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POF pp Qs > POF > Flashcards

POF Flashcards

1
Q

A symmetrical aerofoil has a mean chord line that is ______

A

Straight

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2
Q

AoA of an aerofoil is measured between the mean chord line of the aerofoil and the ______

A

Relative AF

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3
Q

What are the characteristics of the fully articulated rotor head

A

They are extremely complex and heavy

The freedom of movement provided my mechanical

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4
Q

Characteristics of rigid main rotor head

A

Simple design, cheaper

Uses flexible structures to allow blade movement in one or more directions

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5
Q

Characteristics of teetering main rotor head

A

Simple design

Prone to mast bumping

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6
Q

The manufactured twist in rotor blades to distribute lift is called:

A

Washout

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7
Q

Asymmetrical aerofoil rotor blade can be described as_____

A

Having a curved mean chord line

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8
Q

A vector differs from a line as it has both

A

Direction and magnitude

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9
Q

The angle between chord of aerofoil and relative airflow is termed ______

A

Angle of attack

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10
Q

Elaborate the lift equation terms

A

Cl= coefficient of lift
S=wing surface area
p= air density
V = wing speed over aerofoil

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11
Q

Angle of attack is between aerofoil chord line and ______

A

Relative Air Flow

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12
Q

Rotor disc is best described as

A

Circular area swept by the main rotors

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13
Q

Relative Airflow vector is made up of______

A

Rotational airflow
Induces Flow

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14
Q

Increasing the rotor speed will _____ the amount of lift

A

Increase

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15
Q

Will a wider or thinner blade of equal length create the most lift?

A

Wider

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16
Q

Will a helicopter at sea level generate equal lift to helicopter at 28,000ft

A

No (air density)

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17
Q

Induced flow is caused by drawing air from _____ the rotor

A

Above

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18
Q

The combination of IF and rotational AF creates _____

A

RAF

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19
Q

The path described by the tips of the rotor blades during rotation is the _____

A

Tip path plane

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20
Q

TR is the vector or rotor thrust and

A

Rotor drag

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21
Q

The force opposing rotor drag is?

A

Torque

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22
Q

The ability of a wing to provide lift increases with_____ until ______ is reached

A

Angle of attack

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23
Q

To lift off the ground TRT must be ____ all up weight (AUW)

A

Greater than

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24
Q

In the BVD when IF increases the AoA _____. Why?

A

Decreases

The RAF vector changes position the lessen the angle between RAF and chord line

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25
Q

HIGE requires less power as the IF vector is reduced which _____ the AoA, hence creating more lift

A

Increases

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26
Q

4 factors that effect the amount of HIGE

A

Height above ground, weight, wind and nature of surface

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27
Q

Recirculated air is likely to be induced when the ACFT is ____

A

Hovering near:
- building,
- solid fences,
- cliff faces,
- near other helicopters
- over long grass

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28
Q

Reduced power required to hover due to ground effect is experienced at ______

A

Half rotor diameter

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29
Q

Recirculation causes a reduction in lift generated due to an ______ in the IF vector

A

Increase

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30
Q

IAW BVD how does recirculation impact TRT

A

As air passes through the system a second time the V increases

As V increases so does IF and therefore a reduction in TRT

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31
Q

4 factors

A

Ligma

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32
Q

The increased rotor thrust due to forward speed during transition from hover to toward flight is refereed to as _____ and occurs at____

A

ETL - Effective translational lift
10-20k

33
Q

ETL causes the ACFT to ______

A

Balloon

34
Q

As the helicopter transitions and accelerates, what aerodynamic structure helps compensate the ACFTs tendency to pitch nose down?

A

The horizontal stabiliser

35
Q

Induced Flow Roll is exhibited at slow speed due to?

A

Difference in magnitude of the IF experienced by portions of the rotor disc

36
Q

IFR is due to the IF experienced by the front half of the rotor being ____ then the back

A

Less

37
Q

During flapback the advancing blade flaps _____ and the retreating blade flaps _____

A

Up
Down

38
Q

Order of forward flight transition effects

A

1) initial height loss
2) flapback and IFR
3) ETL
4) Torque reduction

39
Q

Source of low frequency lateral vibs

A

Main rotor blades out of balance

40
Q

Low freq vertical vibes cause

A

Rain rotor blades out of track

41
Q

Medium freq vibration due to?

A

Downwash from main rotor impinging on the structure

42
Q

High frequency vibes due to

A

Engines, gearbox and hydraulic pumps

43
Q

To dampen vertical vibrations the the rotor system and dampening mass vibrate with the same frequency but _____

A

180• out of phase

44
Q

Parasite Power is?

A

The power required to overcome parasite drag

45
Q

Power available is?

A

The maximum power the engines can deliver under particular conditions

46
Q

Power required is:

A

The power required to climb,hover, accelerate, turn or maintain speed at a AUW in particular conditions

47
Q

When does over pitching occur?

A

When collective pitch is applied to the rotor blades without having sufficient engine power to overcome increased rotor drag

48
Q

Density altitude is pressure altitude adjusted for _____

A

Temperature

49
Q

Over pitching will result in ______

A

RPM decay until collective lowered

50
Q

What unit disconnects to allow rotors to spin freely?

A

Free wheeling

51
Q

Instead of IF during autorotations we have _____ airflow moving through rotor system

A

Rate of descent

52
Q

Why does forward auto rotations have reduced RoD

A
  • Forward airspeed increases descent airflow
  • which increases AoA
    -which increases TRT
    -which reduces RoD
53
Q

3 benefits of flare

A
  • decelerates
  • increases thrust
  • increases rotor RPM
54
Q

Dead man’s curve depicts flight regimes to avoid relative to

A

Height and airspeed

55
Q

Stability is classified as either? Subcategories

A

Dynamic or static

Positive (stable), neutral or negative (unstable)

56
Q

An ACFT that returns to it original attitude after being disturbed is said to be statically _____

A

Stable or have positive static stability

57
Q

An ACFT that remains in its new attitude after being disturbed is said to be statically ____

A

Neutral or have neutral static stability

58
Q

An ACFT that continues to move away from its original attitude after being disturbed is said to be statically ______

A

Unstable or have negative static stability

59
Q

Lateral, longitudinal and directional stability is stability in

A

Lat: roll
Long: pitch
Directional:yaw

60
Q

What do vertical stabilisers do?

A

Assist by dampening yawing movements in the hover and forward flight

Reduces power required for anti torque in forward flight

61
Q

What do horizontal stabilisers do

A

Provide static stability in pitch and assist in dampening the pitching movements of the fuselage in response to wind gust

Add to dynamic stability

End plates aide in anti torque during forward flight

62
Q

What are the 3 stability aids on the EC135

A
  • horizontal stabiliser
  • vertical stabiliser
  • automatic flight control system
63
Q

Retreating blade stall would be exhibited in the EC135 by?

A

Nose pitching up
Roll to the left

64
Q

What factors can lead to RBS

A

High forward speed
AUW
HIGH DA
excessive movements
High G manoeuvres
Turbulence

65
Q

Ground resonance occurs primarily with _____ rotor heads

A

Fully articulated

66
Q

Helicopters with a _____ undercarriage are more prone to ground resonance

A

Wheeled

67
Q

3 areas contributing to ground resonance

A
  • rotor systems
  • landing gear
  • construction of landing platform
68
Q

Static roll over angle

A

45•

69
Q

Static roll over occurs when___

A

CoG moves outside base of support

70
Q

Conditions for static roll over

A

-slope
-soft ground/undercarriage sinks
-undercarriage failure
-structure failure of landing platform
- ship exceeds critical roll angle

71
Q

For dynamic roll over to occur the rotors must be ____ and generating _____ and have a wheel or skid _____

A

Turing
Lift
Fixed to ground

72
Q

Recovery from dynamic roll over

A

Lower collective
Balance/level the rotor disk

73
Q

3 conditions for vortex ring state

A
  • be in powered flight, generating IF
    -descending with rate of descent airflow
    -must be operating at a low forward airspeed
74
Q

Symptoms of vortex ring state

A
  • vibes
  • pitching rolling
    -Fluctuating power and torque
  • decrease in flight controls
  • rapid descent
  • random yawing
75
Q

Flight situations that induce a Vortex Ring State

A

-pulling power during auto rotations
- too steep and angle of approach
-RoD increase in a low air speed descent
-landing or operating at low toward speed in a downwind situation
-allowing RoD to develop in a harshly executed quick-stop

76
Q

Recovery from VRS

A

Increase forward air speed THEN increase collective. Can enter auto rotation if you have the height

77
Q

Loss of Tail Rotor effectiveness (LTE) is generally caused by one of the three events. Name them

A

Weathercock effect
Tail Rotor Vortex wind state
Main rotor vortex interference

78
Q

Main Rotor Vortex Intefernce is most likely to occurs in which position?

A

10-11 o’clock

79
Q

How to counter loss of tail rotor effect

A
  • don’t initiate
  • gently use pedals to turn
  • be prepared for tail “Flick”

POF pp Qs (1 decks)

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