Basic Aerodynamics

Question 1

Understand Bernoulli’s Law

Answer 1

Total pressure equals static (P) plus dynamic pressure (q) Assuming constant density, an increase in velocity will increase dynamic pressure, causing a drop in static pressure

Question 2

Discuss and understand basic aerodynamic forces

Label a picture of the following: Lift, Drag, CP, AC, Resultant AF, Weight, Thrust

Answer 2

Question 3

Discuss Equal Time Theory

Answer 3

The difference in pressure across the airfoil produces lift Air molecules flowing over the top of a wing have father to travel than along the bottom

Question 4

Lift is the force component _________ to the oncoming flow

Answer 4

Perpendicular

Question 5

Drag is the force component __________ to the oncoming flow

Answer 5

Parallel

Question 6

How does an airfoil effecting flow

Answer 6

Air is turned both above and below the wing so upper and lower surface contribute to the flow turning and producing lift. For typical airfoils at subsonic speeds, the top surface contributes more flow turning than the bottom surface, causing pressure differential along the top to be significantly larger

Question 7

C_L is constant for each ______, but varies with ______

Answer 7

C_L is constant for each wing shape, but varies with AoA (Angle of Attack)

Question 8

Label a picture with Airfoil Forces; include Center of Pressure, Aerodynamic Center, Center of Gravity, Angle of Attack, Relative Wind, Chord, Lift, Drag, Weight, Resultant AF.

Answer 8

Question 9

Define Airfoil Forces:

Chord Line

AoA

cg

cp

AF

AC

ROT

Answer 9

Chord Line: Straight line from leading edge to trailing edge

AoA: Angle between relative wind and the chord

cg: Point on the chord line where all effective weight is realized
cp: Point on the chord where resultant AF act (moves with AoA)

AF acts through the cp and is the vector sum of lift and drag

AC: Point around which the pitching moment occurs (also the central point of the lateral axis)

ROT: The AC is an average of the cp and cg

Question 10

Discuss the difference between Aerodynamic Center vs Center of Gravity

Answer 10

AC moves dynamically- function of speed and AoA

cg moves statically- function of aircraft loading (fuel, stores, etc)

Question 11

Define Static Margin

Answer 11

Static margin is the difference between the location of the cg and the AC

Positive: cg forward of AC

Neutral: cg at AC

Negative: cg aft of AC

Question 12

Explain how Aircrew can modify C_L

Answer 12

Flaps modify camber and wing area, so increases in AoA modify flow separation and lift production of a given wing or shape

For a given AoA, trailing edge flaps increase C_L, but decrease stall AoA

Question 13

Define Fowler Flaps

Answer 13

Fowler Flaps move aft and down producing significant modifications in Camber and Surface Area

Question 14

Define Stall

Answer 14

Stall is defined as an increase in AoA with no increase in C_L, or where you exceed the critical AoA

Question 15

Define Induced Drag

Answer 15

Drag due to the production of lift

Question 16

Define Thrust Available

Answer 16

Generates velocity to produce lift, required to overcome drag

Thrust available is relatively constant, increases slightly with velocity

Question 17

Label Drag Curves and where “behind the power curve” is located

Answer 17

Question 18

Label AoA, Flight Path Angle, and Pitch Angle on a chart

Answer 18

Question 19

What is AoA

Answer 19

The angle between the oncoming air or relative wind and a reference line on the airplane or wing

Question 20

What is pitch

Answer 20

Pitch angle, or attitude, is the angle between the longitudinal axis and the horizon

Question 21

What is flight path angle

Answer 21

Angle between horizon and climb/descent angle

Question 22

Define P-Factor

Answer 22

The horizontal blade moving down will have greater AoA producing more thrust than the horizonal blade moving up.