Aerodynamics

Question 1

What are the forces of flight that act on the plane in relation to straight -and-level, unaccelerated flight.

Answer 1

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

Question 2

What causes lift?

Answer 2

There are several theories.
1. Conservation of Momentum. The airfoil of the wing forces the air molecules down. Newton’s second law states that Force (F) = Mass (m) x Acceleration (a). F = ma. Acceleration is the change in velocity over time.
Velocity is the speed of something in a given direction.
Velocity is a Vector ( it has both magnitude and direction ). You can change the Velocity by changing either the magnitude or direction. The airfoil changes the direction, this changes the velocity creating a force (F). This force is the lift.

2. Equal Transit Theory. The air on top of the wing meets up with the same are on the bottom of the wing It has been proven wrong but is still listed in some of the texts. The air has a shorter distance to travel under the wing than over, so air is travelling faster over the wing and this creates a low pressure area above and high pressure area below that pushes up on the wing.
3. Bernoulli’s Principle: As the speed of a fluid increases, it’s pressure decreases. The air on the top of the wing does speed up. This creates a lower pressure on the top of the wing relative to the bottom, giving the wing, lift.

Question 3

Which statement relates to Bernoulli’s Principle?

1. For every action there is an equal and opposite reaction.
2. An additional upwards force is generated as the lower surface of the wing deflects wind downward.
3. Air travelling faster as it move over the upper curved surface of the airfoil causes lower pressure on on the surface.

Answer 3

3. Air travelling faster as it move over the upper curved surface of the airfoil causes lower pressure on on the surface.

Question 4

What causes Thrust?

Answer 4

The Power Plant (Engine) / Propellar.