Aerodynamics and Flight Quiz

True or False. The reaction of downwash causes an downward reaction according to Newton's Third Law of Motion.

• True

• False

Which of the following is true for an airplane in steady flight? Select all that apply.

• The sum of all upward components of forces equals the sum of all downward components of forces

• The sum of all forward components of forces is greater than the sum of all backward components of forces

• The sum of all upward components of forces equals the sum of all forward components of forces

• The sum of all upward components of forces is greater than the sum of all downward components of forces

• The sum of all forward components of forces equals the sum of all backward components of forces

Increasing an airplane's wing area will __________. Select all that apply.

• reduce pressure below the wing

• increase drag

• increase lift

• increase the camber

Torque effect is most pronounced under which conditions? Select all that apply.

• High power setting

• High airspeed

• Low angle of attack

• Low airspeed

• Low power setting

Describe two of the three ways a pilot can control lift during flight.

Answer explanation

A pilot can control lift by changing the angle of attack by varying the pitch of the
airplane using the elevator, by changing the airspeed by adjusting the power setting of the engine or by climbing or descending, or by adjusting the camber of
the wing by extending or retracting lift-enhancing devices like flaps.

Describe how Newton's Third Law of Motion and Bernoulli's Principle explain the generation of lift by an airfoil.

Answer explanation

According to Bernoulli’s Principle, when air moving over the top of a wing surface travels
faster than air moving over the bottom of the wing surface, pressure above the wing is
reduced, producing lift. These pressure changes cause the airflow to curve downwards,
creating downwash behind the airfoil. 

Newton’s Third Law states that for every action there is an equal and opposite reaction, so that a downward force is met with an equal and opposite upward force. When an airfoil bends air traveling across its surface downward, this action results in an equal and opposite upward force called lift.

Is it more desirable for the wing root or wing tip to stall first and why?

Answer explanation

It is preferable for the wing root to stall first. If the wingtip stalls before the root, the
disrupted airflow near the wingtip can reduce aileron effectiveness to such an extent that
that the pilot can lose control over the roll of the aircraft as the aircraft stalls, causing a
wing to drop, which in extreme cases could lead to entering a spin.

Explain how weight and balance of an airplane can change during flight.

Answer explanation

An airplane’s weight can change during flight by the burning of fuel or dropping of cargo.
The balance of an airplane can change by the movement of passengers or the incidental
shifting or sliding of luggage or cargo during flight.

Explain how ground effect can both help and hinder during takeoff.

Answer explanation

Ground effect can be a double edged sword on takeoff. On the positive side, it will allow an airplane to
fly at a slower speed than it could outside of ground effect. This is because induced drag is reduced so
less thrust is needed to produce lift. This can be used to get the airplane into the air more quickly to
allow easier and faster acceleration than would be possible on the ground. 

On the other hand, if the aircraft lifts off at too low an airspeed because of ground effect, it may not have enough speed to fly outside of ground effect, and could end up settling back onto the runway.

Forces are vectors because __________.

• they involve gravity

• they have length and width

• they have magnitude and direction

• they can point in two directions