FAA Mechanic Powerplant (AMP) Knowledge Test, Practice Exams

Why is carburetor ice possible even on a warm, humid day?

1. Fuel evaporation and the venturi pressure drop can lower the induction air temperature below freezing despite warm ambient air ✓
2. The exhaust is too cold on warm days per the applicable maintenance manual under normal operating conditions per the applicable maintenance manual
3. Warm air holds no moisture

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?

1. The propeller drive shaft, hub, and spinner must be accommodated in the inlet ✓
2. It needs no anti-icing at all according to the manufacturer's service data
3. It uses a carburetor

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.

Besides current-carrying capacity, wire selection must limit the voltage drop to protect what?

1. Proper operation of the equipment (excess drop starves the load of voltage) ✓
2. The color of the insulation as noted in the manufacturer's instructions
3. The engine oil pressure

Why: Wire is sized so the voltage drop over its length stays within limits; excessive drop leaves too little voltage at the equipment, causing it to malfunction, so longer runs use larger wire. FAA-H-8083-32B ch.4.

An indication that a turbine engine anti-ice (bleed air) system is functioning may include what?

1. A slight change in engine parameters (e.g., a small rise in EGT/EPR) when anti-ice is selected on ✓
2. A large drop in oil quantity
3. Illumination of the landing gear warning per the applicable maintenance manual under normal operating conditions

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?

1. To reduce cooling drag once adequate cooling is achieved at cruise airspeed ✓
2. To increase the fuel flow according to the manufacturer's service data
3. To feather the propeller

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.

A sudden increase in oil consumption accompanied by metal in the filter suggests what?

1. Serious internal wear or component distress requiring investigation before further flight ✓
2. That the oil grade is simply too high according to the manufacturer's service data
3. That the filter needs to be tightened

Why: A sudden rise in oil consumption together with metal particles in the filter/chip detector points to serious internal wear or a failing component; the cause must be found and corrected before further operation. FAA-H-8083-32B ch.6.

Approximately half of all muffler and heat exchanger failures can be traced to what?

1. Cracks or ruptures in the heat-exchanger surfaces used for cabin and carburetor heat ✓
2. Loose spark plugs
3. Worn propeller blades according to the manufacturer's service data under normal operating conditions

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.

Why do most piston aircraft engines use a dual ignition system (two spark plugs per cylinder, two magnetos)?

1. For redundancy/safety and to burn the charge more completely for better performance ✓
2. Because one plug fires the intake charge and the other the exhaust under normal operating conditions
3. To allow the engine to run on either avgas or jet fuel

Why: Aircraft piston engines use dual ignition (two spark plugs per cylinder fired by two independent magnetos) for redundancy/safety and for more complete, even combustion, which improves power and efficiency. FAA-H-8083-32B ch.1.

What is the function of the igniter plugs in a gas turbine engine?

1. To ignite the fuel-air mixture during engine start (after which combustion is continuous and self-sustaining) ✓
2. To fire continuously throughout every combustion cycle like a spark plug per the applicable maintenance manual
3. To measure the exhaust gas temperature

Why: Turbine igniter plugs provide a high-energy spark to light the fuel-air mixture during starting; once combustion is established it is continuous and self-sustaining, and the igniters are turned off. FAA-H-8083-32B ch.1.

Why must a thermocouple lead never be shortened or lengthened from its specified length?

1. The lead's calibrated resistance is part of the circuit; changing its length gives an incorrect temperature reading ✓
2. A longer lead would short-circuit the aircraft battery under normal operating conditions per the applicable maintenance manual
3. The lead length sets the engine's redline rpm

Why: Thermocouple leads have a calibrated resistance built into the indicating circuit; if the lead length is changed, the resistance changes and the indicated temperature is incorrect, so excess length is coiled, not cut. FAA-H-8083-32B ch.10.

The scope and detail of items for an engine annual/100-hour inspection are found where?

1. 14 CFR part 43, Appendix D ✓
2. 14 CFR part 43, Appendix A
3. 14 CFR part 39

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.

In a DC generation system, the point from which the various circuits draw power is the what?

1. The distribution bus (bus bar) ✓
2. The commutator under normal operating conditions
3. The field coil

Why: The distribution bus (bus bar) is the common point supplied by the generator/battery, from which the individual circuits (through their protection devices) draw power. FAA-H-8083-32B ch.4.

A fire extinguisher bottle's discharge indicators tell maintenance what?

1. Whether the bottle discharged normally (crew-commanded) or thermally (from overheat), via colored disks ✓
2. The remaining engine oil quantity according to the manufacturer's service data under normal operating conditions
3. The next inspection due date

Why: Colored discharge-indicator disks at the bottle show whether it discharged normally from a crew command or thermally from an over-temperature (a red disk blown out indicates a thermal discharge), guiding the corrective action. FAA-H-8083-32B ch.9.

Turbine engine internal air cooling directs compressor air to cool which hot-section parts?

1. The turbine blades, disks, and nozzle guide vanes ✓
2. The fuel pump and oil tank under normal operating conditions
3. The propeller hub

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

1. fatigue failure. ✓
2. material debond.
3. warpage.

Why: Dye-penetrant inspection of aluminum propeller blades detects fatigue-failure cracks per FAA-H-8083-32B ch.7.

What is the purpose of dynamic dampers on a reciprocating engine crankshaft?

1. To reduce torsional vibration of the crankshaft during operation ✓
2. To increase the compression ratio of the cylinders
3. To pump oil to the connecting-rod bearings

Why: Dynamic dampers (pendulum-type counterweights) are incorporated on the crankshaft to reduce torsional vibration to a minimum during engine operation. FAA-H-8083-32B ch.1.

What is the purpose of the diffuser section (just ahead of the combustor) in a gas turbine engine?

1. To slow the high-velocity compressor discharge air and raise its static pressure before combustion ✓
2. To speed up the air so the flame burns faster
3. To extract energy from the gas to drive the fan as noted in the manufacturer's instructions

Why: The diffuser slows the high-velocity air leaving the compressor and increases its static pressure before it enters the combustor; slowing the air keeps the flame from being blown out. FAA-H-8083-32B ch.1.

Spectrometric oil analysis (SOAP) monitors engine condition by measuring what?

1. Trace wear metals dissolved in the oil, trended over time ✓
2. The oil's octane rating
3. The cabin carbon monoxide level as noted in the manufacturer's instructions

Why: SOAP measures the parts-per-million of wear metals (iron, aluminum, silver, copper, etc.) in an oil sample; trends in specific metals point to which components are wearing, supporting condition monitoring. FAA-H-8083-32B ch.6.

When inspecting engine mounts, the technician looks primarily for what?

1. Cracks, distortion, corrosion, and security of the mount structure and hardware, and condition of the vibration isolators ✓
2. The specific gravity of the mount material under normal operating conditions per the applicable maintenance manual
3. The octane rating of the mount bushings

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.

An engine that has been submerged (e.g., in a flood or ditching) requires what?

1. A special inspection/overhaul, because water and contaminants cause internal corrosion and damage ✓
2. Only an oil change before further flight per the applicable maintenance manual under normal operating conditions
3. No action if it still starts

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 'shower of sparks' starting system uses what to aid starting?

1. An induction vibrator that delivers a series of retarded sparks during cranking ✓
2. A second battery connected in series per the applicable maintenance manual under normal operating conditions
3. A larger spark plug gap only

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?

1. Leaks, security and condition of lines/fittings, filter condition, and correct operation of the pump and metering unit ✓
2. Only the color of the fuel under normal operating conditions per the applicable maintenance manual under normal operating conditions
3. Only the ignition timing

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 turbine engine 'hot start' is prevented/limited by monitoring what during start?

1. The exhaust gas temperature (EGT/ITT), aborting the start if it approaches the limit ✓
2. The oil quantity gauge under normal operating conditions per the applicable maintenance manual
3. The cabin altitude

Why: During a turbine start the crew monitors EGT/ITT; if it rises too fast toward the start limit (a hot start), the start is aborted (fuel off) to avoid turbine damage. FAA-H-8083-32B ch.4.

On a turbosupercharged engine, the exhaust system operates under what condition compared with a normally aspirated one?

1. Greatly increased pressure and temperature, requiring extra care in maintenance ✓
2. Much lower pressure and temperature as noted in the manufacturer's instructions
3. Identical conditions

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.

An alternator produces what type of current, and how is it made usable for a DC system?

1. Alternating current (often three-phase), rectified to DC by built-in diodes ✓
2. Direct current, then inverted to AC
3. Alternating current used directly with no conversion per the applicable maintenance manual

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.

A recurring AD on an engine requires what recordkeeping?

1. The records must show the method of compliance and the next-due time or date for each recurrence ✓
2. Only the date the AD was first published
3. Nothing, because recurring ADs are optional as noted in the manufacturer's instructions

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.

A generator control unit (GCU) on a modern engine electrical system performs what functions?

1. Voltage regulation plus overvoltage, overcurrent, and reverse-current protection and paralleling control ✓
2. Only the metering of fuel to the engine as noted in the manufacturer's instructions as noted in the manufacturer's instructions
3. Only the cabin temperature control

Why: A generator control unit (GCU) integrates voltage regulation with the protective functions (overvoltage, overcurrent, differential/reverse-current) and, on multi-generator systems, paralleling/load-sharing control. FAA-H-8083-32B ch.4.