SS&C-1

Question 1

What aileron deflections are required for a positive rolling moment?

Answer 1

Right aileron up and left aileron down. RAU, LAD

Extra Notes: This creates a right roll about the x-axis.

Lect. 23

Question 2

What control surface deflections are required for a positive pitching moment (+M) about the y-axis?

Answer 2

Elevator Up (EU)

Extra Notes: The elevator control surfaces are deflected up which generates a downward lift force. This causes the aircraft nose to pitch up creating a positive pitching moment (M).

Lect. 23

Question 3

What control surface deflections are required to create a positive yawing moment (+N)?

Answer 3

RA - Rudder Right

Extra: (When viewed from above) The vertical rudder is deflected to the right. This creates a force toward the left wing which rotates the aircraft clockwise (when looking from above) about the z-axis.

Lect. 23

Question 4

Define “statically stable.” Does this refer to positive, neutral, or negative static stability?

Answer 4

If forces and moments acting on a body caused by a disturbance tend to return the body towards its equilibrium position, the body is statically stable and the body has positive static stability.

Lect. 23

Question 5

If forces and moments caused by a disturbance cause the aircraft to diverge from its equilibrium position, this is referred to as _________.
In other words, the aircraft would have ______ static stability.

Answer 5

Static instability
Negative

Lect. 23

Question 6

How would an aircraft react to a disturbance if it has neutral stability?

Answer 6

The body will stay in the disturbed position and no restorative or divergent forces will be created to change it from that state.

Lect. 23

Question 7

If the aircraft monotonically “homes in” to its original equilibrium position with time, the motion is called _____.

Answer 7

Aperiodic.

Lect. 23, S11

Question 8

Monotonic motion implies an _______ system.

Answer 8

Overdamped

Lect. 23 S11

Question 9

If an aircraft has monotonic characteristics and returns to its original point of equilibrium, it can be said that the aircraft has __________ stability.

Answer 9

Dynamic

Lect. 23 S11

Question 10

Describe damped oscillatory motion with respect to an aircraft.

Answer 10

If after a series of oscillations with decreasing amplitude, the aircraft homes in to its original equilibrium position with time, the motion is called damped oscillatory motion.

Lect. 23 S12

Question 11

Oscillatory motion implies the aircraft is ___ damped.

Answer 11

Lightly

Lect. 23 S12

Question 12

True or False
If an aircraft experiences damped oscillatory motion in which it returns to its original position with time the aircraft is considered to be dynamically stable.

Answer 12

True

Lect. 23 S12

Question 13

If the aircraft attempts to return to its original equilibrium position but overshoots and continues to overshoot with increasing amplitude this is referred to as _____.

Answer 13

Dynamic instability.

Lect. 23 S13

Question 14

What is the zero-lift angle of attack?

Answer 14

The angle between the zero-lift line and the chord line of an airfoil.

Note: This is the same alpha_L = 0 found on the alpha vs. CL graph.

Lect. 23 S17

Question 15

What is the absolute angle of attack?

Answer 15

The absolute angle of attack is the angle as measured from the zero-lift line to the freestream direction.
It consists of the angle of attack at zero lift plus the geometric angle of attack (denoted simply as alpha)

alpha = alpha_geo + alpha_L=0

Lect. 23 S17-18

Question 16

What are the two basic requirements for static stability for any aircraft?

Answer 16

1. C_M_cg vs alpha_absolute must be negative (C_M_alpha<0).
2. C_M_0 (C_M at zero lift) must be greater than zero.

Lect. 23 S28

Question 17

What are the symbols for angular velocity about the x, y, and z axis’ respectively?

Answer 17

p
q
r

Lect. 23 S2

Question 18

What are the roll, pitch, and yaw symbols?

Answer 18

Roll = phi
Pitch = theta
Yaw = psi

Lect. 23 S2

Question 19

True or False

Monotonic motion –> Aperiodic –> Overdamped

Answer 19

True