Chapter 4: Principles of Flight

Question 1

What is the composition of the Earth’s atmosphere?

Answer 1

78% nitrogen, 21% oxygen, 1% other gases (e.g., argon, helium).

Question 2

What is viscosity?

Answer 2

The property of a fluid that causes it to resist flowing.

Question 3

What does standard atmospheric pressure at sea level equal?

Answer 3

29.92 inches of mercury (Hg) or 1013.2 millibars (mb).

Question 4

Name three factors affecting air density.

Answer 4

1. Altitude
2. Temperature
3. Humidity

Question 5

What are Newton’s three laws of motion?

Answer 5

1. First Law: Object at rest stays at rest unless acted upon by a force.
2. Second Law: Force equals mass times acceleration (F=ma).
3. Third Law: Every action has an equal and opposite reaction.

Question 6

What does Bernoulli’s Principle state?

Answer 6

As the velocity of a fluid increases, its pressure decreases.

Question 7

What is the purpose of an airfoil?

Answer 7

To generate lift by reacting to airflow.

Question 8

Name two effects of high density altitude.

Answer 8

1. Reduced engine power.
2. Reduced thrust and lift.

Question 9

What is a boundary layer?

Answer 9

A thin layer of air molecules that stick to the surface of a wing due to friction.

Question 10

What is the role of winglets on an airfoil?

Answer 10

Reduce tip vortex and improve lift efficiency.

Question 11

What are the properties of a standard atmosphere?

Answer 11

Temperature: 15°C (59°F) at sea level
Pressure: 29.92 inches of mercury (Hg)
Pressure lapse rate: 1 inch Hg per 1,000 feet
Temperature lapse rate: 2°C per 1,000 feet up to 36,000 feet.

Question 12

Define pressure altitude.

Answer 12

The altitude above a standard datum plane where the pressure is 29.92 inches Hg.

Question 13

What is density altitude?

Answer 13

Pressure altitude corrected for nonstandard temperature variations.

Question 14

What are two effects of friction on airflow?

Answer 14

1. Slows air near surfaces.
2. Creates the boundary layer on wings.

Question 15

What is Bernoulli’s Principle’s application in aviation?

Answer 15

Explains lift: Air moving faster over a curved surface creates lower pressure, contributing to lift.

Question 16

Name three types of airfoils.

Answer 16

1. Subsonic (e.g., Clark ‘Y’)
2. Supersonic (e.g., Double Wedge)
3. Laminar Flow

Question 17

What is the mean camber line?

Answer 17

A line equidistant from the upper and lower surfaces of an airfoil.

Question 18

What causes a tip vortex?

Answer 18

High-pressure air under the wing moving to the low-pressure area above the wing near the tip.

Question 19

What is the standard temperature lapse rate?

Answer 19

2°C or 3.5°F per 1,000 feet up to 36,000 feet.

Question 20

What are the three forces acting on an aircraft in flight?

Answer 20

1. Lift
2. Weight
3. Drag

Question 21

What are Newton’s three laws of motion’s relevance to flight?

Answer 21

1. First Law: Inertia (aircraft requires force to move).
2. Second Law: Force = mass × acceleration (engine power needed for takeoff).
3. Third Law: Equal and opposite reactions (propeller pushes air backward, thrust moves aircraft forward).