22 Propellers & Governing Practice Questions & Answers

1. 1. How is propeller blade angle defined?

   • A.The angle between the blade chord line and the relative wind that meets the blade
   • B.The acute angle between the blade chord line at a station and the plane of rotation✓ Answer
   • C.The difference between geometric pitch and effective pitch, expressed in degrees
   • D.The distance the propeller would advance in one revolution if it moved through a solid

   Blade angle is an angle measured at a specified blade station between the blade chord line and the plane of rotation, which is why a blade angle check is meaningless unless the reference station is stated. Pitch is a distance travelled per revolution, not an angle, and the angle between the chord line and the relative wind is angle of attack, which changes with airspeed and rpm even though blade angle is unchanged.

   Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (blade angle, pitch and blade stations)Report a problem with this question

2. 2. Why is a propeller blade built with a twist, so that the blade angle is greater at the root than at the tip?

   • A.The root must carry a larger share of the thrust load than the tip carries
   • B.The twist lets centrifugal twisting moment cancel out the thrust bending force
   • C.The thin tip section would stall before the root section does at cruise speed
   • D.Rotational velocity rises with radius, so the twist evens the angle of attack✓ Answer

   Each blade element travels a larger circle and therefore moves faster the farther it is from the hub, so a blade of constant angle would meet the air at a very different angle of attack at the tip than at the root. Building in a twist that decreases the blade angle toward the tip gives nearly uniform angle of attack and thrust distribution along the blade.

   Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (blade twist and blade elements)Report a problem with this question

3. 3. Which statement correctly describes centrifugal twisting force and aerodynamic twisting force on a rotating blade?

   • A.Aerodynamic twisting force is the greater of the two and tends to move the blades toward low pitch
   • B.Both forces act toward high pitch, and only the counterweights oppose them toward low pitch
   • C.Centrifugal twisting force is the larger of the two and tends to turn the blades toward low pitch✓ Answer
   • D.Centrifugal twisting force bends the blades forward while aerodynamic force bends them rearward

   Centrifugal twisting force arises because the mass ahead of the blade's pitch-change axis is thrown outward, and it is the larger of the two twisting forces, always trying to turn the blade to a lower angle. Aerodynamic twisting force, produced because the center of pressure is ahead of that axis, acts toward high pitch but is weaker, which is why some hubs use the stronger centrifugal effect as the working low-pitch force.

   Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (forces acting on a propeller)Report a problem with this question

4. 4. What distinguishes a controllable-pitch propeller from a constant-speed propeller?

   • A.The propeller has two blade positions, one for takeoff and one for cruise
   • B.A governor varies the blade angle to hold the rpm the pilot has selected
   • C.The blade angle can be changed only on the ground with the engine shut down and chocked
   • D.The pilot selects the blade angle, but engine rpm is not held automatically✓ Answer

   A controllable-pitch propeller lets the pilot move the blades to a selected angle in flight, but nothing then keeps rpm constant, so rpm drifts as airspeed, altitude or power changes. A constant-speed propeller adds a governor that continuously varies blade angle to hold the selected rpm, and a ground-adjustable propeller can only be reset with the engine stopped.

   Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (types of propellers)Report a problem with this question

5. 5. On a typical single-acting counterweight propeller used on light aircraft, how do the pitch-change forces act?

   • A.Engine oil only lubricates the hub, and the blade angle is changed by the dome air charge acting alone
   • B.Governor oil pressure drives the blades toward low pitch and the counterweights drive them toward high pitch✓ Answer
   • C.Governor oil pressure drives the blades toward high pitch and the counterweights drive them to low pitch
   • D.Oil pressure acts on both sides of the piston, so oil alone sets both the high and the low blade angle

   In the common single-acting arrangement, governor oil is admitted to one side of the propeller piston to reduce blade angle, and blade counterweights, helped by a spring and an air charge, return the blades to high pitch when that oil is released. At least one nonfeathering aluminum-hub design reverses the roles, and a double-acting propeller uses oil on both sides of the piston, so the maintenance data for the specific propeller must always be consulted.

   Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (single-acting and double-acting pitch-change mechanisms)Report a problem with this question

6. 6. A constant-speed propeller governor is in an underspeed condition. What happens next?

   • A.Oil is trapped in the propeller piston, the blade angle stops changing and rpm holds where it is
   • B.The flyweights move outward, the pilot valve is raised and oil drains out of the propeller piston
   • C.The speeder spring forces the pilot valve down, oil flows to the propeller and blade angle decreases✓ Answer
   • D.The relief valve unseats and dumps boost pressure, so blade angle rises until the rpm falls off

   Underspeed means engine rpm has fallen below the value set by speeder-spring compression, so the flyweights lack the centrifugal force to hold their position and the spring pushes them inward, moving the pilot valve down. That ports governor oil to the propeller, the blade angle decreases, the aerodynamic load on the engine drops and rpm rises back to the selected value.

   Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (governor underspeed, on-speed and overspeed conditions)Report a problem with this question

7. 7. The pilot moves the propeller control forward, increasing speeder-spring compression. What does the governor do?

   • A.It senses an underspeed condition and decreases the blade angle until the higher rpm is reached✓ Answer
   • B.It holds the blade angle where it is and lets the engine reach the new rpm on fuel flow alone
   • C.It senses an overspeed condition and increases the blade angle until the higher rpm is reached
   • D.It senses an overspeed condition and drains oil, so the counterweights carry the blades to feather

   Increasing speeder-spring compression raises the rpm the governor will hold, so the moment the control is moved the engine is turning slower than the new setting and the governor is momentarily in an underspeed condition. It therefore meters oil to the propeller to reduce blade angle, which unloads the engine and lets rpm climb until flyweight force again balances the spring.

   Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (speeder spring and rpm selection)Report a problem with this question

8. 8. What defines the on-speed condition of a propeller governor?

   • A.The boost pump is at relief-valve pressure, so oil is held in the propeller at a fixed value
   • B.Blade angle sits hard against the low-pitch stop, so the propeller cannot change pitch any further
   • C.The flyweights are fully outward against their stops while oil drains out of the propeller
   • D.Flyweight force balances speeder-spring force and the pilot valve neither ports nor drains oil✓ Answer

   On-speed exists when the centrifugal force of the rotating flyweights exactly balances the force of the compressed speeder spring, which centers the pilot valve so that it neither meters oil to the propeller nor allows it to drain. Blade angle is then steady and the propeller holds the selected rpm until some change in power, airspeed or attitude upsets that balance.

   Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (governor on-speed condition)Report a problem with this question

9. 9. How is a feathering propeller of the common light-twin type driven to the feathered position?

   • A.Dome air pressure is vented overboard, letting the airstream windmill the blades around into feather
   • B.Governor oil is dumped out of the propeller and the spring and counterweights turn the blades to feather✓ Answer
   • C.An electric pitch motor drives the blades past the high-pitch stop and holds them there mechanically
   • D.The governor boost pump raises oil pressure to its maximum and forces the piston against the feather stop

   Pulling the propeller control fully aft opens a port that dumps governor oil back to the engine, and with that oil pressure gone the feathering spring and the blade counterweights turn the blades to roughly ninety degrees to the plane of rotation, typically in three to ten seconds. Because the pitch-change oil comes from the engine lubrication system, a complete loss of oil pressure feathers this type of propeller by itself.

   Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (feathering propellers)Report a problem with this question

10. 10. Why are spring-loaded start locks fitted to a feathering propeller?

    • A.They hold the blades in low pitch at shutdown so the engine is not started against a high-pitch load✓ Answer
    • B.They hold the blades in feather at shutdown so wind gusts cannot windmill the stopped propeller
    • C.They keep the blades out of reverse pitch in flight if the power lever is moved below flight idle
    • D.They lock the blades against the high-pitch stop so the governor can be rigged with engine stopped

    Because the feathering spring and counterweights would drive the blades toward feather as the propeller slows at shutdown, latches catch the blades in low pitch so the next start is made against the smallest possible aerodynamic load. In flight the latches cannot interfere, since centrifugal force above roughly six hundred to eight hundred rpm holds them off their seats and leaves the blades free to feather.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (start locks and latches)Report a problem with this question

11. 11. What does an unfeathering accumulator do on a light twin?

    • A.It stores oil for the engine bearings so that a windmilling propeller never turns without lubrication
    • B.It stores oil under an air charge and releases it to the propeller to move the blades out of feather✓ Answer
    • C.It stores oil under an air charge and releases it to the governor to hold rpm during an air restart
    • D.It stores compressed air and vents that air into the propeller dome to drive the blades into feather

    The accumulator holds engine oil under an air or nitrogen charge while the propeller is feathered, and when the propeller control is returned to the governing range that trapped oil is released into the propeller piston. The stored oil moves the blades out of feather far faster than waiting for the governor pump to build pressure during a windmilling restart.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (unfeathering systems and accumulators)Report a problem with this question

12. 12. In the beta range of a turboprop installation, what sets propeller blade angle?

    • A.The propeller governor, which still holds the selected rpm by varying the blade angle
    • B.The fuel control unit, which schedules blade angle against turbine inlet temperature
    • C.The power lever position, acting through a beta valve and the blade-angle feedback linkage✓ Answer
    • D.The overspeed governor, which limits the blade angle whenever the aircraft is on the ground

    Below flight idle the propeller governor no longer sets blade angle; the power lever does, through a beta valve whose position is compared with actual blade angle by a feedback linkage of beta rod, slip ring and carbon block. That direct control is what allows ground fine pitch, taxi and reverse thrust, and moving the lever further aft takes the blades into negative pitch.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (turbopropeller beta range and reversing)Report a problem with this question

13. 13. How does a propeller overspeed governor on a turboprop bring propeller rpm back down?

    • A.It applies a friction brake to the propeller shaft until the reduction gearbox speed is normal
    • B.It bleeds oil out of the propeller servo, so the counterweights and spring increase the blade angle✓ Answer
    • C.It adds boosted oil to the propeller servo, so the piston drives the blades to a larger angle
    • D.It signals the fuel control to cut fuel flow until the power turbine slows back to its rated speed

    The overspeed governor is a protective device that cuts in a few percent above maximum propeller speed, and it works by bleeding servo oil out of the propeller to the reduction gearbox sump. With that oil released the counterweights and spring increase blade angle, the propeller absorbs more torque and rpm comes back down, which is the opposite of the common assumption that it adds pressure.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (turbopropeller overspeed protection)Report a problem with this question

14. 14. What does a propeller synchrophasing system accomplish that plain synchronization does not?

    • A.It feathers the propeller on a failed engine without any action by the flight crew
    • B.It trims fuel flow on each engine so that torque is equal across the installed engines
    • C.It holds a preset angular relationship between the blades of the different propellers✓ Answer
    • D.It matches the rpm of the slave engines to the rpm selected on the master engine

    Synchronization only matches rpm, which removes the audible beat, while synchrophasing goes further and holds the blades of one propeller at a chosen angular position relative to the blades of the other. Keeping that phase relationship constant cancels much of the pressure pulse arriving at the cabin, so noise and vibration drop further than rpm matching alone can achieve.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (propeller synchronization and synchrophasing)Report a problem with this question

15. 15. In a fluid anti-icing system, what carries the fluid from the slinger ring outward along the blades?

    • A.Centrifugal force acting on the fluid as the propeller assembly rotates✓ Answer
    • B.Airstream suction over the blade back that draws the fluid outboard
    • C.Centripetal force that pulls the fluid inward toward the axis of rotation
    • D.Pump discharge pressure delivered through the stationary feed nozzle

    A stationary nozzle only delivers fluid into the U-shaped slinger ring; once the fluid is in that rotating ring, centrifugal force throws it outward to the blade shanks, where feed shoes guide it along the leading edges. Centripetal force acts toward the axis, and the pump has no path to pressurize fluid already thrown clear of the ring.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (fluid anti-icing systems and slinger rings)Report a problem with this question

16. 16. A propeller electrical deicing system energizes its heating elements in a timed sequence. Why?

    • A.So melted water is carried aft and refreezes as runback on the unprotected part of the blade
    • B.So the boots stay warm continuously and ice is prevented from forming anywhere on the blades
    • C.So the total current draw never exceeds the continuous output rating of the starter-generator
    • D.So heating stays balanced between opposite blades and the propeller is not thrown out of balance✓ Answer

    Ice does not build evenly, and ice shed from one blade before its opposite number produces an unbalanced rotating mass and destructive vibration, so a timer energizes each circuit for roughly fifteen to thirty seconds within a total cycle of about two minutes. The heat is applied only long enough to break the bond at the blade surface, since continuous heating would cause runback and can destroy the elements if used with the propeller stopped.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (electric propeller deicing systems)Report a problem with this question

17. 17. A mechanic is checking propeller blade track. Which statement is correct?

    • A.Track shows the relative position of the blade tips in one plane, within 1/16 inch✓ Answer
    • B.Track is measured on the blade face at the reference station with a bench protractor
    • C.Track is checked with the engine running at 1,200 rpm, within 1/32 inch of level
    • D.Track shows the actual path each blade tip cuts through the air, within 1/16 inch

    Tracking compares where the blade tips lie relative to one another in the same plane of rotation, not the path a tip actually travels through the air, and the blades must track within plus or minus one sixteenth of an inch of each other unless the manufacturer publishes a different figure. The check is made with the engine stopped and the propeller turned slowly by hand against a fixed pointer, and an out-of-track condition points to a bent blade, a bent flange or improperly torqued mounting bolts.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (blade tracking)Report a problem with this question

18. 18. A transverse crack is found in an aluminum alloy propeller blade during inspection. What is the correct disposition?

    • A.The blade is dressed out with fine sandpaper, since the crack is shorter than the blade chord
    • B.The blade is returned to service after the crack is stop-drilled and penetrant checked
    • C.The blade is returned to service if a penetrant check shows no growth in ten hours
    • D.The blade is rejected, because a transverse crack of any size condemns an aluminum blade✓ Answer

    A transverse crack or flaw of any size in an aluminum blade is cause for rejection, because the blade is a highly stressed rotating member and such a crack lies across the direction of the tension load that centrifugal force applies. Dye or fluorescent penetrant is used to confirm a suspected crack, not to justify keeping a cracked blade in service, and only shallow surface damage such as nicks may be dressed out within the limits of approved data.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (aluminum blade inspection and rejection criteria)Report a problem with this question

19. 19. Which inspection method is used to find a delamination or debond in a composite propeller blade?

    • A.A dye penetrant check of the blade, which bleeds out over any internal debonded area
    • B.A magnetic particle check of the blade, which shows subsurface flaws in bonded layers
    • C.A knife-edge balance check of the blade, since a debond shifts the spanwise balance
    • D.A coin tap check of the blade, listening for a dull or hollow tone in the suspect area✓ Answer

    A coin tap is the standard field method for composite blades because a debonded or delaminated area returns a dull or hollow sound instead of the sharp ring of sound structure, and the cuff area must be tapped separately since its normal tone differs from the blade. Penetrant finds only cracks open to the surface and magnetic particle works only on ferrous material, so neither can detect an internal debond in a composite blade.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (composite blade inspection and tap testing)Report a problem with this question

20. 20. An engine and propeller combination vibrates. Watching the spinner at 1,200 to 1,500 rpm, the mechanic sees the hub swinging in a slight orbit instead of turning in a true plane. What does this indicate?

    • A.The propeller is at fault, and blade track and low-pitch blade angle come next✓ Answer
    • B.The tachometer is at fault, and a check of indicated rpm accuracy comes next
    • C.The spinner is at fault, and its shims and attaching screws come next
    • D.The engine is at fault, and the engine mounts and induction system come next

    Observing the hub and spinner at a moderate rpm separates the two sources: an apparent orbit of the hub means the propeller is the offender, while a hub that rotates in a true plane points back to the engine. The mechanic then checks blade track and the low-pitch blade angle, and if both are correct the propeller is out of balance and must be rebalanced or replaced.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (propeller vibration troubleshooting)Report a problem with this question

21. 21. A new fixed-pitch wood propeller has just been installed. What does its mounting hardware require?

    • A.A torque recheck after every engine run, because the wood shrinks each flight
    • B.A torque recheck after the first flight and again at about the first 25 hours✓ Answer
    • C.No further torque check, since the bolts were torqued dry and safetied on install
    • D.A torque recheck only at the next 100-hour inspection, once the wood has set

    Wood swells and shrinks with moisture and takes a set under clamping load, so the bolts of a newly installed wood propeller lose preload as the hub compresses. The handbook therefore calls for a torque check after the first flight and again after about the first twenty five hours of operation, with the actual torque value taken from the current maintenance data.

    Source: FAA Aviation Maintenance Technician Handbook — Powerplant, Propellers chapter (wood propeller installation)Report a problem with this question

22. 22. Under 14 CFR part 43, appendix A, which of the following is a propeller major repair?

    • A.Dressing out a minor nick in an aluminum blade and repolishing the worked area
    • B.Repairing a propeller governor, or overhauling a controllable-pitch propeller✓ Answer
    • C.Removing and reinstalling a propeller on a flanged shaft and retorquing the nuts
    • D.Checking blade track and resetting a ground-adjustable blade to a listed angle

    Appendix A of part 43 lists repair of propeller governors and overhaul of controllable-pitch propellers among propeller major repairs, along with work such as straightening steel blades, shortening blades and repairing deep damage in aluminum blades. Those items must go to an appropriately rated propeller repair station, while routine work such as dressing minor nicks, checking track and measuring blade angle stays within the privileges of a mechanic with a powerplant rating.

    Source: 14 CFR part 43, appendix A, paragraph (b)(3) — propeller major repairsReport a problem with this question

Practice questions based on the Aviation Mechanic Airman Certification Standards (FAA-S-ACS-1), 14 CFR parts 43, 65, and 91, and the FAA Aviation Maintenance Technician Handbook—Powerplant (FAA-H-8083-32). This site is not affiliated with or endorsed by the Federal Aviation Administration. This bank covers the POWERPLANT written test only; the General and Airframe written tests and the oral and practical tests are separate. Torque values, running clearances, compression limits, magneto timing angles, spark plug gaps, temperature and pressure limits, servicing quantities, and overhaul intervals always come from the manufacturer's current maintenance data, the type certificate data sheet, and the applicable airworthiness directives — never from a practice test. Confirm current eligibility and testing requirements with the FAA before you test. About the A&P mechanic certificate →