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NZ Aircraft Systems > Flight theory > Flashcards

Flight theory Flashcards

1
Q

What is a vector?

A

Magnitude + Direction

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2
Q

How do we add vectors?

A

F1 points to start of F2
Resultant force starts and tail of F1 and goes to head of F2

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3
Q

What are Newtons Laws

A
  1. Object will stay stationary, unless force is applied
  2. Object will move in direction of and proportional to force
  3. Every action has an equal and opposite reaction
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4
Q

Formula for Force and units?

A

F=MA
F = kg m/s2 = Newton

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5
Q

What is a moment?

A

Weight * Distance from a fixed point.

Units: Kg m

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6
Q

How do we calculate CG?

A

Calculate all moments using fixed Datum
Add all moments up ( kg m )
Divide by total weight ( kg )

CG is the distance from the Datum +/- the distance

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7
Q

What is density and the formula?

A

How much matter in a volume.
Measure as weight per cubic meter

m/v = kg/m3

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8
Q

ISO Standard measures?
-Pressure
-Temp
-Height measured at

A

15 c
1013.2 HPa

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9
Q

What is pressure and the measures?

A

Force exterted on each m2.

1 pascal = 1 Newton / m2
1 HPa = 100 Pascals

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10
Q

What is the formula for the general gas law?

Relationship between Pressure, Volume and Temp

A

P*V / T = constant

Pressure * Volume / Temp = constant

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11
Q

What is torque?

A

The angular version of linear force

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12
Q

Formula for CPF?

Centripedal Force

A

Centripetal Force =
m*v2 / r

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13
Q

Formula for Radial Acceleration?

A

v2/r

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14
Q

What is the total energy of Air?

A

Total Energy = Pressure Energy + Kinectic Energy

Ps + 1/2 sigma V2

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15
Q

What is the Chord Line and Mean Camber line in an Aerofoil

A

Chord
Line from front to back

Camber
Line equidistance from top and bottom.

These are equal if the aerofoil is symmetrical.

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16
Q

Forces for Lift on an Aerofoil?

A

Lift - at the Centre of Pressure. This is the sum of all of the pressure forces.
Operates at 90 degrees to Relative Wind
Drag - operates opposite to Relative wind

Center of Pressure moves forward as the angle of attack increases

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17
Q

What is the Total Reaction Force?

With regards to lift

A

Resultant Force = Lift - Drag
(Expressed as a VECTOR)

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18
Q

What happens to lift as AoA increases?

A

Increases Linierly, then reducing, then stall.

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19
Q

What is the aspect ratio AR?

A

The wing span to the mean chord

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20
Q

What is the formula for Lift?

A

Lift co-effiecent * 1/2p * v2 * S

1/2p = air density
v = velocity
s = surface area of the wing

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21
Q

What factors increase the Lift co-efficient?

A

The lift co-effeicient is not constant, but varies.

Shape of the wing
Angle of attack

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22
Q

How is the sweep angle of a wing calculated?

A

Angle between fuslage center of the wing compared to the 1/4 chord to the wing tip

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23
Q

What is the stagnation point?

A

Point at which the wind splits on the leading edge.

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24
Q

Describe the laminar air, boundary air, turbulent air and transition point

A

Boundary Air - air layer closest to the wing.
Laminar air - smooth air flowing over the wing
Turbulent air - not smooth air flowing over the wing
Transistion point - point on the between laminar and turbulent air

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25
Q

What the standard aerofoil shapes

A
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26
Q

What is the taper ratio for a wing?

A

Length of the tip / length of the root

Ct/Cr

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27
Q

What are the factors of Drag

A
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28
Q

What is the drag formula?

A

CD * 1/2p * v2 * S

CD - Co-efficent of drag
1/2p - air density
v2 - velocity squared
S - cross sectional surface area

29
Q

What are the 4 factors for Profile Drag?

A
  • Form Factor
  • Cross Sectional
  • Area
  • Airflow speed
30
Q

Interactions between parasite drag and induced drag

A

Parasite Drag - increases with Speed.
Induced Drag - decreases with Speed.
Therefore there is an optimal speed/AoA ( 4 - 5 degrees ) to maximise range.

31
Q

What can be done to reduce Induced Drag?

A

Goal: Create elpictal lift. Done by

  • Reduce wingtip vortexs
  • Increase AR ( span to surface area ) - wider span = less induced drag
32
Q

What does downwash do to the lift co-efficent?
( and how does downwash occur? )

A

Downwash is caused as the pressure equalises at the wingtips ( creating Vortexs )

It reduces the lift co-efficient, meaning a high AoA for the same life, meaning more drag.

33
Q

For a light aircraft - what is ‘normal’ stall AoA and best cruise AoA

A

16 degrees
4 - 5 degrees

34
Q

How do we estimate AoA in a light aircraft?

A

There is not an AoA indicator. Therefore the POH has recommended speeds.
Note: These are proxy, esp. Stall speed.
However they are good guidance for cruise, climb and glide speeds.

35
Q

What is the formula for wing loading?

A

Weight / Area

36
Q

What increases stall speed?

A
  • Weight
  • Load factor ( apparent weight )

This means that in straight and level the heavier the plane the higher the stall speed

37
Q

What are the 2 stall speeds on the Airspeed Indicator?

A

Vs0 - bottom of white arc. Full landing config
Vs1 - bottom of the green arc. Cruise config

38
Q

What is the most important factor with regards to stall speed?

A

Aerofoil shape. Dictates the stall angle of attack, and how gentle or abrupt the stall is.

39
Q

What is the formula for load factor and stall speed increase

A
40
Q

What is the most important part of the plane to keep free of ice/dirt?

A

The leading edge.
Ice buildup / dirt - will have the biggest impact on stall speed.

41
Q

What is the impact of Slipstream on Stall Speed?

A

The stall speed will be lower, due to the airflow over the wing. Could be as much as 5 knts.

This is why a ‘bump of power’ on landing can prevent a hard landing… even if the plane does not actually go faster.

42
Q

What is the power condition for the stall speed in the POH?

A

Idle. (as power will decrease stall speed )

43
Q

Where do we want to the wing to stall first?
Why?
What shape should the wing be?

A

At the wing root, keeping the aerilons in undistured air. AND reducing wing drop

More rectangular wings will do this
AND
Twisting the tips

44
Q

What is the load factor?

A

Relationship between weight and lift.

45
Q

What is a spin ( and the cause ) ?

A

A yaw aggirvated stall.

Caused because the lower wing is slower than the upper - therefore stalls first
AND
The lower wing has more drag and is slower - therefore tendancy to increase

46
Q

Why does the stall risk go up in a turn?

A

Two factors:
- Load factor increases, increasing stall speed
- The lower wing is going slower and has more drag.

Un-conordiated turns agreviate stall risk

47
Q

What are the risk times for turns to cause stall/spin?

A

Turn on to final
Already low speed
May increase bank if overshoot

Valley turns
May increase bank angle

Way to avoid
- Use power when doing a turn
- Know how much space you have

48
Q

What is the impact of stall speed with a 60 degree bank angle?

A

41%

49
Q

Symptom of a stall?

A
  • decreasing airspeed
  • Possible nose high ( angle of attack )
  • MAYBE stall warning
  • Ariframe buffet or vibration
50
Q

Spin recovery procedure?

A

P power close throttle
Identify you are in spin
A - Ailerons neutral
R - Rudder oposite spin.
E - Elevators slowly forward
S - Spin stops. Slowly pull out of dive and power back in

51
Q

What are the phases of a spin?

A

Stall
Incipient Spin
Full developed Spin
Recovery

52
Q

What is a graveyard spiral and recovery?

A

Not a spin.
Causes is because plane is not level and pulling back on yoke to recover just tighens the turn

Recovery
Power out
Aileron to level plane
WHEN LEVEL - Gently pull to recover from dive
Power back in.

53
Q

Formula and rule of thumb to calculate turn radius

A

V2 / 11.26 * Tangent of Bank Angle

OR

1% of the airspeed will give the diameter with standard rate turn.

54
Q

How do we find max endurance speed?

A

It is the lowest point on the power required.
High air density = better , so fly as a low as possible

55
Q

How do we find max Range speed?

A

A tangent line is drawn from zero to the bottom point of the power required.
The point at which is crosses is the best TAS

Other considerations:
Lean to minimise fuel burn
Higher Altitude = less drag.
Winds

Therefore is it a winds / altitude trade-off

56
Q

What is the formula for performance at all phases of flight

A

Power + Attitude = Performance

Means if the IAS fails OR the power fails we can still fly - use the other indicator

57
Q

The altitude at which full power is only capable of sustaining level flight at one airspeed is called the

This is two words.. not performance ceiling

A

Absolute Ceiling

58
Q

What is the thrust to drag formula for a climb?

A

T = D + RCW ( Rearward component of weight )
Lift is < Weight ( the plane is ‘driving’ upwards )

59
Q

Where on the Power / TAS Graph is the Max ROC ( Rate of Climb)

This graph has the power needed and power available.

A

At the largest difference between power required and power available

60
Q

How do the following affect Climb Performance?
Flaps
Weight
Wind

A

Flaps
reduces the rate and angle of climb
Weigh
Increases Rearward Component of Weight - therefore decreases rate and angle
Wind Headwind
Rate of Climb not affected vs tail wind
Angle increases
Ground Speed Reduced

61
Q

How does do following affect Descents?
Flaps
Wind
Power

A

Flaps - increases Drag, therefore reduces range.
Wind - Headwind reduces range
Power - More power increases range

62
Q

How does the Weight affect Descents?

A

More weight = same range.
BECAUSE
More weigh increases the forward componet of weight, meaning the glide path is flown faster.

63
Q

How does L/D affect range in a descent?

A

Best L/D is achieved by fliying best glide speed.
Resulting in lowest angle of attack vs drag

64
Q

What are CPF ( Centripedial Force) and CFF ( Centrifegual Force )

A

CPF is inwards force
CFF is outwards force

65
Q

How do the forces work in a turn ( Weight and Lift )

A

VCL must be equal to Weight.
Due to the turn, we need to back stick

66
Q

What is the load factor?

A

The lift needs to increase in a turn, due to the HCL
This results in an Weight force on an angle, called ‘G’

67
Q

At what angle of bank will power be required to maintain altitude?

A

As drag increases, more power is required at 45 degrees to overcome the incresed drag.
Full power is required about 60 degrees… therefore max bank angle

68
Q

Under / Over banking tendancies in a climbing/ descending turn

A

Outer wing is always travelling faster, therefore more lift.
In Climbing turn - results in overbanking tendancy.
In descending turn - inner wing has a higher angle of attack, so often cancel out. Depending on aircraft design, can result in underbanking tendancies.

69
Q

What is a rate 1 turn?
How to calculate it?

A

3 degrees per second
Angle of bank = TAS /10 + 7

NZ Aircraft Systems (6 decks)

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