Key Aerodynamics | Part 1

Question 1

The Principle of Continuity:

The air mass flow, or mass per unit time, through the tube will be the product of the cross-sectional area (A), the airflow velocity (V) and the air density (ρ). Mass flow will remain a constant value at all points along the tube. The Equation of Continuity is:

A × V × ρ = Constant

Because air is a compressible fluid, any pressure change in the flow will affect the air density.
However, at low subsonic speeds (< M 0.4) density changes will be _________ and can be
disregarded. The equation of continuity can now be simplified to: A × V = constant.

In other words -

Answer 1

Density remains constant below speed of M 0.4

Question 2

With increasing angle of attack the CP moves -

Answer 2

forward

Question 3

Feature of a symmetrical aero foil related to CP?`

Answer 3

CP position does not change

Question 4

The coefficient of lift (CL) is the ratio between -

Answer 4

lift per unit wing area and dynamic pressure

Question 5

As the angle of attack increases from -4°, the leading edge stagnation point moves from the
_____ surface around the leading edge to the _____ surface.

Answer 5

As the angle of attack increases from -4°, the leading edge stagnation point moves from the
upper surface around the leading edge to the lower surface.`

Question 6

As the angle of attack increases from -4°, the leading edge stagnation point moves from the
_____ surface around the leading edge to the _____ surface

Answer 6

As the angle of attack increases from -4°, the leading edge stagnation point moves from the
upper surface around the leading edge to the lower surface.`

Question 7

Dynamic pressure(Q) =

Answer 7

1/2 rho(air density) x v2(velocity x velocity)

KE = 1/2 m v2

Question 8

The “optimum” angle of attack(best lift/drag ratio) where maximum aerodynamic efficiency is obtained, for most aircraft is -

Answer 8

4 degrees

Question 9

Assume V = 100

Since V2 applies in the lift formula, if you double V, the result will increase by a factor of?

Answer 9

4.

Example:

100 squared = 1 000

200 squared = 4 000

Question 10

Lift coefficient increases with angle of attack up to a maximum called ____, which corresponds to
the “Critical” angle of attack

Answer 10

Lift coefficient increases with angle of attack up to a maximum (CLMAX), which corresponds to
the “Critical” angle of attack

Question 11

Wing tip vortices:

The upper flow moves -

The lower flow moves -

Answer 11

spanwise to the aircraft

spanwise away from the aircraft

Question 12

Main effect when in ground effect:

Answer 12

1. Reduced induced drag
2. Increase in effective angle of attack
3. Stalling angle decreases
4. Decreased effective angle of attack of the tail-plane, resulting in pitch up moment
5. ASI and altimeter under-read

Question 13

Camber line and chord line:

Answer 13

A line connecting the leading and trailing edge midway between the upper and lower surface of an aerofoil is the camber line.

Chord line is the same but straight

Question 14

asymmetrical aerofoil will produce 0 lift at -

Symmetrical aerofoil -

Answer 14

-4 degrees AoA

0 degree angle for