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Multi-Engine Instructor > Aerodynamics > Flashcards

Aerodynamics Flashcards

1
Q

4-forces of flight

A

Lift, Weight, Thrust, Drag

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2
Q

How is lift created?

A

Bernoulli principle…
faster airflow = lower pressure

Newton’s 3rd law…
action - airfoil (wing) turns airflow down
re-action - airflow pushes wing up

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3
Q

Draw an airfoil and explain chord line, relative wind, and angle of attack.

A
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4
Q

Draw an airfoil with low AOA, higher AOA, and beyond critical AOA. Depict laminar and turbulent airflow.

Explain relationship between AOA and…
…lift.
…drag.

A
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5
Q

Explain how angle of attack is NOT the same as pitch angle.

A
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6
Q

Two types of drag

A

Parasite and induced drag

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7
Q

Explain the relationship between parasite drag and airspeed. Draw a graph to illustrate.

A
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8
Q

Explain the relationship between induced drag and airspeed. Draw a graph to illustrate.

A
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9
Q

Explain the relationship between total drag and airspeed. Draw a graph including L/D max.

A

U-shaped curve. L/D max is at the minimum.

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10
Q

Explain the relationship between the four forces of flight and when they are in equilibrium.

A
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11
Q

Types of parasite drag

A

Form

Skin

Interference

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12
Q

Illustrate induced drag.

A

Draw an airfoil including relative wind, downwash, vortices, average relative wind, lift vector components. Show relationship of induced drag with higher AOA, increased vortices and downwash, and in/out of ground effect. Make a connection of lowered speed > higher AoA > greater induced drag.

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13
Q

Using a model airplane, explain the relationship of airspeed and AOA during level flight.

A
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14
Q

What is a stall? What causes it? What are the indicators? Recovery?

A
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15
Q

What’s a spin? Causes? Indicators? Recovery?

A
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16
Q

Spin avoidance. Common scenarios?

A
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17
Q

Phases of a spin?

A
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18
Q

Aerodynamics (ground)

A

Slipstream
- pushes tail right
- yaw nose left

Torque
- equal opposite reaction
- props CW, airplane CCW
- rolls left > yaws left (drag)

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19
Q

Aerodynamics (Lift off)

A
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20
Q

P-Factor

A

at high AOA (CW rotating propeller)… right descending blade produces more thrust than the left ascending blade.

Airplane will rotate about its center of mass. Because thrust line is offset to the right, the airplane will yaw left.

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21
Q

Accelerated Slipstream

A

aka Induced Lift.

The prop wash / slipstream encounters the wing and produces/induces more lift.

Because the center of thrust / slipstream is offset to the right, then the induced lift is also offset right, that causes the airplane to roll left

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22
Q

Spiral Slipstream

A

The slipstream / prop wash (primarily from the left engine) tends to spiral around the fuselage and hit the left side of the vertical tail > pushes tail right > nose yaws left

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23
Q

Torque

A

Equal and opposite reaction
Props CW > Airplane CCW > left roll

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24
Q

Spiral Slipstream (airspeed effect)

A
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25
Q

How much lift from… Accel Slipstream / Induced Lift

A

Accounts for… 50-60% lift

26
Q

Problems w/ losing an engine

A

1 control problem
2 performance problem
3 sideslip problem

27
Q

Adverse Effects of an Engine Failure (draw this)

A

1 Control issue
pitch - down (loss of slipstream over tail & )
rolls - toward dead (loss of accelerated slipstream /induced lift)
yaws - toward dead (less thrust, more drag)
See “Circle of Doom”.

2 Performance Issue
loss 50% thrust, loss 80-90% performance
- thrust (50%),
- lift (loss induced lift),
weight (same),
+ drag (from prop & induced drag)
Depending on weight and DA, climb rate may be negative! Calculate SE performance

3 Sideslip issue
Assuming wings level flight…
+ more parasite drag with sideslip (bad for performance)
- less rudder effectiveness with sideslip (bad for control)
See SE Level Flight.

28
Q

Why 80-90% decrease in performance when OEI?

A

Thrust - loss of 50%
Lift - less induced lift
Drag - increase prop drag and + induced drag
Weight - unchanged

29
Q

Circle of Doom

A

Less lift > descent > higher AoA > more induced drag > decreases velocity > less lift

…decreases velocity > also, rudder less effective at control!
…higher AoA > more p-factor

30
Q

SE Level Flight aka 3 Sideslip Problem (draw this)

A

3 Sideslip issue
Assuming wings level flight…

Force vectors from rudder and SE thrust creates a Sideslip condition

+ more parasite drag with sideslip (bad for performance)
- less rudder effectiveness with sideslip (bad for control)

Corrected by banking (~5°) into the operating engine and splitting the ball (inclinometer) towards the good engine.

31
Q

Wings level flight vs bank into good engine (draw this)
(Effect on Vmc)

A
32
Q

Critical Engine

A

Engine that most adversely affects performance and control when inop.

Typically the left on a convention light-twin with CW rotating engines.

Each engine is equally critical with counter rotating engines.

33
Q

Torque - OEI Left vs Right

A

Airplane rolls toward dead engine.

Torque rolls airplane left.

Left inop - torque rolls airplane to dead ):

Right inop - torque rolls airplane to operating engine (:

34
Q

Critical Engine (draw PAST)

A
35
Q

Vmc Condition

A

25.149

  • critical engine inop and…
  • propeller windmilling
  • operating engine full power with…
  • DA at Sea Level
  • bank 5° towards operating engine
  • outside ground effect
  • aft CG
  • light weight
  • clean configuration
36
Q

Define Vmc

What are the dangers of operation below Vmc?

A

Vmc

  • Minimum speed at which control can be maintained.
  • determined by manufacturer IAW 23.2135(c)
  • ensures directional control (airflow to rudder), but airplane will not necessarily be able to maintain altitude. (P/2)v^2=dynamic press

WARNING: attempting to operate < Vmc = loss of control (Vmc roll) due to loss of rudder effectiveness.

37
Q

How does FLAPS affect Vmc and Performance?

A

Induced lift > roll moment towards good engine

Lower AoA > less p-factor

Flaps - help control, hurt performance

38
Q

How does FLAPS affect Vmc and Performance?

A

Induced lift > roll moment towards good engine

Lower AoA > less p-factor

Flaps - help control, hurt performance

39
Q

How does GEAR affect Vmc and Performance?

A

G-dn > more drag behind CG > stabilizing keel effect

G-dn - helps control, hurts performance

40
Q

Ground Effect on Vmc and Performance

A

Helps with control when dead engine drops into ground effect (decreases induced drag)

Decreases induced drag and improves performance and control

41
Q

CG effect Vmc and Performance

A

Aft CG - hurts control (shorter arm to rudder), helps performance

Fwd CG - helps control (greater moment arm to rudder), hurts performance.

  • Load nose first
42
Q

Weight on Vmc and Performance

A

More Wgt > more horizontal component of weight when banking to good engine > more effective rudder

More Wgt - helps control, hurts performance

43
Q

Density Altitude on Vmc and Performance

A

higher DA > less asym thrust (less power, less prop efficiency) > helps control > lowers Vmc (Vmc decreases with altitude)

DA - helps control, hurts performance

44
Q

DA on Vs and Vmc

A

Vs - unchanged with DA
Vmc - decreases with DA

Above “Critical DA” - stall indication occurs first

At “Critical DA” - stall and loss of directional control occurs at the same time > spin EXTREMELY DANGEROUS!

Below “Critical DA” - loss of directional control occurs first

45
Q

3-axis of flight

A

Yaws about Vertical Axis

Rolls/Banks about Longitudinal Axis

Pitches about Lateral Axis

46
Q

Yaw

A

movement about vertical axis

primarily controlled with rudder

47
Q

Roll/bank

A

Movement about Longitudinal Axis

Primarily controlled with Ailerons

48
Q

Pitch

A

Movement about Lateral Axis

Primarily controlled by Elevator or Stabilator

49
Q

Lateral Axis

A

Through the Center of Gravity/Mass

Pitches with Elevator about the Lateral Axis

50
Q

Longitudinal Axis

A

Through the Center of Gravity/Mass

Rolls/banks with Aileron about the Longitudinal Axis

51
Q

Vertical Axis

A

Through the Center of Gravity/Mass

Yaws with Rudder about the Vertical Axis

52
Q

Turn

A

Bank lift vector to turn

Horizontal component of lift turns an airplane

53
Q

Turn Rate and Radius

A

Are effected by bank and speed

Greater bank - faster rate, smaller radius
Shallow bank - slower rate, larger radius

Greater speed - slower rate, larger radius
Slower Speed - faster rate, smaller radius

54
Q

How to turn with the smallest radius

A

Slow down and Bank steeper

Caution ⚠️ stall/spin hazard

55
Q

Slip vs Skid

A

Slip
- greater horizontal lift
- ball inside of turn
- useful to create drag (ex fwd slip)
- useful to counter Xwind or OEI Sideslip

Skid
- greater centrifugal effect
- ball outside of turn

Coordinated
- horizontal lift = centrifugal force
- ball centered

56
Q

Adverse Yaw

A

Yaw to outside of turn / furtherance of turn due to the aileron creating lift and drag during roll in/out of bank.

57
Q

Overbanking and lateral stability with bank

A

Overbanking
- steeper banks
- differential radius/airspeed/lift

Lateral stability
- shallower banks
- wings level tendency
- dihedral, sweep wings, and keel effect

At medium banks they cancel

58
Q

Turns and Load factor

A

Load factor increases with bank angle and speed

59
Q

Limit Load Factor

A

Normal category certification limits
+3.8 G
-1.52 G

Beyond these limits it’s possible to experience structural damage

60
Q

Does stall speed change?

A

Vs increases with Load (Mass or Gs)

Vnew = Vold * ^1/2(new wgt/old wgt) or G

Published Vs & Vso are 1G/level/MGTOW
See POH section 5 for tables

61
Q

Load Factor

A

G ratio = Lift force / Mass

60° bank = 2 G

62
Q

Critical Engine and Vmc

A

Multi-Engine Instructor (12 decks)

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