01 Subsonic Airflow and the 4Forces on an Aircraft

Dynamic Pressure may be expressed by the formula:

• Q = ½ ρ V²

• Q = 2 ρ V²

• Q = ρ V

• Q = 2 ρ V

The horizontal stabilizer usually provides a downwards load in level flight because:

• The main-plane lift is always positive.

• The lift/weight and thrust/drag couples combine to give a nose down pitch.

• The lift produced is greater than required at high speed.

• This configuration gives less interference.

Considering the forces acting upon an aeroplane, at constant airspeed, which statement is correct?

• Weight always acts vertically downwards towards the centre of the Earth.

• Lift acts perpendicular to the chord line and must always be greater than weight.

• Thrust acts parallel to the relative airflow and is greater than drag.

• The lift force generated by the wings always acts in the opposite direction to the aircraft's weight.

An aircraft’s mass is a result of:

• Its weight.

• How big it is.

• How much matter it contains.

• Its volume.

Read the following statements about the properties of air: - Air has mass. - Air is incompressible at all airspeeds. - Air is able to flow or change its shape when subject to even small pressures. - The viscosity of air is very high. - Moving air has kinetic energy. The correct combination of all true statements is:

• 1, 2, 3 and 5.

• 2, 3 and 4.

• 1 and 4.

• 1, 3, and 5.

The boundary layer consists of:

• Laminar flow.

• Turbulent flow.

• Laminar and Turbulent flow.

• Turbulent flow at low speeds only.

Which of the four answer options most correctly completes the sentence? Increasing speed also increases lift because:

• Lift is directly proportional to velocity.

• The increased speed of the air passing over an aerofoil's upper surface decreases the static pressure above the wing, thus creating a greater pressure differential across the upper and lower surface.

• The increased velocity of the relative wind overcomes the increased drag.

• Increasing speed decreases drag.

Dynamic pressure equals:

• Total pressure plus static pressure.

• Static pressure minus total pressure.

• Total pressure divided by static pressure.

• Total pressure minus static pressure.

The smooth flow of air, where each molecule follows the path of the preceding molecule, is a definition of:

• Laminar flow.

• Turbulent flow.

• Free stream flow.

• Wind.

The air flow over the wing's upper surface in straight and level flight, when compared with the airflow that is unaffected by the wing, will have:

• A higher velocity.

• A higher density.

• A reduced velocity.

• The same velocity.