Principles of Flight

Question 1

Define viscosity

Answer 1

The property of fluid that causes it to resist flowing

Question 2

Define friction

Answer 2

The resistence that one surface or object encounters when moving over another

Question 3

Define pressure

Answer 3

The force applied in a perpendicular direction to the surface of an object

Question 4

What is the average pressure exerted by the weight of the atmosphere at sea level

Answer 4

14.7 PSI or 1,013.2 millibars

Question 5

At what altitude is the weight of the atmosphere one-half of what it is at sea-level?

Answer 5

18,000 ft above sea level

Question 6

What is the standard atmosphere conditions at sea-level?

Answer 6

59ºF or 15ºC and surface pressure of 29.92 hg or 1,013.2 mb

Question 7

What is the standard temperature lapse rate?

Answer 7

Decrease of 3.5ºF or 2ºC per thousande feet up to 36,000 ft MSL

Question 8

What is the lapse rate above 36,000 ft MSL?

Answer 8

Constant, up to 80,000 ft MSL

Question 9

What is the standard pressure lapse rate?

Answer 9

Decrease of 1 hg per thousand feet up to 10,000 ft MSL.

Question 10

What is pressure altitude?

Answer 10

The height above a standard datum plane, which is a theoretical level where the weight if the atmosphere is 29.92 hg as measured by a barometer.

Question 11

How can pressure altitude be determined?

Answer 11

1. Setting the barometric scale of the altimeter to 29.92 and reading the indicated altitude
2. Applying a correction factor to the indicated altitude according to the reported altimeter setting

Question 12

What is density altitude?

Answer 12

The vertical distance above sea level in the standard atmosphere at which a give density is to be found. Density altitude is pressure altitude corrected for nonstandard temperature.

Question 13

As air becomes less dense, explain the performance of the aircraft

Answer 13

1. Reduces power because the engine takes in less air
2. Reduces thrust because the propeller is less effecient in thin air
3. Reduces lift becuase the thin air exerts less force on the airfoils (wings)

Question 14

As the density of the air increases ____

Answer 14

The lower the desity altitude and the aircraft performance increases

Question 15

As the density of the air decreases ____

Answer 15

The higher the desity altitude and the aircraft performance decreases

Question 16

A decrease in air density means ___

Answer 16

A high density altitude

Question 17

A increase in air density means ___

Answer 17

A lower density altitude

Question 18

How is density altitude determined?

Answer 18

Finding the pressure altitude and then correcting it for non-standard temperature variations

Question 19

What conditions result in a high density altitude?

Answer 19

1. High elevation
2. Low atmospheric pressure
3. High temperature
4. High humidity

Question 20

What conditions result in a low density altitude?

Answer 20

1. Low elevation
2. High atmospheric pressure
3. Low temperature
4. Low humidity

Question 21

At a lower pressure, the column of air contains a ___

Answer 21

Smaller amount of air

Question 22

Explain the effect of pressure on density

Answer 22

When air is compressed, a greater amount of air occupy a given volume

Question 23

Explain the effect of temperature on density

Answer 23

Increasing temperature of air decreases its density

Question 24

Explain the effect of humidty on density

Answer 24

As water content of the air increases, the air becomes less dense, increasing density altitude

Question 25

What is Newtan’s First Law

Answer 25

Every object persists in its state of rest or uniform motion in a straight line unless it is compelled to change that state by forces impessed on it

Question 26

Explain Newtan’s First Law in English

Answer 26

Nothing start or stops moving until some outside force causes it to do so

Question 27

What is Newtan’s Second Law

Answer 27

Force is equal to the change in momentum per change in time. For a constant mass, force equal mass times acceleration

Question 28

Explain Newtan’s Second Law in English

Answer 28

When a body is acted upon by a constant force, its resulting acceleration is inversely proportional to the mass of the body and is directly proportional to the applied force

Question 29

What is Newtan’s Third Law

Answer 29

For every action, there is an equal and opposite reaction

Question 30

Explain Newtan’s Third Law in English

Answer 30

In an airplane, the propeller moves and pushes back the air, the air pushes the propeller in the opposite direction, forward

Question 31

What is Bernoulli’s Principle?

Answer 31

States that as the velocity of a moving fluid increases, the pressure within the fluid decreases

Question 32

Explain how lift is generated on the air foil (wings)

Answer 32

1. The increase in speed of air on top of the wing produces a drop in pressure on top of the wing (Bernoulli’s Principle)
2. The downward, backward flow from the top surface of an airfoil creates a downwash
3. The downwash meets the flow from the bottom of the airfoil at the trailing edge
4. The reaction of this donward backward flow results in an upward force on the airfoil (Newtan’s Third Law)