Propellers — FAA A&P Test Questions (ACS AM.III.M)
Propellers is the Powerplant subject area where blade geometry meets governor hydraulics. The FAA expects you to define blade angle and geometric pitch precisely, explain why a blade is twisted from shank to tip, and trace what happens inside a constant-speed system when the engine drifts off the selected rpm. Questions run from single-engine constant-speed installations through feathering and reverse thrust, plus the inspection and ground-safety rules that go with a propeller that can turn. This page shows what the area covers, where candidates lose points, and lets you drill the published questions.
Written by the AMTprep editorial team · Published · Last reviewed
Written against the FAA primary sources cited at the foot of this page.
What ACS AM.III.M covers
Propeller questions start with definitions, and the FAA words them tightly. Blade angle is the angle between the blade chord line and the plane of rotation, measured at a stated blade station. Geometric pitch is the theoretical distance the propeller would advance in one revolution with no slip; effective pitch is the distance it actually advances, and slip is the difference. Blades are twisted so the blade angle is greatest near the shank and smallest at the tip, which holds the angle of attack roughly even along a blade whose tip travels far faster than its root. From there the area moves into control. On a typical single-engine constant-speed system, governor-boosted engine oil pressure works against a spring, an air charge and counterweights to set blade angle. The propeller is on-speed when engine rpm matches the rpm the governor is set for and the flyweights balance the speeder spring, so no oil moves to or from the piston; underspeed and overspeed conditions and the pilot valve response are tested directly. Multiengine work adds feathering, driving the blade to roughly 80 to 90 degrees so it stops windmilling and sheds drag after an engine failure, and turboprop work adds reverse, where blades rotate below flat pitch into a negative angle. The rest is maintenance: blade tracking, static balance, torque and safetying, dressing damage within published limits, ice control by electric blade boots or slinger-ring alcohol, and safe handling around a propeller. FAA-H-8083-32 is the reference behind most of these items, and 14 CFR Part 65 sets what a certificated mechanic may and may not do to a propeller.
Where this sits on the test
ACS AM.III.M is tested on the FAA Powerplant written test, one of 1,353 ACS-tagged questions in the Powerplant bank. Every question tagged to this area carries a worked rationale and its FAA handbook reference, so you can drill the code itself rather than the whole test.
FAA handbook references
- FAA-H-8083-32
Three traps candidates fall into
- Geometric pitch gets read as how far the propeller actually moves forward in one revolution. That is effective pitch. Geometric pitch is the theoretical no-slip distance, effective pitch is the real distance, and slip is the gap between them. Reverse the two and every slip question falls apart.
- Because the tip moves fastest, candidates assume the tip carries the largest blade angle. It is the opposite. Blade angle is greatest at the shank and decreases toward the tip, and the twist exists precisely because the fast-moving tip needs a smaller angle to hold a workable angle of attack.
- Centrifugal force is assumed to throw the blades toward high pitch. Centrifugal twisting moment actually rotates a blade toward low pitch, and it is the stronger of the two twisting forces. Aerodynamic twisting force is the one that tries to increase blade angle. Swapping the pair costs points repeatedly.
50 free sample questions from ACS AM.III.M
- AM.III.MTap an answer
On a propeller, the blade angle is best defined as the angle between the
Show the answer and explanation
Answer: blade chord line and the plane of rotation
Why: Blade angle is the angle formed between the chord line of a propeller blade section and the plane of rotation of the propeller. It is a geometric, built-in or set value. This is distinct from the angle of attack, which is measured between the chord line and the relative wind and changes with airspeed and rpm. Defining blade angle relative to the plane of rotation is fundamental to understanding pitch and pitch distribution.· FAA-H-8083-32 — Propellers: blade angle and pitch terminology
- AM.III.MTap an answer
Propeller blades are usually given a twist so that the blade angle is
Show the answer and explanation
Answer: greater near the hub than at the tip
Why: Because a propeller is a rotating airfoil, sections near the tip travel through a much greater distance per revolution and therefore move faster than sections near the hub. To produce a more uniform angle of attack and thrust along the blade, the blade is twisted so the blade angle is highest near the hub (slower-moving root) and decreases toward the tip (faster-moving). This blade twist, called pitch distribution, compensates for the difference in section speeds.· FAA-H-8083-32 — Propellers: blade twist and pitch distribution
- AM.III.MTap an answer
Geometric pitch of a propeller is defined as the
Show the answer and explanation
Answer: distance the propeller would advance in one revolution with no slippage
Why: Geometric pitch is the theoretical distance a propeller would move forward in one revolution if it were advancing through a solid medium with no slippage, based on the blade angle. Effective pitch is the actual distance it advances through the air, which is less because air is not solid. The difference between geometric and effective pitch is propeller slip. Distinguishing these three terms is core propeller theory.· FAA-H-8083-32 — Propellers: geometric pitch, effective pitch, and slip
- AM.III.MTap an answer
In a typical single-engine constant-speed propeller system, engine oil pressure acting on the propeller piston is used to
Show the answer and explanation
Answer: move the blades toward low pitch (high rpm)
Why: In most single-engine constant-speed propellers, governor-boosted engine oil pressure is directed to the propeller piston to drive the blades toward the low blade-angle, high-rpm position. Opposing forces such as counterweights, springs, or nitrogen pressure move the blades toward high pitch when oil pressure is reduced. The governor meters oil to and from the piston to hold the selected rpm. Knowing which direction oil drives the blades is essential for troubleshooting.· FAA-H-8083-32 — Propellers: constant-speed propeller operation
- AM.III.MTap an answer
A propeller is in the on-speed condition when the
Show the answer and explanation
Answer: speeder spring force and governor flyweight force are in balance
Why: In a governor, centrifugal flyweights tend to fly outward with rpm while the speeder spring pushes them inward according to the pilot's rpm setting. When these two forces are balanced, the pilot valve is centered, no oil flows to or from the propeller, and the system is on-speed at the selected rpm. When flyweight force exceeds spring force the system is overspeed, and when spring force exceeds flyweight force it is underspeed. Recognizing these three conditions explains governor response.· FAA-H-8083-32 — Propellers: governor on-speed, overspeed, and underspeed conditions
- AM.III.MTap an answer
Feathering a propeller on a multiengine airplane following an engine failure is done primarily to
Show the answer and explanation
Answer: reduce drag from the windmilling propeller
Why: Feathering rotates the blades to an angle of approximately 90 degrees, edge-on to the airflow, so the propeller stops rotating and presents minimal frontal area. This greatly reduces the drag that a stopped or windmilling propeller would otherwise create on an inoperative engine, improving controllability and performance on the remaining engine. Feathering also protects a damaged engine from further wear, but reducing drag is the primary aerodynamic purpose.· FAA-H-8083-32 — Propellers: feathering and full-feathering propellers
- AM.III.MTap an answer
When a propeller blade is in the feathered position, the blade angle is approximately
Show the answer and explanation
Answer: 90 degrees
Why: In the feathered position the propeller blades are turned to approximately 90 degrees so the blade chord is roughly aligned with the line of flight, presenting the edge of the blade to the airstream. This stops the propeller from windmilling and minimizes drag on a failed engine. A near-zero or flat blade angle would instead create maximum drag, the opposite of the feathering goal. Knowing the feather angle is basic to feathering-system work.· FAA-H-8083-32 — Propellers: feathered blade angle
- AM.III.MTap an answer
During ground operation, reverse thrust from a reversing propeller is produced by moving the blades to
Show the answer and explanation
Answer: a negative blade angle
Why: Reversing propellers are capable of rotating their blades to a negative blade angle, below the normal low-pitch range. At a negative angle the rotating propeller directs airflow forward instead of rearward, producing reverse thrust that helps slow the aircraft during the landing roll. Feathering and the low-pitch stop are normal forward-flight or shutdown positions and do not produce reverse thrust. Understanding negative pitch is key to reversing systems.· FAA-H-8083-32 — Propellers: reversing propeller operation
- AM.III.MTap an answer
Minor surface damage such as a small nick on the leading edge of an aluminum propeller blade is repaired by
Show the answer and explanation
Answer: filing or sanding it out to a smooth radius within limits
Why: Small nicks, gouges, and scratches in aluminum alloy propeller blades are dressed out by carefully filing or sanding the damage into a smooth, rounded depression that blends into the surrounding surface, staying within the manufacturer's allowable repair limits. This removes the stress riser that could otherwise grow into a crack. Welding and doublers are not approved repairs for aluminum propeller blades, which is why dressing out within limits is the standard practice.· FAA-H-8083-32 — Propellers: inspection and repair of aluminum blades
- AM.III.MTap an answer
High-speed propellers are designed primarily to
Show the answer and explanation
Answer: operate efficiently at high forward airspeeds.
Why: High-speed propellers are optimized for high forward airspeeds rather than for high rotational speed. The blade design controls angle of attack and tip speed at cruise velocity so the propeller stays efficient where the aircraft normally operates. Tip speed is deliberately kept subsonic, so supersonic tips are avoided, per FAA-H-8083-32 propeller theory.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
For a fixed-pitch propeller blade section, the most efficient angle of attack at the design cruise condition is approximately
Show the answer and explanation
Answer: 2 to 4 degrees.
Why: A propeller blade section behaves like an airfoil and produces its best lift-to-drag ratio at a small angle of attack of roughly 2 to 4 degrees. The fixed blade angle is chosen so the design cruise condition keeps the angle of attack near this efficient value; much larger angles such as 15 degrees would stall or produce excessive drag, per FAA-H-8083-32 propeller aerodynamics.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
A left-hand propeller is one that
Show the answer and explanation
Answer: rotates clockwise when viewed from the front.
Why: Propeller rotation sense is defined as viewed from the rear, looking forward in the direction of flight. A left-hand propeller turns counterclockwise as seen from the rear, which is the same as turning clockwise when viewed from the front. The side of the aircraft it is installed on does not define handedness, per FAA-H-8083-32 propeller nomenclature.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Compared with the blade angle at the tip, the blade angle at the root of a propeller is
Show the answer and explanation
Answer: greater than the tip angle.
Why: A propeller blade is twisted so the blade angle is greatest at the root and smallest at the tip. This is necessary because the tip moves through the air much faster than the root, so a smaller tip angle keeps the angle of attack roughly constant along the blade. The root angle is therefore greater than the tip angle, per FAA-H-8083-32 propeller blade twist.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Which force acting on a rotating propeller blade tends to rotate the blade toward a finer (lower) pitch angle?
Show the answer and explanation
Answer: Centrifugal twisting moment (CTM).
Why: Centrifugal force acting on the blade mass produces the centrifugal twisting moment (CTM), which always tries to rotate the blade toward fine (lower) pitch. Constant-speed systems must counter this moment. Torque and the aerodynamic twisting moment do not drive the blade toward fine pitch in normal operation, per FAA-H-8083-32 propeller pitch-change forces.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The purpose of propeller blade twist is to
Show the answer and explanation
Answer: maintain a nearly constant angle of attack along the length of the blade.
Why: Because the rotational speed of a blade section increases with radius, the resultant airflow angle changes from root to tip. Twisting the blade so the blade angle decreases toward the tip keeps the angle of attack roughly constant along the span, giving efficient, even aerodynamic loading rather than a single uniform blade angle, per FAA-H-8083-32 propeller blade twist.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Blade angle is measured between the blade chord line and the
Show the answer and explanation
Answer: plane of rotation.
Why: Blade angle is the angle measured between the blade chord line and the propeller's plane of rotation. It is a purely geometric measurement of how the blade is set in the hub and does not involve the relative airflow, which instead defines angle of attack and the helix angle, per FAA-H-8083-32 propeller geometry.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
When moving a propeller blade from reverse pitch back to normal operating pitch, the blade angle
Show the answer and explanation
Answer: passes through the fine-pitch range.
Why: Reverse pitch is a negative blade angle, while normal operating pitch is positive. To return from reverse to a normal positive setting, the blade angle must increase through zero, passing through the fine (low positive) range first. It does not pass through coarse pitch on the way back to normal, per FAA-H-8083-32 reversing-propeller operation.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
While a constant-speed propeller is operating in reverse pitch, the centrifugal twisting moment (CTM) tends to move the blades toward
Show the answer and explanation
Answer: a positive pitch angle.
Why: Centrifugal twisting moment acts to rotate each blade into the plane of rotation, that is, toward a zero blade angle. In normal positive pitch this means toward fine (low) pitch. In reverse, where the blade angle is negative, the same moment drives the blade in the positive-pitch direction (toward zero), not further negative. The effect depends on blade mass distribution, not on engine rpm setting.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
If the blade angle of a propeller is increased, the
Show the answer and explanation
Answer: pitch becomes coarser.
Why: Pitch describes how far the propeller would advance per revolution, which depends directly on blade angle. Increasing the blade angle increases this advance, so the pitch becomes coarser. Decreasing the blade angle makes the pitch finer; blade angle has no direct effect on the aircraft's lateral stability, per FAA-H-8083-32 propeller pitch fundamentals.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The net useful aerodynamic forces produced by a rotating propeller are conventionally described as
Show the answer and explanation
Answer: thrust and torque.
Why: As a propeller blade moves through the air it generates an aerodynamic resultant that resolves into thrust, acting forward along the flight axis, and torque, the rotational resistance the engine must overcome. While each blade section produces lift and drag, the propeller's net useful forces are conventionally described as thrust and torque, per FAA-H-8083-32 propeller theory.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
A propeller produces thrust most efficiently at low aircraft speeds by
Show the answer and explanation
Answer: accelerating a large mass of air to a low velocity.
Why: A propeller produces thrust by accelerating a large mass of air rearward by a relatively small amount, giving a low velocity change. Moving a large mass at low velocity is more efficient at low aircraft speeds than giving a small mass a high velocity, which is the turbojet approach rather than the propeller approach, per FAA-H-8083-32 propeller propulsion theory.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Propeller efficiency is defined as the ratio of
Show the answer and explanation
Answer: useful work done by the propeller to the work the engine does on the propeller.
Why: Propeller efficiency compares output with input: it is the useful propulsive work delivered (thrust times forward speed) divided by the shaft work the engine puts into the propeller. The remainder is lost mainly to drag and slipstream rotation, so the ratio is always less than one, per FAA-H-8083-32 propeller performance.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Geometric pitch is the theoretical distance a propeller advances in one revolution
Show the answer and explanation
Answer: with no slippage through the air.
Why: Geometric pitch is the distance the propeller would move forward in one revolution if it advanced through the air with no slippage, like a screw through a solid. Because the air yields, the actual advance (effective pitch) is less; the difference is propeller slip.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The angle between the resultant relative airflow and the propeller blade's plane of rotation is called the
Show the answer and explanation
Answer: helix angle, or angle of advance.
Why: The resultant relative airflow combines the rotational and forward velocity components, and the angle between this resultant and the plane of rotation is the helix or advance angle. Blade angle is measured from the chord to the plane of rotation, and angle of attack is between the chord and the resultant airflow.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
A high (coarse) blade angle is best suited for
Show the answer and explanation
Answer: maximum economical cruise in level flight.
Why: A high (coarse) blade angle suits high forward speeds, so it is used for economical cruise in level flight, keeping the blade angle of attack efficient as the aircraft moves quickly. A low (fine) blade angle is selected for takeoff and climb, where a smaller angle allows high rpm and thrust at low airspeed.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Effective pitch is best described as the
Show the answer and explanation
Answer: actual distance the aircraft advances in one revolution.
Why: Effective pitch is the actual distance the aircraft advances in one propeller revolution. It is less than geometric pitch because the air slips; effective pitch equals geometric pitch minus slip, not plus slip.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
A windmilling propeller operates with
Show the answer and explanation
Answer: a small negative angle of attack.
Why: When a propeller windmills, the engine no longer drives it; instead the airflow turns it. The relative airflow strikes the blade from the front face, producing a small negative angle of attack so the blade generates drag rather than thrust, which keeps the propeller rotating.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
A windmilling propeller on a failed engine causes
Show the answer and explanation
Answer: maximum propeller drag.
Why: A windmilling propeller is driven by the airflow at a negative angle of attack, so it produces large rearward drag instead of thrust. In the fine-pitch windmilling state this drag is greatest, which is why the propeller on a failed engine is feathered to remove the drag.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The reaction produced by propeller torque acts
Show the answer and explanation
Answer: opposite to the direction of rotation.
Why: Propeller torque is the resistance to being turned through the air, so the reaction it produces acts opposite to the direction of rotation, and the engine must supply a turning moment to overcome it. Thrust, by contrast, acts along the shaft axis at right angles to the plane of rotation.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The purpose of propeller blade twist (the change in blade angle from root to tip) is to
Show the answer and explanation
Answer: even out the thrust distribution across the blade.
Why: Because section speed increases with radius, an untwisted blade would have a varying angle of attack and uneven loading. Twisting the blade keeps the angle of attack and lift roughly uniform along the span, evening out the thrust distribution. Limiting tip Mach number is achieved by tip section design, not by twist.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The greatest thrust along a propeller blade is produced at approximately
Show the answer and explanation
Answer: 70 to 80 percent of the blade length from the hub.
Why: Thrust is not uniform along the blade. Near the root the section speed and angle are inefficient, and right at the tip losses and reduced section size cut output. The most effective part of the blade, producing the greatest thrust, lies at roughly 70 to 80 percent of the blade length from the hub.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The centrifugal twisting moment (CTM) tends to rotate a propeller blade
Show the answer and explanation
Answer: about its pitch-change (twisting) axis toward low pitch.
Why: The centrifugal twisting moment acts to rotate the blade about its own pitch-change (twisting) axis, driving it toward low (fine) pitch. It is a pitch-changing effect, not a forward-bending one, and it works against the feather position rather than toward it.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Compared with the surrounding ambient air, the velocity of the slipstream behind the propeller is
Show the answer and explanation
Answer: greater than the ambient air velocity.
Why: The propeller adds energy to the air it passes, accelerating it rearward, so the slipstream behind the propeller moves faster than the surrounding ambient air. This increase in velocity is the reaction that produces forward thrust.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Thin, high-speed airfoil sections are used on a propeller blade at the
Show the answer and explanation
Answer: blade tips.
Why: The blade tips travel through the air far faster than the root because of their larger radius, approaching high subsonic speeds. To keep drag low and delay compressibility effects, thin high-speed airfoil sections are used at the tips, while thicker sections are used at the slower root.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
A right-hand propeller is one that
Show the answer and explanation
Answer: rotates clockwise when viewed from the rear.
Why: By convention, propeller rotation is described as viewed from behind the engine, looking forward. A right-hand propeller turns clockwise when viewed from the rear. Handedness is defined by rotation sense, not by which engine it is installed on.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Because of blade twist, the blade angle measured near the hub (root) is the
Show the answer and explanation
Answer: highest along the blade.
Why: Owing to blade twist, the blade angle is greatest near the hub or root and decreases toward the tip. The large angle at the root compensates for the low rotational speed there, keeping the angle of attack efficient. So the blade angle at the hub is the highest along the blade.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
A windmilling propeller creates the most drag when it is set to
Show the answer and explanation
Answer: low (fine) pitch.
Why: A windmilling propeller produces the most drag in low (fine) pitch, where the broad blade faces present a large obstruction and high negative angle of attack to the airflow. High (coarse) pitch reduces this, and feathering aligns the blades edge-on for minimum drag, which is why a failed engine is feathered.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The plane of rotation of a propeller is
Show the answer and explanation
Answer: the plane in which the propeller rotates.
Why: The plane of rotation is the plane swept by the rotating propeller, perpendicular to the propeller shaft, and blade angle is measured from the chord to this plane. Thrust acts along the shaft axis, and the angle at which the blade meets the airflow is the angle of attack.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The thrust bending force acting on a rotating propeller blade tends to
Show the answer and explanation
Answer: bend the blade forward at the tip.
Why: Thrust acts forward along the blade and is concentrated toward the outer span, so it tends to bend the blade forward, deflecting the tips ahead of the hub. Centrifugal force largely opposes this by pulling the blade straight, but the thrust bending force itself acts to bow the blade forward at the tip.· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
What conditions exist at a propeller blade that is windmilling?
Show the answer and explanation
Answer: Negative angle of attack, negative thrust.
Why: When a propeller windmills, the engine is no longer driving it; instead airflow rotates the propeller. The relative wind meets the blade from the front, producing a negative angle of attack, and the resulting aerodynamic force acts rearward as drag, so thrust is negative. Both the angle of attack and the thrust are therefore negative (FAA-H-8083-32, Propellers).· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The primary purpose of a propeller is to
Show the answer and explanation
Answer: convert engine horsepower into thrust.
Why: The propeller converts the shaft horsepower delivered by the engine into propulsive thrust by accelerating a mass of air rearward. It does not generate wing lift or provide aircraft stability, so its primary purpose is converting engine power into thrust (FAA-H-8083-32, Propellers).· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The primary purpose of a feathering propeller is to
Show the answer and explanation
Answer: eliminate the drag created by a windmilling propeller when an engine fails in flight.
Why: Feathering rotates the blades nearly edge-on to the airflow so a stopped propeller offers minimum drag after an engine fails. This eliminates the large drag and yaw a windmilling propeller would create, improving control and performance. Protecting the engine or propeller from damage is a secondary benefit, not the primary purpose (FAA-H-8083-32, Propellers).· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
A fiberglass composite propeller blade
Show the answer and explanation
Answer: requires lightning-strike protection.
Why: Fiberglass composite is non-conductive, so a composite blade cannot safely carry a lightning strike on its own and can be struck. To conduct the discharge away and prevent damage, such blades incorporate lightning-strike protection such as a metallic mesh or strips, so this protection is required (FAA-H-8083-32, Propellers).· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
The wood most commonly used today for wooden propeller construction is
Show the answer and explanation
Answer: birch.
Why: Wooden propellers are built from laminated hardwood, and birch is the wood most commonly used because of its strength, fine grain, and good gluing properties. Lighter woods such as spruce, and especially balsa, lack the strength and durability needed for the highly stressed propeller blade (FAA-H-8083-32, Propellers).· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Electronic torque-measuring systems on turbine engines typically use
Show the answer and explanation
Answer: strain gauges in the reduction gear.
Why: Electronic torque-measuring systems sense the slight deflection of a shaft or reduction-gear component under load using strain gauges, whose electrical resistance changes with strain and is converted into a torque reading. Strain, not stress, is the measured quantity, and the gauges are bonded to the structure rather than relying on pressure transducers (FAA-H-8083-32, Propellers).· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
A conventional turboprop hydromechanical torquemeter uses
Show the answer and explanation
Answer: engine oil as the pressure medium.
Why: A conventional turboprop torquemeter is hydromechanical: gear loads displace a piston whose movement is opposed by engine oil pressure, and that oil pressure becomes a measure of torque. It uses the engine's own oil as the pressure medium rather than a separate hydraulic supply or spring levers (FAA-H-8083-32, Propellers).· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Metal sheathing at the tip and along the leading edge of a wooden propeller is provided for
Show the answer and explanation
Answer: protection against erosion and impact.
Why: A wooden propeller is vulnerable to erosion and impact damage, especially along the leading edge and tip. A metal sheath fitted there protects the wood from stones, water, and abrasion. Its purpose is protection, not balancing or anti-icing, which are accomplished by other means (FAA-H-8083-32, Propellers).· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Blade cuffs fitted to the roots of propeller blades are used to
Show the answer and explanation
Answer: increase the flow of cooling air into the engine nacelle.
Why: Blade cuffs are airfoil-shaped fairings fitted around the otherwise round, aerodynamically inactive blade roots. By giving the root region some airfoil action, they draw additional air rearward, increasing cooling airflow into the cowling or nacelle. Their main role is cooling airflow, not added structural strength or significant extra thrust (FAA-H-8083-32, Propellers).· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
Low-torque sensing on a turboprop is used to
Show the answer and explanation
Answer: initiate autofeather.
Why: Engine torque falls sharply when an engine fails. A low-torque sensing system detects this drop and uses it to trigger the autofeather sequence, which feathers the propeller automatically to minimize drag. It is a protective sensing function, not a means of increasing power or directly commanding pitch (FAA-H-8083-32, Propellers).· FAA-H-8083-32 — Propellers
- AM.III.MTap an answer
On a turboprop, torque sensing is used to
Show the answer and explanation
Answer: reduce drag following an engine shutdown.
Why: Torque sensing supports the autofeather system: when sensed torque collapses after an engine shuts down, the system feathers the propeller so its blades go edge-on to the airflow. This reduces the large windmilling drag that would otherwise follow shutdown, aiding control and performance, rather than synchronizing blade angles (FAA-H-8083-32, Propellers).· FAA-H-8083-32 — Propellers
That is a free sample of the 252 questions tagged to ACS AM.III.M. A free account adds three practice sessions a day and one timed exam-simulator attempt; the full bank, the adaptive engine that serves you more of whatever you keep missing, and unlimited exam simulations come with the Complete plan.
Failed AM.III.M on your AKTR?
Enter the ACS codes from your FAA fail report and get a targeted study plan — the exact areas the examiner must re-test you on, with the handbook references for each.
Build my remediation planRelated subject areas
The areas that share the most ground with AM.III.M — study them alongside it.
- Reciprocating Engines (AM.III.A)
- Turbine Engines (AM.III.B)
- Physics for Aviation (AM.I.J)
Frequently asked questions
- What is the blade angle of a feathered propeller?
- Feathering drives the blades to roughly 80 to 90 degrees, close to parallel with the oncoming air. At that angle the blade produces almost no lift, the propeller stops windmilling, and the drag of the dead engine drops sharply. That drag reduction, not engine protection, is the reason the FAA gives for feathering a propeller after an engine failure on a multiengine airplane.
- What is the difference between blade angle and pitch?
- Blade angle is a physical measurement: the angle between the blade chord line and the plane of rotation at a given blade station. Pitch describes travel per revolution. Geometric pitch is the distance the propeller would advance in one turn if it did not slip, and effective pitch is the distance it really advances. Blade angle sets pitch, but the two are not the same number.
- How does a constant-speed propeller governor hold rpm?
- Engine-driven flyweights are balanced against a speeder spring that the propeller control loads. On-speed, flyweights and spring balance, the pilot valve sits neutral and blade angle holds. If rpm drops, the flyweights tilt inward and the valve ports oil to reduce blade angle; if rpm rises, they tilt outward and blade angle increases until rpm returns to the selected value.
- Are propellers on the Airframe or Powerplant written test?
- Propellers sit in the Powerplant section of the Mechanic ACS as subject area AM.III.M, so propeller questions appear on the Powerplant written test rather than the Airframe test. Blade geometry, governor operation, feathering, reverse and propeller inspection all come from that area, and the supporting public-domain reading is the powerplant handbook, FAA-H-8083-32.
- Can an A&P mechanic repair a nicked propeller blade?
- Small nicks and scratches can often be dressed out, but only within the limits the propeller manufacturer publishes: depth, location and permitted material removal are all specified, and blending must leave no sharp edges. Major repairs are different. 14 CFR Part 65 bars a certificated mechanic from performing major repairs or major alterations to propellers, so retipping or straightening a bent blade goes to a propeller repair station.
All 40 ACS areas
General
- Fundamentals of Electricity and Electronics
- Aircraft Drawings
- Weight and Balance
- Fluid Lines and Fittings
- Aircraft Materials, Hardware, and Processes
- Ground Operations and Servicing
- Cleaning and Corrosion Control
- Mathematics
- Regulations, Maintenance Forms, Records, and Publications
- Physics for Aviation
- Inspection Concepts and Techniques
- Human Factors
Airframe
- Metallic Structures
- Non-Metallic Structures
- Flight Controls
- Airframe Inspection
- Landing Gear Systems
- Hydraulic and Pneumatic Systems
- Environmental Systems
- Aircraft Instrument Systems
- Communications, Light Signals, and Runway Lighting Systems
- Aircraft Fuel Systems
- Aircraft Electrical Systems
- Ice and Rain Control Systems
- Airframe Fire Protection Systems
- Rotorcraft Fundamentals
- Water and Waste Systems
Powerplant
- Reciprocating Engines
- Turbine Engines
- Engine Inspection
- Engine Instrument Systems
- Engine Fire Protection Systems
- Engine Electrical Systems
- Engine Lubrication Systems
- Ignition and Starting Systems
- Engine Fuel and Fuel Metering Systems
- Reciprocating Engine Induction and Cooling Systems
- Turbine Engine Air Systems
- Engine Exhaust and Reverser Systems
- Propellers
Primary sources
Drill ACS AM.III.M inside the full Powerplant bank
Adaptive engine, timed exam simulator, ACS-code remediation, and oral prep — everything you need to pass.