Free AMT Aircraft Propeller Systems Questions and Answers 1 — Questions and Answers
Question 1: In a constant-speed propeller governor, what is the primary function of the flyweights?
- To directly change the propeller blade angle.
- To sense engine RPM and control the position of the pilot valve. (Correct answer)
- To provide the oil pressure needed for pitch changes.
- To set the desired RPM as selected by the pilot.
Correct answer: To sense engine RPM and control the position of the pilot valve.
The flyweights spin at a speed proportional to the engine RPM. Through centrifugal force, they move inward or outward depending on speed. This movement directly controls the pilot valve, which then ports oil to or from the propeller hub to change the blade pitch and maintain the selected RPM.
Question 2: What is the primary reason for feathering the propeller of a failed engine on a multi-engine aircraft?
- To allow the propeller to windmill, providing electrical power.
- To increase the blade pitch to the highest possible angle for maximum braking.
- To align the blades with the relative wind to minimize aerodynamic drag. (Correct answer)
- To move the blades to a low pitch setting for an easier in-flight restart.
Correct answer: To align the blades with the relative wind to minimize aerodynamic drag.
Feathering involves turning the propeller blades to be nearly parallel with the direction of flight. This presents the smallest profile to the oncoming air, which significantly reduces the drag produced by the windmilling propeller of a failed engine, improving the aircraft's single-engine performance.
Question 3: During takeoff in an aircraft with a constant-speed propeller, the propeller blade pitch is set to:
- A high pitch, low RPM position to take a large bite of air.
- The feathered position to reduce initial engine load.
- A low pitch, high RPM position to allow the engine to develop maximum power. (Correct answer)
- An intermediate pitch that is averaged between climb and cruise settings.
Correct answer: A low pitch, high RPM position to allow the engine to develop maximum power.
For takeoff, the propeller is set to a low pitch (high RPM) position. This light load allows the engine to accelerate to its maximum rated RPM and produce maximum power for takeoff and initial climb.
Question 4: A pilot reports that after an in-flight engine shutdown on a multi-engine aircraft, the propeller failed to feather and continued to windmill. Which of the following is a plausible mechanical reason for this failure?
- The governor speeder spring tension was set too high.
- The propeller synchronization system was left on.
- Centrifugal latch pins failed to retract due to high RPM.
- The centrifugal 'stop pins' engaged because the engine RPM dropped too low before feathering was initiated. (Correct answer)
Correct answer: The centrifugal 'stop pins' engaged because the engine RPM dropped too low before feathering was initiated.
Many propeller systems have centrifugal stop pins (or latches) that prevent the propeller from feathering during normal engine shutdown on the ground. These pins are held in place by springs and are only retracted by centrifugal force above a certain low RPM (e.g., 500-800 RPM). If the pilot waits too long to feather a failed engine and the RPM drops below this threshold, the pins will engage and prevent the blades from moving to the feather position.
Question 5: Which of the following describes the function of a propeller synchronization system on a multi-engine aircraft?
- It ensures all propeller blades are at the exact same pitch angle.
- It adjusts the RPM of the 'slave' engine(s) to exactly match the RPM of the 'master' engine. (Correct answer)
- It automatically feathers all propellers in the event of a dual engine failure.
- It reverses the pitch of all propellers simultaneously for braking after landing.
Correct answer: It adjusts the RPM of the 'slave' engine(s) to exactly match the RPM of the 'master' engine.
A propeller synchronization system is used to eliminate the unpleasant 'beat' or 'drone' caused by propellers turning at slightly different speeds. It designates one engine as the 'master' and automatically adjusts the propeller governor of the 'slave' engine(s) to maintain exactly the same RPM.
Question 6: A propeller is equipped with electrically heated de-ice boots on the leading edges of the blades. How does this system typically operate to remove ice?
- The boots are continuously heated to a high temperature to prevent any ice from ever forming.
- A chemical de-icing fluid is secreted through small pores in the heated boots.
- The boots are heated in a repeating cycle, melting the layer of ice closest to the blade so it can be thrown off by centrifugal force. (Correct answer)
- High-frequency vibrations are induced in the boots to shatter the accumulated ice.
Correct answer: The boots are heated in a repeating cycle, melting the layer of ice closest to the blade so it can be thrown off by centrifugal force.
Propeller de-ice systems work by cyclically heating the elements in the boots. This heating is not meant to evaporate all the ice, but rather to melt the thin layer adhering to the blade surface. Once this bond is broken, the centrifugal force of the rotating propeller slings the remaining ice off the blades.
Free AMT Aircraft Propeller Systems Questions and Answers 1
In a constant-speed propeller governor, what is the primary function of the flyweights?