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Mod 8 basic aerodynamics > 8.4 stability > Flashcards

8.4 stability Flashcards

1
Q

what is maneuverability?

A

how easily the aircraft and ability to withstand stresses imposed by maneuvers

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2
Q

what is controllability?

A

ability to respond to pilots control regardless of stability characteristics

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3
Q

the aircraft is free to rotate about what axis?

A

yaw
pitch
roll

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4
Q

what axis is yaw, pitch, roll on?

A

yaw is vertical axis
pitch is lateral axis
roll is longitudinal axis

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5
Q

what is a positive yaw?

A

positive yaw is right

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6
Q

what is the primary control of yaw?

A

rudder

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7
Q

what is a positive pitch?

A

nose up

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8
Q

what is the primary control of pitch?

A

elevators

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9
Q

what is a positive roll?

A

left wing up
right wing down

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10
Q

what is the primary control of roll what is also the secondary control?

A

ailerons are primary control
rudder also has effect

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11
Q

what movement, rotation and stability does aileron do?

A

movement - roll
rotation - longitudinal
stability - lateral

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12
Q

what movement, rotation and stability does elevators/ stabilizers do?

A

movement - pitch
rotation - lateral
stability - longitudinal

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13
Q

what movement, rotation and stability does rudder do?

A

movement - yaw
rotation - vertical
stability -directional

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14
Q

what does static stability refer to?

A

initial tendency of an aircraft to return back to equilibrium

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15
Q

what are the three types of static stability?

A

positive negative and neutral

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16
Q

what is positive stability?

A

tendency to return to original state of equilibrium after being disturbed

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17
Q

what is neutral stability?

A

once disturbed it will remain in its new altitude

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18
Q

what is negative stability?

A

aircraft will continue to move away from its original altitude once disturbed

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19
Q

what is dynamic stability?

A

refers to aircraft response over time when given pitch, yaw or bank

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20
Q

what are the three types of dynamic stability?

A

positive
negative
neutral

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21
Q

what is positive dynamic stability?

A

has oscillations that dampen over time as it returns to its equilibrium stage

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22
Q

what is neutral dynamic stability?

A

have oscillations that never dampen out

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23
Q

what is negative dynamic stability?

A

have oscillations that worsen over time

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24
Q

what is longitudinal stability?

A

tendency for the nose to pitch up or pitch down around the lateral axis

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25
Q

what does a longitudinal unstable aircraft do?

A

dive or climb progressively or into a deep dive or stall

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26
Q

what are the three factors of longitudinal stability?

A

location of the wing with respect to the center of gravity
location of horizontal tail surface with respect to center of gravity
area or size of the tail surface

27
Q

what is stability?

A

a body free to rotate always turns about its center of gravity

28
Q

what does a horizontal stabilizer produce during level flight?

A

downward force acting with the center of gravity

29
Q

if the moment arm is balanced between what there will be no change in altitude?

A

force acting on the horizontal stabilizer and the force from the wings

30
Q

when does positive longitudinal stability occur?

A

when the center of gravity as a result of the aircrafts weight is forward of the aerodynamic center

31
Q

when will the longitudinal stability be high or low?

A

will be high when the distance between CoG and aerodynamic center is great
will be negative when the distance between CoG and aerodynamic center is small

32
Q

what is directional stability?

A

stability around vertical axis

33
Q

what can improve directional stability?

A

increase the surface behind the center of gravity by using a dorsal fin
sweep back of a wing

34
Q

what happens when an aircraft is deflected from its original flight path?

A

the forward going wing has a larger frontal area to the airflow

35
Q

what are the 4 factors that make an aircraft latterly stable?

A

dihedral
sweep back
keel effect
weight distribution

36
Q

more specifically what is lateral stability determined by?

A

AOA
dihedral angle
sweep back angle

37
Q

during level flight the AOA is equal to what?

A

to the weight

38
Q

what is the effective AOA?

A

angle between resultant velocity and the chord line

39
Q

when there is a gust one one side of the aircraft what will happen?

A

the wing the gust is on will rise and have a up going velocity and the other wing will have a down going velocity

40
Q

what do dihedral angles do?

A

help restore level flight

41
Q

what creates a resultant force?

A

lift and weight

42
Q

what does the resultant force create?

A

a sideslip

43
Q

what does a sideslip cause?

A

flow of air in opposite direction to the relative wind

44
Q

what stops the slide slip?

A

difference in lift

45
Q

what affects lateral stability?

A

directional stability

46
Q

what is sideslip?

A

angle between the aircraft centerline and direction of side slip

47
Q

what is relative wind opposite to?

A

sideslip direction

48
Q

in slide slip what brings the aircraft back to level flight?

A

difference in lift on wings

49
Q

what is the keel effect?

A

type of lateral stability

50
Q

an aircraft with a positive static stability with a strong keel effect would make what difficult?

A

to roll left and right

51
Q

what acts as the keel?

A

the fuselage as it keeps aircraft pointed in desired direction

52
Q

what aircraft have a higher keel effect?

A

high wing aircraft

53
Q

what is a spiral dive?

A

exits when there is a grater effect on directional stability on the lateral stability

54
Q

the rate of divergence in the spiral motion is usually what?

A

so gradual that the pilot can control it without difficulty

55
Q

what type of oscillation is Dutch roll?

A

lateral directional oscillation

56
Q

what is Dutch roll?

A

exits when there is a grater effect on lateral stability than directional stability

57
Q

how can Dutch roll be partially overcome?

A

by reducing the sweep angle of the wing to improve directional stability

58
Q

how can directional stability be improved?

A

by increasing the size of the vertical stabilizer

59
Q

what can a yaw dampener assist with in terms of Dutch roll?

A

assist during single engine failure and coordinated turns

60
Q

what is relaxed stability?

A

allows the aircraft to be designed for aerodynamic efficiency opposed to handling

61
Q

stability increases with what?

A

with speed

62
Q

to keep an aircraft level what has to be done?

A

tail has to apply torque to trim out the tendency to pitch down

63
Q

what system do most modern aircraft use?

A

fly by wire

Mod 8 basic aerodynamics (4 decks)

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