Based on our vast experience with EASA PART 66 examination questions and question databanks, we have prepared a practice example of questions with explanations to practice for your next exam.
Disclaimer: This questions are for training purposes only! They are in no way appearing on Suntech’s’ controlled examination sessions.
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Module 17 – Propellers
1. An aircraft’s propeller system ‘beta range’ is used to:
a) refers to the most fuel efficient pitch range to use at a given engine RPM
b) is used to achieve maximum thrust during take-off
c) is used to produce zero or negative thrust
Correct Answer: c) is used to produce zero or negative thrust
Explanation: The beta range on a turbopropeller refers to a specific range of blade angles (usually from flight idle through ground idle to reverse pitch) where the pilot directly controls blade angle rather than RPM, primarily to produce zero or negative (reverse) thrust for ground handling and braking.
2. How is oil pressure delivery to a hydromatic propeller normally stopped after the blades have reached their full-feathered position?
a) Stop lugs in the teeth of the rotating cam
b) Electric cut-out pressure switch
c) Pulling out the feathering push-button
Correct Answer: b) Electric cut-out pressure switch
Explanation: In a hydromatic propeller, once the blades reach the full feathered position, an electric cut-out pressure switch detects the increased pressure (as the blades hit their mechanical stop) and deactivates the feathering pump, stopping oil flow.
3. What are the optimal rotational speed and blade pitch angle requirements of a constant-speed propeller during take-off?
a) High speed and low pitch angle
b) High speed and high pitch angle
c) Low speed and high pitch angle
Correct Answer: a) High speed and low pitch angle
Explanation: During takeoff, a constant-speed propeller is set to a high RPM (high speed) and a low blade pitch angle (fine pitch). This allows the engine to develop maximum power and accelerates a large volume of air for maximum thrust at low airspeeds.
4. How does synchrophasing in a propeller system primarily reduce vibration?
a) by the use of pulse probes and a single synchrophase unit
b) tachometers and correction motors
c) coordinating the rpm of each engine
Correct Answer: a) by the use of pulse probes and a single synchrophase unit
Explanation: Synchrophasing is an advanced propeller synchronization system that not only matches the RPM of multiple propellers but also precisely aligns their rotational phase relative to each other (using pulse probes and a synchrophase unit). This minimizes noise and vibration by ensuring the blades pass specific points at the same time.
5. Synchronization in a propeller system is primarily used:
a) on the ground
b) in flight except landing and take off
c) in flight
Correct Answer: c) in flight
Explanation: Propeller synchronization is used in multi-engine aircraft during flight to ensure that all propellers rotate at precisely the same RPM. This reduces noise and vibration within the cabin, enhancing passenger comfort.
6. Propellers are typically synchronized by the:
a) power lever
b) PCU governor
c) prop lever
Correct Answer: c) prop lever
Explanation: While the PCU governor controls the individual propeller speed, the pilot initiates synchronization and selects the master/slave engine relationship using the propeller levers (or a dedicated sync switch), which then instructs the governors to adjust accordingly.
7. In a propeller synchrophasing system, what does an electric actuator typically control?
a) rotates (controls) the slave engine governor
b) equalizes the governor signals
c) turns the flexible shaft leading to the trimmer assembly
Correct Answer: a) rotates (controls) the slave engine governor
Explanation: In a synchrophasing system, an electric actuator typically fine-tunes the speed of the slave engine’s governor to precisely match the phase of the master engine’s propeller, often by rotating a component within the governor mechanism.
8. If one signal is lost into the comparator unit when synchrophasing is operating, what is the usual outcome?
a) both engines remain running until there is a difference, of commonly, (4 to 5 percent), at which the slower of the engines is then feathered
b) the slower engine immediately goes to feather
c) synchrophasing is lost and the engines continue to function normally
Correct Answer: c) synchrophasing is lost and the engines continue to function normally
Explanation: If a signal is lost to the synchrophasing comparator unit, the system will typically detect the loss of valid input, disengage the synchrophasing function, and the engines will revert to their individual governing control, continuing to run normally but without phase synchronization.
9. In relation to a propeller aircraft, synchrophasing would primarily be used on:
a) all Aircraft
b) All multi engine aircraft
c) Single turbo prop Aircraft
Correct Answer: b) All multi engine aircraft
Explanation: Synchrophasing is only applicable to aircraft with multiple propellers, as it involves coordinating the rotational phase of two or more propellers to reduce cumulative noise and vibration.
10. Electrical de-iced propeller slip rings require regular resistance checks for:
a) oxidisation due to altitude
b) open circuit heating elements
c) wear between brushes and slip ring
Correct Answer: c) wear between brushes and slip ring
Explanation: Regular resistance checks on electrical de-iced propeller slip rings are crucial to monitor for wear between the carbon brushes and the slip ring surfaces. Excessive wear can lead to poor contact, arcing, overheating, and loss of de-icing capability.
11. Why should insulation checks on propeller electrical heating elements be carried out frequently?
a) due to short/open circuits in the heating system wires along the propeller blade
b) oxidation of slip ring and brush gear assembly
c) deposits formed due to the wear of slip ring and brush gear assembly
Correct Answer: a) due to short/open circuits in the heating system wires along the propeller blade
Explanation: Frequent insulation checks are vital for electrical heating elements on propeller blades to detect any degradation of insulation that could lead to short circuits or open circuits in the heating wires embedded within the blade, ensuring efficient and safe operation of the de-icing system.
12. For electrical de-icing systems on large aircraft, the typical power supply is:
a) AC
b) DC
c) Both AC or DC
Correct Answer: a) AC
Explanation: Electrical de-icing systems on larger aircraft often utilize AC (Alternating Current) power, which can be generated by the aircraft’s alternators. AC is efficient for transmitting power over distances within the aircraft and can handle the high current demands of heating elements.
13. On an electrical de-icing system, when is the ‘fast cycle’ typically used?
a) at low air temperature
b) at high air temperature
c) on the ground
Correct Answer: a) at low air temperature
Explanation: The ‘fast cycle’ setting on an electrical de-icing system is used when icing conditions are severe or temperatures are very low, requiring more frequent and aggressive heating cycles to prevent or remove ice accumulation effectively.
14. What is the best way to determine the proper operation of electric de-icing boots on individual propeller blades?
a) feeling the sequence of boot heating and have an assistant observe the loadmeter indications
b) feeling the boots to see if they are heating
c) observing the ammeter or loadmeter for current flow
Correct Answer: a) feeling the sequence of boot heating and have an assistant observe the loadmeter indications
Explanation: The most comprehensive way to check the operation of de-icing boots is to physically feel the boots to confirm they are heating in the correct sequence, while simultaneously observing the ammeter or loadmeter in the cockpit for proper current draw, indicating the elements are active and drawing power.
15. Which unit in the propeller anti-icing system controls the output of the pump?
a) Pressure relief valve
b) Rheostat
c) Cycling timer
Correct Answer: c) Cycling timer
Explanation: In a propeller anti-icing system (often fluid-based), a cycling timer controls the intermittent operation of the pump, regulating the flow of anti-icing fluid to the propeller blades to ensure efficient and even distribution.
16. To correct a defect, thrust and camber faces of a propeller should be blended out to what approximate factor of the damage depth?
a) 5 times the depth of damage
b) 10 times to the depth of damage
c) 30 times to the depth of damage
Correct Answer: b) 10 times to the depth of damage
Explanation: When blending out damage on propeller blades, particularly on the thrust and camber faces, standard practice often dictates a blend ratio of 10:1 (or sometimes 20:1) to the depth of the damage. This means the length of the blend should be 10 times the depth of the damage to create a smooth, gradual transition and prevent stress concentrations.
17. An aerodynamic correction factor preceded by the letter ‘Q’ typically indicates which type of balance?
a) thrust balance
b) dynamic balance
c) torque balance
Correct Answer: b) dynamic balance
Explanation: In propeller balancing, ‘Q’ or ‘Q-factor’ is often associated with the quality factor or unbalance in dynamic balancing. It’s a measure of the balance condition as the propeller rotates.
18. If the tip of an electrical overshoe (de-icing boot) is torn, what is the typical disposition?
a) it may be cut back
b) it may be classified as acceptable damage
c) it must not be cut back
Correct Answer: c) it must not be cut back
Explanation: Tears or damage to the tip of an electrical overshoe (de-icing boot) are generally considered unacceptable damage that cannot be simply cut back. It can compromise the integrity of the heating element, lead to ice accretion, or cause aerodynamic imbalance. Such damage usually requires replacement of the boot or the blade if the boot is integral.
19. What is the general policy regarding repairs to wooden propellers?
a) repairs that do not affect weight and balance
b) no repairs
c) repairs using sawdust and aeroglue
Correct Answer: a) repairs that do not affect weight and balance
Explanation: Repairs to wooden propellers are often permissible, but they must be carried out strictly according to the manufacturer’s approved repair procedures. Critical considerations include maintaining the propeller’s structural integrity, aerodynamic shape, and ensuring it remains properly balanced and within weight limits.
20. Minor repairs on composite propellers may generally be carried out by:
a) any approved 3rd party maintenance organization
b) the operator
c) any approved composite repair facility
Correct Answer: c) any approved composite repair facility
Explanation: Minor repairs on composite propellers require specialized knowledge and equipment. They are typically performed by an approved composite repair facility or a repair station specifically authorized and equipped for composite propeller repairs, not necessarily any general maintenance organization or the operator themselves.
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