A&P Propeller Systems and Maintenance 2 — Questions and Answers
Question 1: What is the correct repair method for a small nick found on a propeller blade leading edge?
- File the nick smooth and blend it into the surrounding blade contour (Correct answer)
- Apply aviation epoxy filler to the nick and sand to the original profile
- Replace the propeller blade regardless of nick depth or location
- Weld the nick closed using approved filler rod and refinish the blade
Correct answer: File the nick smooth and blend it into the surrounding blade contour
Small nicks are repaired by filing smooth and blending into the surrounding contour to eliminate stress concentrations that could initiate fatigue cracks.
Question 2: On a counterweight-type constant-speed propeller, what force moves the blades toward high pitch (coarse)?
- Engine oil pressure directed into the propeller cylinder
- Governor flyweight spring tension acting on the pitch change mechanism
- Centrifugal force acting on the propeller counterweights (Correct answer)
- A coarse-pitch spring assembly installed inside the hub
Correct answer: Centrifugal force acting on the propeller counterweights
In counterweight-type propellers, centrifugal force acts on the counterweights mounted offset from the blade centerline, twisting the blades toward high (coarse) pitch.
Question 3: Why is dynamic propeller balancing performed in addition to static balancing?
- To verify blade angle uniformity across all blades at operating RPM
- To confirm propeller track is within manufacturer-specified tolerances
- To ensure the propeller hub assembly is properly sealed against oil leakage
- To correct vibration from mass imbalance that only manifests at operating rotational speed (Correct answer)
Correct answer: To correct vibration from mass imbalance that only manifests at operating rotational speed
Dynamic balancing corrects vibration caused by mass imbalance that can only be detected at operating RPM, which static balancing on a mandrel cannot reveal.
Question 4: What metal is most commonly used in manufacturing modern fixed-pitch propellers?
- Stainless steel for superior corrosion resistance
- Titanium alloy for high strength at reduced weight
- Aluminum alloy for its favorable strength-to-weight ratio (Correct answer)
- Magnesium alloy for minimum blade weight
Correct answer: Aluminum alloy for its favorable strength-to-weight ratio
Aluminum alloy is the most common material for modern fixed-pitch propellers due to its excellent strength-to-weight ratio, ease of manufacture, and corrosion resistance.
Question 5: Which condition mandates removal of a propeller from service for mandatory inspection before return to flight?
- Minor leading edge erosion pitting from normal service exposure
- Light surface corrosion identified visually on the blade shank area
- Propeller involved in a sudden engine stoppage or ground strike event (Correct answer)
- Blade tip rounding exceeding 1/2-inch radius during normal operation
Correct answer: Propeller involved in a sudden engine stoppage or ground strike event
Sudden engine stoppage or ground strike can cause internal stress or cracks not visible externally, requiring manufacturer inspection before the propeller is returned to service.
Question 6: What is the function of the 'beta range' on a turboprop propeller control system?
- To provide reverse thrust capability during the landing roll only
- To allow direct manual control of blade angle below the normal governing range (Correct answer)
- To automatically feather the propeller upon engine failure detection
- To hold blade pitch fixed at a preset angle during cruise flight
Correct answer: To allow direct manual control of blade angle below the normal governing range
The beta range allows the pilot to manually control blade pitch below the normal governing range, enabling ground fine pitch, zero thrust, and reverse pitch for ground maneuvering.
Question 7: How is a propeller checked for static balance during inspection?
- By supporting the propeller horizontally on a mandrel and observing if it rotates due to uneven blade weight (Correct answer)
- By installing it on the aircraft and measuring airframe vibration at engine idle
- By spinning the propeller on a dedicated test stand and recording vibration sensor data
- By individually weighing each blade and comparing their measured masses
Correct answer: By supporting the propeller horizontally on a mandrel and observing if it rotates due to uneven blade weight
Static balance is checked by mounting the propeller on a horizontal mandrel; if one blade is heavier, it will rotate downward, indicating a balance correction is needed.
A&P Propeller Systems and Maintenance 2
What is the correct repair method for a small nick found on a propeller blade leading edge?