AME Aircraft Propeller Systems and Theory 1 — Questions and Answers
Question 1: What is the primary purpose of a constant-speed propeller governor?
- To maintain a constant blade angle regardless of airspeed
- To maintain a constant engine RPM by varying blade pitch (Correct answer)
- To prevent propeller overspeed by reducing throttle
- To synchronize propeller rotation with engine firing order
Correct answer: To maintain a constant engine RPM by varying blade pitch
A constant-speed governor maintains engine RPM by automatically adjusting propeller blade pitch to match varying flight conditions.
Question 2: On a hydraulically actuated variable-pitch propeller, what fluid is typically used as the actuating medium?
- Skydrol hydraulic fluid
- Engine oil (Correct answer)
- MIL-H-5606 hydraulic fluid
- Water-glycol mixture
Correct answer: Engine oil
Most variable-pitch propeller systems use engine oil as the actuating fluid because it is readily available and provides the required pressure.
Question 3: What is 'propeller feathering'?
- Rotating blades to minimum pitch for maximum thrust
- Rotating blades to approximately 90° pitch to minimize drag on a failed engine (Correct answer)
- Balancing the propeller by adding weights to blade tips
- Applying a protective coating to the leading edges of the blades
Correct answer: Rotating blades to approximately 90° pitch to minimize drag on a failed engine
Feathering turns propeller blades edge-on to the airflow (approximately 90°) to reduce drag when an engine fails in flight.
Question 4: Propeller 'tracking' is a maintenance check that verifies:
- The propeller RPM is within limits
- Each blade tip follows the same plane of rotation (Correct answer)
- The propeller governor is correctly calibrated
- Blade angle settings are within specified tolerance
Correct answer: Each blade tip follows the same plane of rotation
Tracking ensures all propeller blade tips rotate in the same plane, indicating the hub is not bent and blades are properly installed.
Question 5: What typically happens to a constant-speed propeller if the governor oil pressure is lost?
- The blades move to low pitch (fine)
- The blades move to high pitch (coarse) or feather (Correct answer)
- The blades freeze in their current position
- The propeller immediately overspeeds
Correct answer: The blades move to high pitch (coarse) or feather
Most constant-speed propellers are designed so that loss of oil pressure causes blades to move toward high pitch or feather as a fail-safe against overspeeding.
Question 6: A propeller static balance check ensures:
- The propeller generates equal thrust from all blades
- The center of gravity of the propeller assembly is on the axis of rotation (Correct answer)
- Each blade has the same pitch angle
- The propeller can withstand centrifugal force loads
Correct answer: The center of gravity of the propeller assembly is on the axis of rotation
Static balance ensures the propeller's center of gravity coincides with its rotational axis, preventing vibration when spinning.
AME Aircraft Propeller Systems and Theory 1
What is the primary purpose of a constant-speed propeller governor?