Free CPL Aircraft Systems and Aerodynamics Questions and Answers 1 — Questions and Answers
Question 1: In a conventional twin-engine aircraft with clockwise rotating propellers, which engine is considered the 'critical engine' and why?
- The right engine, because its failure results in a greater loss of rudder effectiveness due to spiraling slipstream.
- The left engine, because P-factor and torque from the right engine create the most adverse yawing and rolling moments. (Correct answer)
- Neither engine is critical if the aircraft is equipped with counter-rotating propellers.
- The inboard engine on a four-engine aircraft, because its thrust line is closest to the fuselage.
Correct answer: The left engine, because P-factor and torque from the right engine create the most adverse yawing and rolling moments.
In a conventional twin-engine aircraft (both propellers rotating clockwise as seen from the cockpit), the failure of the left engine results in the most adverse effects on control and performance. This is due to the combination of asymmetrical thrust (P-factor), which creates a longer arm for the right engine's thrust vector from the aircraft's center of gravity, and torque effects. The resulting yaw and roll towards the dead left engine are more severe than if the right engine had failed.
Question 2: A pilot is flying an aircraft with a constant-speed propeller. During a descent with power reduced, the pilot notices the RPM is increasing. To maintain the desired RPM, the propeller governor will automatically:
- decrease the blade pitch angle, allowing the propeller to spin faster.
- increase the blade pitch angle, which increases aerodynamic load and slows the propeller. (Correct answer)
- send oil pressure to the feathering mechanism to prevent an overspeed condition.
- adjust the wastegate to reduce engine manifold pressure.
Correct answer: increase the blade pitch angle, which increases aerodynamic load and slows the propeller.
In an overspeed condition (RPM higher than selected), the flyweights in the propeller governor are forced outward by centrifugal force. This action directs high-pressure oil to the propeller hub, which increases the blade pitch angle (takes a bigger 'bite' of air). This increased aerodynamic load slows the propeller back to the desired RPM.
Question 3: What is the primary function of a hydraulic accumulator in an aircraft landing gear system?
- To mix hydraulic fluid with compressed nitrogen for better lubrication.
- To cool the hydraulic fluid after repeated gear extensions and retractions.
- To store hydraulic fluid under pressure to dampen pressure fluctuations and provide emergency pressure. (Correct answer)
- To act as the main reservoir for the aircraft's entire hydraulic system.
Correct answer: To store hydraulic fluid under pressure to dampen pressure fluctuations and provide emergency pressure.
A hydraulic accumulator stores hydraulic fluid under pressure from a compressed gas (usually nitrogen). Its primary roles are to absorb pressure surges and shocks in the system, supplement the hydraulic pump during periods of high demand (like gear retraction), and provide a source of stored energy for emergency operation of systems like landing gear or brakes if the main hydraulic pump fails.
Question 4: During a level, coordinated turn, the load factor on an aircraft will:
- remain at 1 G, regardless of the bank angle.
- decrease as the angle of bank increases.
- increase as the angle of bank increases. (Correct answer)
- be determined solely by the airspeed, not the bank angle.
Correct answer: increase as the angle of bank increases.
In a level turn, the vertical component of lift must still equal the aircraft's weight to maintain altitude. As the bank angle increases, the total lift vector must increase to provide this necessary vertical component. This increase in total lift, which is the sum of the vertical component and the horizontal component (which causes the turn), results in a higher load factor. For example, a 60-degree bank in a level turn produces a load factor of 2 Gs.
Question 5: A pilot of a large, swept-wing aircraft encounters an uncommanded, coupled oscillation of rolling and yawing. This aerodynamic characteristic is known as:
- a phugoid oscillation.
- spiral instability.
- adverse yaw.
- Dutch roll. (Correct answer)
Correct answer: Dutch roll.
Dutch roll is a coupled lateral-directional oscillation that is characteristic of swept-wing aircraft. It consists of an out-of-phase combination of yawing ('tail-wagging') and rolling. It occurs due to an imbalance where dihedral effect (strong lateral stability) is stronger than directional stability. Modern transport aircraft use a yaw damper system to automatically counteract this tendency.
Question 6: Which of the following is a significant aerodynamic benefit of retracting the landing gear after takeoff?
- A forward shift in the center of gravity, increasing longitudinal stability.
- A significant reduction in parasite drag, improving climb performance and cruise efficiency. (Correct answer)
- An increase in the effectiveness of the rudder for better directional control.
- A decrease in induced drag, allowing for a steeper angle of climb.
Correct answer: A significant reduction in parasite drag, improving climb performance and cruise efficiency.
The landing gear, when extended, creates a significant amount of parasite drag due to its un-aerodynamic shape. Retracting the gear into the wings or fuselage smooths the aircraft's profile, substantially reducing parasite drag. This reduction in drag leads to a better rate of climb, a higher cruising speed, and improved fuel efficiency.
Free CPL Aircraft Systems and Aerodynamics Questions and Answers 1
In a conventional twin-engine aircraft with clockwise rotating propellers, which engine is considered the 'critical engine' and why?