AMT Aircraft Propeller Systems 5 — Questions and Answers
Question 1: When an oil-counterweight propeller loses oil pressure, the blades will move toward:
- Full feather
- Low pitch (flat)
- High pitch (coarse) (Correct answer)
- Reverse pitch
Correct answer: High pitch (coarse)
In a counterweight-type propeller, counterweights move blades toward high pitch (coarse); oil pressure moves them toward low pitch, so loss of oil causes blades to go high pitch.
Question 2: Which maintenance action requires weighing each propeller blade individually?
- Checking blade track
- Determining balance station for static balance
- Replacing a blade in a composite multi-piece hub (Correct answer)
- Performing a torque seal inspection
Correct answer: Replacing a blade in a composite multi-piece hub
When replacing a blade in a removable-blade composite hub, each blade must be weighed to select a matched-weight replacement and restore propeller balance.
Question 3: A propeller tachometer reads 300 RPM lower than the engine tachometer on a direct-drive engine. The technician should:
- Accept the difference as normal for high-altitude flight
- Calibrate the propeller tachometer
- Suspect a slipping propeller hub or flange (Correct answer)
- Reduce manifold pressure to bring readings into agreement
Correct answer: Suspect a slipping propeller hub or flange
On a direct-drive engine, the propeller must turn at the same RPM as the crankshaft; a large discrepancy suggests propeller slippage on the shaft.
Question 4: Corrosion found on the bore of an aluminum propeller hub should be:
- Treated with zinc chromate and returned to service
- Cleaned, evaluated against manufacturer limits, and re-inspected at next 100-hour
- Sent to a certificated propeller repair station for evaluation (Correct answer)
- Polished out with 600-grit abrasive and sealed
Correct answer: Sent to a certificated propeller repair station for evaluation
Hub bore corrosion is a critical area; the propeller must be sent to a certificated repair station because improper repairs can cause hub failure.
Question 5: What happens to blade pitch in a constant-speed propeller when the aircraft descends and engine RPM tends to increase above the governor set point?
- Pitch decreases to unload the engine
- Pitch increases to absorb the additional power and maintain RPM (Correct answer)
- The governor bypasses oil to the sump
- The propeller automatically feathers to prevent overspeed
Correct answer: Pitch increases to absorb the additional power and maintain RPM
When RPM rises above the set point, governor flyweights open a port directing oil to increase blade pitch, adding load to bring RPM back to the selected value.
Question 6: The primary advantage of a composite propeller blade over an aluminum blade is:
- Lower cost to manufacture
- Greater resistance to leading edge erosion without protective tape
- Improved fatigue life and lighter weight (Correct answer)
- Simpler repair procedures requiring no certificated shop
Correct answer: Improved fatigue life and lighter weight
Composite blades offer superior fatigue resistance and are lighter than equivalent aluminum blades, improving overall aircraft performance.
Question 7: According to FAA regulations, a major propeller repair must be performed by:
- Any A&P mechanic with an Airframe rating
- A certificated propeller repair station or the propeller manufacturer (Correct answer)
- An A&P mechanic holding an Inspection Authorization
- Any certificated repair station regardless of rating class
Correct answer: A certificated propeller repair station or the propeller manufacturer
14 CFR Part 65 and Part 145 require that major propeller repairs be accomplished by a certificated propeller repair station or the original manufacturer.
AMT Aircraft Propeller Systems 5
When an oil-counterweight propeller loses oil pressure, the blades will move toward: