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Module 17A Propeller: 50 practice questions

Real EASA paper: Category A 20 Q / 25 min · B1.1 32 Q / 40 min · B1.2 32 Q / 40 min. Three options, 75% to pass. Answer key on the last page. From part66exam.com · independent study aid, not an official exam or a past paper.

1. Before storing a feathering propeller that has been removed, which precaution helps prevent internal corrosion of the pitch-change mechanism?
1. A. Leave the piston extended to expose the shaft
2. B. Drain all grease from the bearings
3. C. Keep the piston in the high-pitch position
2. Synchrophasing reduces:
1. A. fuel consumption significantly
2. B. propeller blade erosion
3. C. cabin noise and structural vibration
3. During take-off, a constant-speed propeller is set to a low blade angle because this:
1. A. gives the largest mass of air per revolution at low rpm
2. B. reduces engine rpm to protect the engine at full throttle
3. C. allows high engine rpm and maximum power and thrust at low airspeed
4. Cabin vibration can sometimes be improved by re-indexing the propeller on the crankshaft by:
1. A. 180°
2. B. 90°
3. C. 45°
5. How does governor oil reach the propeller piston on many light-aircraft installations?
1. A. Through an external hose to the spinner
2. B. Through the propeller slip rings
3. C. Through a hollow engine crankshaft/propeller shaft
6. Why is ice asymmetry on propeller blades particularly dangerous?
1. A. It increases propeller efficiency
2. B. It causes the propeller to feather
3. C. It causes severe imbalance and vibration
7. Which part of a propeller transmits the blade centrifugal loads to the propeller shaft on a steel-hub controllable propeller?
1. A. The spinner dome, through its bulkhead
2. B. The pitch-change piston and cylinder
3. C. The hub spider, through blade clamps and bearings
8. A propeller hub bore and flange that will be exposed in storage should be:
1. A. polished and left bare to the air
2. B. coated with preservative and capped
3. C. painted over with enamel
9. What unpleasant effect is eliminated by synchronising the propellers of a twin-engine aircraft?
1. A. Engine overheating in the cruise
2. B. Propeller icing on the slave engine
3. C. A beat produced by slightly different rpm
10. A 'climb' fixed-pitch propeller compared with a 'cruise' propeller for the same aircraft has a:
1. A. lower blade angle, allowing higher rpm and better take-off thrust
2. B. higher blade angle, giving better take-off acceleration and climb
3. C. larger diameter with the same blade angle at the 75 % station
11. When running a propeller engine on the ground for propeller checks, a key safety precaution is to:
1. A. chock the aircraft and clear the propeller arc
2. B. run with all cowlings removed for better cooling
3. C. run with the tail of the aircraft into wind
12. With a constant-speed propeller in the governing range, advancing the throttle will mainly:
1. A. increase rpm while blade angle stays constant
2. B. reduce blade angle to absorb the extra power
3. C. increase power while rpm stays constant
13. During an inspection of an electric propeller de-icing system, which item is checked for wear and correct contact?
1. A. The brushes and slip rings
2. B. The governor flyweights
3. C. The slinger ring nozzle
14. Composite propeller blades commonly have a leading-edge protection made of:
1. A. nickel
2. B. lead
3. C. balsa wood
15. Storage instructions for a propeller are found in:
1. A. the aircraft flight manual
2. B. the manufacturer's maintenance manual
3. C. the aircraft maintenance manual only
16. The synchrophaser receives blade position signals from:
1. A. the flight deck tachometers only
2. B. a magnetic pickup at each propeller
3. C. the fuel flow transmitters
17. As airspeed increases after take-off, a constant-speed propeller will:
1. A. increase blade angle to hold an efficient angle of attack and constant rpm
2. B. decrease blade angle to maintain thrust as the airspeed rises
3. C. keep the same blade angle while the engine rpm rises with speed
18. Why must the manufacturer's propeller greasing schedule be followed?
1. A. Water entering the blade bearings causes corrosion
2. B. Grease is needed to maintain the air charge
3. C. Grease lowers the blade angle at start-up
19. The action of a governor 'hunting' is:
1. A. a single large rpm excursion followed by a return to set speed
2. B. a cyclic variation of rpm above and below the selected speed
3. C. the time taken for the propeller to feather
20. If one blade's de-ice boot fails to heat while the others do, the most likely effect in icing is:
1. A. total loss of engine power
2. B. propeller imbalance and vibration
3. C. automatic feathering of the propeller
21. The blade butt (root) is the:
1. A. end of the blade that fits into the hub
2. B. cambered side of the blade airfoil
3. C. leading edge section at the 75 % station
22. Why are propellers often stored in covers or containers?
1. A. To keep the blades at full feather
2. B. To protect them from moisture, dirt and damage
3. C. To maintain the governor oil level
23. Synchrophasing reduces noise by:
1. A. setting a fixed blade phase between propellers
2. B. setting different rpm on each engine
3. C. feathering one propeller in cruise
24. Why do excessive propeller tip speeds reduce efficiency?
1. A. Centrifugal force twists the tip sections to a zero blade angle
2. B. The tips approach sonic speed, causing shock waves, drag and noise
3. C. The engine cannot deliver its rated torque above a set tip speed
25. A negative torque sensing (NTS) system:
1. A. prevents the blades from entering the beta range in flight
2. B. drives the blades toward feather when torque turns negative
3. C. increases fuel flow whenever the torque becomes negative
26. The resistance of propeller de-icing heater elements is checked with:
1. A. a tachometer during an engine run
2. B. an ohmmeter against manual values
3. C. a static balance stand and level
27. On many hydraulic constant-speed propellers, where is the pitch-change piston located?
1. A. Inside the engine crankcase nose
2. B. In the body of the propeller governor
3. C. In a dome at the front of the hub
28. When handling a propeller for storage or transport, it should be supported:
1. A. by one of the blade tips
2. B. by the hub, using a sling
3. C. by the spinner dome only
29. In a master/slave synchronising system, the master engine is the one whose:
1. A. propeller always turns fastest
2. B. governor has been disconnected
3. C. rpm the slave propellers follow
30. Why do some aircraft use propellers with more blades rather than a larger diameter?
1. A. To reduce the overall weight of the propeller
2. B. To eliminate the need for a propeller governor
3. C. To absorb more power without a larger diameter
31. A propeller governor is basically:
1. A. an rpm-sensing device and high-pressure oil pump
2. B. a torque-sensing device and fuel metering valve
3. C. an electrical generator that powers the pitch motor
32. Why does a feathering propeller on a light twin have start locks (high-pitch latches)?
1. A. To prevent the blades going into reverse on the ground
2. B. To lock the blades at maximum pitch during take-off
3. C. To stop the blades feathering when the engine stops, easing restart
33. When the synchrophaser is switched on but one engine is shut down and feathered, a correctly designed system will:
1. A. drive the running engine to maximum rpm
2. B. limit any change to the running engine's rpm
3. C. unfeather the stopped propeller
34. Propeller blade flutter is best described as:
1. A. rapid twisting vibration of the blade tips perpendicular to the crankshaft axis
2. B. a slow cyclic variation of engine speed above and below the governed rpm
3. C. steady forward bending of the blades under the thrust load in flight
35. In most light-aircraft constant-speed propeller systems, governor oil pressure moves the blades toward:
1. A. high pitch (low rpm)
2. B. feather in every model
3. C. low pitch (high rpm)
36. On a variable-pitch propeller, what allows each blade to rotate in the hub while carrying centrifugal load?
1. A. Blade retention bearings at the roots
2. B. The spinner's rear bulkhead
3. C. The propeller governor flyweights
37. Why do pusher propellers on land aircraft tend to suffer more damage than tractor propellers?
1. A. Stones and debris thrown up by the wheels are drawn into it
2. B. They operate in cleaner air ahead of the wing and fuselage
3. C. They always turn at higher tip speeds than tractor propellers
38. In a constant-speed propeller governor, what opposes the outward movement of the flyweights?
1. A. The pilot valve return spring
2. B. Governor oil pump pressure
3. C. The speeder spring
39. On feathering propellers that use an air charge, the preferred charging medium is:
1. A. oxygen
2. B. dry nitrogen
3. C. compressed shop air containing moisture
40. Why does the descending blade of a propeller produce more thrust than the ascending blade at a high nose-up attitude (P-factor)?
1. A. The descending blade has a higher angle of attack
2. B. The descending blade turns faster
3. C. The ascending blade is in the slipstream
41. With a constant-speed propeller, loss of oil to the propeller on a non-feathering model that uses oil for low pitch results in:
1. A. the blades moving to full reverse
2. B. rpm rising uncontrollably to overspeed
3. C. the blades moving toward high pitch (low rpm)
42. A flange-mounted light-aircraft propeller is indexed to the crankshaft and transmits torque via:
1. A. special dowel studs in the flange
2. B. the friction of the spinner backplate alone
3. C. a key and keyway in the hub bore
43. A tractor propeller differs from a pusher propeller in that the tractor propeller is:
1. A. mounted behind its supporting structure
2. B. always of a fixed-pitch design
3. C. mounted in front of its supporting structure
44. During engine run-up, why is a constant-speed propeller cycled from high to low rpm several times?
1. A. To circulate warm oil in the hub and check the governor
2. B. To seat the blade retention bearings on their races
3. C. To discharge the unfeathering accumulator
45. An aircraft flies at 60 m/s with its propeller turning at 2400 rpm. What is the effective pitch (distance advanced per revolution)?
1. A. 0.03 m
2. B. 1.5 m
3. C. 0.67 m
46. Which method may be used to unfeather a light-twin propeller that has no accumulator?
1. A. Restart the engine so the governor pumps oil back into the hub
2. B. Pull the propeller lever further aft to release the latches
3. C. Windmill the blades by diving until they unfeather
47. During the early take-off roll with a fixed-pitch propeller, the blade sections operate at:
1. A. a high angle of attack, perhaps partly stalled
2. B. a very low, near-zero angle of attack
3. C. a negative angle of attack, as in reverse
48. Which item should be checked first if a propeller will not feather or feathers slowly?
1. A. The propeller synchrophaser selector
2. B. The engine fuel flow indication
3. C. The air charge pressure in the propeller dome
49. According to the FAA handbook, propeller efficiency varies between about:
1. A. 10 % and 30 %
2. B. 90 % and 99 %
3. C. 50 % and 87 %
50. At constant rpm, what happens to the helix angle of the relative airflow at a blade section as forward speed increases?
1. A. It decreases
2. B. It increases
3. C. It stays constant

Answer key

1. C — The FAA text notes that feathering propellers are normally placed in high pitch before shutdown to prevent exposure and corrosion of the pitch-changing mechanism. The same principle applies to storage.
2. C — Correct phasing makes pressure pulses from the propellers interfere favourably at the fuselage.
3. C — At low airspeed a low blade angle keeps the angle of attack efficient and lightly loads the engine, letting it reach rated rpm and develop full power. High rpm and high slipstream velocity give maximum thrust for take-off.
4. A — The propeller can be removed, rotated 180° and reinstalled, which can reduce vibration by changing its relationship to crankshaft imbalance. Check manuals for any required mounting position.
5. C — Governor oil is transferred to the propeller through the hollow engine shaft (with a transfer bearing where required) to the piston and cylinder mounted on the hub.
6. C — Ice collects unevenly, adding weight and distorting airfoils, producing unbalance and destructive vibration.
7. C — On steel-hub designs a central spider supports the blades. Centrifugal force (up to about 25 tons) passes from the blades through the blade clamps and ball bearings to the spider.
8. B — Exposed mating surfaces are coated with corrosion-preventive compound and covered, keeping moisture and dirt out. Before installation, the compound is removed with solvent.
9. C — Propellers turning at slightly different speeds produce a rhythmic beat. Synchronisation matches the rpm, reducing vibration and removing the beat.
10. A — A climb propeller has lower pitch, so the engine reaches higher rpm at low airspeed and produces more take-off thrust, at the cost of cruise speed. A cruise propeller has higher pitch for efficiency at speed.
11. A — Before any engine run the aircraft is chocked, the propeller arc and area behind the aircraft kept clear, and the aircraft faced into wind. A fire extinguisher and competent observer should be available.
12. C — The governor holds rpm, so extra power from the throttle is absorbed by a larger blade angle. Manifold pressure and power rise; rpm is set by the propeller control.
13. A — Brush wear, slip ring condition and alignment determine whether current reaches the boots reliably. Boot bonding, heater continuity and harness security are also inspected.
14. A — A typical composite blade has carbon-fibre spars, a foam core, a carbon/glass envelope, a polyurethane coat and a nickel leading-edge erosion shield; a lightning conductor is earthed to the metal root.
15. B — Follow the propeller manufacturer's instructions for preservation, storage and return to service.
16. B — Magnetic pickups sense each propeller; the controller computes the error and trims the slave governor.
17. A — Increasing forward speed reduces the angle of attack and unloads the propeller, which would overspeed the engine. The governor increases the blade angle, restoring the small, efficient angle of attack at the selected rpm.
18. A — Experience shows water can enter blade bearing assemblies. Lubrication per schedule protects moving parts and prevents corrosion; most propeller defects are unseen internal corrosion found at overhaul.
19. B — Hunting is a cyclic rise and fall of rpm about the desired value. Surging is a large increase or decrease followed by a return after one or two occurrences. Governor, fuel control and synchroniser should be checked.
20. B — Ice remaining on one blade while shedding from the others unbalances the propeller and produces vibration. The loadmeter may show reduced current during that blade's heating period.
21. A — The blade butt, also called the base or root, is retained in the hub. The shank lies just outboard of it and the airfoil sections continue to the tip.
22. B — Covers and containers protect blades and hubs from moisture, dust and accidental damage in storage and transport. Desiccants may be included where recommended.
23. A — By holding a preset angular phase between master and slave blades, pressure pulses from the propellers are arranged to reduce cabin noise and vibration.
24. B — As the resultant tip velocity nears the speed of sound, shock waves form, drag and noise rise sharply and efficiency falls. This is why reduction gearing is used on high-rpm engines and why propeller aircraft are limited to about 400 mph.
25. B — When a predetermined negative torque is sensed, the NTS plunger shifts the feather valve and sends the blades toward feather; negative torque falls and the valve closes. The result is rpm cycling slightly below the level where negative torque occurred.
26. B — Element resistance shows open or shorted heaters.
27. C — The pitch-change piston usually works in a cylinder or dome at the front of the hub. Oil moving it is linked to the blade roots by links or cams to change blade angle.
28. B — The FAA removal procedure uses a sling to support the assembly and a cart for transport. Supporting the propeller by the hub avoids bending loads on blades and damage to tips and edges.
29. C — One engine is designated the master; the synchroniser adjusts the slave governors so the slave propellers follow the master's rpm (and, in synchrophasing, phase).
30. C — Adding blades lets the propeller absorb more engine power without increasing diameter, which is limited by ground clearance and tip speed (compressibility and noise).
31. A — The governor senses engine rpm with flyweights and has a gear pump that boosts engine oil pressure. It directs oil to, or releases it from, the propeller cylinder to change blade angle and hold rpm.
32. C — Oil is lost at shutdown, so the spring/air charge would feather the blades. Spring-loaded latches engage below about 600-800 rpm, holding the blades in low pitch so the engine is not heavily loaded at the next start.
33. B — The slave's rpm can only be trimmed within a narrow band, so even if the reference is lost the running engine's rpm stays near its selected value. Manuals usually require the system to be off for take-off, landing and single-engine operation.
34. A — A propeller must be rigid enough to prevent flutter, in which the blade ends twist back and forth at high frequency. It is accompanied by a distinctive noise (often mistaken for exhaust noise) and can fatigue the blade to failure.
35. C — On most light-aircraft propellers the governor supplies oil to decrease pitch. Blade counterweights, springs, air charge and aerodynamic twisting moment move the blades to higher pitch when oil is released.
36. A — Blade retention bearings in the hub carry the large centrifugal load of each blade while letting it turn about its axis for pitch change.
37. A — The FAA text notes that rocks, gravel and small objects dislodged by the wheels are thrown or drawn into a pusher propeller. For this reason pushers are often mounted high, above and behind the wing.
38. C — A speeder spring above the flyweights opposes their centrifugal tendency to fly outward. The pilot's propeller control adjusts the speeder spring compression and so sets the governed rpm.
39. B — The cylinder is charged with dry air or nitrogen, nitrogen being preferred. Charge pressure depends on temperature and is taken from the manufacturer's chart; the propeller is positioned on the start locks while charging.
40. A — With the propeller axis inclined to the flight path, the descending blade meets the relative airflow at a greater angle of attack than the ascending blade, so it makes more thrust, causing a yaw.
41. C — On models where oil drives the blades to low pitch, counterweights take the blades toward high pitch if oil is lost. The engine then runs at lower rpm, a safe failure mode.
42. A — The FAA example describes six studs in a 4-inch circle, two of which also act as dowel pins to transfer torque and index the propeller. The propeller may be fitted in a given position or 180° from it.
43. C — Tractor propellers are mounted in front of the structure and operate in relatively undisturbed air, giving lower induced stresses. Pusher propellers are mounted behind and are more prone to damage from debris and water spray.
44. A — Exercising the propeller at run-up replaces cold, congealed oil in the hub with warm oil and confirms that rpm drops and recovers correctly. It verifies governor and pitch-change operation before flight.
45. B — Effective pitch = V ÷ (rev/s) = 60 m/s ÷ (2400/60) = 1.5 m per revolution.
46. A — In most light twins the engine is restarted with the starter; as it turns, the governor pumps oil into the propeller and reduces pitch. Windmilling then speeds up the process.
47. A — At low forward speed the helix angle is small, so the angle of attack is close to the blade angle. Sections may be at a high, near-stall angle, which lowers efficiency and holds rpm below its in-flight value.
48. C — The FAA troubleshooting list for failure to feather starts with the air charge, then control rigging, governor drain function and internal friction or corrosion in the blade bearings and pitch-change mechanism.
49. C — Propeller efficiency (thrust horsepower ÷ brake horsepower) varies from about 50 % to 87 %, depending on how much the propeller slips.
50. B — The relative airflow is the vector sum of rotational speed and forward speed. Higher forward speed at the same rpm tilts the relative wind further from the plane of rotation, so the helix angle rises and the angle of attack of a fixed blade falls.

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