Section 1.1

Question 1

Define Flight Mechanics

Answer 1

The science of predicting and controlling aircraft motion.

Pg. 1

Question 2

What are the three forces/moments exerted on an aircraft in flight?

Answer 2

1. Aerodynamic forces/moments
2. Propulsive forces
3. Gravity

Pg. 1

Question 3

The aerodynamic forces and moments acting on any arbitrary body moving through the atmosphere originate from what two sources?

Answer 3

1. The pressure distribution over the body’s surface.
2. The shear stress distribution over the body’s surface.

Pg. 1

Question 4

What is the most commonly used coordinate system used in flight mechanics?

Answer 4

The Cartesian aerodynamic coordinate system (CACS).

Pg. 1

Question 5

With respect to the CACS, describe the orientation of the x-axis relative to the aircraft.

Answer 5

The x-axis lies parallel to the chord and points in the general direction of airflow.

Pg. 1

Question 6

With respect to the CACS, where is the origin typically located?

Answer 6

At the leading edge, or the front of the body.

Pg. 1

Question 7

With respect to the CACS, what is the orientation of the y-axis?

Answer 7

Pointing upward relative to the Earth.

Pg. 1

Question 8

With respect to the CACS, describe the z-axis orientation.

Answer 8

Pointing left to right along the span.

Pg. 1

Question 9

For the rolling moment l (little L), the positive direction is ____.

Answer 9

Right wing down.

Pg. 2

Question 10

For the yawing moment (n), the positive direction is _____.

Answer 10

Nose rotates right.

Pg. 2

Question 11

For the pitching moment (m), the positive direction is _____.

Answer 11

Nose up.

Pg. 2

Question 12

What is the meaning of section force and section moment?

Answer 12

The forces and moment per unit span.

Pg. 2

Question 13

How is section force and section moment defined in terms of notation in the book?

Answer 13

With a tilde ~ over the top of the variable.

Pg. 2

Question 14

The resultant aerodynamic force acting on a 2D airfoil is completely specified in terms of ______. These two equivalent descriptions of the resultant aerodynamic force are related to each other through ______.

Answer 14

1. Either life and drag or axial and normal force.
2. The angle of attack.

Pg. 3

Question 15

The axial force (A) is often _____ even though the angle of attack may be small.

Answer 15

Negative.

Pg. 4

Question 16

The resultant aerodynamic force (RAF) and moment acting on a body must have the same effect as _____.

Answer 16

The distributed loads.

Pg. 4

Question 17

The resultant moment (RM) will depend on _______.

Answer 17

Where the RAF is placed.

Pg. 4

Question 18

What are the two special locations along the chord of special interest?

Answer 18

The center of pressure (xcp) and the aerodynamic center (xac).

Pg. 5

Question 19

What is the definition of the center of pressure (COP)?

Answer 19

The point about which the moment produced by a distributed load is zero.

Pg. 5

Question 20

What is the definition of the aerodynamic center (AC)?

Answer 20

The point about which the change in the resultant moment (RM) is invariant with respect to the angle of attack.

Pg. 5

Question 21

How are derivatives annotated in the textbook?

Answer 21

A two-letter subscript with a comma between the two letters.

Pg. 6

Question 22

True or False

The location of the center of pressure varies considerably with angle of attack for chambered airfoils.

Answer 22

True

Pg. 7

Question 23

True or False

The location of the aerodynamic center (AC) carries very little with respect to angle of attack.

Answer 23

True

Pg. 7

Question 24

Downard deflection of the elevator is _____.

Answer 24

Positive

Pg. 9

Question 25

Deflection of the rudder to the left is _____.

Answer 25

Positive.

Pg. 9

Question 26

Deflection of the rudder to the right is ____.

Answer 26

Negative.

Pg. 9

Question 27

When is aileron deflection positive?

Answer 27

The right aileron is deflected down and the left aileron is deflected up (roll left).

Pg. 9

Question 28

What is the Von Karman line?

Answer 28

The boundary between Earth’s atmosphere and space. It is the altitude where aerodynamic forces no longer provide support to maintain S&L flight.

Lecture Notes