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ATPL POF > Stability 😱 > Flashcards

Stability 😱 Flashcards

1
Q

What increases longitudinal stability

A

Larger tailplane area

Further forward cg

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2
Q

What does reduced stability do to manoeuvrability and controllability

A

Increases manoeuvrability but reduces controllability

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3
Q

Where does the aerodynamic centre need to be for it to be stable

A

Behind the cg

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4
Q

What does forward cg do to drag

A

Increase trim drag

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5
Q

What is absolute AOA

A

Angle between zero lift line and the raf

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6
Q

What is the most significant factor for pitching coefficient

A

Dynamic pressure

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7
Q

What type of gradient will a longitudinally stable aircraft have

A

Negative

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8
Q

What is the most important contributor to longitudinal stability

A

Tailplane

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9
Q

What is the area of the tailplane and the distance from aircraft cg collectively known as

A

Tail volume

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10
Q

What effect does the fuselage have on the stability of a aircraft

A

Destabilised

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11
Q

Do the engine nacelles have a stabilising or destabilising effect

A

As AOA increases air catches on the lips of the intake = upwards moment = less stable

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12
Q

How does cg position in relation to engines affect stability

A

Closer cg is to engines = less instability

Further away cg is to engines = more instability

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13
Q

What is a static margin

A

Safety margin between the neutral point and aft cg

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14
Q

What affect do trailing edge flaps THEMSELVES have on the stability

A

Stabilise

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15
Q

What effect do flaps have on the overall stability of the aircraft

A

Increase in downwash

= reduced effectiveness at tailplane

= less stable

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16
Q

How does flaps affect the neutral point

A

Flaps extended results in neutral point further forward resulting in reduced longitudinal static stability

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17
Q

What is stick position stability

A

The position you expect the stick to be in for a certain phase of flight

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18
Q

What would be a unstable stick position stability

A

Push forward when you slow down and want to increase AOA

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19
Q

Does trim affect stick position stability or over all stability

A

No

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20
Q

What is stick force stability

A

Size of force required is greater for further distance from trim position

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21
Q

What is manoeuvre stability

A

Having the right amount of control force to produce a given pitch rate

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22
Q

What are the risks of light manoeuvre stability

A

Overstress

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23
Q

What is stick force gradient

A

The amount of extra stick force that must be applied per unit increase in load factor

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24
Q

Do airliners have a high or low stick force gradient

A

High

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25
Q

How does cg affect stick force gradient

A

Bigger if cg is forward

26
Q

How does aerodynamic damping affect stick force gradient

A

More aerodynamic damping at low level = more stickforce required

27
Q

How does aerodynamic damping work

A

During manoeuvre = reduces effectiveness of tailplane

28
Q

How does being stick free of stick fixed affect the manoeuvre point

A

Stick fixed = manoeuvre point further back

29
Q

What is the manoeuvre point

A

The neutral point adjusted for aerodynamic damping (only during the actual manoeuvre)

Always aft of neutral point

30
Q

Is the aircraft more or less stable during a manoeuvre

A

More stable due to damping

31
Q

Can a aircraft be dynamically stable and statically unstable

A

No for dynamic stability it must be statically stable

32
Q

How do you work out the degree of dynamic stability

A

Time taken for oscillations to reduce by half

33
Q

What are short period oscillations

A

Little variation in height or airspeed

Large variations in AOA and load factor

34
Q

What is pilot induced oscillations

A

Pilot trying to correct for short period oscillations but being behind the aircraft and making it worse

35
Q

What is long period oscillations (phugoid)

A

Little change of AOA or load factor

Large variations in height and airspeed

36
Q

How does altitude affect dynamic and static stability

A

Altitude decreases static and dynamic stability

37
Q

For directional stability what does a positive gradient mean

A

Positive directional stability

38
Q

What will a aircraft with positive directional stability do

A

Yaw into the direction of sideslip

39
Q

What is the biggest contributing factor to directional stability

A

Fin

40
Q

When will the directional stability yawing moment be stronger

A

Cg further forward
Fin is larger
Higher IAS
Size of side slip angle

41
Q

How does the shape of the fin affect cl and AOA

A

Straight fin with high aspect ratio

Higher lower AOA and higher Cl

42
Q

What does a dorsal fin do

A

Increases directional stability
Greater sweepback
Lower aspect ratio

43
Q

What does a ventral fin do

A

Increase directional stability

44
Q

What do strakes do

A

In slow flight rear of aircraft dips into air = creates ventral fin

45
Q

How does sweep back affect directional stability

A

One wing is more straight on to airflow = more lift (but more drag) therefor yaws towards raf = more stable

46
Q

What does a fuselage do to stability

A

Destabilises

47
Q

What does weak lateral stability mean

A

Slow to recover from wing drop

48
Q

What will happen if you have positive lateral stability during a sideslip

A

Roll in opposite direction of sideslip

49
Q

What gradient does positive lateral stability have

A

Negative gradient

50
Q

What affect does a dihedral wing have on lateral stability

A

Increases it

51
Q

What effect does sweepback have on lateral stability

A

More stable

52
Q

What effect does High wing have on lateral stability

A

More stable

Centre of pressure moves slightly down the downgoing wing creating a moment

53
Q

What affect does High keel surface have on lateral stability

A

More stable

54
Q

What is spiral instability

A

When directional stability is strong

Lateral stability is weak

55
Q

What is a Dutch roll

A

Strong lateral stability

Weak directional stability

Wing drop = wings level (however more drag with extra lift = yaw in direction of wing drop)

56
Q

What does a aircraft that suffers from Dutch roll require

A

Yaw damper which inputs rudder to prevent yaw

57
Q

Can you fly with an inoperative yaw damper

A

No

58
Q

How does altitude affect dynamic stability

A

Reduces with altitude

59
Q

For a canard where must the AC and neutral point me

A

Forward or the cg

60
Q

What must you remember when calculating stick force per G

A

To take of 1G for normal gravity

ATPL POF (12 decks)

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