AMT Aircraft Propeller Systems 2 — Questions and Answers
Question 1: What is the primary purpose of a propeller governor in a constant-speed propeller system?
- Control fuel flow to maintain RPM
- Maintain a selected RPM by varying blade pitch (Correct answer)
- Limit maximum propeller diameter
- Regulate oil temperature to the pitch change mechanism
Correct answer: Maintain a selected RPM by varying blade pitch
The governor senses propeller RPM and adjusts oil pressure to the pitch change mechanism to vary blade angle, maintaining the pilot-selected RPM.
Question 2: When inspecting a wood propeller, small cracks running parallel to the grain are typically treated by:
- Applying epoxy filler and refinishing
- Rejecting the propeller from service (Correct answer)
- Filling with wood putty and varnishing
- Monitoring until cracks exceed 1 inch
Correct answer: Rejecting the propeller from service
Cracks parallel to the grain in a wood propeller are cause for rejection because they can rapidly propagate and lead to structural failure.
Question 3: A turboprop engine's propeller is in the FEATHER position when blade angle is approximately:
- 0° to 5° (flat pitch)
- 15° to 20° (cruise pitch)
- 80° to 90° (parallel to airflow) (Correct answer)
- –5° (reverse pitch)
Correct answer: 80° to 90° (parallel to airflow)
Feather positions blades nearly parallel to the airflow (≈85–90°) to minimize drag in the event of an engine failure.
Question 4: Which condition is indicated when a constant-speed propeller surges (hunts) repeatedly between high and low RPM?
- Incorrect torque on the propeller retaining nut
- Governor speeder spring set too high
- Air or contaminants in the propeller governor oil system (Correct answer)
- Excessive blade track error
Correct answer: Air or contaminants in the propeller governor oil system
Air or contamination in the governor oil system causes erratic oil pressure delivery, producing the characteristic hunting or surging of RPM.
Question 5: On a single-engine aircraft with a right-hand rotating propeller, P-factor is most pronounced during:
- High-speed level flight
- Low airspeed, high angle of attack flight (Correct answer)
- Descent at idle power
- Ground roll at takeoff speed
Correct answer: Low airspeed, high angle of attack flight
P-factor is greatest at low airspeed and high angle of attack because the descending blade has a much higher angle of attack than the ascending blade.
Question 6: The blade angle of a propeller is measured from the plane of rotation to the:
- Leading edge of the blade
- Chord line of the blade (Correct answer)
- Trailing edge of the blade
- Thrust face of the blade
Correct answer: Chord line of the blade
Blade angle is defined as the angle between the propeller plane of rotation and the chord line of the blade at a specified station.
Question 7: What is the purpose of the centrifugal twisting moment acting on propeller blades?
- It tends to move blades toward low pitch (flat pitch) (Correct answer)
- It tends to move blades toward high pitch (coarse pitch)
- It counters the gyroscopic effect during turns
- It is used to drive the pitch change mechanism
Correct answer: It tends to move blades toward low pitch (flat pitch)
The centrifugal twisting moment tends to rotate blades toward flat (low) pitch because centrifugal force acts on the blade's center of mass, which is ahead of the pitch change axis.
AMT Aircraft Propeller Systems 2
What is the primary purpose of a propeller governor in a constant-speed propeller system?