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The real Aviation Mechanic - Powerplant written test has 100 multiple-choice questions (3 options each), a 2-hour time limit, and requires 70% to pass. Questions are drawn across 13 knowledge areas. These follow the FAA-S-ACS-1 blueprint, and this bank mirrors those areas and their weights.
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The live test bank is not published. Our questions include the FAA's own published sample questions plus original questions written to the FAA-S-ACS-1 blueprint and grounded in the FAA handbooks (FAA-H-8083-30B, 31B and 32B) and 14 CFR, with the source cited in each explanation.
The full Aviation Mechanic - Powerplant bank contains 577 questions with explanations. The free sample gives you roughly two exams' worth per knowledge area.
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It is organised into 13 modules that follow the exam's own content areas: 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 and Propellers. Each module is drilled and scored separately, so you can see exactly which areas are exam-ready and which still need work.
Last updated 6 July 2026. The bank is revised whenever the source material it cites changes, and every question carries the source its explanation is drawn from.
A selection of free questions with answers and explanations. Use the interactive modules above for timed, scored drills.
A wet-sump lubrication system stores the engine oil where?
Why: In a wet-sump system the oil supply is carried in the engine's own crankcase sump; most horizontally opposed engines use wet-sump lubrication. FAA-H-8083-32B ch.6.
During a turbine engine air-system inspection, cooling-air ducting and baffle seals are checked for what?
Why: Cooling ducting (rigid/flexible) and baffle seals are inspected for cracks, leaks, security, and deterioration, because any leakage reduces the cooling airflow reaching the components. FAA-H-8083-32B ch.1.
During start, a starter-generator draws heavy current from the battery/ground power to do what, then reverses role how?
Why: As a starter, the starter-generator draws heavy current to crank the engine; once the engine is self-sustaining, its circuitry reconfigures it as a generator that supplies the bus and recharges the battery. FAA-H-8083-32B ch.5.
Why is carburetor ice possible even on a warm, humid day?
Why: Because fuel evaporation absorbs heat and the venturi drops the pressure/temperature, the induction air can cool below freezing even when the outside air is warm (e.g., 70-100 F) and humid — a common cause of carburetor ice. FAA-H-8083-32B ch.3.
A turboprop air inlet presents an extra design problem compared with a turbojet because of what?
Why: A turboprop inlet must be designed around the propeller drive shaft, hub, and spinner; a ducted arrangement is generally the best design for airflow and aerodynamic characteristics. FAA-H-8083-32B ch.3.
A DC generator's output voltage is controlled by adjusting what?
Why: A DC generator's output voltage is controlled by varying the field current; the voltage regulator increases or decreases field current to keep the output constant as speed and load change. FAA-H-8083-32B ch.4.
An indication that a turbine engine anti-ice (bleed air) system is functioning may include what?
Why: Selecting engine anti-ice bleeds warm air, which slightly changes engine parameters (a small EGT rise and thrust change) — a normal indication used to confirm the anti-ice valves have opened. FAA-H-8083-32B ch.3.
During cruise, why are cowl flaps normally closed?
Why: At cruise the higher airspeed provides ample cooling airflow, so the cowl flaps are closed to reduce the aerodynamic drag (and improve efficiency); they are opened for climb/ground operation where more cooling is needed. FAA-H-8083-32B ch.3.
Turbine engine oils are typically what type?
Why: Turbine engines use synthetic oils formulated to withstand the high operating temperatures and to resist thermal breakdown; they are not interchangeable with reciprocating-engine mineral/AD oils. FAA-H-8083-32B ch.6.
Approximately half of all muffler and heat exchanger failures can be traced to what?
Why: About half of muffler/heat-exchanger failures are cracks or ruptures in the heat-exchanger surface (usually the outer wall) that supplies cabin and carburetor heat, allowing exhaust gas into those systems. FAA-H-8083-32B ch.3.
During reciprocating engine ground run-up, a magneto check that shows an excessive rpm drop on one magneto indicates what?
Why: During the mag check, switching to one magneto normally causes a small rpm drop; an excessive drop (or no drop) indicates an ignition fault such as a fouled spark plug, a defective lead, or a magneto problem on that side. FAA-H-8083-32B ch.1.
On a twin-spool turbofan, what do the terms N1 and N2 refer to?
Why: N1 is the rotational speed of the low-pressure spool (fan/LP compressor and LP turbine) and N2 is the speed of the high-pressure spool (HP compressor and HP turbine), each expressed as a percent of maximum rpm. FAA-H-8083-32B ch.1.
Turbine inlet temperature (TIT) is monitored because it reflects what?
Why: TIT (or ITT) measures the gas temperature at/near the turbine inlet, the hottest practical measuring point; it is monitored closely because the turbine operates near its material temperature limit and overtemperature causes rapid damage. FAA-H-8083-32B ch.10.
When inspecting engine mounts, the technician looks primarily for what?
Why: Engine mount inspection checks the mount structure and hardware for cracks, distortion, corrosion, and security, and checks the vibration isolators (shock mounts) for deterioration, since a failed mount is a serious hazard. FAA-H-8083-32B ch.8.
What is the function of a voltage regulator in an engine-driven electrical system?
Why: The voltage regulator holds the system voltage constant by adjusting the field current of the generator or alternator as engine speed and electrical load vary. FAA-H-8083-32B ch.4.
After maintenance on an engine fire detection/extinguishing system, a key final step is to do what?
Why: A functional (built-in) test after fire-system maintenance confirms the detection loop and warning circuit operate and, for extinguishing systems, that squib firing-circuit continuity is correct, without actually discharging the bottle. FAA-H-8083-32B ch.9.
Turbine engine internal air cooling directs compressor air to cool which hot-section parts?
Why: Internal cooling air (from the compressor) is directed over the hottest parts — turbine nozzle guide vanes, turbine blades, and disks — to keep their temperatures within limits despite the high gas temperatures. FAA-H-8083-32B ch.1.
Inspection of aluminum propeller blades by dye-penetrant inspection is accomplished to detect
Why: Dye-penetrant inspection of aluminum propeller blades detects fatigue-failure cracks per FAA-H-8083-32B ch.7.
The firing order of a nine-cylinder single-row radial engine is what?
Why: The firing order of a nine-cylinder radial engine is 1-3-5-7-9-2-4-6-8, arranged so the firing impulses are evenly distributed around the crankcase. FAA-H-8083-32B ch.1.
Who establishes the recommended operating time between overhauls (TBO) of a turbine engine used in general aviation?
Why: Recommended TBO is specified by the engine manufacturer per FAA-H-8083-32B ch.1.
What is the purpose of the de-aerator (air separator) in a turbine engine oil tank?
Why: The scavenge pumps return oil mixed with air; a de-aerator in the tank separates this air out so that solid, air-free oil is supplied to the pressure pump, ensuring proper lubrication and accurate quantity. FAA-H-8083-32B ch.6.
An engine that has been submerged (e.g., in a flood or ditching) requires what?
Why: A submerged (flood/immersion) engine requires a special inspection and usually a teardown/overhaul because water and contaminants enter the engine and cause corrosion and bearing/component damage. FAA-H-8083-32B ch.8.
A progressive inspection program for an engine/aircraft is authorized under which regulation?
Why: A progressive inspection may be used under 14 CFR 91.409(d) as an alternative to the annual, provided the complete aircraft/engine is inspected within each 12 calendar months. 14 CFR 91.409(d).
A 'shower of sparks' starting system uses what to aid starting?
Why: The shower of sparks system uses an induction vibrator to feed a rapid series of sparks to a retard breaker/points during starting, giving a 'shower' of retarded sparks that improves starting and prevents kickback. FAA-H-8083-32B ch.4.
An engine fuel system inspection includes checking for what?
Why: Fuel system inspection covers leaks, the security and condition of lines, hoses, and fittings, filter/strainer condition (water/sediment), and correct operation of the fuel pump and metering (carburetor/injection/FCU) unit. FAA-H-8083-32B ch.2.
A starter-generator combines which functions on a turbine engine?
Why: A starter-generator is one unit that serves as the starter to crank the engine and then as the generator once running, saving the weight of separate components; it is common on turbine engines. FAA-H-8083-32B ch.5.
On a turbosupercharged engine, the exhaust system operates under what condition compared with a normally aspirated one?
Why: With a turbocharger/turbosupercharger the exhaust system runs under greatly increased pressure and temperature; extra precautions in care and maintenance are required, especially at high-altitude operation. FAA-H-8083-32B ch.3.
A starter-generator combines which two functions, and where is it common?
Why: A starter-generator serves as the starter to crank the engine, then functions as the generator once the engine is running; combining the two units saves weight and is common on turbine engines. FAA-H-8083-32B ch.5.
The scope and detail of items for an engine annual/100-hour inspection are found where?
Why: The scope and detail of items to include in an annual or 100-hour inspection (including engine items) are listed in 14 CFR part 43, Appendix D. 14 CFR part 43 App D.
A term commonly used when two or more electrical terminals are installed on a single lug of a terminal strip is
Why: Installing two or more terminals on a single lug of a terminal strip is commonly called stacking per FAA electrical references.
On a high-bypass turbofan, most of the thrust is produced by what?
Why: On a high-bypass turbofan the large fan moves a great mass of bypass air that produces most (often 80%+) of the thrust; only a minority comes from the hot core exhaust. This makes high-bypass engines efficient and quiet. FAA-H-8083-32B ch.1.
A bellmouth inlet is chiefly used in what situation?
Why: A bellmouth inlet is a bell-shaped funnel with negligible duct loss used mainly for test-cell running (and on some helicopters); its high efficiency lets accurate engine performance data be gathered. FAA-H-8083-32B ch.3.
Why do reciprocating aircraft engines use two spark plugs per cylinder fired by two magnetos?
Why: Dual ignition (two plugs per cylinder, two independent magnetos) provides redundancy if one system fails and burns the charge more completely and evenly from two points, improving power and efficiency. FAA-H-8083-32B ch.4.
Propellers exposed to salt spray should be flushed with
Why: Propellers exposed to salt spray/salt water should be flushed with fresh water per FAA-H-8083-32B ch.7.
The 'hot section' of a gas turbine engine generally includes which components?
Why: The hot section comprises the combustion section and the turbine section (and often the exhaust), which operate at the highest temperatures and receive the most frequent, detailed inspections. FAA-H-8083-32B ch.1.
Engine control cables and linkages are rigged and inspected to ensure what?
Why: Engine controls (throttle, mixture, propeller) are rigged and inspected for full, free travel to their stops with the specified cushion, and for security and condition, so the pilot has full control authority. FAA-H-8083-32B ch.8.
When a wet-sump engine's oil is checked with the dipstick, the reciprocating engine should be checked when?
Why: A reciprocating (wet-sump) engine's oil is checked after it has been inactive long enough for the oil to drain to the sump; a turbine engine is checked shortly after shutdown before the oil drains from the tank. FAA-H-8083-32B ch.6.
A fuel flow indicator on a turbine engine displays what?
Why: A turbine fuel flow indicator shows the rate at which fuel is being consumed, typically in pounds per hour, sensed by a fuel flow transmitter in the fuel line; it helps monitor engine performance and fuel management. FAA-H-8083-32B ch.10.
The reason for flashing the field in a generator is to
Why: Flashing the field restores residual magnetism to the generator field frame per FAA-H-8083-30B.
In an underspeed condition, the governor responds how?
Why: In underspeed there is not enough centrifugal force, so the flyweights tilt inward; the speeder spring forces the pilot valve down, metering oil to decrease pitch (lower blade angle), which unloads the engine and raises rpm to on-speed. FAA-H-8083-32B ch.7.
A recurring AD on an engine requires what recordkeeping?
Why: For a recurring AD, the maintenance records must show the method of compliance and the next-due time/date, so the recurring inspection or action is tracked and not missed. FAA-H-8083-32B ch.8.
On EICAS/ECAM, the primary engine parameters (such as N1 and EGT) are normally displayed how?
Why: The primary engine parameters (N1, EGT, N2, etc.) are shown continuously on the EICAS/ECAM primary display because they are the most critical for monitoring; secondary parameters may be on a selectable page. FAA-H-8083-32B ch.10.
Which engine type most commonly uses a wet-sump lubrication system?
Why: Horizontally opposed light-aircraft engines commonly use wet-sump lubrication (oil in the crankcase sump); radial and turbine engines generally use dry-sump systems. FAA-H-8083-32B ch.6.
Propeller blade station numbers increase from
Why: Propeller blade station numbers increase from the hub center line to the tip (measured in inches from center of hub) per FAA-H-8083-32B ch.7.
An advantage of a continuous-loop detector over spot detectors is that it does what?
Why: A continuous-loop (sensing-element) detector covers the whole length of the element routed around the fire zone, giving broader coverage than individual spot detectors. FAA-H-8083-32B ch.9.
A single-speed internally driven supercharger is geared to run at what relation to the engine?
Why: An internally driven (gear-driven) supercharger runs at a fixed multiple of crankshaft speed (single-speed) or selectable ratios (two-speed); it always takes some engine power to drive, unlike an exhaust-driven turbocharger. FAA-H-8083-32B ch.3.
A supercharger on a reciprocating engine is driven by what, and does what?
Why: An (internally driven) supercharger is geared to the engine crankshaft and compresses the induction air, raising manifold pressure so the engine can maintain power at altitude or exceed sea-level power. FAA-H-8083-32B ch.3.
A liquid-cooled reciprocating engine transfers heat how?
Why: A liquid-cooled engine circulates a coolant (water/glycol) through jackets around the cylinders to absorb heat, then passes the coolant through a radiator where the airflow removes the heat; a pump and thermostat control the flow. FAA-H-8083-32B ch.3.
Which measured temperature is generally the most critical to observe when starting and operating a turbine engine?
Why: EGT/TIT/ITT is the most temperature-critical parameter: the turbine runs near its material limit, so a hot start or overtemperature can damage the turbine in seconds; limits and time-at-temperature are strictly observed. FAA-H-8083-32B ch.10.
If a flanged propeller shaft has dowel pins,
Why: If a flanged propeller shaft has dowel pins, the propeller can only be installed in a given (indexed) position per FAA-H-8083-32B ch.7.
Multiple splices in an engine/airframe wire bundle should be arranged how?
Why: When several splices are needed in a wire bundle, they are staggered along the length so the bundle does not bulge and each splice can be inspected. FAA-H-8083-32B ch.4.
Exhaust gas temperature (EGT) is monitored on a turbine engine primarily to do what?
Why: EGT (or interstage/turbine temperature) is monitored because the turbine section operates near its material limits; an overtemperature can quickly damage the turbine blades, so EGT limits must not be exceeded. FAA-H-8083-32B ch.1.
An inverter in an engine electrical system does what?
Why: An inverter changes DC into AC to supply AC-powered instruments/equipment on a primarily DC aircraft; a transformer-rectifier does the opposite (AC to DC) on AC aircraft. FAA-H-8083-32B ch.4.
Where do wires require a suitable grommet during installation?
Why: A grommet protects wires from chafing where they pass through holes in bulkheads, firewalls, and ribs; a firewall grommet/fitting must also maintain the firewall's fire integrity. FAA-H-8083-32B ch.4.
What happens in the combustion section of a gas turbine engine?
Why: In the combustion section, fuel is sprayed into the high-pressure air from the compressor and burned continuously, greatly increasing the temperature/energy of the gas before it enters the turbine. FAA-H-8083-32B ch.1.
What is the function of the camshaft (or cam ring) in a reciprocating engine?
Why: The camshaft (in opposed/inline engines) or cam ring (in radials) opens and closes the intake and exhaust valves in the proper sequence and timing, driven at half crankshaft speed on a four-stroke engine. FAA-H-8083-32B ch.1.
An optical (infrared/ultraviolet) fire detector responds to what?
Why: Optical fire detectors sense the infrared or ultraviolet radiation emitted by flames, giving a very fast response to an open fire; they are designed to reject non-fire light sources to avoid false alarms. FAA-H-8083-32B ch.9.
On a light-aircraft alternator charging system, the field is typically controlled by what?
Why: A light-aircraft alternator's output is set by a voltage regulator controlling the small field (rotor) current through the slip rings; the higher-current AC output is rectified to DC by the diode bridge. FAA-H-8083-32B ch.4.
Compressor bleed air tapped from a gas turbine engine is used for what?
Why: Bleed air is high-pressure air tapped from the compressor; it powers aircraft services such as cabin pressurization and air conditioning, thermal anti-ice, engine start (air turbine starter), and pneumatic systems. FAA-H-8083-32B ch.1.
An alternator produces what type of current, and how is it made usable for a DC system?
Why: An alternator generates alternating current (commonly three-phase); on light aircraft it is rectified to DC by built-in diodes before reaching the DC bus. FAA-H-8083-32B ch.4.
If one magneto fails in flight on a dual-ignition engine, what happens?
Why: Because of dual ignition, the engine keeps running on the remaining magneto if one fails; there is a slight loss of power/smoothness (each cylinder now fires on one plug), and the fault is corrected on the ground. FAA-H-8083-32B ch.4.
A continuous-flow fuel injection system (e.g., the RSA type) consists of which main components?
Why: A continuous-flow (RSA) fuel injection system consists of an injector/fuel control unit that meters fuel with airflow, a flow divider that distributes it, and a discharge nozzle at each cylinder that sprays fuel continuously into the intake port. FAA-H-8083-32B ch.2.
A turbine engine fuel heater is used to do what?
Why: A turbine fuel heater (often a fuel/oil heat exchanger) warms the fuel enough to prevent water in it from forming ice crystals that would clog the fuel filter, especially at high-altitude low temperatures. FAA-H-8083-32B ch.2.
After installing a turbine or reciprocating exhaust system, low or dented spots should be inspected for what?
Why: Dented areas or low spots are probed and inspected for thinning and pitting caused by internal erosion from combustion products or accumulated moisture, which can lead to failure. FAA-H-8083-32B ch.3.
A carburetor meters fuel in proportion to airflow using what principle?
Why: A carburetor uses a venturi: as air accelerates through the venturi its pressure drops, and this low pressure draws fuel from the discharge nozzle in proportion to the airflow, metering the fuel-air mixture. FAA-H-8083-32B ch.2.
What is the purpose of a supercharger or turbocharger on a reciprocating engine?
Why: A supercharger (gear-driven) or turbocharger (exhaust-driven) compresses the induction air, restoring or increasing manifold pressure so the engine maintains sea-level power at altitude (or is boosted above it). FAA-H-8083-32B ch.1.
An electrical chip detector differs from a plain magnetic plug in that it does what?
Why: An electrical chip detector has two contacts; when ferrous particles bridge the gap, it completes a circuit and illuminates a chip-detector warning light, alerting the crew to possible internal wear in flight. FAA-H-8083-32B ch.6.
A torquemeter on a turboprop engine measures what, and why is it important?
Why: A turboprop torquemeter measures the torque (twisting force) the engine delivers to the propeller reduction gear, often via an oil pressure proportional to torque; it is the primary power-setting indication for a turboprop. FAA-H-8083-32B ch.10.
The compressor bleed air used for cabin functions is taken from where?
Why: Bleed air for cabin pressurization, heating, cooling, and anti-ice is tapped from the compressor, where the air is already compressed and hot. FAA-H-8083-32B ch.1.
How does a manufacturer's engine Service Bulletin (SB) generally differ from an AD?
Why: An engine Service Bulletin is a manufacturer's recommendation (improvement/correction) and is not mandatory for part 91 operators unless incorporated into an AD; ADs are always mandatory. FAA-H-8083-32B ch.8.
After a false (wet) start on a turbine engine (fuel but no light-off), a key action before re-start is to do what?
Why: After a wet/false start (fuel introduced but no ignition), the engine is motored (dry cranked) with the fuel off to clear the accumulated fuel and vapor from the combustor/tailpipe, preventing a hot start or tailpipe fire on the next attempt. FAA-H-8083-32B ch.4.
Ice forming on a propeller blade is a problem because it does what?
Why: Ice on a blade distorts the airfoil section, reducing propeller efficiency and thrust, and uneven shedding can cause imbalance and vibration — so ice control systems are provided. FAA-H-8083-32B ch.7.
After an engine overspeed exceedance, the manufacturer's inspection typically focuses on which components?
Why: An overspeed special inspection focuses on the highly stressed rotating components (crankshaft or turbine rotor, accessory gears, and propeller) for overstress cracks or deformation, per the manufacturer's instructions. FAA-H-8083-32B ch.8.
A resistance (thermistor) continuous-loop fire detector signals a fire when the element does what with temperature?
Why: In a thermistor (resistance) continuous-loop detector (Kidde/Fenwal), the core material's electrical resistance drops as temperature rises; when it drops enough, current flows and triggers the fire warning. FAA-H-8083-32B ch.9.
What is the function of the compressor section of a gas turbine engine?
Why: The compressor section raises the pressure (and temperature) of the incoming air and supplies it in sufficient quantity to the combustion section; higher pressure ratio improves efficiency and thrust. FAA-H-8083-32B ch.1.
Which of the following instrument conditions is acceptable and does not require immediate correction?
Why: Chipped case paint is a cosmetic instrument condition that is acceptable and does not require immediate correction (fogged glass and loose mounting screws must be corrected) per FAA guidance.
In an overspeed condition, the governor responds how?
Why: In overspeed the flyweights overcome the speeder spring and fly out, moving the pilot valve to release oil from the propeller piston; the blade angle increases (higher pitch), loading and slowing the propeller back to on-speed. FAA-H-8083-32B ch.7.
Which agents have been the principal engine fire extinguishing agents in civil aircraft?
Why: Halon (notably Halon 1301, a total flooding agent) and carbon dioxide have been the principal fixed-system engine fire extinguishing agents in civil aircraft; halon replacements are being introduced. FAA-H-8083-32B ch.9.
Continuous-loop fire detectors include which two widely used types?
Why: Continuous-loop detectors include the thermistor (resistance) type (Kidde, Fenwal systems) and the pneumatic pressure type (Lindberg/Systron-Donner); both sense over the whole length of the element. FAA-H-8083-32B ch.9.
Noise suppression on some engines is achieved with which of the following?
Why: Engine noise is reduced by devices such as mufflers, hush kits, and augmenter tubes, which lower the noise produced by the exhaust. FAA-H-8083-32B ch.3.