FAA Aviation Mechanic Powerplant (AMP) flashcards

The float level sets the fuel level in the carburetor bowl relative to the discharge nozzle, directly controlling mixture strength.

• Float too high = fuel level too high = rich mixture/possible leakage
• Float too low = fuel level too low = lean mixture/possible starvation
• Level is checked per manufacturer's dimension using a float gauge

Memory trick: High float, high fuel, high richness

A cold-weather starting aid that mixes raw fuel into engine oil before shutdown to reduce viscosity for easier starting; the fuel evaporates from the oil after the engine warms up.

• Fuel is introduced into oil supply just before shutdown
• Thinned oil circulates more easily during cold starts
• Gasoline evaporates from oil as engine warms after starting

Memory trick: Dilution thins the oil like adding water to syrup for easy pouring in the cold

A turbine engine start condition where EGT exceeds the specified limit due to excess fuel relative to airflow before the engine reaches idle.

• Caused by too much fuel or insufficient starter airflow
• Requires immediate abort to prevent turbine damage
• Different from a hung start, which involves low RPM, not high EGT

Memory trick: Hot start = 'too hot, too fast fuel' — EGT spikes before RPM catches up.

Deposits of lead bromide on spark plug electrodes caused by extended low-power/idle operation with leaded avgas, leading to intermittent misfire that often clears with a brief high-power run.

• Most common during prolonged ground idle or descent at low power
• Leaning the mixture during ground ops reduces lead deposit formation
• A brief high-power 'clearing' runup can help burn off deposits

Memory trick: Lead fouling = 'idle too long, lead builds strong' — lean it out to keep it clean

A wax-pellet type thermostatic valve in the oil system that routes cold oil around the oil cooler and directs hot oil through the cooler core once operating temperature is reached.

• Bypasses cooler when oil is cold for faster warm-up
• Expands with heat to route oil through cooler core
• Stuck-in-bypass failure causes chronic high oil temperature with normal pressure

Memory trick: Vernatherm stuck in bypass = oil takes the detour and skips the cooler entirely, staying hot.

An auxiliary pump that pressurizes fuel lines to prevent vapor formation and assist the engine-driven pump during high altitude, hot weather, takeoff, and engine starting.

• Maintains positive fuel pressure to prevent vaporization
• Used during takeoff, landing, high altitude cruise, and priming
• Backs up the engine-driven fuel pump if it fails

Memory trick: Boost pump keeps fuel a liquid, not a bubble.

The ratio of total cylinder volume (piston at BDC) to clearance volume (piston at TDC), indicating how much the fuel-air charge is compressed.

• CR = (swept volume + clearance volume) / clearance volume
• Higher CR increases thermal efficiency but risk of detonation
• Typical aircraft reciprocating engines run 7:1 to 10:1

Memory trick: Big volume over small volume tells the squeeze story

A design/control feature where the fuel control limits engine thrust so rated thrust is maintained across ambient temperatures up to a specified 'flat rate' temperature, beyond which available thrust decreases.

• Protects the engine from overtemperature on cold/moderate days by limiting fuel flow
• Rated thrust is constant below the flat-rate temperature
• Above flat-rate temp, thrust falls off to protect turbine limits

Memory trick: Flat rating = thrust plateau until the heat gets too much, then it slides downhill

A turbine engine ignition unit that charges a storage capacitor to high voltage and rapidly discharges it through a trigger transformer to produce a high-energy spark at the igniter plug.

• Produces much higher spark energy than reciprocating magnetos
• Used because turbine fuel ignition needs a strong, reliable spark
• Capacitor charges continuously and discharges intermittently at set intervals
• Only used during starting and, in some cases, continuous ignition for icing/turbulence

Memory trick: Charge the capacitor, then unleash a lightning bolt

A valve lifter that uses a spring-loaded plunger and one-way check valve, filled with pressurized engine oil, to automatically maintain zero valve clearance during engine operation.

• Uses engine oil pressure to extend the internal plunger
• Check valve traps oil to maintain zero-lash clearance
• Automatically compensates for thermal expansion and wear

Memory trick: Oil fills the plunger like a hydraulic jack, quietly taking up all the slack automatically.

The procedure of positioning the crankshaft at the specified degrees BTDC on the compression stroke, then rotating the magneto on its mounting until the breaker points just open, to synchronize spark timing with piston position.

• Uses crankshaft timing marks/degree wheel and a timing light or buzzer box
• Performed after internal E-gap timing is already set within the magneto
• Ensures spark occurs at the correct crank angle for combustion

Memory trick: Internal E-gap sets the spark inside the mag; external timing lines the mag up with the crank.

A valve, usually pilot-operated, that directs fuel from a selected tank (or tanks) to the engine and provides an OFF position for shutdown or emergencies.

• Common positions: LEFT, RIGHT, BOTH, OFF
• Located between tanks and fuel pump/strainer
• Allows tank balancing and isolation of a leaking tank

Memory trick: Tank picks, valve flicks, strainer sticks (catches dirt), pump kicks fuel to the engine.

The clearance between the ends of a piston ring when installed squarely in the cylinder bore, required to allow for thermal expansion during engine operation.

• Measured with a feeler gauge while ring is squared using an inverted piston
• Insufficient gap causes ring butting, scuffing, or seizure when hot
• Excessive gap causes blow-by and loss of compression
• Corrected by carefully filing the ring ends if gap is too small

Memory trick: Too tight, rings fight (butt) — file for space to expand.

A starter drive mechanism that uses the inertia of a pinion gear on helical splines to automatically engage and disengage the engine ring gear.

• Pinion lags behind the rapidly accelerating shaft due to inertia, screwing into mesh.
• Automatically disengages when the engine overspeeds the starter after starting.
• Simple, self-contained mechanism requiring no separate solenoid to shift the pinion.

Memory trick: Bendix lags behind and screws itself in — inertia does the work.

A system using engine bleed air to pressurize the oil tank, ensuring positive oil pump inlet pressure and preventing cavitation at altitude.

• Uses bleed air through a pressurization valve
• Prevents pump cavitation and foaming
• Tank relief valve limits maximum pressure

Memory trick: Pressurized tank = 'pushing' oil steadily into the pump so it never runs dry-mouthed (cavitates).

An ignition system where low voltage is distributed to individual transformer coils near each spark plug, which then step up the voltage just before the plug fires.

• Reduces high-voltage wire length exposed to low air pressure
• Minimizes flashover/leakage at altitude
• Step-up coils located near spark plugs, not at the magneto
• Common on some radial and high-altitude engines

Memory trick: Keep the high voltage short and close to the plug

A start condition where EGT exceeds the specified limit due to an excessively rich fuel-to-air ratio, usually from fuel introduced too early or in excess relative to airflow.

• Caused by too much fuel flow for available airflow during light-off
• Can result from low starter cranking speed limiting airflow
• Requires immediate abort per checklist to protect turbine section
• Different from a hung start, which involves insufficient acceleration

Memory trick: Too much fuel, too little air, too much heat

A gear reduction assembly between the starter motor and crankshaft containing a clutch to disengage the starter automatically and a shear section to protect the drive train from overtorque.

• Clutch allows freewheeling once engine starts
• Shear section fails intentionally under excessive torque
• Common on radial and some large reciprocating engines

Memory trick: Adapter = a bodyguard that lets go (clutch) and sacrifices itself (shear) to protect the starter.

A torquemeter measures twisting force on a turboprop's propeller shaft; shaft horsepower is calculated using HP = (Torque × RPM) / 5,252.

• Torquemeters are essential since turboprop thrust is measured as SHP, not EPR
• Formula: HP = Torque(ft-lb) × RPM / 5,252
• 5,252 is the constant derived from 33,000 ft-lb/min per HP divided by 2π

Memory trick: Remember '5,252' as the magic number that turns torque and RPM into horsepower.

Bearings that support a rotating shaft through a full-surface sliding contact rather than rolling elements, offering greater load distribution and shock absorption when supplied with pressurized oil.

• Larger contact area than ball/roller bearings
• Require continuous pressurized oil film to prevent metal-to-metal contact
• Common for main and connecting rod bearings in reciprocating engines

Memory trick: Plain bearings SPREAD the load like a wide hand catching a ball, cushioning the shock.

A magnetized plug installed in a turbine engine's oil system to collect ferrous metal particles, serving as an early indicator of bearing or gear wear.

• Located in scavenge lines or sumps
• Some are electrically monitored (chip detector light in cockpit)
• Fine fuzz may be normal wear; large chips indicate a developing failure

Memory trick: The chip detector is a magnet fishing for metal trouble in the oil.

The throw is the offset distance between the main journal and rod journal centerlines; stroke equals twice the throw since the piston travels the full diameter of the crank circle.

• Stroke = 2 × throw
• Throw is also called crank radius
• Determines piston travel distance in the cylinder

Memory trick: Throw is the RADIUS, stroke is the full DIAMETER of the crank's circle.

A standardized system of numbers assigned along the length of a gas turbine engine, from inlet to exhaust, used to reference specific measurement or component locations (e.g., Pt2, Pt7).

• Station 2 is typically compressor/fan inlet
• Numbers increase moving aft through engine
• Used in EPR and other performance calculations

Memory trick: 'Front to back, numbers stack' - stations increase moving rearward

An unstable airflow condition in a turbocharger's compressor caused by abrupt throttle changes, producing banging noise and fluctuating manifold pressure.

• Triggered by rapid throttle movement
• Produces audible banging/chugging
• Can cause fluctuating manifold pressure
• Avoided by smooth, gradual throttle application

Memory trick: Slam the throttle, the compressor coughs and bangs back

The float level sets the fuel height maintained in the carburetor bowl, which controls fuel delivery through the discharge nozzle.

• Float level is set per manufacturer specs using a float gauge
• High float level = rich mixture/flooding
• Low float level = lean mixture/fuel starvation at high power

Memory trick: Float high, fuel flies high (too rich)

Excessive radial/axial shaft play in a turbocharger indicates worn center bearings, which can lead to wheel-to-housing contact and eventual failure.

• Checked by hand-moving the shaft radially and axially
• Rub marks on housing confirm bearing wear
• Oil starvation/contamination is a common cause
• Left unaddressed, can lead to catastrophic turbo failure

Memory trick: 'Wobbly Wheel, Worn Bearing' — play in the shaft means the bearing is going bad.

Rotating propeller blades to approximately 90 degrees to the plane of rotation to minimize drag when an engine is shut down in flight.

• Blade angle set near 90° (parallel to airflow)
• Reduces drag and prevents windmilling damage
• Common on multi-engine and turboprop aircraft

Memory trick: Feather like a bird's wing edge-on to the wind to cut drag

Standard method of identifying cylinders on horizontally opposed engines, viewed from the rear, with odd numbers on the right bank starting at the front and even numbers on the left bank.

• Cylinder 1 is the right front cylinder viewed from rear
• Odd numbers are on the right bank, even on the left
• Numbering is used to reference firing order and timing

Memory trick: Right side, Rear view, cylinder 1 is up front on the Right

A disruption of smooth airflow through the compressor, causing pressure surges, loud banging, vibration, and increased EGT, often due to distorted inlet airflow or excess fuel flow.

• Caused by FOD, damaged blades, or rapid throttle movement
• Symptoms include bangs, vibration, and EGT rise
• Corrected by reducing throttle/fuel flow

Memory trick: 'Stall? Pull it back!' - reduce throttle to fix a stall

The exhaust valve opens before BDC on the power stroke to use residual cylinder pressure for initial scavenging, reducing pumping losses during the exhaust stroke.

• Occurs before BDC while cylinder pressure is still elevated
• Reduces exhaust stroke pumping work
• Sacrifices small amount of power stroke for better scavenging

Memory trick: Exhaust valve opens EARLY to let the pressure blow itself out before the piston even asks.

A ground test where the mixture control is moved toward idle cutoff to verify idle fuel/air ratio by observing tachometer response.

• Correct setting: momentary 25-50 RPM rise before engine dies
• No rise/immediate drop = too lean
• Rise greater than spec = too rich
• Return mixture to rich promptly after the check

Memory trick: 'Rise then die' means it's set just right.

On a normally aspirated engine, manifold pressure at idle is far below atmospheric because the nearly closed throttle valve restricts airflow, creating a vacuum downstream.

• Idle throttle plate is nearly closed
• Low MP reading indicates high throttle restriction
• At full throttle, sea level, MP approaches atmospheric pressure
• Supercharged engines can exceed atmospheric pressure

Memory trick: Closed throttle = closed door = low pressure inside

The actual distance a propeller advances through the air in one revolution, which is less than geometric pitch due to slippage.

• Always less than geometric pitch
• Difference between the two is called 'slip'
• Affected by blade angle, RPM, and forward airspeed

Memory trick: Geometric is the goal, Effective is what's real

Fuel injection systems introduce fuel near the cylinder rather than in a venturi, significantly reducing the risk of induction icing compared to float carburetors.

• Fuel injected near intake port, not in venturi
• Reduces induction icing risk substantially
• Still requires mixture control for altitude
• Requires higher-pressure engine-driven fuel pump

Memory trick: Injection skips the icy venturi, delivering fuel straight to the cylinder's door

A laboratory technique that measures trace metal content in engine oil to detect abnormal internal wear trends before component failure occurs.

• Iron/chromium indicate steel or chrome-plated part wear (cylinders, rings, cam)
• Copper/tin/silver indicate bearing or bushing wear
• Aluminum indicates piston or crankcase wear
• Trend analysis over multiple samples is more valuable than a single reading

Memory trick: Iron and chrome climbing = steel parts grinding down inside

Total engine displacement is the swept volume of one cylinder multiplied by the number of cylinders, using the formula 0.7854 x bore^2 x stroke.

• 0.7854 = pi/4, area of a circle formula constant
• Bore is squared, stroke is not
• Multiply per-cylinder displacement by number of cylinders for total

Memory trick: 0.7854 times bore-squared times stroke — the circle's area sweeping through the stroke.

A system that allows outside air to enter the fuel tank as fuel is consumed, preventing a vacuum from forming that would restrict fuel flow.

• Blocked vents can cause fuel starvation due to vacuum formation
• Vents can be blocked by ice, insects, or debris
• Some aircraft have vent line heating or check valves to prevent icing

Memory trick: Blocked vent = a straw with your thumb over the top, fuel won't flow

A streamlined dome-shaped fairing covering the propeller hub to reduce drag and improve airflow.

• Reduces aerodynamic drag
• May direct cooling air to the engine
• Can be a two-piece or one-piece design

Memory trick: Spinner smooths the storm of air

A turbine engine fuel nozzle with two orifices (primary and secondary) designed to maintain proper atomization across the full range of engine power settings.

• Primary orifice handles fine atomization at low flow (idle/start)
• Secondary orifice opens at higher fuel pressures for high power
• Flow divider routes fuel appropriately between primary and secondary manifolds

Memory trick: Two doors for fuel: a small one for a whisper, a big one for a roar.

The magneto coil uses primary and secondary windings on a common core to transform low-voltage primary current into the high voltage needed to fire spark plugs.

• Primary winding: few turns of heavy wire, carries low-voltage current.
• Secondary winding: many turns of fine wire, produces high voltage via mutual induction.
• Voltage is induced when the primary circuit is interrupted by the breaker points.

Memory trick: Few thick turns in, many thin turns out — high voltage shout.

A preflight procedure where fuel is drained from the lowest point of the fuel system to check for water and sediment contamination.

• Water is denser than avgas and settles at the bottom
• Sediment and water appear as distinct droplets in the sample
• Performed before each flight and after refueling

Memory trick: Sump drain sinks out the sinkers (water/sediment)

An auxiliary set of breaker points in some magnetos that fires the spark after top dead center during starting to prevent engine kickback.

• Used mainly on radial/large engines
• Fires spark retarded (late) only during cranking
• Normal running points resume advanced timing after start
• Alternative to impulse coupling for kickback prevention

Memory trick: Retard = 'wait a moment' before sparking, so the prop doesn't punch back.

A slight excess in bearing shell circumference over the housing bore that creates radial pressure, holding the bearing firmly in place once the cap is torqued.

• Prevents bearing rotation (spinning) in the housing
• Ensures full metal-to-metal contact for heat transfer
• Distinct from bearing spread, which holds the shell in place before final torque

Memory trick: Crush it tight so it won't spin in flight!

A structural design requirement where the fan case is built to contain a fan blade failure, preventing debris from exiting the engine and damaging the aircraft.

• Required by 14 CFR Part 33 certification standards
• Made of Kevlar wrap or heavy steel/titanium
• Prevents uncontained failure events

Memory trick: Think of the fan case as a bulletproof vest for a broken fan blade.

A mechanical/hydraulic device that meters fuel flow to a turbine engine based on compressor inlet conditions, rotor speed, and throttle position.

• Uses Pt2/Tt2, N speed, and throttle position
• Prevents overtemperature and compressor stall during transients
• Being replaced in modern engines by FADEC

Memory trick: Think 'PETS' - Pressure, Engine speed, Temperature, Stick (throttle) for FCU inputs.

Excessive clearance between a valve stem and its guide can allow oil to be drawn into the combustion chamber, especially on the intake valve during the intake stroke, causing increased oil consumption and blue exhaust smoke.

• Common on intake guides due to manifold vacuum pulling oil down the stem
• Differential compression test may remain normal since it tests seat/ring sealing, not guide wear
• Symptoms: bluish-gray smoke, high oil consumption without compression loss

Memory trick: A loose guide lets oil sneak down the stem like water down a wide straw!

A calibrated orifice at each cylinder's intake port that continuously sprays metered fuel into the airstream for vaporization before entering the cylinder.

• Fuel flow is continuous, not timed to valve events
• Located at intake port near intake valve, not inside cylinder
• Flow divider (not nozzles) apportions fuel equally to each cylinder

Memory trick: 'Nozzles never stop spraying — timing is the divider's job'

A propeller whose blade angle can only be changed on the ground with the engine stopped, by loosening a hub clamp, rotating the blades, and re-securing them; it then operates as a fixed-pitch propeller in flight.

• Blade angle set only on the ground
• Engine must be stopped for adjustment
• Acts as fixed pitch once set and locked
• No in-flight pitch control capability

Memory trick: Set it on the ground, fly it fixed — no in-air changes allowed.

Turbine engine oil scavenge pumps are built with greater capacity than the pressure pump to handle the increased volume of aerated oil returning from bearing sumps.

• Oil becomes aerated (foamy) after lubricating bearings
• Aeration increases oil volume without increasing mass
• Scavenge pump capacity must exceed pressure pump capacity to prevent sump flooding

Memory trick: Foamy oil takes up more room, so scavenge needs a bigger scoop.

Small holes/slots in the combustor liner admit compressor discharge air to form an insulating film that protects the liner from combustion heat.

• Uses compressor discharge (P3) air
• Forms a boundary-layer cooling film
• Protects liner from radiant/convective heat
• Also dilutes gases before turbine entry

Memory trick: Film holes = a fire blanket of air

A digital electronic system with complete authority over turbine engine operation, including fuel scheduling, starting, and limit protection.

• Full Authority = no separate hydromechanical backup needed
• Uses engine sensors and an Electronic Engine Control (EEC) computer
• Automatically protects against exceedances like overspeed and overtemperature

Memory trick: FADEC: Fully Automatic, Digital, Engine Command

A start malfunction where the engine ignites but fails to accelerate past a certain RPM due to insufficient starter torque or airflow, requiring an aborted start.

• Engine lights off but RPM plateaus below idle
• Usually caused by low starter air pressure or weak electrical starter power
• Must be aborted per checklist to prevent overheating
• Distinct from hot start (temperature) and no-light start (no ignition)

Memory trick: Not enough push to climb the hill to idle

Avgas is graded by an antiknock/performance number that indicates its resistance to detonation under lean and rich mixture conditions.

• 100LL = 100 octane rating, low lead
• Higher numbers indicate greater detonation resistance
• Grade is dyed blue for 100LL identification

Memory trick: '100' fights knock, 'LL' keeps lead low.

Rotational tip speed = pi x diameter x RPM, used to evaluate how close propeller tips are approaching the speed of sound.

• Formula: tip speed (ft/min) = pi x D x RPM
• Convert ft/min to mph by multiplying by 60 and dividing by 5,280
• Forward airspeed must be added for total resultant tip speed

Memory trick: Pi times D times RPM gives you the spin speed king

A spring-loaded valve in the lubrication system that opens when oil pressure exceeds a preset limit, bypassing excess oil back to the pump inlet or sump to protect the system from overpressure.

• Located near the oil pump discharge
• Opens at a calibrated spring pressure setting
• Stuck closed causes high pressure; stuck open causes low pressure

Memory trick: Closed valve traps oil in, pressure climbs high.

Grounded braided metal covering over each ignition lead that suppresses radio-frequency interference generated by the high-voltage spark discharge.

• Grounded at both magneto and spark plug ends
• Prevents radio/avionics interference
• Must be checked for continuity and corrosion
• Damaged shielding can cause static in radios

Memory trick: Shield = Static Shield for the radio.

A localized area of overheating or burn-through on a turbine combustor liner, usually caused by an uneven fuel spray pattern from a malfunctioning nozzle.

• Found during borescope inspection of the combustion section
• Concentrated near one nozzle indicates a nozzle spray defect
• Left unrepaired, can lead to liner cracking or distortion
• Requires nozzle inspection/replacement and liner assessment

Memory trick: One hot spot, one bad nozzle — find the culprit spraying crooked.

An ignition analyzer displays firing voltage patterns for each cylinder; abnormal peak voltages help diagnose plug gap, fouling, or circuit resistance problems.

• Higher-than-normal firing voltage suggests a wide gap or added circuit resistance.
• Lower-than-normal firing voltage suggests fouling or a partial short.
• No trace at all suggests an open circuit with no spark produced.

Memory trick: Bigger gap, bigger push — high voltage means the spark had to work harder.

Wear-through of the soft overlay plating on a main or connecting rod bearing shell, exposing the harder base alloy underneath, indicating bearing replacement is required.

• Bearings have a soft overlay bonded to a stronger backing material
• Copper/bronze color showing through overlay = base metal exposed
• Indicates bearing has reached end of service life
• Often caused by oil contamination, misalignment, or extended service

Memory trick: See copper shine? Time's up — retire the bearing.

Minor nicks on aluminum propeller blades may be blended or stop-drilled within limits specified by the manufacturer's approved data, preventing stress risers and crack propagation.

• Repairs must follow manufacturer's allowable limits chart
• Stop-drilling can arrest crack propagation from a nick
• Nicks in high-stress areas (like near the tip or on leading edge) are more critical

Memory trick: Small nick? Check the BOOK before you touch the blade