Aerodynamics

Question 1

What are the four aerodynamic forces acting on an airplane? What is the relationship between them in straight and level flight?

Answer 1

Lift, weight, thrust, drag.

Lift = weight.
Thrust = drag.

Question 2

When are the four aerodynamic forces said to be in equilibrium?

Answer 2

When the airplane is in unaccelerated flight.

Question 3

What is the angle of attack?

Answer 3

The angle between the wing chord line and the relative wind.

Question 4

Describe Bernoulli’s principle as it applies to aviation.

Answer 4

An increase in the speed of a fluid occurs simultaneously with a decrease in pressure.

The air traveling faster over the curved upper surface of an airfoil causes lower pressure on the top surface.

Question 5

Does the angle of attack change with gross weight?

Answer 5

No. It remains the same regardless of gross weight.

Question 6

Does stall speed alter with altitude?

Answer 6

No. The altitude at which a plane stalls in a particular configuration remains the same regardless of altitude.

Question 7

What is necessary for an airplane to spin?

Answer 7

A stall.

Question 8

During a spin to the right, which wing is stalled?

Answer 8

Both.

Question 9

How does frost affect the wing of an airplane?

Answer 9

It disrupts the smooth flow of air over the wing, adversely affecting its lifting quality.

Question 10

What can happen if frost is not removed from an airplane’s wings before flight?

Answer 10

It may prevent the airplane from becoming airborne at normal takeoff speed.

Question 11

What are three other terms for left-turning tendency?

Answer 11

P-factor, torque effect, and asymmetric propeller loading.

Question 12

What causes left-turning tendency?

Answer 12

The descending propeller blade on the right produces more thrust than the ascending blade on the left.

Question 13

When is torque effect greatest?

Answer 13

In a single-engine airplane at low airspeed, high power, and high angle of attack.

Question 14

What determines the longitudinal stability of an airplane?

Answer 14

The location of the center of gravity with respect to the center of lift.

Question 15

What happens when the airplane is loaded to the most aft CG limit?

Answer 15

It makes the airplane less stable at all speeds.

Question 16

What happens if an airplane is loaded aft of the most aft CG limit?

Answer 16

The pilot might experience difficulty in recovering from a stalled condition.

Question 17

What causes the nosedown pitch tendency of an airplane when the power is reduced?

Answer 17

The downwash on the elevators from the propeller slipstream is reduced, and elevator effectiveness is reduced.

Question 18

What do changes in the center of pressure of a wing do?

Answer 18

They affect the aircraft’s aerodynamic balance and controllability.

Question 19

What makes the airplane turn?

Answer 19

The horizontal component of lift.

Question 20

What is the purpose of the rudder?

Answer 20

To control yaw.

Question 21

Which basic flight maneuver increases the load factor on an airplane, when compared with straight-and-level flight?

Answer 21

Turns.

Question 22

During an approach to a stall, increased load factor will cause…

Answer 22

…the airplane to stall at a higher speed.

Question 23

What can increased load factor do?

Answer 23

Stress the airplane beyond its design limits.

Question 24

The amount of excess load that can be imposed on the wing of an airplane depends on…

Answer 24

…the speed of the airplane.

Question 25

What are the load factors for 30°, 45°, and 60° turns?

Answer 25

1.2,1.4, 2.

Question 26

How much lift is required to support a 4,000 pound airplane in a 45° turn?

Answer 26

4,000 pounds * load factor of 1.4 = 5600 pounds.

Question 27

What is one purpose of wing flaps?

Answer 27

To enable the pilot to make steeper approaches to a landing, without increasing airspeed.

Question 28

Describe the following v-speeds:

Vle
Vx
Vy
Va
Vfe
Vne
Vr
Vso
Vs
Vno

Answer 28

Vle - maximum landing gear extended speed.
Vx - best angle of climb.
Vy - best rate of climb.
Va - maneuvering speed. (the speed above which it is unwise to make full application of any flight control – to “pull the stops”, because the force may exceed the aircraft’s general limitations)
Vf - maximum flap extended speed.
Vne - never exceed speed.
Vr - rotation speed.
Vso - stall speed in landing configuration.
Vs - stall speed.
Vno - maximum structural cruising speed.

Question 29

What should you do in severe turbulence?

Answer 29

Reduce to maneuvering speed or slightly below, maintain level flight attitude, and allow minor variations in airspeed and altitude.

Question 30

What indicates the flap operating range?

Answer 30

The white arc on the airspeed indicator.

Question 31

What does the lower limit of the white arc on the airspeed indicator show?

Answer 31

The power-off stalling speed in landing configuration.

Question 32

What does the lower limit of the green arc on the airspeed indicator show?

Answer 32

Power-off stalling speed with flaps and landing gear retracted.

Question 33

What does the upper limit of the green arc show?

Answer 33

Maximum structural cruising speed.

Question 34

What is the “normal operating range”?

Answer 34

From power off stalling speed with flaps and landing gear retracted, to maximum structural cruising speed.

Question 35

What is the yellow arc on the airspeed indicator?

Answer 35

The caution range of the airplane.

Question 36

What is the red radial line on the airspeed indicator?

Answer 36

Vne, the never-exceed speed.

Question 37

When are wingtip vortices created?

Answer 37

When an aircraft is generating lift.

Question 38

How do wake turbulence vortices circulate?

Answer 38

Outward, upward, and around each wing tip.

Question 39

When does the greatest wingtip vortex strength exist?

Answer 39

When the aircraft is heavy, clean, and slow.

Question 40

Where do wingtip vortices tend to move?

Answer 40

They tend to sink below the aircraft generating the lift, into the flight path of airplanes below.

Question 41

What happens to vortices when they reach the ground?

Answer 41

They spread apart, and tend to drift with the wind.

Question 42

How should you avoid wake turbulence when departing and landing?

Answer 42

When departing, maneuver the aircraft above and upwind from the heavy aircraft.

When landing, stay above the large aircraft’s final approach path, and land beyond the large aircraft’s touchdown point.

Question 43

What is ground effect? What does it do? How does it affect takeoffs and landings?

Answer 43

The result of the interference of the surface of the earth with the airflow patterns about an airplane.

Aircraft fly more efficiently in ground effect; induced drag decreases. On landings, this causes floating, especially when the flare is entered with excess speed. When taking off, it may result in the aircraft becoming airborne before reaching the recommended takeoff speed.

Question 44

When is floating during ground effect most pronounced?

Answer 44

When at less than the length of the wingspan above the surface.