CPL Aircraft Systems and Aerodynamics 2 — Questions and Answers
Question 1: What is the primary purpose of a fuel injector in a reciprocating aircraft engine compared to a carburetor?
- It mixes fuel with oil before combustion
- It delivers fuel directly to each cylinder intake port, eliminating carburetor icing (Correct answer)
- It increases the fuel octane rating before delivery
- It recirculates unburned fuel back to the tank
Correct answer: It delivers fuel directly to each cylinder intake port, eliminating carburetor icing
Fuel injection delivers fuel directly to each cylinder's intake port, eliminating the venturi and float chamber that make carburetors susceptible to icing.
Question 2: In a hydraulic system, what is the function of an accumulator?
- To filter hydraulic fluid of contaminants
- To store pressurized fluid and dampen pressure surges (Correct answer)
- To convert hydraulic pressure to electrical signals
- To regulate the direction of hydraulic flow
Correct answer: To store pressurized fluid and dampen pressure surges
An accumulator stores pressurized hydraulic fluid and absorbs pressure surges, providing a reserve of pressure when demand exceeds pump output.
Question 3: Which type of drag increases as airspeed decreases during slow flight?
- Parasite drag
- Induced drag (Correct answer)
- Wave drag
- Form drag
Correct answer: Induced drag
Induced drag increases as airspeed decreases because the wing must operate at a higher angle of attack to generate the required lift, strengthening wingtip vortices.
Question 4: What happens to the manifold pressure of a naturally aspirated engine as altitude increases (throttle fixed)?
- It increases due to reduced ambient pressure
- It remains constant due to the throttle position
- It decreases as ambient air density and pressure drop (Correct answer)
- It fluctuates unpredictably with temperature changes
Correct answer: It decreases as ambient air density and pressure drop
With a fixed throttle, manifold pressure decreases with altitude because the ambient air pressure supplying the intake is lower, reducing the pressure available to the engine.
Question 5: What is 'Mach tuck' as it applies to high-speed aircraft?
- A nose-up pitching moment caused by compressibility effects near the critical Mach number
- A nose-down pitching moment caused by aft movement of the center of pressure at high Mach numbers (Correct answer)
- Wing flutter occurring at exactly Mach 1.0
- Rudder buffet caused by supersonic airflow over the vertical stabilizer
Correct answer: A nose-down pitching moment caused by aft movement of the center of pressure at high Mach numbers
Mach tuck is a nose-down pitching tendency that occurs as the aircraft approaches its critical Mach number, caused by the aft shift of the center of pressure as the shock wave forms.
Question 6: In a multi-engine aircraft with asymmetric thrust, what is the 'critical engine'?
- The engine with the highest thrust output
- The engine whose failure creates the greatest adverse yaw and handling difficulty (Correct answer)
- The engine closest to the aircraft centerline
- The engine that powers the primary hydraulic pump
Correct answer: The engine whose failure creates the greatest adverse yaw and handling difficulty
The critical engine is the one whose failure produces the worst handling characteristics; on conventional US-configured twins with clockwise-rotating props, this is typically the left engine.
Question 7: What is the purpose of 'intercoolers' in turbocharged aircraft engines?
- To cool engine oil before it enters the main gallery
- To reduce the temperature of compressed intake air after it exits the turbocharger (Correct answer)
- To maintain cylinder head temperature within limits
- To pre-heat fuel before injection
Correct answer: To reduce the temperature of compressed intake air after it exits the turbocharger
Intercoolers lower the temperature of air compressed by the turbocharger, increasing its density before it enters the engine, improving efficiency and reducing the risk of detonation.
CPL Aircraft Systems and Aerodynamics 2
What is the primary purpose of a fuel injector in a reciprocating aircraft engine compared to a carburetor?