Kruger flaps result in when extended?
Blunt leading edge leading to better lower speed handling
40
Where may leading edge flaps be found?
Large aircraft at wing root
41
What are flaperons?
Aileron that can also act as a flap
42
When would a flaperon be used?
Take-off/landing
43
What are the 3 types of spoilers?
- Flight
- Ground
- Roll
44
When would flight spoilers be used?
Too slow the aircraft inflight, max deflection is not used.
- Only a few spoilers used not all
45
When would ground spoilers be used?
Rejected take off or landing
46
What happens when roll spoilers are deployed?
Only a few spoilers deployed on the wing of the direction you want to turn in
47
When can speed brakes be used?
- Final approach to touchdown
- Landing
48
What do speed brakes not have an affect on?
Lift
49
What affect does span wise flow have on the boundary layer?
Makes it thicker and at the wing tip
50
What is the danger of swept back wings?
Tip stalls first
51
What do wing fences do?
Delay onset of boundary layer separation at wing tip
52
What does a saw tooth leading edge do?
Creates a small vortex that limits boundary layer outflow and redirects span wise flow
53
Where are vortex generators placed?
Trailing edge of the wing
54
How and why are they installed like this? (Vortex generators)
They are installed opposite so that the vortices mix
55
Where would a stall strip be installed?
Leading edge at wing root
56
What do stall strips encourage?
Encourage the root to stall before the wing tip
57
Where would a trim tab be found?
Trailing edge of primary control surface
58
Besides anti-balance what direction are the trim tabs moved?
opposite to the control surface
59
What is the purpose of the trim tabs?
Reduce the load for the pilots by making it easier to move the control surface
60
A trimmed aircraft has what?
0 aerodynamic moments
61
What is the disadvantage of a balance trim tab?
Reduces efficiency of the control surface
62
How does a pilot operate the control surface with a servo tab?
By moving the tab not the control surface
63
What is a spring tab?
A spring tab is like a servo tab however it only moves at a certain load
- High speed only
64
When would an anti balance tab be used?
Used when input off control is too sensitive and needs some resistance
65
What is a disadvantage of anti balance tabs?
More effort to deflect
66
When does mass balance flutter occur?
C of G of control surface aft of hinge line
67
What is control surface bias?
Control surfaces set at a slight angle from neutral to create a continuous aerodynamic force to offset forces during flight
68
What is a horn balance?
A weight placed forward of the hinge line on a control surface
69
What is an insert hinge?
An insert hinge is where the hinge line is moved back
70
How does a balance panel work?
Creates a chamber of higher and lower pressure and uses this to help move the control surface
71
What is the equation for mach number?
Velocity/Speed of sound
72
What are the 3 speed ranges?
- Subsonic <0.8 mach
- Transonic 0.8 to 1.2 mach
- Supersonic >1.2 mach
73
Is the local airspeed of airflow over the wing greater or less than true speed?
Greater than
74
What range can local airflow be in if true speed is in transonic?
Supersonic
75
Is air incompressible or compressible at supersonic?
Compressible
76
Describe the pressure waves of transonic?
Piled up
77
Describe the pressure waves of Subsonic?
Equally spaced
78
Describe the pressure waves of Supersonic?
Intersecting
79
What is the critical mach number?
The min true speed that will result in local air speed being the speed of sound
80
Air is considered compressible at what speeds?
Mach 0.4 and above
81
What problems occur when a shock wave is formed?
- Reduce lift
- Increase in drag
- Buffeting
- Control problems
- Uncommanded changes in trim and stability
82
Normal shockwaves occur at what angles to the airflow?
90 degrees
83
What direction do shockwaves move if the speed is increased?
Aft towards trailing edge
84
What happens when supersonic airflow passes through a shockwave?
- Velocity decrease
- Density and pressure increase
- Temperature increase
85
What angles do oblique shockwaves occur to the airflow?
Not 90
86
What happens to the airflow speed when passing through an oblique shockwave?
Slightly reduced
87
When is an expansion wave formed?
When a supersonic airflow changes direction around a curve or corner
88
What occurs to the airflow of an expansion wave?
- Increase in velocity
- Decrease in pressure, density and temp
89
What does the wave profile on a flat plate profile look like?
Positive AoA
Leading edge:
- Underside oblique wave
- Top expansion wave
Trailing edge:
- Underside expansion wave
- Top oblique wave
90
As the speed increases, where does a shockwave occur?
Underside of the wing
91
What occurs to the flow after the shockwave?
Turbulent flow
92
What are the two supersonic wing profiles
- Double wedge
- Circular arc
93
Where is centre of pressure located on a wing if the airflow is supersonic?
50% aft of Chord line
94
Where is centre of pressure located on a wing if the airflow is subsonic?
25% aft of chord line
95
What can be said about the expansion wave on a circular arc profile?
Continuous
96
What is the benefit of vortex generators?
They create a small oblique shock wave when airflow is supersonic, this reduces the normal shock. This means less flow separation and reduced wave drag
97
What is the body type with the lowest theoretical wave drag?
Sears-Haack body
98
To ensure volume distribution, what can be done to the fuselage at the wing attachment position?
Narrowed/ waisted fuselage
99
What is aerodynamic heating caused by?
Friction from the air
100
What can be done to supersonic aircraft to eliminate aluminiums strength problem at high temperature?
Use of titanium alloys
101
How does a normal shock diffuser inlet slow air to subsonic speeds?
Normal shock wave
102
What speed is a normal shock diffuser suitable for?
Low supersonic
103
In a single/ multiple oblique shock inlet, oblique shock waves reduce what?
The strength of the normal shockwave
104
How does a variable supersonic inlet work?
Actuators move a panel to change the size of the inlet. This affects the normal shock and at high speeds moves further to create oblique shockwaves to reduce the normal shock strength
105
What happens in a divergent intake of a subsonic engine?
- Velocity decrease
- Pressure and density increases
106
When a wing is swept back what can be said for the thickness?
Reduced profile thickness
Profile thickness = Actual thickness/ chord length
107
What is the most common angle for swept wings?
30 degrees
108
What do swept wings reduce?
- Critical mach no.
- Profile drag
- Improved stability laterally
- Overall frontal area
109
What is the drawback of sweptback wings?
- Tip stalls first
- Increased span wise flow
