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Private & Commercial Pilot (DA 40NG) > PPL Oral - Aerodynamics & Performance > Flashcards

PPL Oral - Aerodynamics & Performance Flashcards

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Charter Pilot (Part 135) - Oral flashcards
1
Q

What are the 6 main forces acting in a turn?

A
  1. Lift
    * Keeps the aircraft in the air, but is reduced, due to the added Horizontal lift component
  2. Horizontal Component of Lift (Centripital force)
    * Turns the aircraft
    * causes the aircraft to descend because lift upward lift is now split into a horizontal component
  3. Total Lift
    * The Sum of the lift holding the airplane in the air, and the Horizontal lift causing the turn
  4. Weight
    * The force of the aircrafts weight that counteracts lift
  5. Centrifugal Force
    * Acts equal and opposite to the Horizontal lift
  6. Resultant Load Factor
    * A result of Weght and Centrifugal Force
    * Increases weight
    * Increases stall speed
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2
Q

Why do we need to apply back pressure when in a turn?

A

Because we have less vertical Lift keeping the airplane in the air due to part of the total lift now acting horizontally.

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3
Q

Why do we need rudder in a turn?

A

Because the upward wing creates more drag, pulling the nose above the horizon (A Slip). Deflect rudder slightly into the turn to combat this.

This is called Adverse Yaw

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4
Q

Explain Overbanking tendency

A
  1. In a turn, the outside wing is traveling slightly faster than the inside wing, thus, the outside wing will produce more lift than the inside wing and continue to bank.
  2. Combat this by slightly pushing the stick in the opposite direction of the turn until the turn stabilizes.
  3. Overbanking tendency is especially dangerous at low airspeeds, like in the traffic pattern, as our stall speed will increase as the bank increases the load factor.

Most prevelant durring Steep turns

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5
Q

What is known as Slipping?

A

When the nose of the aircraft is yawing towards the outside of a turn.

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6
Q

What is Skidding?

A

When the nose of the airplane is yawed towards the inside of the turn.
Usually due to excess rudder usage.

NEVER use yaw (rudder) to tighten a turn!

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7
Q

What is more dangerous, a Skid or a Slip?

A

A skid is more dangerous especially at low speeds as it will likely lead to an accelerated stall into a spin.

NEVER use the rudder to tighten a turn!

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8
Q

What are the two basic types of drag?

A

Parasitic and Induced drag

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9
Q

What are the 3 types of Parasitic Drag?

A
  • Form drag
    Drag generated by the different shapes of objects
  • Interference Drag
    Drag generated by the intersection of airstream currents a cross a meeting point between two objects.
  • Skin Friction Drag
    Drag generated by tiny imperfections in the surface of an object
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10
Q

What is Parasitic Drag?

A

Drag that is produced by an object as it moves through the air

(not associated with the product lift?

3 Types: Form, Interference, & Skin Friction

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11
Q

What is Induced Drag

A

Drag that is generated as a byproduct of Lift
* The Wingtip Vortices and Downwash angle downwards behind the wing, this changes the angle of the relative wind.
* Since Lift always acts perpendicular to the relative wind, this causes the Lift Vector to have a reward component to it, reducing lift.

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12
Q

What are Wingtip Vortices?

A

Areas of turbulent air behind the wingtips of aircraft, generated by Induced Drag
* they form because this is the area where the High pressure below the wing and the Low pressure above the wing mix, and create a vortex

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13
Q

When are Wingtip Vortices greatest?

A

When the generating aircraft is heavy, clean, and slow.

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14
Q

How should one avoid Wingtip Vortices or Wake Turbulence?

A
  • Avoid flying through another aircrafts flight path
  • Avoid following within 1,000ft of another aircrafts flight path
  • When taking off behind and aircraft, rotate prior to its rotation point
  • Land above the aircrafts flight path and touchdown beyond their TD point.
  • Watch out for wake turbulence when using parallel runways.
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15
Q

What are the Four Forces of flight and how are they related?

A
  1. Lift
    * Opposes Weight
  2. Weight
    * Opposes Lift
  3. Thrust
    * Opposes Drag
  4. Drag
    * Opposes Thrust
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16
Q

What is Ground Effect?

A

The tendency of the aircraft to remain or become airborne very close to the ground.
* Occurs due to Wingtip Vortices and Wing Downwash not being able to fully form, they push on the ground createing a cushion of air that keeps the airplane airborne.
* This is because Induced drag is greatly reduced due to the Vortices and Downwash not being able to form

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17
Q

Why should you be wary of Ground Effect when landing?

A

Because the aircraft will want to stay airborne too long, especially if your speed is too high. This will increase your float time.

-Combat this by maintaining appropriate speed and reducing power prior to landing.

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18
Q

Why should you be wary of Ground Effect when taking off?

A

Because Ground Effect can allow the aircraft to become airborne before it has the speed/lift required to maintain a climb.

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19
Q

What are the 3 Axis of an aircraft and what are their associated control surfaces?

A
  • Longitudinal, Roll = Aileron
  • Lateral, Pitch = Elevator
  • Vertical, Yaw = Rudder
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20
Q

What is Positive Static Stability?

A

The INITIAL tendency for the aircraft to return to its original attitude after being disturbed about one of its axes, due to its inherent design characteristics.

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21
Q

What are the 4 Left Turning Tendencies?

A
  1. Torque
  2. Spiraling Slip Stream
  3. P-Factor
  4. Gyroscopic Precession
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22
Q

What is Torque that causes a left turn?

A

The clockwise turning engine produces a reactive force causing the aircraft to ROLL to the left.

Newtons 3rd Law
-For every action there is an equal but opposite reaction

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23
Q

What is Spiraling Slip Stream?

A

The prop wash from the propeller spirals around the fuselage where it eventually hits the left side of the vertical stabilizer, causing the aircraft to yaw to the left.

Most noticeable at low airspeeds.

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24
Q

What is Gyroscopic Precession?

A

A force applied to a spinning disc will be felt 90 degrees in the direction and plane of rotation.

This occurs whenever the aircraft pitches up or down. Causing a left/right turning tendency due to the clockwise turning propeller blade.

This is most prevalent in conventional (tail wheel) aircraft on take off.

This can also create a RIGHT turning tendency

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25
Q

What is P-Factor?

A
  1. Due to the designed blade angle of the propeller, the descending blade on the right takes a larger “bite” (AOA) of air than the ascending blade on the left resulting in the creation of asymmetrical thrust and a left turning tendency.
  2. Most noticeable at high AOA and high airspeed.
26
Q

What is a Stall?

A

When the airfoil is no longer creating enough lift to support the weight of the aircraft. Exceeding the critical AOA

27
Q

What is happening during a stall?

A
  • The airflow is separated from the wing, disrupting the creation of lift. This happens when the relative wind is no longer able to fully wrap itself along the surface of the wind due to the critical AOA being exceeded.

The LAMINER airflow over the wing is disrupted

28
Q

Why does the nose usually drop in a Stall?

A

The CG being designed to always be ahead of the CL forces the nose of the airplane down. (Safety feature).

29
Q

What are some aircraft design characteristics that can improve Stall recovery?

A
  1. The CL being aft of the CG forces the nose down in a stall.
  2. The aircraft stalling at the wing root first. The Root (inboard side) has a higher AOA than the tip (outboard). Stall strips installed on the leading edge near the root. This is called Wing Wash
  3. Ensuring we have a forwardly placed CG during W&B checks.
30
Q

What kind of conditions contribute to adverse Stall characteristics

A
  • Turns = Load factor is increased, requiring a higher AOA to maintain enough lift to support the extra weight due to centrifugal
    force in a turn.
  • Wing Icing = It only takes .8 mm of ice to decrease lift and increase drag by 25%. This increases the AOA we need to maintain lift.
    Getting us closer to critical AOA
31
Q

Why is AOA a more reliable metric than Stall speed to measure how close you are to stalling the aircraft

A

Because published stall speeds are dependent on specific parameters:

  • Unaccelerated flight (1G load factor)
  • Coordinated flight
  • At a specific weight (usually max gross weight)
32
Q

Why don’t we use Aileron in a Spin?

A
  1. Aileron will be ineffective due to lack of air flowing properly over the wing to produce Lift
  2. It would increase drag and aggravate the spin further.
33
Q

Why do wings fly?

A
  1. The curvature of the wing causes the air at the top to speed up, resulting in a DECREASE in pressure ABOVE the wing (Venturi Effect & Bernoulis Principle), this creates higher pressure below the wing, pushing the wing up and creating LIFT.

Why does the air speed up?
2. Centrifugal force

34
Q

What are the two scientific principles that allow us to fly?

A
  1. Bernoulli’s principle (Venturi Effect) - An Increase in the speed of a fluid (air) will also result in a DECREASE in pressure (as a fluid speeds up, its pressure decreases)
  2. Newtons 3rd Law of Motion - For every action there is an equal and opposite reaction
35
Q

What are the conditions for necessary for high Density Altitude?

A
  • High elevations
  • Higher than standard temperature
  • Lower than Standard atmospheric pressure
  • High humidity (moist air. Decreases air density)
    ..Or a combination of these factors
36
Q

What kind of things can effect stall speed?

A

AC 62-67C

  1. Weight
  2. CG
  3. Bank angle (Load Factor)
  4. Turbulence
  5. Wing Contamination (Ice, snow, frost)
37
Q

Why is it wise to fly a higher than normal approach speed during moderate to severe turbulence or strong crosswinds?

A

AC 62-67C

Because drastic changes in the Relative Wind to the airfoil can increase stall speed or cause the aircraft to exceed Critical AOA.

38
Q

What is the Glide Ratio of the DA 40 NG?

A

Glide ratio is 9.4

For every 1,000FT of altitude lost, 1.54 NM distance can be gained

39
Q

What is Newtons 1st Law?

A

An object at rest or in motion will remain so until acted upon by another force
* For example: An aircraft must overcome its forward Inertia in order to turn, it does this by producing horizontal lift.

This is known as INERTIA: Newtons Inertia Law

40
Q

What is Newtons 2nd law?

A

Every action has an equal & opposite reaction
* For example: An aircraft producing Horizontal lift in a turn, will also produce Centrifugal force in the opposite direction of the turn.

Newtons Reactioinary Law

41
Q

What is: Mean Wing Camber?

A

Mean Wing Camber is an imaginary line that is equadistant from the upper and lower portion of an airfoil, following the curve of the wing, and meeting the Chord line at the leading and trailing edges.

In a turn, the outside wing produces more lift because the downward aileron INCREASES the Camber of the wing, in addition to moving slightly faster than the inside wing.

42
Q

In a turn, why does the upward, outside wing create more lift than the downward, inside wing?

A
  1. In a turn, the outside wing produces more lift because the downward aileron INCREASES the Camber of the wing.
  2. In addition, it also moves slightly faster (more lift) than the inside wing.
43
Q

What are the two main categories of aircraft stability?

A
  1. Static Stability
  2. Dynamic Stability

https://www.youtube.com/watch?v=Q2DOus05Qso&list=WL&index=16

44
Q

What is Static Aircraft Stability?

A

How an aircraft initially responds to a distrubence placed upon one of its axis (yaw, pitch, roll)

https://www.youtube.com/watch?v=Q2DOus05Qso&list=WL&index=16

45
Q

What is Dynamic Aircraft Stablity

A

How an aircraft responds over time to a disturbance placed upon one of its axis (yaw, pitch, roll)

https://www.youtube.com/watch?v=Q2DOus05Qso&list=WL&index=16

46
Q

What kind of Aircraft Stability are most training aircraft designed to have?

A

Positive Dynamic Stability.
* The tendency for the aircraft to return to its original state after it has been distrubed.

https://www.youtube.com/watch?v=Q2DOus05Qso&list=WL&index=16

47
Q

Explain what Positive, Neutral, and Negative stability are.

A

Positive
* The aircraft will return to level flight when distrubed (static), or will climb back up to its original altitude and level off after a few oscilations (dynamic)

Neutral
* The aircraft will maintain the pitch up or pitch down attitde after being distrubed (statoc), or maintain equal oscilations over time (dynamic)

Negative
* The aircraft will continue to increase the nose down or nose up pitch of the original disturbance (static), or will have increasingly exaggerated oscillations (dynamic)

https://www.youtube.com/watch?v=Q2DOus05Qso&list=WL&index=16

The example in the answer is given in the form of a disturbance in Pitch, but a distrubance on any axis could be used to explain.

48
Q

Which loading scenario is preferable, a more Forward CG, or an Aft CG?

A

An Aft CG is preferable because:
- Much more fuel efficient
- Lower stall speed

49
Q

What are the characteristics of a Forward CG and why?

A

Pros:
1. More Stable longitudinally (CG & CL are farther away from eachother
2. Good stall recovery (nose heavy)

Cons:
1. Higher Stall speed (higher AOA to fly straight and level because tail-down force adds weight)
2. Less fuel efficient (more drag due to higher AOA and large tail-down force)

50
Q

What are the characteristics of an Aft CG and why?

A

Pros:
1. More Fuel efficient (less drag from taildown foce is needed to stay in level flight)
2. Lower Stall Speed (lower AOA is required to maintain level flight)

Cons:
1. Less Stability, Longituinally: CG & CL are closer together
2. Poor stall recovery

51
Q

Why is a higher AOA required when an aircraft is loaded with a more Forward CG?

A
  • This is because more tail downforce is needed to counteract the nose down tendency of a forwardly loaded CG, the extra tail downforce essentially adds ‘weight’ to the aircraft which requires more Lift to be produced (higher AOA) to maintain straight and level flight.

PHAK

52
Q

What aircraft design charactoristics are utilized to increase Longitudinal Stability (Pitch Stability)?

A
  1. The Center of Gravity is placed forward of the Center of Lift.
    * This creates a nose down tendancy which aids in stall recovery
  2. The Horizontal Stabalizer is designed as an inverted wing to create Tail-Down Force.
    * This helps keep the nose up and will balance out the nose heavy aircraft design.

https://www.youtube.com/watch?v=BWx8m4G0nEc&list=WL&index=14

53
Q

What aircraft design charactoristics are utilized to increase Lateral Stability (Roll stability)?

A
  1. Dihedral - The upward tilted angle of the wings relative to the aircraft being viewed from head on
    * When a wingtip is lowered (roll, without yaw), the aircraft will enter a sideslip, and due to the relative wind changing the way the air flows over both wings, the lower wing is now producing more lift and will begin to raise itself back to level flight.

https://www.youtube.com/watch?v=BWx8m4G0nEc&list=WL&index=14

54
Q

What is Dihedral?

A

Dihedral - The upward tilted angle of the wings relative to the aircraft being viewed from head on

55
Q

When do True Air Speed and Groundspeed increase proportionally?

A

When Density Altitude is high

56
Q

What two important things can be achieved by flying an aircraft at its Maximum Lift to Drag Ration (L/D max)?

A
  1. Max range
  2. Max glide distance
57
Q

Lift is most properly defined as..

A

The force acting perpendicular to the relative wind

Shephard Air: Commercial

58
Q

As fuel is consumed enroute, what action should be taken as the aircraft becomes lighter?

A

Decrease power to maintain a constant airspeed for maximum efficiency
* As weight decreases, optimum airspeed and power setting may also decrease

PHAK Pg 11-10 & 11-11

59
Q

Why would you expect lower aircraft performance when Relative Humidity is high?

A

Because water vapor is LESS DENSE than air, and since there is a lot of water in the air durring High Relative Humidity conditions, the air also becomes LESS DENSE due to the excess moisture.

60
Q

How would you expect a strong Headwind to effect your aircraft performance durring the Enroute, TO, and Landing phases?

A

Enroute
* Low Ground Speed
* Longer Enroute time (ETA effected)
* More fuel required

T/O & Landing
* Shorter T/O roll
* Shorter Landing roll, stopping sooner
* Steeper Climb/Descent Gradient (altitude gained over distance)

61
Q

How would you expect a strong Tailwind to effect your aircraft performance durring the Enroute, TO, and Landing phases?

A

Enroute
* Higher Groundspeed
* Shorter Enroute time (ETA)
* Less fuel required

T/O & Landing
* Longer takeoff roll
* Longer landing roll
* Shallower Climb/Descent Gradient (altitude gained over distance), obstacle clearance may be of concern

Approach
* A steeper descent will be required due to the increased groundspeed

62
Q

Explain what Wing Washout is and why it is useful

A

Wing Washout is the ‘twisting of the wing’
* The root (inboard) part of the wing has a higher AOA than the tip (outboard) part of the wing
* This is to ensure that the wing will stall at the root first and not at the tip where the Ailerons are, if the Aileron section of the wing stalls, they will be rendered ineffective

Private & Commercial Pilot (DA 40NG) (28 decks)

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