FAA Powerplant Written Test Questions
The Aviation Mechanic Powerplant test (FAA test code AMP) is 100 multiple-choice questions in two hours, with a 70 percent pass mark. It covers thirteen ACS subject areas across reciprocating engines, turbine engines, and the systems that feed, ignite, lubricate, instrument and protect them. This page covers what each area asks, how the test is scored, where candidates lose points, and free practice questions with worked rationales.
Written by the AMTprep editorial team · Published · Last reviewed
Written against the FAA primary sources cited at the foot of this page.
- FAA test code
- AMP
- Questions
- 100
- Time limit
- 2 hours
- Pass mark
- 70%
- Results valid
- 24 months
What is on the Powerplant written test
The Powerplant test draws from the thirteen subject areas in Section III of the FAA Aviation Mechanic Airman Certification Standards, and they organise naturally around two engine families and the systems common to both.
The two large anchor areas are reciprocating engines and turbine engines. Between them they carry more of the test than any other pair. Reciprocating covers cylinder and valve arrangement, firing order, compression, timing, overhaul limits and troubleshooting from symptoms. Turbine covers the gas path in order — inlet, compressor, combustor, turbine, exhaust — plus compressor types, combustor designs, bypass ratio, free versus fixed turbines, and starting malfunctions such as hot, hung and false starts.
The systems areas surround them: engine fuel and fuel metering, ignition and starting, engine lubrication, engine electrical, engine instrument systems, engine fire protection, reciprocating engine induction and cooling, turbine engine air systems, and engine exhaust and reverser systems. Propellers is its own area and covers constant-speed operation, governors, feathering, blade stations and angles.
Engine inspection completes the set and is as much regulatory as mechanical: what a 100-hour engine inspection requires, compression testing, and how findings get recorded and approved for return to service.
The reference text is the Aviation Maintenance Technician Handbook — Powerplant, FAA-H-8083-32B (2023), a single-volume handbook free from the FAA.
How the test is administered and scored
Computer-based at a PSI testing center, 100 questions, two hours, three answer choices per question, 70 percent to pass. Mechanically it is identical to the Airframe test; what differs is the shape of the material.
Powerplant rewards depth over breadth. Thirteen areas across 100 questions is fewer headings than Airframe's fifteen, and two of those headings account for a large share of the questions. A candidate who genuinely understands both engine cycles — what each section does to the air or charge passing through it — can reason out a substantial number of questions rather than recalling them. That is the opposite of the Airframe test, where unrecalled tolerances are simply lost.
You receive the Airman Knowledge Test Report before leaving, valid 24 calendar months, with an ACS code against every miss. The Designated Mechanic Examiner must re-examine you on each area named, and Powerplant fail reports have a habit of clustering: a candidate weak on the turbine gas path tends to miss questions across turbine engines, turbine air systems, and exhaust and reversers, which turns into a long and uncomfortable stretch of the oral.
Seventy percent means you can miss 30. In practice, candidates who fail the Powerplant test are usually strong on one engine family and hollow on the other.
Where candidates lose points on the Powerplant
The dominant failure pattern is a lopsided background. General aviation piston mechanics arrive fluent on reciprocating engines and thin on turbines; airline and corporate technicians arrive with the mirror image. The test does not care which half you know. Whichever engine family you touch less at work is the one to over-study, and candidates consistently underestimate how far behind they are on it.
Second is the turbine gas path learned as a list of names rather than a sequence of functions. If you know that the compressor raises pressure, the combustor adds heat at roughly constant pressure, and the turbine extracts work to drive the compressor, a large family of questions answers itself. Candidates who memorised section names in order but not what each section does to the airflow have nothing to fall back on when the stem is phrased unusually.
Third is propeller theory. Constant-speed operation, governor action and the relationship between blade angle and RPM are conceptually slippery, and the area is often skipped in favour of the bigger engine headings. It is a discrete, learnable body of material and skipping it concedes real points.
Fourth is fuel metering. Carburettor and fuel-injection questions, mixture control, and the effect of altitude on mixture generate reliable misses because candidates learn the hardware without learning why the mixture has to change.
How to study for it
Split your time by engine family first and by subject area second. Take a diagnostic run across all thirteen areas, then look at the reciprocating and turbine scores as two separate numbers. If they differ by more than about ten points, the low one gets the majority of your study time until they converge — that gap is the single best predictor of a Powerplant failure.
Learn each engine as a path rather than a parts list. For a turbine, trace what happens to a parcel of air from inlet to exhaust nozzle and say what each section did to its pressure, temperature and velocity. For a reciprocating engine, walk the four strokes and then the induction, fuel, ignition, lubrication and cooling systems as things that serve those strokes. Questions phrased in unfamiliar language become tractable once the underlying sequence is solid.
Keep a symptoms sheet. A recognisable share of Powerplant questions is diagnostic: given this indication, what is the likely cause. Hot start, hung start, false start, high oil temperature with normal pressure, a magneto drop outside limits, a cylinder failing a compression check — collect these as symptom-to-cause pairs and review them together, because that is how the test presents them.
Read the rationale on every miss and return to FAA-H-8083-32B whenever one cites material you do not recognise. Work by ACS area so your practice scores are denominated in the same codes your AKTR will be.
What to bring on test day
A government-issued photo ID carrying your name, date of birth, signature, and a physical residential address; bring a second document if the first is missing any of those elements.
Confirm PSI's current calculator and personal-item rules when you book. Scratch material and something to write with are supplied at the center. Phones, watches, notes and reference material stay outside the room.
Use the scratch paper deliberately on this test. Sketching the gas path or the four strokes takes twenty seconds at the start and pays for itself several times over across a two-hour sitting, because a large number of Powerplant questions are answerable by pointing at the right place on that sketch. Work a fast first pass, flag anything requiring thought, then return to the flagged set. Answer every question — an unanswered one scores the same as a wrong one.
The AKTR is issued before you leave. If you passed, the ACS codes on it still matter, because they set the agenda for part of your oral. If you failed, they are your study list and §65.19 governs your retest.
The ACS subject areas this test draws from
Every question on the Powerplant test is tagged to one of these subject areas, and so is every code that appears on your Airman Knowledge Test Report. Each page below explains what that area covers, its FAA handbook reference, the traps candidates fall into, and free practice questions drawn from the same bank.
- Reciprocating Engines (AM.III.A)
- Turbine Engines (AM.III.B)
- Engine Inspection (AM.III.C)
- Engine Instrument Systems (AM.III.D)
- Engine Fire Protection Systems (AM.III.E)
- Engine Electrical Systems (AM.III.F)
- Engine Lubrication Systems (AM.III.G)
- Ignition and Starting Systems (AM.III.H)
- Engine Fuel and Fuel Metering Systems (AM.III.I)
- Reciprocating Engine Induction and Cooling Systems (AM.III.J)
- Turbine Engine Air Systems (AM.III.K)
- Engine Exhaust and Reverser Systems (AM.III.L)
- Propellers (AM.III.M)
40 free Powerplant practice questions
Tap an answer to reveal the correct choice and its worked rationale. Every question carries its ACS code and FAA handbook reference, so a miss tells you exactly which subject area to go and read.
- AM.III.ATap an answer
In a four-stroke-cycle reciprocating engine, how many times does the crankshaft rotate to complete one full cycle of operation in a single cylinder?
Show the answer and explanation
Answer: Two complete revolutions (720 degrees).
Why: The four-stroke Otto cycle consists of the intake, compression, power, and exhaust strokes. Each stroke moves the piston the length of the cylinder, which corresponds to one-half crankshaft revolution. Four strokes therefore require two full crankshaft revolutions, or 720 degrees, to complete one cycle in a given cylinder.· FAA-H-8083-32 — Reciprocating Engines, four-stroke (Otto) cycle
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In a gas turbine engine, which section is responsible for raising the pressure of the incoming air before it reaches the combustion section?
Show the answer and explanation
Answer: The compressor section
Why: In a gas turbine engine the compressor section draws in air and increases its pressure, delivering high-pressure air to the combustion section where fuel is added and burned. The turbine section extracts energy from the expanding gases to drive the compressor, and the exhaust section directs spent gases overboard. Only the compressor raises the pressure of the incoming air, which is why it is sometimes described as the heart of the engine's airflow path.· FAA-H-8083-32 — Turbine Engines: compressor section
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While performing a differential compression test, air is heard escaping from the engine exhaust outlet. This indicates a leaking
Show the answer and explanation
Answer: exhaust valve
Why: Air heard at the exhaust outlet means it is leaking past the exhaust valve. Air at the carburetor/intake indicates an intake valve leak, and air at the crankcase breather indicates worn or broken piston rings. Listening for the escape point localizes the leak during inspection.· FAA-H-8083-32 — Cylinder leakage diagnosis during compression testing
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A thermocouple-type cylinder head temperature (CHT) indicating system generates a voltage based on what principle?
Show the answer and explanation
Answer: The temperature difference between two junctions of dissimilar metals
Why: A thermocouple consists of two wires of dissimilar metals (commonly iron and constantan, or chromel and alumel) joined at a hot junction. When the hot junction is heated relative to the cold (reference) junction, a small voltage proportional to the temperature difference is produced. The handbook explains that CHT thermocouple systems rely on this thermoelectric (Seebeck) effect, not on resistance change (which describes a resistance bulb) or liquid expansion (which describes a vapor/liquid bourdon system).· FAA-H-8083-32 — Engine Instrument Systems (temperature indicating / thermocouples)
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A complete engine fire protection system on a turbine-powered aircraft consists of which two basic subsystems?
Show the answer and explanation
Answer: A fire detection system and a fire extinguishing system
Why: A fire protection system is divided into two functional parts: a detection system that warns the crew of a fire or overheat condition, and an extinguishing system that delivers an agent to put the fire out. The other choices name individual components but not the two-part division of the overall protection system.· FAA-H-8083-32 — Engine Fire Protection Systems (overview)
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In a high-tension magneto ignition system, the primary winding circuit current is interrupted by the action of the:
Show the answer and explanation
Answer: breaker points opening
Why: In a high-tension magneto, primary current flows while the breaker (contact) points are closed, building a magnetic field. When the points open, the primary circuit is interrupted, the field collapses rapidly, and the changing flux induces the high voltage in the secondary winding that fires the plug. The distributor only routes the high voltage to the correct cylinder; the secondary does not interrupt primary current.· FAA-H-8083-32 — Ignition Systems (high-tension magneto, breaker points)
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What is the primary purpose of the oil system in a reciprocating aircraft engine?
Show the answer and explanation
Answer: To reduce friction between moving parts by lubricating bearing surfaces
Why: The handbook lists several functions of engine oil, but the principal one is lubrication—forming an oil film between moving parts to reduce friction and wear. Oil also cools, cleans, seals, and cushions, but lubrication is the primary purpose. Oil does not raise combustion temperature and is not the source of landing-gear hydraulic power.· FAA-H-8083-32 — Lubricating System / Purpose of Engine Oil
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In a reciprocating engine magneto ignition system, what is the primary function of the breaker points?
Show the answer and explanation
Answer: To interrupt current flow in the primary coil and induce high voltage
Why: The breaker points are in series with the primary winding. When they open, they interrupt the primary current; the collapsing magnetic field induces a high voltage in the secondary winding that fires the spark plug. Distribution is the distributor's job, and a magneto produces AC by rotation rather than rectifying it.· FAA-H-8083-32 — Ignition Systems (magneto operating principles)
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What is the primary purpose of the idle cutoff (ICO) position on the mixture control of a float-type carburetor?
Show the answer and explanation
Answer: To shut off fuel flow to the engine for normal shutdown
Why: Stopping a reciprocating engine by moving the mixture to idle cutoff cuts off fuel flow entirely, clearing the cylinders and induction system of fuel and reducing the chance of an inadvertent start (kickback). The handbook recommends idle cutoff over closing the throttle because the cylinders are left free of raw fuel, preventing fouling and fire hazards. ICO does not enrich the mixture (that is the full-rich position) and has no effect on venturi airflow.· FAA-H-8083-32 — Fuel Metering Systems (float carburetor mixture control / idle cutoff)
- AM.III.JTap an answer
What is the primary purpose of the carburetor heat system on a reciprocating engine induction system?
Show the answer and explanation
Answer: To prevent or eliminate ice forming in the carburetor venturi and throttle area
Why: Carburetor heat routes air that has been warmed by passing over an exhaust-heated muff into the carburetor. The fuel pressure drop and vaporization at the venturi cool the air and can drop it below freezing even on warm days, forming ice that restricts airflow. Heated air melts existing ice and prevents its formation. Because warm air is less dense, applying carb heat actually reduces power output, so it is not used to increase power.· FAA-H-8083-32 — Induction Systems / Carburetor Icing and Heat
- AM.III.KTap an answer
In a typical gas turbine engine, approximately what percentage of the total airflow through the engine is used as primary air for combustion?
Show the answer and explanation
Answer: 25 percent
Why: Only about 25 percent of the compressor discharge air is used as primary air to support combustion at the desired fuel-air ratio. The remaining 75 percent is secondary air, used to cool the liner and dilute the hot gases before they reach the turbine. This is why the overall engine air-fuel ratio is far leaner than the ideal 15:1 burning ratio.· FAA-H-8083-32 — Combustion Section / Engine Air Systems (primary vs. secondary air)
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Why is carbon monoxide contamination of cabin air a concern with exhaust-shroud heating systems?
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Answer: A crack in the exhaust can allow gases to enter the heated cabin air
Why: Because the cabin air is heated by passing through a shroud in direct contact with the hot exhaust, a crack or leak in the muffler or stack lets exhaust gas, which contains carbon monoxide, mix into the air being ducted to the cabin. This is why exhaust integrity is critical on shroud-heated aircraft. Carbon monoxide is a product of combustion in the engine, not created by the heat valve position or by the shroud altering oxygen.· FAA-H-8083-32 — Exhaust system inspection / CO hazard
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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
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What is the correct order of the four strokes in the Otto-cycle reciprocating engine?
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Answer: Intake, compression, power, exhaust.
Why: The Otto cycle proceeds in a fixed sequence: the intake stroke draws in the fuel/air charge, the compression stroke compresses it, the power stroke delivers usable work after ignition, and the exhaust stroke expels the burned gases. This intake-compression-power-exhaust order is fundamental to four-stroke engine operation.· FAA-H-8083-32 — Reciprocating Engines, operating principles
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Which type of compressor uses a series of rotating and stationary blade rows to compress air in stages along the engine axis?
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Answer: Axial-flow compressor
Why: An axial-flow compressor moves air parallel to the engine's axis through alternating rows of rotating blades (rotors) and stationary blades (stators), with each rotor-stator pair forming a stage that adds a small pressure rise. A centrifugal compressor instead slings air radially outward with an impeller. Reverse-flow describes a combustor arrangement, not a compressor type.· FAA-H-8083-32 — Turbine Engines: compressor types
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Local heat discoloration and small cracks found on turbine engine combustion liners and nozzle vanes are generally the result of
Show the answer and explanation
Answer: high operating temperatures and thermal stress
Why: Combustion liners and turbine nozzle vanes operate in the hottest gas path. Repeated heating and cooling produces thermal stress that leads to localized discoloration, warping, and cracking. FOD typically dents or nicks compressor blades, and fuel-borne moisture is not the usual cause of hot-section cracking.· FAA-H-8083-32 — Turbine hot-section inspection
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A typical engine oil pressure gauge of the bourdon-tube type indicates pressure by which mechanical action?
Show the answer and explanation
Answer: A curved tube tends to straighten as internal pressure increases
Why: A bourdon-tube gauge uses a sealed, curved metal tube that tends to straighten when pressurized internally; this motion is transmitted through a gear-and-sector mechanism to the pointer. The handbook describes the bourdon tube as the classic mechanical pressure-sensing element. A diaphragm/resistor describes an electrical transmitter, and a bimetallic strip is a temperature-sensing device, not a pressure element.· FAA-H-8083-32 — Engine Instrument Systems (pressure indicating / bourdon tube)
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Which type of fire detector senses fire by responding to the rate at which a monitored area's temperature increases?
Show the answer and explanation
Answer: Rate-of-rise (thermal switch) detector
Why: A rate-of-rise detector uses thermocouples or bimetallic elements arranged so that a rapid temperature increase, faster than normal engine warm-up, triggers the warning. Optical detectors sense radiant energy, and CO detectors sense a gas, not a rate of temperature change.· FAA-H-8083-32 — Fire Detection Systems (thermal switch / rate-of-rise)
- AM.III.FTap an answer
What is the function of the capacitor (condenser) connected across the breaker points in a magneto?
Show the answer and explanation
Answer: Reduce arcing at the points and speed collapse of the primary field
Why: The capacitor is connected in parallel with the breaker points. As the points open, the capacitor momentarily absorbs the primary current, which minimizes arcing and pitting of the points and causes the primary magnetic field to collapse more rapidly. A faster field collapse produces a higher induced secondary voltage. It does not increase primary current or directly step up secondary voltage by transformer action.· FAA-H-8083-32 — Ignition Systems (magneto capacitor/condenser)
- AM.III.GTap an answer
Besides lubrication, which additional function does engine oil perform in a reciprocating engine?
Show the answer and explanation
Answer: It carries heat away from internal engine parts
Why: In addition to reducing friction, oil cools the engine by absorbing heat from pistons, bearings, and other internal parts and transferring it to the oil cooler. Oil also seals, cleans, and cushions, but it has no role in fuel delivery to the carburetor or in producing ignition spark.· FAA-H-8083-32 — Functions of Engine Oil (cooling, sealing, cleaning)
- AM.III.HTap an answer
What is the purpose of the capacitor (condenser) connected across the breaker points in a magneto?
Show the answer and explanation
Answer: To absorb the primary current surge and reduce arcing at the points
Why: The capacitor is wired in parallel with the breaker points. As the points open it momentarily accepts the primary current, speeding the collapse of the magnetic field and minimizing arcing that would otherwise burn the contact surfaces. Voltage step-up is done by the secondary winding, not the capacitor.· FAA-H-8083-32 — Ignition Systems (magneto components)
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In a float-type carburetor, the venturi is used primarily to
Show the answer and explanation
Answer: create a pressure drop that draws fuel from the discharge nozzle
Why: As air accelerates through the restricted throat of the venturi, its velocity increases and its static pressure decreases (Bernoulli's principle). This low pressure at the venturi throat, compared to the higher pressure acting on the fuel in the bowl, draws fuel out of the discharge nozzle. The venturi does not itself vaporize fuel or control float level; the float and needle valve maintain bowl level.· FAA-H-8083-32 — Fuel Metering Systems (venturi principle / float carburetor)
- AM.III.JTap an answer
When carburetor heat is applied on an engine running with no carburetor ice present, what is the normal effect on engine RPM?
Show the answer and explanation
Answer: RPM decreases because the warmer, less dense air reduces power
Why: Heated induction air is less dense than ambient air, so the engine takes in less mass of air per cycle, enriching the mixture and reducing power. With no ice present, the result is a drop in RPM. If ice had been present, RPM would first drop, then rise as the ice melted and airflow was restored, which is how a mechanic confirms icing.· FAA-H-8083-32 — Induction Systems / Carburetor Heat Operation
- AM.III.KTap an answer
Secondary air passing through and around the combustion liner cools the combustion gases to approximately what temperature before they enter the turbine?
Show the answer and explanation
Answer: 1,500 °F
Why: Combustion can produce flame temperatures near 3,500 °F, which would destroy the turbine. Secondary (cooling) air dilutes and films the gases, reducing turbine inlet temperature to roughly 1,500 °F so the turbine nozzle and blades survive. The 3,500 °F figure is the undiluted combustion temperature, not the turbine inlet temperature.· FAA-H-8083-32 — Combustion Section (gas temperature reduction)
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In a turbine engine, the convergent exhaust nozzle is used primarily to:
Show the answer and explanation
Answer: Increase the velocity of the exhaust gases as they leave the engine
Why: A convergent exhaust nozzle has a decreasing cross-sectional area, which accelerates the subsonic exhaust gas and increases its velocity as it exits, converting pressure energy into kinetic energy to produce thrust. A divergent shape would be used to recover pressure or to handle supersonic flow; the convergent nozzle is not a cooling device.· FAA-H-8083-32 — Turbine engine exhaust nozzles
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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
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The compression ratio of a reciprocating engine is defined as the ratio of the cylinder volume with the piston at:
Show the answer and explanation
Answer: Bottom center compared to the volume at top center.
Why: Compression ratio is the total cylinder volume (piston at bottom center) divided by the clearance volume (piston at top center). It expresses how much the fuel/air charge is compressed during the compression stroke. A higher compression ratio generally increases power and efficiency but raises the tendency toward detonation.· FAA-H-8083-32 — Reciprocating Engines, compression ratio
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Which combustion chamber design consists of individual cans, each with its own liner and outer case, arranged around the engine?
Show the answer and explanation
Answer: Can (multiple-can) type
Why: The can-type combustor uses several separate cylindrical chambers, each with an individual perforated liner inside its own outer housing, spaced around the engine. The annular type uses a single continuous combustion chamber surrounding the engine axis. The reverse-flow turbine choice is not a combustor classification, so the multiple individual chambers describe the can type.· FAA-H-8083-32 — Turbine Engines: combustion section
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A defect described as a sharp, V-shaped depression in the edge of a turbine compressor blade is properly called a
Show the answer and explanation
Answer: nick
Why: Standardized inspection terminology defines a nick as a sharp, V-shaped depression in an edge or surface, typically caused by foreign objects. A score is a deeper scratch from a harder material, and a pit is a small, rounded cavity often from corrosion. Using correct terms ensures accurate defect reporting.· FAA-H-8083-32 — Turbine blade defect definitions
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On a turbine engine, exhaust gas temperature (EGT) is most commonly sensed using which type of device?
Show the answer and explanation
Answer: Several thermocouples wired in parallel
Why: Turbine EGT systems use multiple thermocouples positioned around the gas path and connected in parallel so the indication represents an average exhaust gas temperature. The handbook explains that averaging several probes reduces error from local hot spots. A bourdon tube senses pressure, and a bimetallic spring is used in simple direct-reading thermometers, not turbine EGT.· FAA-H-8083-32 — Engine Instrument Systems (exhaust gas temperature)
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What is the principal advantage of a continuous-loop fire detection system over a series of individual spot detectors?
Show the answer and explanation
Answer: It provides more complete coverage of the fire hazard area
Why: A continuous loop runs as an unbroken sensing element around the entire hazard zone, so a fire anywhere along its length is detected, giving better area coverage than discrete spot units. Loop systems still require power and, like any system, can give false warnings, so those statements are incorrect.· FAA-H-8083-32 — Continuous-Loop Detector Systems
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When an aircraft magneto switch is placed in the OFF position, the primary circuit is:
Show the answer and explanation
Answer: grounded so the magneto cannot produce a spark
Why: The ignition switch is wired through the P-lead to ground the magneto primary circuit. With the switch OFF, the primary is grounded, so the field cannot collapse to induce high voltage and the magneto cannot fire. This is why a broken or disconnected P-lead leaves a magneto 'hot,' and a propeller must always be treated as if the ignition is on. The switch does not open the primary or connect it to the battery.· FAA-H-8083-32 — Ignition Systems (ignition switch, P-lead grounding)
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In a dry-sump oil system, where is the main supply of engine oil stored?
Show the answer and explanation
Answer: In a separate external oil tank
Why: A dry-sump system stores the bulk of its oil in a separate tank mounted away from the engine, and a scavenge pump returns oil from the engine sump to that tank. A wet-sump system, by contrast, keeps the oil supply in the crankcase sump. The oil cooler is a heat exchanger, not a storage reservoir.· FAA-H-8083-32 — Dry-Sump vs. Wet-Sump Systems
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Why is the rotating magnet in a high-tension magneto positioned for maximum voltage when the points open?
Show the answer and explanation
Answer: Because the rate of magnetic flux change in the coil is then greatest
Why: Maximum voltage is induced when the rate of change of magnetic flux is greatest, which occurs just past the magnet's neutral position. The points are timed to open at this point (the E-gap), so the primary collapse produces the strongest secondary voltage. Distributor and capacitor positions do not set the induced voltage peak.· FAA-H-8083-32 — Ignition Systems (E-gap and magneto timing)
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What is the function of the economizer (power enrichment) system in a carburetor?
Show the answer and explanation
Answer: To supply additional fuel at high power settings
Why: The economizer (also called the power enrichment system) provides a richer mixture only at high power output settings, where the additional fuel is needed for cooling and to develop maximum power. At cruise and lower settings the system is closed so the engine runs on the leaner, more economical main metering mixture. It is not a leaning device and does not act at idle.· FAA-H-8083-32 — Fuel Metering Systems (economizer / power enrichment)
- AM.III.JTap an answer
What is the function of the induction air filter on a reciprocating engine?
Show the answer and explanation
Answer: To remove dust and foreign particles from the air entering the engine
Why: The induction air filter cleans incoming air to prevent abrasive dust and debris from entering the cylinders, where it would accelerate wear on rings, cylinder walls, and valves. Metering of air is done by the throttle, and preheating is the job of the carburetor heat or alternate air system, not the filter.· FAA-H-8083-32 — Induction Systems / Induction Air Filters
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Which engine area is generally considered the hottest and therefore receives the largest share of cooling air?
Show the answer and explanation
Answer: Turbine section
Why: The turbine section is exposed to the highest gas temperatures in the engine because it sits directly behind the combustion section. It therefore receives large amounts of relatively cool secondary air directed at the nozzle, disks, and blades. The compressor and inlet operate at far lower temperatures and need much less cooling.· FAA-H-8083-32 — Turbine Section Cooling
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What is the primary purpose of the exhaust cone (tail cone) located at the rear of a turbine engine exhaust section?
Show the answer and explanation
Answer: To smooth the gas flow and reduce turbulence at the turbine exit
Why: The exhaust cone, supported by struts in the exhaust collector, fills the center of the gas path behind the turbine to convert turbulent flow into a smoother, more uniform stream and to prevent the gases from flowing across the rear face of the turbine disk. Adding swirl is undesirable in the exhaust, and the cone does not ignite fuel.· FAA-H-8083-32 — Turbine exhaust section (exhaust cone and struts)
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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
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Detonation in a reciprocating engine is best described as:
Show the answer and explanation
Answer: An uncontrolled, explosive burning of the fuel/air charge after normal ignition.
Why: Detonation is the spontaneous, almost instantaneous combustion of the remaining unburned charge after the normal flame front has been started by the spark plug. The resulting sudden rise in pressure and temperature can damage pistons, rings, and cylinders. It is distinct from preignition, which occurs before the spark fires.· FAA-H-8083-32 — Reciprocating Engines, detonation and preignition
Frequently asked questions
- How many questions are on the FAA Powerplant written test?
- One hundred multiple-choice questions in two hours, with a 70 percent pass mark — 70 correct out of 100. Each question offers three choices. The format is identical to the Airframe test; the material is narrower and deeper.
- Is the Powerplant test harder than the Airframe test?
- They fail candidates for different reasons. Airframe is broad, so its failure mode is thin coverage across fifteen areas. Powerplant is deep on two engine families, so its failure mode is being fluent on one and hollow on the other. Candidates from a piston background usually find Powerplant harder because of the turbine material, and airline technicians often find the reverse.
- How much turbine engine material is on the Powerplant test?
- Turbine engines is one of the two largest subject areas on the test, and turbine content also appears in turbine engine air systems and in engine exhaust and reverser systems. If your experience is entirely piston general aviation, treat the turbine material as a substantial block of study rather than a topic to skim — it is too large a share of the questions to concede.
- What happens if I fail the Powerplant test?
- Under 14 CFR §65.19 you may reapply 30 days after a failed test. You can retest sooner only by presenting a signed statement from an airman who holds the certificate and rating you are seeking, certifying that they have given you additional instruction in each subject you failed and consider you ready to retest.
- Do I need to know propellers for the Powerplant test?
- Yes — propellers is one of the thirteen Powerplant subject areas. Expect questions on constant-speed operation and governor action, feathering and reversing, blade stations and blade angle, and propeller inspection and track and balance. It is a self-contained body of material that candidates often skip in favour of the larger engine areas, which makes it reliable points for anyone who does study it.
- Which FAA handbook covers the Powerplant test?
- The Aviation Maintenance Technician Handbook — Powerplant, FAA-H-8083-32B (2023), a single-volume handbook free from faa.gov covering both the engines themselves and the systems around them. The Mechanic ACS (FAA-S-ACS-1) defines the thirteen subject areas and the knowledge codes used on the test and your fail report.
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