ATPL Principles of Flight and Aerodynamics 2 — Questions and Answers
Question 1: Positive static stability in an aircraft means that after a disturbance, the aircraft will:
- Continue to diverge from its original attitude
- Remain fixed in the disturbed attitude
- Initially develop restoring forces toward the original attitude (Correct answer)
- Oscillate with increasing amplitude
Correct answer: Initially develop restoring forces toward the original attitude
A statically stable aircraft generates restoring forces that initially move it back toward its trimmed equilibrium position after a disturbance from that position.
Question 2: Dutch roll is a lateral-directional oscillation that involves coupling of:
- Pitch and roll axes
- Roll and yaw axes (Correct answer)
- Pitch and yaw axes
- All three axes in equal measure
Correct answer: Roll and yaw axes
Dutch roll is a coupled rolling and yawing oscillation that is common in swept-wing aircraft with low directional stability relative to lateral stability.
Question 3: Wing dihedral angle primarily provides stability about the:
- Longitudinal axis (lateral/roll stability) (Correct answer)
- Lateral axis (pitch stability)
- Vertical axis (directional/yaw stability)
- All three axes equally
Correct answer: Longitudinal axis (lateral/roll stability)
Dihedral creates a restoring rolling moment when the aircraft sideslips, since the lower wing develops more lift, providing positive lateral stability.
Question 4: Adverse yaw in conventional aircraft is caused by:
- Differential engine thrust during a turn
- Differential aileron drag during a roll input (Correct answer)
- Rudder deflection creating a secondary rolling moment
- Asymmetric flap extension
Correct answer: Differential aileron drag during a roll input
The downward (lift-producing) aileron creates more drag than the upward aileron, yawing the nose toward the rising wing and opposing the intended turn direction.
Question 5: The primary purpose of a yaw damper in a modern transport jet is to:
- Increase yaw stability during crosswind landings automatically
- Automatically damp Dutch roll oscillations with small rudder inputs (Correct answer)
- Prevent rudder input reversal during high-speed flight
- Coordinate turns by applying rudder proportional to bank angle
Correct answer: Automatically damp Dutch roll oscillations with small rudder inputs
Yaw dampers sense yaw rate via gyroscopes and apply small automatic rudder corrections to suppress Dutch roll oscillations inherent in swept-wing jets.
Question 6: A neutrally stable aircraft, when disturbed from its trimmed attitude and released, will:
- Return to its original trimmed attitude
- Continue to diverge from its original attitude
- Maintain the new disturbed attitude indefinitely (Correct answer)
- Oscillate symmetrically about its original attitude with constant amplitude
Correct answer: Maintain the new disturbed attitude indefinitely
A neutrally stable aircraft develops neither restoring nor diverging forces — it simply holds whatever attitude results after the disturbance is removed.
Question 7: The aerodynamic center of an airfoil is the point about which the pitching moment coefficient:
- Is always zero for all angles of attack
- Changes significantly with angle of attack
- Remains approximately constant with changes in angle of attack (Correct answer)
- Equals the center of pressure at low speeds
Correct answer: Remains approximately constant with changes in angle of attack
The aerodynamic center is the point about which the pitching moment coefficient remains essentially constant with changes in angle of attack, located approximately at the quarter-chord point.
ATPL Principles of Flight and Aerodynamics 2
Positive static stability in an aircraft means that after a disturbance, the aircraft will: