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Module 13 EASA Part 1 > 13.1 Theory of Flight > Flashcards

13.1 Theory of Flight Flashcards

1
Q

Which controls provide lateral control about the longitudinal axis?

A

Ailerons

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2
Q

Which controls provide longitudinal control about the lateral axis?

A

Elevators

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3
Q

Which control provides directional control about the normal axis?

A

Rudder

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4
Q

Why are the control surfaces placed at the maximum distance from the centre of gravity?

A

Produce the greatest turning moment

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5
Q

What is meant by the term ‘instinctive’ in relation to control surface movement?

A

The pilot moves the cockpit control in the direction the aircraft is desired to fly

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6
Q

What are used to limit the angular range of movement of the control surfaces?

A

Mechanical stops at both the control surface and at the controls in the cockpit

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7
Q

The down going aileron has a greater angle of attack compared to the up going aileron.

What effect does this lead to? How can this be overcome?

A

More lift and drag on the down going aileron, aircraft will tend to yaw in the direction of the down going aileron (aileron drag or adverse aileron yaw)

Differential aileron
Frise type aileron
Slotted aileron
Spoilers (augment roll)
Wing tip washout

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8
Q

Describe a frise aileron.

A

Special section with hinges set back in the leading edge

The leading edge of the upgoing aileron protrudes below the wing, creating more drag

Thus, greater drag is produced on the aileron on the inner wing in the turn, helping to turn the aircraft in that direction

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9
Q

What is washout?

A

Reduction of wing incidence towards the wing tip

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10
Q

What movement of the elevators is necessary to pitch the aircraft nose up?

A

Elevator moving up

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11
Q

Stabilators provide stability, control and what else?

A

Trim

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12
Q

If a stabilator has an anti balance tab, what direction will the tab move in relation to the stabilator?

A

In the same direction as the stabilator trailing edge

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13
Q

How does an anti balance tab provide feel?

A

Increases the aerodynamic load which has to be overcome by the pilot

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14
Q

What is the primary advantage of a variable incidence stabiliser?

A

Having the elevator in continuation with the stabiliser ensures that drag is minimised

Full range of elevator travel is available

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15
Q

How would the rudder be positioned to achieve a yaw to the right?

A

Rudder will move right

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16
Q

How can sideslip or spinning be prevented when the rudder is operated?

A

Interconnecting the ailerons, therefore when the rudder is applied, the ailerons are automatically operated

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17
Q

What is the purpose of a rudder limiter?

A

At high speeds, large rudder movements cause large stresses on the aircraft

At lower speeds, large rudder movements are required for adequate yaw control

Rudder must be limited at high speeds, but free to move at low speeds

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18
Q

What does yaw damping prevent and how is this achieved?

A

Automatically moves the rudder approximately 3° either side of the neutral position fast enough to prevent Dutch rolling causing discomfort to the passengers

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19
Q

Why is the foreplane or canard mounted a larger angle of incidence than the mainplane?

A

Makes sure that the foreplane stalls before the mainplane so that the aircraft will not stall or spin

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20
Q

Describe an elevon.

A

Control surface on the trailing edge of delta wing aircraft

Acts both as elevators and ailerons

When acting together, acts as elevators

When acting in opposition, acts as ailerons

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21
Q

Which conventional controls would a ruddervator replace?

A

Rudder and elevator

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22
Q

How do leading edge slats increase lift at low speeds?

A

Slot produced is larger at the leading edge than at the rear

Airflow going through the slot from below wing to the top is accelerated and increases the velocity of the boundary layer above the wing

Delays separation of the airflow from the top surface of the wing

Increases the maximum coefficient of lift

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23
Q

How is deployment of the slat controlled?

A

From the cockpit using the flap selector handle

Move with the trailing edge flaps in the correct sequence

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24
Q

How do leading edge flaps increase lift?

A

Increases the leading edge camber

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25
Q

What additional advantage does a variable camber leading edge flap have over a Krueger flap?

A

Also functions as a slat

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26
Q

What happens to the centre of pressure as the extension flap is deployed? What affect does this have? How is it overcome?

A

The centre of pressure makes a large rearward movement

Causes the aircraft to pitch nose down

Smaller aircraft are fitted with a trim tab which moves down when the flap is lowered to prevent the nose down pitch

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27
Q

What 2 forms of protection are needed for high lift devices?

A

Asymmetry and very high flap loadings

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28
Q

What are flaperons?

A

Control surface that operate both as flaps or ailerons

Operate together as flaps

Operate differentially as ailerons

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29
Q

What is the difference between spoiler use on the ground and in the air?

A

Ground – Reduce wing lift on landing

Air – Assist large aileron control wheel commands, raised to assist the up going aileron

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30
Q

What governs movements of the spoiler’s when the speed brakes are selected?

A

Speedbrake lever in the cockpit, on the centre pedestal

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31
Q

What four conditions must be met to allow lift dump?

A

Speedbrake lever in the armed position
Aircraft weight on the undercarriage (through the air/ground sensing system)
All thrust levers in their idle positions
Aircraft wheels rotating (provides a time delay and ensures the aircraft is on the ground)

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32
Q

What happens to lift dump if the thrust levers are moved forwards after landing?

A

The speedbrake lever automatically moves to the down position

Spoilers retract

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33
Q

What device can be used to initiate a stall at the wing root rather than the tip?

A

Leading edge spoiler or stall wedge

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34
Q

What devices speed up the boundary layer and prevent separation?

A

Vortex generators

35
Q

State the three methods that reduce the spanwise flow and create a chordwise vortex.

A

Wing fence

Vortilon

Saw tooth leading edge

36
Q

State 3 flying faults.

A

Tendency of the aircraft to:

Yaw
Fly nose or tail heavy
One wing low

37
Q

What direction will a trim tab move in relation to the flying control surface?

A

In the opposite direction

38
Q

Describe the trim corrections being made if an aircraft is flying left wing low.

A

Trim tab on the left aileron is moved up by rotating the trim wheel to the right

39
Q

What are the four methods of aerodynamic balance?

A

Horn balance (horn tip)
Inset hinge
Internal balance panels
Various types of tab

40
Q

How does a balance tab automatically oppose control surface movement?

A

Hinged into the trailing edge of the control surface

Normally connected by a rod to a fixed part of the main surface structure

When the control surface moves in one direction, the tab automatically moves in the opposite direction

41
Q

In a geared balance tab, what happens to tab movement as displacement increases?

A

Allows the tab to produce progressive anti–balance effect

42
Q

What is the purpose of a servo tab?

A

Less effort is required to move the tab into the airflow than would be required to move the main control surface, which might be large
Allows pilot to control the tab directly
Aerodynamic force acting on the tab produces a turning moment about the control surface hinge
Makes the control surface move in the required direction until a position equilibrium is reached

43
Q

Describe a spring tab?

A

Similar to servo tab

Direct control of control surface a low speed

At high speed, no control of control surface, force required overcomes spring pressure in the control system which allows control of tab

Tab produces a turning moment which moves the control surface to move in the required direction

Thus, there is direct control at low speed but servo tab control at higher speed

44
Q

How is flutter prevented?

A

Fitting a weight in front of the control surface hinge (mass balancing)

45
Q

What is the Mach number?

A

Ratio of the true speed of the aircraft to the speed of sound in the air through which the aircraft is flying

Mach number = true speed of aircraft/speed of sound locally

46
Q

What happens to the local speed of sound as altitude increases and temperature decreases?

A

Increasing altitude – reduces the speed of sound

Decreasing temperature – reduces the speed of sound

47
Q

What is the Critical Mach number?

A

Airflow over the wing reaches the speed of sound at the point of maximum camber

48
Q

When and where will an incipient shock wave first appear?

A

When the aircraft is moving at about three quarters of the speed of sound

Represented by a line approximately at right angles to the surface of the aerofoil at the point of maximum camber

49
Q

What happens to the supersonic airflow as it passes through the shockwave?

A
  • Sudden rise in pressure, density and temperature
  • Airflow is slowed down by the shock wave
  • Boundary layer breaks away and becomes very turbulent (known as compressibility buffet)
  • Rapid rise in drag
  • Loss of lift and often a rearward shift of the centre of pressure
  • Control surfaces become less effective
  • Turbulent airflow behind the shock wave can cause severe buffeting, especially if the airflow strikes the tailplane
50
Q

How does shock stall differ from low speed stall?

A

Occurs at small angles of attack

51
Q

Define Subsonic, Transonic and Supersonic.

A

Subsonic – Mach number below 0.8, all airflow is subsonic

Transonic – Mach 0.8 to 1.2, some airflow is subsonic, some is supersonic

Supersonic – Mach number above 1.2, all airflow is supersonic

52
Q

What 3 design features can raise the critical Mach number?

A
  • Slimness
  • Sweepback
  • Supercritical wings
53
Q

How can pitching control be maintained at Transonic speed?

A

Power operated all–moving or slab tailplane may be used

54
Q

What is control reversal?

A

The force on the wing is very large, therefore an aileron moving up or down will tend to cause the wing to twist, which changes the angle of incidence of the wing, and therefore the angle of attack

This change in the angle of attack acts in opposition to what is required by the aileron movement

55
Q

Describe Mach trim.

A

Frequent pitch changes to counteract ‘tuck under’

Automatically position an all moving tailplane or variable incidence tailplane

Fuel is also transferred from a front trim tank to a rear trim tank

56
Q

Having a consistent cross sectional area will reduce wave drag. What is this known as?

A

Area rule

57
Q

What causes aerodynamic heating at supersonic speeds?

A

Friction between the air and the surface of the aircraft

58
Q

What happens to supersonic airflow in a diverging duct?

A

Increasing velocity
Decreasing pressure
Decreasing density

59
Q

What happens to supersonic air flow in a converging duct?

A

Decreasing velocity
Increasing pressure
Increasing density

60
Q

Name the three types of shockwave.

A

Oblique shock waves
Normal shockwave
Expansion wave

61
Q

For a conventional blunt nosed aerofoil where will the centre of pressure be for supersonic flow?

A

At approximately 50% of the chord

62
Q

What additional advantage does the OGEE Delta platform have over the Arrowhead platform?

A

The stalling angle is large and unlikely to be reached during normal flight

63
Q

How can the ineffectiveness of the elevators be overcome at supersonic speeds?

A

Hydraulically operated all–flying or all–moving tailplane

64
Q

What is a pitot intake?

A

Diverging duct

65
Q

What type of shock waves are best for slowing down the airflow in a supersonic intake?

A

Oblique shockwaves

66
Q

When is a foreplane known as a canard?

A

When it provides less than one quarter of the total aircraft lift

67
Q

Why do propeller driven aircraft not tend to have leading edge high lift devices?

A

Lift of the wing is increased in that area affected by the propeller slipstream

68
Q

How are Krueger flaps and variable camber flaps controlled?

A

Using the trailing edge flap selector handle

69
Q

What is the undesirable feature of a split flap?

A

Sudden decrease in lift at the stall

70
Q

When the extension or Fowler flap is lowered, what does this increase?

A

Both the area and the camber of the wing

71
Q

What does adding a slat to an extension flap setup do?

A

Prevent the large rearward shift of the centre of pressure caused by extension flaps

72
Q

What will the asymmetry protection system do?

A

Stops the movement of the high lift devices if the angular difference between them exceeds predetermined limits

73
Q

What does the automatic system of flap load relief do?

A

Partially retract the flaps if they are lowered at too high a speed

74
Q

Due to the speedbrake system, what does the loss of lift putting the aircraft’s weight on the undercarriage do?

A
  • Increases directional control
  • Improves braking
  • Reduces the risk of aquaplaning on wet runways
75
Q

What can cause flying faults?

A

Changes in weight and CofG position due to the consumption of fuel

Varying positions of passengers and cargo

Flight under asymmetric power conditions

Pitch changes caused by lowering the flaps

76
Q

In a horn balance or horn tip, how does it assist the pilot in overcoming the aerodynamic forces of moving a control surface?

A

Horn in front of the hinge line ‘catches’ the airflow, to counteract the force of the airflow acting on the control surface behind the hinge

77
Q

What might a balance tab also be called?

A

Lagging tab

78
Q

What might an anti–balance tab also be called?

A

Leading tab

79
Q

What instrument is used to display the speed of the aircraft in relation to the local speed of sound?

A

Machmeter

80
Q

What is ‘tuck under’?

A

At transonic flights, downwash is eliminated

The tailplane angle of attack becomes positive and it now produces an upload

Causes the nose to pitch down

81
Q

What is the speed of airflow behind a normal shockwave?

A

Subsonic

82
Q

For a conventional blunt nosed aerofoil where will the centre of pressure be for subsonic flow?

A

Located at about 25% of the chord

83
Q

How can rudder limiting be implemented?

A

Automatically reducing the hydraulic pressure being supplied to the rudder actuators as the speed of the aircraft increases

Using a ratio changer which reduces rudder travel in relation to rudder pedal travel with increase in forward speed

Using an airspeed sensing device which adjusts the position of the rudder travel stops to reduce the travel of the rudder as the aircraft speed increases

Module 13 EASA Part 1 (20 decks)

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