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PPL Training > PHAK 5 > Flashcards

PHAK 5 Flashcards

1
Q

What are the four forces acting on an aircraft in flight?

A
  1. Thrust
  2. Drag
  3. Lift
  4. Weight
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2
Q

What is the relationship of forces in steady flight?

A

The sum of opposing forces is zero:
- Upward forces equal downward forces.
- Forward forces equal backward forces.

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3
Q

Define angle of attack (AOA).

A

The acute angle between the chord line of the airfoil and the direction of the relative wind.

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4
Q

Name the three types of parasite drag.

A
  1. Form drag
  2. Interference drag
  3. Skin friction drag
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5
Q

What is induced drag?

A

Drag caused by the creation of lift, proportional to the pressure difference between the upper and lower airfoil surfaces.

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6
Q

What is the purpose of winglets?

A

Reduce wingtip vortices and improve lift efficiency.

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7
Q

What is ground effect?

A

A phenomenon where airflow around the wing is altered by proximity to the ground, reducing induced drag.

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8
Q

What are the three axes of an aircraft?

A
  1. Longitudinal axis (roll)
  2. Lateral axis (pitch)
  3. Vertical axis (yaw)
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9
Q

Define static stability.

A

The initial tendency of an aircraft to return to equilibrium after being disturbed.

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10
Q

Define dynamic stability.

A

The overall tendency of an aircraft to return to equilibrium over time after being disturbed.

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11
Q

What is the critical angle of attack?

A

The angle at which the wing produces maximum lift before stalling.

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12
Q

What is the lift-to-drag ratio (L/D)?

A

The efficiency of an airfoil, calculated as lift divided by drag. Maximum efficiency occurs at L/DMAX.

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13
Q

What are the effects of high aspect ratio on wing performance?

A
  1. Decreased drag
  2. Improved climb performance
  3. Increased structural weight
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14
Q

What causes Dutch roll?

A

Coupled oscillation of roll and yaw, typically corrected with yaw dampers in modern aircraft.

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15
Q

What is the role of dihedral in lateral stability?

A

Provides stability by increasing lift on the lower wing during a sideslip.

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16
Q

What is the relationship between thrust and drag during constant airspeed?

A

Thrust equals drag.

17
Q

What is parasite drag?

A

Drag that does not contribute to lift, including form drag, interference drag, and skin friction drag.

18
Q

What factors increase induced drag?

A
  1. High angle of attack
  2. Low airspeed
19
Q

Define wingtip vortices.

A

Rotating airflows created by the pressure difference at wingtips as lift is produced.

20
Q

How can wake turbulence be avoided?

A
  1. Avoid flight paths below and behind larger aircraft.
  2. Take off before or land after their rotation points.
21
Q

What is the effect of ground effect on induced drag?

A

Reduces induced drag significantly when close to the ground.

22
Q

What are the three motions of an aircraft and their corresponding axes?

A
  1. Roll - Longitudinal axis
  2. Pitch - Lateral axis
  3. Yaw - Vertical axis
23
Q

What is the function of ailerons, elevators, and rudders?

A

Ailerons: Control roll
Elevators: Control pitch
Rudders: Control yaw

24
Q

What is the center of gravity (CG)?

A

The point where the total weight of the aircraft is concentrated.

25
Q

What happens if the CG is forward of the center of pressure (CP)?

A

The aircraft tends to pitch nose-down, requiring tail force to balance.

26
Q

What is dihedral?

A

The upward angle of wings from horizontal, providing lateral stability.

27
Q

How does sweepback contribute to stability?

A

Increases lift on the lower wing during yaw, restoring directional stability.

28
Q

What is Dutch roll?

A

A coupled oscillation in roll and yaw, typically seen in swept-wing aircraft.

29
Q

What is spiral instability?

A

A condition where strong directional stability and weak lateral stability cause a steep spiral descent.

30
Q

What is the impact of a high aspect ratio on wing performance?

A

Decreases drag, improves climb efficiency, and increases structural weight.

31
Q

Define the critical angle of attack.

A

The angle at which maximum lift occurs before the wing stalls.

32
Q

What is L/DMAX?

A

The angle of attack at which the lift-to-drag ratio is maximized, representing maximum efficiency.

33
Q

What are the two types of stability?

A
  1. Static stability (initial response)
  2. Dynamic stability (long-term response)
34
Q

What are the effects of forward and rearward CG locations?

A

Forward CG: Increases stability, decreases maneuverability.
Rearward CG: Decreases stability, increases maneuverability.

35
Q

What are the three types of static stability?

A
  1. Positive: Returns to equilibrium
  2. Neutral: Maintains new state
  3. Negative: Diverges from equilibrium.

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