FAA Aviation Mechanic Powerplant (AMP) flashcards

Carbon deposits in continuous-flow injector nozzles typically result from residual fuel boiling off due to heat soak after a hot engine shutdown, restricting the nozzle orifice.

• Common in fuel-injected reciprocating engines after hot shutdowns
• Restricts nozzle orifice, causing lean mixture and rough idle
• Inspected and cleaned per manufacturer procedures
• Air pressure test used to check nozzle flow pattern and calibration

Memory trick: 'Hot Soak, Nozzle Choke' — heat after shutdown cooks fuel into carbon.

The impeller speed of a gear-driven supercharger is found by multiplying the crankshaft RPM by the supercharger's step-up gear ratio.

• Formula: Crankshaft RPM × Gear Ratio = Impeller RPM
• Superchargers use high step-up ratios (commonly 6:1 to 12:1) since the crank turns much slower than the impeller needs to
• High impeller speeds increase induction air pressure and density

Memory trick: Multiply crank RPM by the gear ratio to find how fast the impeller spins.

Ignition of the fuel/air charge by a hot spot (such as a carbon deposit or overheated plug) before the timed spark occurs, distinct from detonation which follows normal ignition.

• Caused by hot spots: carbon deposits, overheated plugs, sharp edges
• Occurs before the timed spark fires
• Can be triggered or worsened by prior detonation damage

Memory trick: Pre-ignition jumps the gun before the spark even fires!

The intake valve remains open somewhat past BDC on the compression stroke to use the momentum of the incoming charge for improved cylinder filling (volumetric efficiency).

• Exploits inertia/momentum of intake charge (ram effect)
• Improves volumetric efficiency at normal operating RPM
• Part of the overall valve timing diagram along with overlap and lead

Memory trick: 'Momentum keeps filling even after BDC — don't shut the door too soon'

Turbine ignition exciters are designed for intermittent operation, used mainly for starting and during conditions with flameout risk, not continuously throughout flight.

• Energized during ground/air starts until stable combustion is achieved.
• Re-energized during icing, heavy rain, or turbulence to guard against flameout.
• Continuous use would shorten igniter plug and exciter service life.

Memory trick: Ignite to start, rest at cruise, ignite again if the sky gets rough.

A small gas turbine engine installed on the aircraft that provides electrical power and bleed air for air conditioning and engine starting independent of ground support equipment.

• Self-contained small turbine engine
• Supplies electrical and pneumatic power
• Used for main engine starting via bleed air
• Typically mounted in the tail cone

Memory trick: APU = the airplane's own little engine, always ready

Spinner domes are inspected for cracking, especially near screw holes and the bulkhead attachment, since they are subject to vibration and centrifugal loading.

• Cracks concentrate at fastener holes due to vibration
• No field stop-drill or patch repairs are approved
• Must follow OEM repair/replacement data

Memory trick: A cracked spinner is a spinning bomb — replace, don't patch

Magnesium and aluminum crankcases require dye penetrant inspection for crack detection since they cannot be magnetized for magnetic particle testing.

• Magnetic particle inspection is limited to ferrous metals
• Dye penetrant works on both ferrous and nonferrous surfaces
• Crankcase must be clean and free of paint/oil before testing
• Fluorescent or visible dye penetrant kits are commonly used

Memory trick: 'Mag Won't Stick to Mag(nesium)' — magnetic particle fails on nonferrous metal, so use dye penetrant.

The angle formed between the chord line of a propeller blade section and the plane of rotation.

• Measured at a specified blade station (often 75% radius)
• Different from angle of attack, which includes relative wind
• Fixed-pitch props have one blade angle; constant-speed props vary it

Memory trick: Chord to rotation plane = blade angle, chord to wind = angle of attack

A density-sensing device (bellows or bimetallic) in the carburetor that automatically leans the mixture as altitude increases, compensating for reduced air density.

• Senses air temperature and pressure
• Automatically leans mixture with altitude
• Reduces pilot workload versus manual leaning

Memory trick: AMC is a built-in altitude 'brain' that thins the fuel as air gets thin.

A mechanism that rotates the exhaust valve slightly each time it opens, distributing heat evenly and preventing localized hot spots and carbon buildup on the valve face.

• Prevents same spot on valve face from always contacting the same seat area
• A stuck rotator leads to hot spots and eventual valve burning
• Inspected during top overhaul for proper rotation/function

Memory trick: A valve that won't spin will surely burn one spot thin

A wood propeller is built from multiple laminated wood layers glued together, covered with fabric or plastic, varnished, and fitted with metal leading-edge tipping to protect against moisture and erosion.

• Laminated wood layers glued together
• Fabric/plastic covering with varnish finish
• Metal tipping protects leading edge
• Sensitive to moisture and requires careful storage

Memory trick: Wrap it, varnish it, tip it in metal — keep the wood dry and whole.

Contact wear marks with metal transfer found on turbine blade tips where they have rubbed against the surrounding shroud, often signaling a mechanical clearance problem.

• Found during borescope inspection of the turbine section
• Can result from bearing wear, rotor imbalance, or case distortion
• Requires root-cause investigation, not just cosmetic repair
• Left unaddressed, can progress to more serious rotor or case damage

Memory trick: Scraped tips tell tales — something shifted the spinning wheel.

Tracking exhaust gas temperature at a standard reference power setting over time to detect gradual turbine engine performance deterioration before reaching the EGT redline limit.

• EGT margin = redline temperature − actual EGT at reference power
• A shrinking margin over time indicates hot section or compressor deterioration
• Used to schedule engine removal/overhaul proactively
• Sudden EGT spikes (not gradual trend) may indicate a different fault, like FOD

Memory trick: Shrinking margin, aging engine — the gap to redline keeps closing.

A maintenance procedure using water (sometimes with a cleaning solution) to remove salt, dirt, and contaminant buildup from compressor airfoils to restore efficiency.

• Restores compressor efficiency and reduces EGT
• Common in coastal/dusty operating environments
• Performed with engine motoring, not running, in most procedures

Memory trick: Water wash = giving the compressor a bath to wash off salt and grime buildup.

A turbocharger safety device that senses manifold absolute pressure and automatically overrides wastegate control to prevent the engine from being overboosted.

• Protects against overboost regardless of throttle input
• Works with, not instead of, the wastegate
• Common on turbocharged reciprocating engines

Memory trick: APC is the 'safety cop' that grabs the wastegate wheel if MAP gets too high.

Fuel and ignition are introduced only after the starter has rotated the engine to a specified minimum speed, ensuring adequate airflow for proper light-off and preventing hot starts.

• Starter rotates compressor first
• Fuel/ignition introduced at min N2/N1 speed
• Light-off produces EGT rise
• Starter disengages at self-sustaining speed

Memory trick: Spin first, then spark — airflow before fire

FOD damage on compressor blades is blended out with a gradual taper whose length is a specified multiple of the damage depth to avoid creating a stress concentration point.

• Blend length is typically a multiple (e.g., 10x) of the blend depth
• Sharp-edged repairs create stress risers that can lead to fatigue cracking
• Borescope inspection allows FOD assessment without engine disassembly
• Manufacturer manuals specify exact blend ratios and depth limits

Memory trick: 'Ten Times the Depth Keeps the Stress at Bay' — always multiply depth by the blend ratio.

A system using accelerometers on the engine case to detect abnormal vibration levels indicating imbalance, blade damage, or bearing wear.

• Accelerometers convert mechanical vibration into electrical signals
• Cockpit vibration indicator alerts crew to abnormal readings
• Early detection helps prevent catastrophic mechanical failure

Memory trick: Vibration sensor = the engine's pulse monitor for shaking sickness

Manufacturer's recommended number of operating hours (or calendar time) before an engine should be overhauled, based on reliability data.

• Advisory, not regulatory, for Part 91 operators
• Some commercial operations may require overhaul at TBO
• Engines can be operated 'on-condition' past TBO if maintained properly

Memory trick: TBO is a 'suggestion,' not a 'summons'

The difference in cylinder bore diameter measured at the top versus the bottom of piston ring travel, caused by uneven wear, checked against a maximum allowable limit in the overhaul manual.

• Taper = top diameter − bottom diameter of ring travel
• Compared against maximum allowable taper limit in manual
• Excessive taper causes poor ring seating, blow-by, and oil consumption
• Corrected by honing/regrinding to oversize or cylinder replacement

Memory trick: Wide at the top, narrow below — that's taper telling you the bore must go.

In a Bendix RSA continuous-flow fuel injection system, the servo diaphragm balances impact and venturi air pressures to meter fuel proportional to engine airflow.

• Used in continuous-flow fuel injection systems
• Balances impact vs venturi (suction) air pressure
• Positions fuel metering valve accordingly
• Ensures fuel flow matches airflow demand

Memory trick: Servo diaphragm is the referee balancing two air pressures to set fuel flow

Jet A turbine fuel has a standard weight of approximately 6.7 pounds per U.S. gallon, used for weight and balance calculations.

• Jet A standard weight ≈ 6.7 lb/gal
• Avgas (100LL) standard weight ≈ 6.0 lb/gal
• Weight = gallons × lb/gal
• Fuel weight varies slightly with temperature

Memory trick: Jet fuel is heavier — 6.7, not 6.0 like avgas

Composite propeller blades include an embedded metal mesh or foil layer that conducts lightning strike current away from the blade to prevent structural damage.

• Metal mesh/foil embedded near surface
• Conducts lightning current to hub/airframe
• Reduces delamination/burn damage risk
• Standard feature on modern composite blades

Memory trick: Mesh catches the lightning like a net, sending it safely to ground.

A pilot-selectable mode that keeps turbine igniter plugs firing continuously (instead of only during start) to prevent flameout during heavy precipitation, icing, or turbulence.

• Normally used during takeoff/landing in rain/icing conditions and severe turbulence
• Increases igniter duty cycle far beyond the short start-only duty cycle
• Does not affect fuel scheduling or EGT directly

Memory trick: Rain falls, sparks stay on — continuous ignition keeps the flame alive.

Inspection of a cut-open oil filter element for metal particles to detect internal engine wear or failure.

• Ferrous particles suggest steel/iron component wear (gears, bearings)
• Nonferrous particles suggest bronze/aluminum wear (bushings, pistons)
• Excessive or unusual debris warrants further engine teardown investigation

Memory trick: 'Metal in the filter tells the engine's secret story'

A starting aid that delivers a metered charge of raw fuel directly to the cylinder intake ports or manifold, bypassing the carburetor, to assist cold-weather engine starts.

• Bypasses carburetor metering entirely
• Delivers fuel directly to cylinders/manifold
• Most useful in cold weather when vaporization is poor

Memory trick: Primer is a direct 'injection shot' of fuel straight to the cylinders, skipping the carb line.

A constant-speed propeller design using engine oil pressure boosted by a pump to move blades toward both increase and decrease pitch, without relying on counterweights.

• Double-acting: oil used for both pitch directions
• Counterweight-type: oil for one direction, counterweights/springs for the other
• Hydromatic uses a piston within the propeller dome

Memory trick: Hydromatic = oil does double duty both ways

A condition where low fuel quantity combined with aircraft maneuvering causes fuel to shift away from the tank outlet, temporarily uncovering it and allowing air to enter the fuel line.

• Occurs with low fuel and aggressive maneuvers
• Outlet is momentarily uncovered, admitting air
• Causes brief power interruption
• Risk increases in steep turns, slips, or negative-G flight

Memory trick: Low fuel + steep turn = fuel sloshes away, outlet gasps air

Best power mixture is set slightly rich of peak EGT for maximum power output; best economy mixture is set at peak EGT for minimum fuel consumption per unit of power.

• Best economy = peak EGT
• Best power = 50-125°F rich of peak EGT
• Leaning too far past peak can cause roughness or excessive CHT

Memory trick: Peak EGT is the sweet spot for sipping fuel; rich of peak is for muscle!

A relay that automatically disconnects the starter circuit once the engine reaches self-sustaining speed, preventing the starter-generator from overheating while operating as a motor.

• Prevents continued heavy starter current draw after the engine no longer needs starter assist.
• Allows smooth automatic transition from starter mode to generator mode.
• Protects starter-generator windings from thermal damage.

Memory trick: Cutout relay pulls the plug on the starter before it cooks itself.

A safety device on some hydraulic constant-speed propellers that mechanically locks blade angle if governor oil pressure is lost and the propeller begins to overspeed, preventing further pitch decrease.

• Engages on overspeed with oil pressure loss
• Locks blades at current angle
• Prevents uncontrolled fine-pitch overspeed
• Found on some turboprop hydraulic propellers

Memory trick: No oil, no overspeed — the pitch lock freezes the blades in place.

The amount of oil an engine uses per hour of operation, calculated as quarts of oil added divided by flight hours, used to assess engine wear.

• Formula: Quarts Added ÷ Flight Hours = Quarts per Hour
• Compared to manufacturer's maximum allowable consumption limit
• Rising consumption trends can indicate worn rings, valve guides, or seals

Memory trick: Quarts added over hours flown tells you how thirsty the engine is.

Solidity is the ratio of total blade area to propeller disk area; increasing blade width raises solidity, allowing the propeller to absorb more power without increasing diameter.

• Solidity = total blade area / disk area
• Wider blades increase solidity
• Higher solidity absorbs more power at same diameter
• Useful when diameter is limited by clearance

Memory trick: Fatter blades, same circle, more horsepower packed in.

A design feature where blade angle decreases from root to tip to equalize angle of attack, since tip speed exceeds root speed at a given RPM.

• Tip travels faster than root due to greater radius
• Twist keeps angle of attack more uniform along span
• Improves overall aerodynamic efficiency

Memory trick: Twist tames the tip's extra speed

A gear train that reduces the high rotational speed of a turboprop's power turbine shaft to a lower speed suitable for efficient propeller operation.

• Typical reduction ratios can exceed 10:1
• Connects free/power turbine to propeller shaft
• Essential because propellers are inefficient at high RPM

Memory trick: 'Gearbox Grinds Gears down' from fast turbine to slow prop.

A carburetor component that injects a temporary shot of fuel when the throttle is rapidly opened to prevent a lean mixture and engine hesitation.

• Activated by throttle linkage
• Prevents lean-out/hesitation on rapid throttle opening
• Distinct from the economizer/power enrichment valve

Memory trick: Accelerate = quick squirt to catch up with air.

The sequence in which cylinders receive their power stroke, designed to balance the engine and reduce vibration.

• Common four-cylinder opposed engine firing order is 1-3-2-4
• Firing order is determined by crankshaft throw arrangement
• Correct firing order minimizes vibration and uneven loading

Memory trick: One-Three-Two-Four, march the cylinders evermore

A system using hot compressor bleed air ducted through internal passages in the inlet guide vanes and nose dome to prevent ice formation.

• Uses bleed air tapped from compressor stages
• Protects inlet guide vanes, nose dome, and cowl lip
• Prevents FOD damage from shed ice ingested into engine

Memory trick: 'Bleed Air Beats the Freeze' on the nose dome and vanes.

Welded steel-tube engine mounts must be inspected for cracks, corrosion, and distortion, since they support engine weight and absorb vibration loads; cracks at weld joints are airworthiness-critical defects.

• Dye penetrant inspection commonly used to detect cracks near welds
• Elongated bolt holes indicate wear and require attention
• Corrosion under vibration isolators/mounts is a common problem area
• Cracked or bent mounts require repair by certified welder or replacement

Memory trick: 'Cracks at the Weld, Ground the World' — a weld crack grounds the aircraft until fixed.

A speed sensor geared to or positioned near the N1 (fan/low-pressure) shaft that generates an electrical signal proportional to shaft speed for cockpit N1 RPM indication.

• Measures low-pressure spool (N1) speed
• Produces frequency signal proportional to RPM
• Separate sensor exists for N2 (high-pressure spool)
• Distinct from EGT thermocouples and EPR transducers

Memory trick: Tach generator = a tiny speedometer riding the N1 shaft

The number of degrees the magnet rotates past neutral position before the breaker points open, timed to coincide with maximum rate of change of magnetic flux for the hottest spark.

• Neutral position is where flux is zero, not where points open
• E-gap angle is specified by the magneto manufacturer
• Internal timing sets breaker point opening at E-gap for max spark energy

Memory trick: E-gap gives the Extra-hot spark Exactly past neutral

The process of removing excess heat from the engine lubricating oil to maintain optimal operating temperatures.

• Primarily achieved by an oil cooler.
• Oil cooler uses ram air for heat exchange.
• Thermostatic bypass valve regulates oil flow through cooler.

Memory trick: Air cools the oil, just like the engine.

A critical indication of complete lubrication system failure in a reciprocating engine, requiring immediate engine shutdown.

• Indicates no oil flow to critical engine components.
• Rapid engine failure will occur without lubrication.
• Always treat as a genuine emergency unless proven otherwise.

Memory trick: Zero pressure means zero time, shut it down!

An explosion or combustion occurring in the intake manifold or carburetor of a reciprocating engine.

• Often caused by a lean mixture or valve issues.
• Indicates ignition of fuel/air mixture before or during intake.
• Can damage induction system components.

Memory trick: Valves Are Often Leaky, Causing Intake Combustion.

A pre-flight procedure where a small amount of fuel is drained from low points in the fuel system to check for water and sediment contamination.

• Water is denser than fuel and settles at the bottom.
• Sediment can clog filters and fuel nozzles.
• Essential for preventing engine malfunctions due to contaminated fuel.

Memory trick: Drain for Dirt and Drops

An unintended opening in the intake manifold system that allows unmetered air to enter the engine.

• Causes lean fuel/air mixture in affected cylinders.
• Leads to rough engine operation and power loss.
• Can cause fluctuating manifold pressure readings.

Memory trick: Leaky intake, lean and shaky.

An engine design featuring two independent ignition systems, each with its own spark plug, for every cylinder.

• Provides redundancy for increased safety.
• Improves combustion efficiency and power.
• Reduces likelihood of engine failure from ignition issues.

Memory trick: Two sparks, double the safety, better the burn.

A temporary period of zero oil pressure indication at startup, often caused by air in the gauge's sensing line.

• Occurs at initial startup.
• Gauge reads zero, then normalizes.
• Caused by trapped air in sensing line.

Memory trick: Air in the line makes the gauge lie, but only for a 'spell' until oil tells.

A lubrication system where the engine oil supply is stored directly in the crankcase, which also serves as the oil reservoir.

• Simpler design, fewer components.
• Common in smaller, lower-power reciprocating engines.
• Oil capacity limited by crankcase size.

Memory trick: Wet means 'within' the engine, dry means 'distant' tank.

Challenges in starting and initial operation of reciprocating engines in low temperatures, primarily due to poor fuel atomization.

• Low temp reduces fuel vaporization.
• Results in lean, non-combustible mixture.
• Causes hard start, rough running until warm.

Memory trick: Cold air makes fuel lazy; it won't vaporize, leading to a weak, rough start.

The fuel manifold valve (flow divider) in a continuous-flow fuel injection system evenly distributes metered fuel to each engine cylinder's fuel nozzle.

• Ensures equal fuel delivery to all cylinders for smooth operation.
• Contains a diaphragm and spring to open at a specific pressure.
• If faulty, can cause rough running, especially at idle, due to uneven distribution.

Memory trick: Manifold's Mission: Make Mixture Match

Surge baffles are internal structures within aircraft fuel tanks designed to dampen fuel movement and prevent excessive sloshing during flight maneuvers.

• Mitigate dynamic loads on tank structure.
• Help maintain consistent fuel supply to boost pumps.
• Contribute to aircraft stability by reducing center of gravity shifts.

Memory trick: Baffles Block Bouncing Fuel

Calculating the weight of aviation fuel by multiplying its volume by the weight of water per gallon and the fuel's specific gravity.

• Weight of fuel = Volume × (Weight of water per gallon × Specific Gravity).
• Specific gravity is a ratio of a substance's density to water's density.
• Essential for accurate weight and balance calculations.

Memory trick: Gallons times water's weight, then times specific gravity, for fuel's true weight.

A condition where high engine temperatures cause fuel in the lines to vaporize, making it difficult for the fuel pump to deliver liquid fuel to the injectors, leading to hard starting.

• Common in fuel-injected reciprocating engines.
• Mitigated by boost pumps, fuel return lines, or specific hot start procedures.
• Results in a lean mixture or no fuel delivery.

Memory trick: Hot engine, hot fuel, turns to gas, hard to start fast.

A critical seal within the propeller hub assembly that prevents engine oil, used for pitch change, from leaking out.

• Located in constant-speed propeller hub.
• Seals oil for pitch control.
• Failure causes oil leaks from hub.

Memory trick: The dome holds the oil, so a leak means the dome's seal is failing its role.

A common wear pattern in reciprocating engine cylinders where the bore diameter is larger at the combustion end than at the crankshaft end.

• Larger diameter at top (combustion end).
• Gradually tapers smaller towards bottom.
• Caused by heat, pressure, ring forces.

Memory trick: Taper is like a 'T' for Top-heavy wear, getting wider at the top.

A function within the turbine engine fuel control unit that limits fuel flow during rapid throttle movements to prevent compressor stalls and turbine over-temperature.

• Prevents over-fueling, which causes stalls.
• Balances fuel flow with available airflow.
• Ensures smooth, controlled engine acceleration.

Memory trick: FCU's a 'throttle cop', stops over-fueling to keep air flowing fine.

The deceleration limiting section of a turbine engine's Fuel Control Unit (FCU) prevents flameout during rapid power reductions by controlling the rate at which fuel flow is decreased.

• Ensures adequate fuel for combustion stability during decreasing RPM.
• Prevents an overly lean mixture that could extinguish the flame.
• Works in conjunction with other FCU sections to maintain engine control.

Memory trick: FCU: Fuel Control Unit, Finds Critical Ups and Downs

A design feature causing a constant-speed propeller to move to a coarser pitch in the event of oil pressure loss, ensuring a safe, controllable condition.

• Achieved by counterweights, springs, or aerodynamic twisting forces.
• Coarse pitch reduces drag and RPM, preventing overspeed.
• Critical for engine-out procedures.

Memory trick: No oil, no control, prop goes coarse to 'cruise' safe.