CADC: CPL Aerodynamics – all aircraft categories

Question 1

Aerofoil span and it’s effect of lift and drag

Answer 1

Aerofoil span is he distance from wingtip to wingtip.

Question 2

Chord definition

Answer 2

The straight-line distance ( cross section) from the leading edge to the trailing edge of a wing or control surface.

Question 3

Chord effect on lift

Answer 3

Greater chord = greater wing area. Greater wing area = greater lift.

Question 4

Chord effect on drag

Answer 4

Main effect is on induced drag especially in relation to the aspect ratio

Question 5

Parasitic drag

Answer 5

Resistance to motion caused by aircraft moving through the air. No contribution to lift. Increases with speed^2

Question 6

Total drag

Answer 6

Parasitic drag + Induced drag

Question 7

Induced drag

Answer 7

Caused by the pressure difference between the top and bottom of the wing, which causes air to curl around the wingtips, crerating wingtip vortices.

Question 8

Lift Vector

Answer 8

Magnitude and direction of lift

Question 9

Camber definition

Answer 9

The curvature of an airfoil (wing or control outer surface)

Question 10

Mean camber

Answer 10

The curve halfway between the upper and the lower surfaces of the airfoil

Question 11

Camber effect on lift and drag

Answer 11

Increased camber – increase the pressure difference between the upper and lower surfaces
Result – more lift at a given AoA
More camber = more form (parasitic) drag

Question 12

Form drag

Answer 12

Caused by shape (vertical vs. horizontal hand out the window)

Question 13

Skin friction drag

Answer 13

Air molecules rubbing against the aircraft’s surface.
Dirt, bugs, rivets vs. smooth, polished

Question 14

interference drag

Answer 14

Created where surfaces meet at angles causing inefficiency

Question 15

Thickness/chord ratio

Answer 15

Measure of the thickness of an airfoil relatice to its chord length
Max thickness / Chord length

Question 16

Thickness/chord ratio effect on lift

Answer 16

Thicker = more lift
Too thick = Airflow separation/ reduced lift

Question 17

Thickness/chord ratio effect on drag

Answer 17

Thicker = more drag

Question 18

Relative airflow

Answer 18

direction of the air flowing relative to the aircraft.
Opposite to flight path

Question 19

Angle of Attack

Answer 19

the angle between the chord line of the wing and the relative airflow

Question 20

Relative airflow effect on lift and drag

Answer 20

increase RA = increase lift (if AoA is positive)
increase RA = increase parasitic drag

Question 21

AoA effect on lift and drag

Answer 21

As you increas AoA, the pressure difference between the top and bottom surfaces of the wing increase.
This also increases the size and strength of the wingtip vortices, which contribute to induced drag

Question 22

Boundary layer

Answer 22

thin layer of air that forms along the surface of the aircraft where air slows down due to viscous friction between the surface and th airflow

Question 23

Laminar boundary layer

Answer 23

smooth, orderly, and parallel airflow. the air flows in layers with little mixing

Question 24

Laminar boundary layer effect on drag

Answer 24

laminar flow = lower skin friction drag
more likely to separate from the surface (stall) when airflow is disrupted (at high AoA)

Question 25

Turbulant boundary layer

Answer 25

chaotic, swirling, and mixing airflow near the surface

Question 26

Turbulant boundary layer effect on drag

Answer 26

turbulent flow = higher skin friction drag but delays flow separation, which helps maintain lift

Question 27

Explain the different types of drag and state the effect on total drag resulting from changes in IAS, aircraft weight and height, if any

Answer 27

Increased IAS - Parasitic drag increases rapidly, but induced drag decreases forming a U shaped curve Heavier aircraft - needs mor lift, higher AoA, more induced drag Altitude - lower air density reduces parasitic drag. RQ higher TAS for same IAS, total drag may shift

Question 28

Bernounlli's Theorem

Answer 28

In a steady, incompressible, frictionless flow of fluid (like air), the total energy along a streamline remains constant

Question 29

Bernounilli's Theorem applied to an Aerofoil

Answer 29

Upper suface: more curved - air travels faster, increases kinetic energy 9dynamic pressure) Lower surface: flatter - air moves slower, less increrase in kinetic energy, static pressure remains higher

Question 30

kinetic

Answer 30

refers to anything related to the movement of an object or fluid

Question 31

Coanda effect and application to lift production

Answer 31

tendancy of a fluid to follow contours. air sticks to the curve and follows it downward at the trailing edge.

Question 32

IAS

Answer 32

Indicated Air Speed; used for aircraft control, stall speeds

Question 33

CAS

Answer 33

Calibrated Air Speed; corrected for instrument/position effor; used for Accurate performance charts

Question 34

TAS

Answer 34

True Air Speed; Corrected for Altitude and temperature; used for navigation, fuel planning

Question 35

VX

Answer 35

Best angle of climb for height in a short distance. Gains altitiude more slowly but uses less distance. For clearing obstacles close to end of RWY

Question 36

VY

Answer 36

Best rate of climb for height in less time. Gains altitude faster but over a much larger distance. Standard for most runways.

Question 37

Best Endurance

Answer 37

Maximises time aloft. Min power RQ ( bottom of PR curve) Used for loiter (waiting for weather conditions at an aerodrome

Question 38

Best Range

Answer 38

Maximises Distance pepr fuel unit. Tangent (touching but not intersecting) from origin to PR curve. Key use: cross country efficiency