CPL Aerodynamics and Aircraft Systems 2 — Questions and Answers
Question 1: What is a phugoid oscillation?
- A rapid, short-period pitch oscillation caused by turbulence
- A long-period oscillation in pitch where the aircraft trades airspeed for altitude (Correct answer)
- A lateral-directional oscillation involving roll and yaw coupling
- An oscillation in the landing gear hydraulic system under load
Correct answer: A long-period oscillation in pitch where the aircraft trades airspeed for altitude
A phugoid is a long-period (20–100 seconds) longitudinal oscillation where the aircraft exchanges kinetic and potential energy, with relatively little change in angle of attack.
Question 2: Dutch roll is an oscillatory motion that primarily couples which two axes?
- Pitch and roll
- Roll and yaw (Correct answer)
- Pitch and yaw
- Roll and lateral translation
Correct answer: Roll and yaw
Dutch roll is a combined lateral-directional oscillation involving roll and yaw, typically experienced in swept-wing aircraft with high dihedral effect.
Question 3: If an aircraft enters a 60-degree banked level turn, the stall speed increases by a factor of approximately:
- 1.2
- 1.41 (Correct answer)
- 1.73
- 2.0
Correct answer: 1.41
At 60° of bank, the load factor is 2 g, and stall speed increases by the square root of the load factor (√2 ≈ 1.41).
Question 4: What aerodynamic phenomenon causes adverse yaw during a roll input?
- The down-going aileron produces more induced drag than the up-going aileron (Correct answer)
- The up-going aileron produces more parasite drag than the down-going aileron
- Increased lift on the rising wing reduces its induced drag
- P-factor shifts the thrust line during the roll
Correct answer: The down-going aileron produces more induced drag than the up-going aileron
The aileron deflected downward (on the rising wing) generates more lift and therefore more induced drag, yawing the nose toward the descending wing — opposite to the intended turn direction.
Question 5: In ground effect, induced drag is reduced primarily because:
- Airspeed is higher close to the ground due to surface friction
- The ground interrupts wingtip vortex formation, reducing downwash and induced drag (Correct answer)
- Parasite drag increases to compensate for reduced profile drag
- The angle of attack is automatically reduced by the aircraft's proximity sensors
Correct answer: The ground interrupts wingtip vortex formation, reducing downwash and induced drag
Ground effect restricts wingtip vortex development, reducing downwash behind the wing, which decreases induced angle of attack and induced drag.
Question 6: P-factor (asymmetric blade effect) is most pronounced in a single-engine propeller aircraft when:
- At cruise altitude with high RPM and low airspeed
- At a high angle of attack with the propeller developing significant thrust (Correct answer)
- During a dive at maximum airspeed
- During cruise flight with the propeller at low pitch
Correct answer: At a high angle of attack with the propeller developing significant thrust
At high angles of attack, the descending propeller blade has a greater effective angle of attack than the ascending blade, producing more thrust on one side and causing yaw.
Question 7: The 'coffin corner' refers to the flight envelope condition where:
- The structural limit speed and stall speed converge at high altitude
- The low-speed buffet and high-speed buffet margins converge at high altitude (Correct answer)
- Maximum operating altitude and minimum safe altitude are both exceeded
- Fuel starvation and hydraulic failure occur simultaneously
Correct answer: The low-speed buffet and high-speed buffet margins converge at high altitude
At high altitude, the low-speed (aerodynamic) buffet boundary and the high-speed (Mach) buffet boundary converge, leaving a very narrow speed range for safe flight.
CPL Aerodynamics and Aircraft Systems 2
What is a phugoid oscillation?