AMT Aircraft Propeller Systems 3 — Questions and Answers
Question 1: During a propeller track check, one blade is found to be 3/4 inch lower than the others. The most likely cause is:
- A bent blade (Correct answer)
- Normal manufacturing tolerance
- Incorrect blade angle setting
- Improper spinner installation
Correct answer: A bent blade
Track error exceeding acceptable limits (typically 1/16 inch for metal props) usually indicates a bent blade, which must be rejected or repaired by a certificated shop.
Question 2: Which propeller type uses aerodynamic twisting moment as the primary force to increase blade pitch?
- Hartzell compact hub propeller
- McCauley fixed-pitch propeller
- Hydromatic (Hamilton Standard) propeller (Correct answer)
- Electric pitch-change propeller
Correct answer: Hydromatic (Hamilton Standard) propeller
The Hydromatic propeller design relies on aerodynamic twisting moment combined with counterweights to move blades toward high pitch, with oil pressure moving blades toward low pitch.
Question 3: A propeller with a designation of 74DM6A5 has a diameter of:
- 74 centimeters
- 74 inches (Correct answer)
- 7.4 feet
- 740 millimeters
Correct answer: 74 inches
In the propeller designation system, the first two digits represent the nominal diameter in inches; 74 = 74 inches.
Question 4: Before removing a propeller from an engine flange, the technician should FIRST:
- Safety-wire the retaining bolts
- Check the blade track
- Make a index mark on the flange and hub (Correct answer)
- Remove the spinner backplate
Correct answer: Make a index mark on the flange and hub
Marking the hub-to-flange relationship before removal ensures the propeller can be reinstalled in the same position to maintain balance.
Question 5: The beta range of a turboprop propeller system refers to operation:
- Above the governed RPM
- Between flight idle and maximum reverse pitch (Correct answer)
- At the maximum feather angle
- Only during engine start
Correct answer: Between flight idle and maximum reverse pitch
The beta range encompasses blade angles from flight idle through flat pitch to full reverse, used for ground maneuvering and deceleration after landing.
Question 6: An aluminum alloy propeller blade has a nick on the leading edge. The correct repair method is to:
- File the area smooth using longitudinal strokes and blend with surrounding contour (Correct answer)
- Fill the nick with aluminum weld and refinish
- Apply aluminum repair tape over the nick
- Reject the blade immediately regardless of nick size
Correct answer: File the area smooth using longitudinal strokes and blend with surrounding contour
Small nicks on aluminum propeller leading edges are repaired by filing smooth with lengthwise strokes and blending the contour to prevent stress concentration.
Question 7: Propeller slip is defined as the difference between:
- Geometric pitch and effective pitch (Correct answer)
- Blade angle at tip and blade angle at root
- Propeller diameter and hub diameter
- Takeoff RPM and cruise RPM
Correct answer: Geometric pitch and effective pitch
Slip is the difference between geometric pitch (theoretical advance) and effective pitch (actual advance per revolution), representing aerodynamic inefficiency.
AMT Aircraft Propeller Systems 3
During a propeller track check, one blade is found to be 3/4 inch lower than the others.
The most likely cause is: