AVIA 305: AERODYNAMICS-Module
7 Assessment: Aircraft Stability
QUESTIONS AND ANSWERS WITH
RATIONALES/ GRADED A+/2026
UPDATE /100%CORRECT
PART A: FUNDAMENTALS OF STABILITY (Questions 1-15)
1. What is the definition of static stability?
a) The initial tendency of an aircraft to return to its original state after a
disturbance.
b) The time it takes for an aircraft to settle after control input.
c) The magnitude of the force required to move the control surfaces.
d) The aircraft's resistance to spin entry.
Correct Answer: a) Rationale: Static stability concerns the initial tendency after a
disturbance. If the aircraft tries to return to equilibrium, it is statically stable.
2. An aircraft that continues to diverge further from its original flight path
after a disturbance, without any control input, is said to be:
a) Statically stable
b) Neutrally stable
c) Statically unstable
d) Dynamically stable
Correct Answer: c) Rationale: Static instability is characterized by the initial
tendency to move away from the original state of equilibrium.
3. Dynamic stability refers to:
a) The initial reaction to turbulence.
b) The damping of oscillations over time as the aircraft returns to equilibrium.
c) The center of gravity location relative to the mean aerodynamic chord.
d) The effectiveness of the ailerons at high angles of attack.
,Correct Answer: b) Rationale: Dynamic stability describes the time history of the
aircraft’s motion. A dynamically stable aircraft has oscillations that dampen out
over time.
4. An aircraft is dynamically unstable if:
a) It initially tries to return to trim.
b) The oscillations increase in amplitude over time.
c) The center of pressure moves aft.
d) It has a high static margin.
Correct Answer: b) Rationale: Divergent oscillations (increasing amplitude) are
the hallmark of dynamic instability, even if the aircraft possesses positive static
stability.
5. The "Phugoid" oscillation is characterized by:
a) Short period, high frequency changes in angle of attack.
b) Long period, low frequency exchanges between airspeed and altitude.
c) Dutch roll motion primarily in the lateral-directional axis.
d) Rapid aileron reversal at high speeds.
Correct Answer: b) Rationale: The phugoid mode involves a slow, often poorly
damped, exchange of kinetic energy (airspeed) and potential energy (altitude) with
nearly constant angle of attack.
6. The "Short Period" mode primarily involves:
a) Rolling and yawing oscillations.
b) Changes in pitch attitude and angle of attack at nearly constant speed.
c) Spiral divergence.
d) Flutter of the control surfaces.
Correct Answer: b) Rationale: The short period mode is a rapid, heavily damped
oscillation in pitch and angle of attack.
7. The Mean Aerodynamic Chord (MAC) is used to:
a) Calculate wing area only.
b) Define the standard location for the Center of Gravity (CG) percentage.
c) Determine the maximum takeoff weight.
d) Measure the propeller efficiency.
, Correct Answer: b) Rationale: CG location is typically expressed as a percentage
of the MAC (%MAC), providing a standardized reference independent of wing
planform.
8. For a conventionally configured aircraft, positive static longitudinal
stability requires the Center of Gravity (CG) to be:
a) Aft of the Center of Pressure (CP) of the wing.
b) Forward of the Neutral Point (NP).
c) At the same location as the Aerodynamic Center (AC).
d) Aft of the Neutral Point (NP).
Correct Answer: b) Rationale: Stability is achieved when the CG is ahead of the
Neutral Point. This creates a positive static margin, ensuring a nose-down pitching
moment when angle of attack increases.
9. The distance between the CG and the Neutral Point (NP), expressed as a
percentage of MAC, is known as:
a) Stick force gradient
b) Maneuvering margin
c) Static margin
d) Lift coefficient slope
Correct Answer: c) Rationale: Static Margin = (NP - CG) / MAC. A positive static
margin indicates positive static longitudinal stability.
10. What effect does moving the CG aft have on longitudinal static stability?
a) Increases stability (more stable).
b) Decreases stability (less stable).
c) Has no effect on stability, only on control.
d) Increases lateral stability.
Correct Answer: b) Rationale: Moving the CG aft reduces the static margin,
bringing the CG closer to the Neutral Point, which reduces the restoring moment
and thus stability.
11. The Neutral Point (NP) is defined as the CG location at which:
a) The aircraft has maximum range.
b) The static stability is neutral.
c) The aircraft stalls first at the wing root.
d) The control forces become zero.
7 Assessment: Aircraft Stability
QUESTIONS AND ANSWERS WITH
RATIONALES/ GRADED A+/2026
UPDATE /100%CORRECT
PART A: FUNDAMENTALS OF STABILITY (Questions 1-15)
1. What is the definition of static stability?
a) The initial tendency of an aircraft to return to its original state after a
disturbance.
b) The time it takes for an aircraft to settle after control input.
c) The magnitude of the force required to move the control surfaces.
d) The aircraft's resistance to spin entry.
Correct Answer: a) Rationale: Static stability concerns the initial tendency after a
disturbance. If the aircraft tries to return to equilibrium, it is statically stable.
2. An aircraft that continues to diverge further from its original flight path
after a disturbance, without any control input, is said to be:
a) Statically stable
b) Neutrally stable
c) Statically unstable
d) Dynamically stable
Correct Answer: c) Rationale: Static instability is characterized by the initial
tendency to move away from the original state of equilibrium.
3. Dynamic stability refers to:
a) The initial reaction to turbulence.
b) The damping of oscillations over time as the aircraft returns to equilibrium.
c) The center of gravity location relative to the mean aerodynamic chord.
d) The effectiveness of the ailerons at high angles of attack.
,Correct Answer: b) Rationale: Dynamic stability describes the time history of the
aircraft’s motion. A dynamically stable aircraft has oscillations that dampen out
over time.
4. An aircraft is dynamically unstable if:
a) It initially tries to return to trim.
b) The oscillations increase in amplitude over time.
c) The center of pressure moves aft.
d) It has a high static margin.
Correct Answer: b) Rationale: Divergent oscillations (increasing amplitude) are
the hallmark of dynamic instability, even if the aircraft possesses positive static
stability.
5. The "Phugoid" oscillation is characterized by:
a) Short period, high frequency changes in angle of attack.
b) Long period, low frequency exchanges between airspeed and altitude.
c) Dutch roll motion primarily in the lateral-directional axis.
d) Rapid aileron reversal at high speeds.
Correct Answer: b) Rationale: The phugoid mode involves a slow, often poorly
damped, exchange of kinetic energy (airspeed) and potential energy (altitude) with
nearly constant angle of attack.
6. The "Short Period" mode primarily involves:
a) Rolling and yawing oscillations.
b) Changes in pitch attitude and angle of attack at nearly constant speed.
c) Spiral divergence.
d) Flutter of the control surfaces.
Correct Answer: b) Rationale: The short period mode is a rapid, heavily damped
oscillation in pitch and angle of attack.
7. The Mean Aerodynamic Chord (MAC) is used to:
a) Calculate wing area only.
b) Define the standard location for the Center of Gravity (CG) percentage.
c) Determine the maximum takeoff weight.
d) Measure the propeller efficiency.
, Correct Answer: b) Rationale: CG location is typically expressed as a percentage
of the MAC (%MAC), providing a standardized reference independent of wing
planform.
8. For a conventionally configured aircraft, positive static longitudinal
stability requires the Center of Gravity (CG) to be:
a) Aft of the Center of Pressure (CP) of the wing.
b) Forward of the Neutral Point (NP).
c) At the same location as the Aerodynamic Center (AC).
d) Aft of the Neutral Point (NP).
Correct Answer: b) Rationale: Stability is achieved when the CG is ahead of the
Neutral Point. This creates a positive static margin, ensuring a nose-down pitching
moment when angle of attack increases.
9. The distance between the CG and the Neutral Point (NP), expressed as a
percentage of MAC, is known as:
a) Stick force gradient
b) Maneuvering margin
c) Static margin
d) Lift coefficient slope
Correct Answer: c) Rationale: Static Margin = (NP - CG) / MAC. A positive static
margin indicates positive static longitudinal stability.
10. What effect does moving the CG aft have on longitudinal static stability?
a) Increases stability (more stable).
b) Decreases stability (less stable).
c) Has no effect on stability, only on control.
d) Increases lateral stability.
Correct Answer: b) Rationale: Moving the CG aft reduces the static margin,
bringing the CG closer to the Neutral Point, which reduces the restoring moment
and thus stability.
11. The Neutral Point (NP) is defined as the CG location at which:
a) The aircraft has maximum range.
b) The static stability is neutral.
c) The aircraft stalls first at the wing root.
d) The control forces become zero.
