FAA Aviation Mechanic Powerplant (AMP) flashcards

A turbine engine igniter with a semiconductive material bridging its electrode gap, allowing a high-intensity capacitor discharge spark even when contaminated.

• Used with capacitor discharge (CD) exciters
• Semiconductive material ionizes to trigger discharge
• Produces very high energy, short-duration spark
• Resistant to fouling from fuel/carbon deposits

Memory trick: Semi-conductor = 'semi-open door' letting the spark jump through grime.

A preflight/maintenance check using sumping and chemical water-detecting capsules or paste to verify fuel is free of water and sediment before flight.

• Water settles at low points due to higher density than fuel
• Chemical capsules/paste change color when water is present
• Draining continues until samples are clean

Memory trick: Color change = 'red flag' — keep draining until the sample runs clean.

A fuel quantity indicating system that measures fuel level via changes in electrical capacitance between tank probes, using fuel as the dielectric.

• Probes act as capacitor plates in the tank
• Fuel's dielectric constant differs from air, changing capacitance with level
• Calibrated to read fuel quantity by weight, compensating for density/temperature changes

Memory trick: Fuel is the 'in-between stuff' that changes the capacitor's story.

A thrust indicator on many turbofan engines, calculated as the ratio of turbine discharge total pressure (Pt7) to compressor/fan inlet total pressure (Pt2).

• EPR = Pt7 / Pt2
• Displayed in cockpit as a thrust setting parameter
• Alternative to N1 for setting thrust on some engines

Memory trick: 'EPR: End over Entry' - discharge pressure over inlet pressure

A fire detection system using a sensing element that runs through the engine fire zone, changing electrical characteristics (resistance or capacitance) with heat to trigger a warning anywhere along its length.

• Detects fire/overheat anywhere along the loop, not just at fixed points
• Common types: thermistor (resistance decreases with heat) and capacitance-type elements
• Preferred for large coverage areas like engine nacelles

Memory trick: Continuous loop = a fire alarm wire that never sleeps along its whole length

The crisscross, incremental tightening pattern used on cylinder hold-down nuts (and similar circular fastener patterns) to achieve even clamping and prevent distortion.

• Crisscross/star pattern spreads load evenly
• Torque applied in 2-3 incremental steps to final value
• Prevents cylinder base flange warping and gasket leaks

Memory trick: Star pattern spreads the squeeze evenly — no favorites!

A calibration step for compression testers using a fixed restrictor that should produce a known output pressure at a given input pressure.

• Ensures accuracy of compression tester regulator and gauges
• Must be performed before every testing session
• Out-of-range readings mean the tester needs adjustment, not the engine

Memory trick: 'Trust but verify the tool before you test the jewel (engine)'

A visual inspection technique using a flexible or rigid optical instrument inserted through access ports to examine internal engine components, such as the hot section, without disassembly.

• Used to detect cracks, erosion, and burning on blades and liners
• Avoids costly engine teardown
• Performed at scheduled intervals per maintenance manual

Memory trick: 'Borescope peeks inside without a break-up' - inspect without disassembly

The overall fuel-to-air ratio in a turbine combustor is much leaner than stoichiometric because most air is used for liner cooling and dilution rather than combustion.

• Primary zone burns near stoichiometric (~15:1) with about a third of the air
• Secondary/dilution zones add the remaining air to cool gases
• Overall ratio may be around 60:1 by weight

Memory trick: Only a third of the air lights the fire; the rest keeps things cool.

Listening at various engine openings during a differential compression test helps isolate the source of air leakage past a cylinder's sealing surfaces.

• Exhaust stack hiss = leaking exhaust valve
• Intake/carburetor hiss = leaking intake valve
• Crankcase breather hiss = worn/broken piston rings

Memory trick: Follow the hiss to find the miss (leak).

An exhaust valve with a hollow stem partially filled with metallic sodium that liquefies in operation to improve heat transfer from the valve head to the stem/guide.

• Sodium melts around 208°F and sloshes during operation
• Improves cooling of the hottest engine component (exhaust valve)
• Used mainly on high-performance/high-output engines

Memory trick: Sodium sloshes heat away like a tiny liquid heat pipe.

A turboprop propeller protection system that automatically increases blade pitch when the propeller starts driving the engine (negative torque) due to a power loss, reducing drag and asymmetric thrust.

• Senses reversed torque flow
• Automatically coarsens pitch
• Protects against excessive drag/yaw
• Common on turboprop engines like PT6

Memory trick: NTS = 'No Torque, Stop the drag' — coarsens pitch when power dies.

Applying carburetor heat routes warm, unfiltered, less dense air into the induction system, temporarily enriching the mixture and reducing power slightly before ice melts and power is restored.

• Warm air source bypasses air filter
• Less dense air causes temporary rich mixture
• Loss of ram air recovery reduces manifold pressure slightly
• Should always be used at full application, never partial except for specific procedures

Memory trick: Warm air rushes in, mixture goes rich, power dips before ice melts and clears

A turbofan engine design using two independently rotating shafts: N1 (fan, LP compressor, LP turbine) and N2 (HP compressor, HP turbine), each rotating at its own optimum speed.

• N1 = low-pressure spool (fan speed indicator)
• N2 = high-pressure spool (core speed indicator)
• Independent rotation improves efficiency across power settings

Memory trick: 'N1 is the Nice big fan, N2 is the Nimble core' - N1 = fan spool, N2 = core spool

Titanium alloys are typically used in cooler front compressor stages for strength-to-weight benefits, while nickel-based superalloys are used in the hot turbine section for high-temperature strength and creep resistance.

• Titanium: front compressor, moderate temps
• Nickel superalloys: turbine discs/blades, high temps
• Some turbine blades use single-crystal casting
• Ceramic matrix composites emerging in hot sections

Memory trick: Cool front = titanium, hot back = nickel superalloy

The running clearance between a piston pin's outside diameter and the piston pin bore's inside diameter, checked during overhaul against manufacturer limits.

• Clearance = bore ID − pin OD
• Excessive clearance causes pin knock and accelerated wear
• Parts exceeding limits must be rejected, not reworked without approved data

Memory trick: Bore minus pin tells the story — too big a gap, the piston's gone.

A test device connected across magneto breaker points to precisely indicate the instant the points open, used for external magneto-to-engine timing.

• Detects the exact moment of point separation (E-gap position).
• Used with the engine set at the specified degrees BTDC on the correct cylinder.
• Ensures accurate alignment between piston position and spark timing.

Memory trick: Light out, points apart — that's the spark's starting mark.

The continuous-flow thermodynamic cycle used by gas turbine engines, consisting of intake, compression, combustion, expansion, and exhaust.

• Continuous, not intermittent, combustion
• Compression raises pressure/temperature before burning
• Expansion through turbine extracts energy to drive compressor and produce thrust

Memory trick: 'I Cook Chicken Eating Exhaust' - Intake, Compress, Combust, Expand, Exhaust

A geared ring with cam tracks on its circumference that rotates at reduced speed to actuate valve mechanisms on a radial engine via cam rollers and pushrods.

• Rotates at a fraction of crankshaft speed
• Number of lobes depends on cylinders per row
• Actuates pushrods/rocker arms for intake and exhaust valves

Memory trick: The cam RING rings the valves open in RHYTHM around the row.

A propeller ice protection system that pumps isopropyl alcohol to a rotating slinger ring, where centrifugal force distributes it through feed shoes to the blade leading edges to prevent ice buildup.

• Uses isopropyl alcohol fluid
• Slinger ring rotates with spinner/hub
• Centrifugal force distributes fluid outward
• Feed shoes bonded to blade leading edges

Memory trick: Spin the ring, fling the fluid — alcohol races out to the blade edges.

Centrifugal compressors use radial impellers to achieve high pressure ratios per stage, while axial compressors use rows of rotating/stationary blades for efficient high-airflow, multi-stage compression.

• Centrifugal: ~4:1 pressure ratio per stage, rugged, larger frontal area
• Axial: ~1.2:1 per stage, smaller frontal area, higher efficiency at high airflow
• Axial preferred for large high-bypass turbofans

Memory trick: 'Centrifugal = Compact Kick' - one big pressure jump per stage

Fluorescent penetrant inspection is used to detect surface cracks in turbine disks; any crack indication in a rotating, life-limited disk is cause for rejection due to the risk of uncontained failure.

• Disks are life-limited rotating parts subject to high centrifugal stress
• Bolt holes and rim areas are common crack initiation (stress riser) sites
• Uncontained disk failure can penetrate the engine case and aircraft structure

Memory trick: A cracked disk is a bomb spinning at thousands of RPM

Ice that forms on induction system components (air filter, screen, or scoop) when visible moisture strikes surfaces at or below freezing temperature, restricting engine air intake.

• Caused by visible moisture like snow or freezing rain
• Occurs on filters/screens/scoops, not the venturi
• Alternate air source can bypass a blocked filter

Memory trick: Impact ice = snowflakes 'crashing and freezing' onto the filter screen.

Compression rings seal combustion gases in upper piston grooves, while oil control rings, using a spring expander behind a slotted ring, meter oil film thickness in lower grooves.

• Compression rings often have tapered or barrel-shaped faces
• Oil control rings have slots or holes to return oil to the crankcase
• Ring type and position affect sealing, cooling, and lubrication

Memory trick: Top rings seal the fire, bottom rings control the oil

A stationary ring of airfoil-shaped vanes located immediately after the combustor that accelerates and directs combustion gases onto the turbine rotor blades.

• Converts pressure energy to velocity energy
• Sets the correct gas flow angle for turbine rotor blades
• Subject to extreme heat, often air-cooled

Memory trick: Nozzle = the 'aiming device' that points hot gas straight at the spinning turbine blades.

The length of the threaded shell that engages the cylinder head, which must match the manufacturer's specification so the electrode sits at the correct depth in the combustion chamber.

• Too short a reach recesses the electrode, causing poor ignition and fouling in the recess
• Too long a reach exposes threads to combustion gases, risking carbon buildup and piston/valve contact
• Reach specifications are given by engine and cylinder manufacturer, not by plug heat range

Memory trick: Reach too long, threads go wrong — carbon and clash await inside the wall.

A rating describing how rapidly a spark plug transfers heat from its firing tip to the cylinder head; selected based on typical engine operating conditions.

• Cold plugs dissipate heat quickly, resist preignition, but foul easily at low power
• Hot plugs retain heat, resist fouling, but risk preignition at high power
• Manufacturer specifies approved heat range for each engine
• Improper heat range can cause fouling or detonation/preignition

Memory trick: Cold plug = clogs; hot plug = clears

After any propeller strike or sudden stoppage, both the propeller and engine must be inspected per the manufacturer's instructions, since internal shock damage may not be visible.

• Includes crankshaft flange runout checks
• May require engine teardown depending on severity/manufacturer criteria
• Applies even if there is no visible propeller damage

Memory trick: A strike shakes the WHOLE engine, not just the prop tip

A magneto design where a permanent magnet rotates within stationary primary and secondary windings, avoiding current-carrying slip rings.

• Most modern aircraft magnetos use the rotating-magnet design.
• Rotating-armature designs require slip rings/brushes to carry primary current, increasing wear.
• Rotating-magnet design improves reliability, especially at high altitude and temperature.

Memory trick: Spin the magnet, keep the coil still — no brushes to wear or spill.

A clogged or heavily contaminated induction air filter that reduces airflow to the engine, causing an abnormally rich fuel/air mixture and reduced engine power.

• Inspected during scheduled maintenance for dust/oil buildup
• Restriction reduces airflow, enriching the fuel/air mixture
• Can cause rough running, power loss, and increased fuel consumption
• Serviced by cleaning or replacing the filter element per manual

Memory trick: Clogged filter, choked breath — engine gets fuel but not enough air.

A spring retainer mechanism that causes the valve to rotate slightly each time it operates, promoting even wear, heat distribution, and preventing carbon buildup on the valve face and seat.

• Most commonly used on exhaust valves due to higher heat/wear
• Rotation occurs each valve opening cycle
• Extends valve and valve seat service life

Memory trick: Rotocoil spins the valve like a chef rotating meat on a grill — even heat, even wear.

Ice forms in the carburetor venturi due to temperature drop from fuel vaporization and pressure reduction, even in warm, humid conditions.

• Temperature drop can be 60-70°F
• Most likely with high humidity and temps 20-90°F
• Symptoms include rough running and loss of RPM/manifold pressure
• Carburetor heat melts ice by routing unfiltered warm air

Memory trick: Venturi vaporizes fuel, vaporizing chills the air—ice follows even on warm days

A pneumatic starting device that uses compressed air to spin a small turbine wheel geared to the engine's accessory drive, commonly used on turbojet and turbofan engines.

• Air source can be APU, ground cart, or engine cross-bleed
• Includes reduction gearing and often a clutch that disengages after start
• Lightweight compared to electric starters for large engines

Memory trick: Air turbine starter = 'Blow it to go' — compressed air spins the turbine

A visual inspection method using a fiber-optic scope to examine combustor and turbine components without engine disassembly.

• Compares findings to manufacturer serviceable limits charts
• Allows detection of cracks, erosion, and blade damage without teardown
• Reduces maintenance costs by avoiding unnecessary engine removal

Memory trick: 'Peek before you pull the engine'

Wet-sump systems store oil in the engine's crankcase; dry-sump systems store oil in an external tank and use scavenge pumps to return oil from the engine.

• Dry sump allows larger oil capacity and separate tank cooling
• Wet sump is simpler with fewer components
• Dry sump requires pressure and scavenge pump stages

Memory trick: Wet sump = oil pool under the engine; dry sump = oil parked in its own tank.

Warming a cold-soaked reciprocating engine before starting to reduce oil viscosity and prevent damage from inadequate lubrication and thermal shock.

• Cold oil is thick and slow to circulate
• Preheating reduces the risk of bearing/cylinder scoring on start
• Also helps prevent thermal-shock cracking of aluminum crankcases

Memory trick: Cold oil is like cold honey — warm it up before it has to flow!

A remotely operated switch that uses a small control current to close heavy contacts, delivering high battery current to the starter motor.

• Reduces size/weight of cockpit wiring
• Energized by starter switch or starter button
• Contacts carry hundreds of amps to starter motor
• Common on both reciprocating and light turbine starters

Memory trick: Small switch, big solenoid muscle.

A starting aid that rapidly interrupts battery current to produce a series of high-voltage pulses ('shower of sparks'), compensating for low magneto output at cranking speed.

• Used only during engine starting
• Produces a rapid series of sparks, not a single spark
• Works with battery power, independent of magneto rotor speed
• Often paired with, or superseded by, impulse couplings on modern engines

Memory trick: Vibrator buzzes battery power into a shower of sparks

An antiknock compound added to aviation gasoline to increase its octane rating and resistance to detonation.

• Raises effective octane/performance number
• Allows higher compression ratios and manifold pressures safely
• Excess lead deposits can foul spark plugs, requiring lead scavengers like ethylene dibromide

Memory trick: Lead in the tank keeps knock in check.

A start condition in which the engine partially accelerates but stabilizes below idle RPM and fails to reach self-sustaining speed, typically without exceeding EGT limits.

• Often caused by insufficient starter torque or bleed air
• EGT remains within limits, unlike a hot start
• Requires shutdown and troubleshooting before re-attempting start

Memory trick: Hung start = engine gets 'hung up' below idle, stuck and stalled.

A deliberately weak drive coupling between the accessory gear train and magneto shaft that shears if the magneto seizes, preventing damage to the gear train.

• Acts as a mechanical fuse for the magneto drive
• Prevents costly gear train damage
• Failure indicates magneto internal seizure
• Must be replaced along with magneto after shearing

Memory trick: Shear pin = a sacrificial soldier saving the gear army.

The theoretical distance a propeller would advance in one revolution if moving through a solid, based purely on blade angle geometry at a given station.

• Formula: GP = 2πr × tan(blade angle)
• Differs from effective pitch due to slippage in air
• Calculated at a specific blade station radius

Memory trick: Circle the radius, then tilt it with tangent to get geometric pitch

A thrust reverser design using two hinged doors that rotate to fully block the exhaust duct and redirect exhaust gas forward, producing reverse thrust.

• Common on engines without a large bypass duct
• Doors physically close over the tailpipe exit
• Contrasts with cascade-type reversers used on high-bypass turbofans

Memory trick: Clamshell = a clam snapping shut over the exhaust pipe.

Tracking checks that all propeller blade tips travel in the same rotational plane; excessive out-of-track causes vibration.

• Default tolerance is 1/16 inch unless manufacturer states otherwise
• Measured by rotating prop against a fixed pointer
• Out-of-track can result from bent blades or hub wear
• Tracking differs from static/dynamic balance

Memory trick: 'Sixteenth or Shake' — more than 1/16 inch off and the airplane shakes.

Inlet guide vanes are inspected for dents, nicks, and bends against published blend limits; damage exceeding limits requires repair, replacement, or engine removal per the manufacturer's manual, not field correction.

• Minor damage may be blended within specified limits and re-inspected
• Damage beyond limits is not field-repairable by blending or straightening
• Excess damage can disturb airflow and increase loading on downstream blades

Memory trick: Beyond the limit? Don't file it — follow the manual's verdict

Propeller hub mounting bolts should be torqued gradually in incremental steps using a crisscross (star) pattern to ensure even seating and prevent hub distortion.

• Crisscross/star pattern used
• Torque applied gradually in increments
• Prevents hub warping/distortion
• Final torque per manufacturer specification

Memory trick: Star pattern, step by step — even pressure keeps the hub straight.

Enlargement of the valve guide bore beyond service limits, measured with a telescoping gauge and micrometer, that allows excessive valve stem side movement.

• Measured with telescoping gauge and outside micrometer
• Excess clearance on intake guides causes oil consumption and fouling
• Excess clearance on exhaust guides can cause valve guttering from poor seating
• Repaired by reaming oversize or replacing/knurling the guide

Memory trick: Loose guide, oily ride — oil sneaks past a wobbly valve stem.

Baffles direct cooling airflow over cylinder fins on air-cooled engines; damaged or missing seals allow air to bypass the cylinders, reducing cooling.

• Baffle seals are typically flexible rubber or silicone strips
• Torn/missing seals cause localized overheating
• Inspected each 100-hour/annual inspection for cracks, tears, and fit

Memory trick: Torn seal, air steals — heat prevails

A hydromechanical or electronic device that schedules fuel flow to a turbine engine based on compressor inlet conditions, engine speed, and power lever position to maintain safe, efficient operation.

• Prevents compressor stall/surge during acceleration
• Prevents overtemperature by limiting fuel flow rate of increase
• May be hydromechanical, electronic (FADEC), or hybrid

Memory trick: FCU listens to speed, temp, pressure, and pilot's demand.

A pendulum-type damper mounted on the crankshaft cheeks that oscillates in its track to cancel torsional vibration at a specific engine speed.

• Tuned to a precise pendulum frequency matching engine firing order
• Roller-to-track clearance must be checked by hand-rocking during inspection
• Worn dampers are not field-repairable and require crankshaft rejection

Memory trick: A loose swing on the crank's pendulum means it's out of tune — send it away.

A carburetor system that enriches the fuel/air mixture at high power settings to aid cylinder cooling and prevent detonation.

• Activates near full throttle/high manifold pressure
• Adds fuel beyond main metering system output
• Helps prevent detonation and excessive cylinder head temperatures

Memory trick: Economizer = extra fuel firefighter cooling hot cylinders at full power

A spring-loaded door in the induction system that opens automatically to supply unfiltered air if the primary air filter becomes restricted, preventing induction system icing or starvation.

• Opens due to differential pressure across a blocked filter
• Provides unfiltered, often warmer air as backup
• May also be manually selectable by the pilot in some installations

Memory trick: Blocked filter = vacuum pulls the backup door open.

A condition in radial engines where oil or fuel accumulates in the lower cylinders during shutdown, which can bend a connecting rod if the engine is rotated with the starter before the liquid is cleared.

• Most common in radial engines due to cylinder orientation
• Hand-turning the prop through several revolutions checks for resistance
• If resistance is felt, spark plugs should be removed to drain liquid

Memory trick: Turn it by hand before you demand it start

During runup, switching from BOTH to a single magneto should produce a drop within the manufacturer's maximum allowable drop, and the difference between the two individual magneto drops must not exceed the specified differential limit.

• Both the maximum single drop AND the differential must be satisfied
• Typical limits are around 125-150 RPM drop and 50 RPM differential (verify with AFM/POH)
• Excessive drop or differential indicates fouled plugs, bad timing, or ignition faults

Memory trick: Two rules to pass: 'Drop must be small, AND the gap between drops must be small'

A ground run performed after engine maintenance verifies proper operation, checks for leaks, and confirms instrument readings are within limits before flight.

• Checks for fuel, oil, and induction leaks at the repair area
• Verifies oil pressure, oil temperature, and CHT are within limits
• Run across a range of power settings per the maintenance manual

Memory trick: Run it, watch it, leak-check it before you fly it

A test that measures cylinder leakage by comparing air pressure applied to the cylinder against pressure retained, using a calibrated orifice.

• Standard input pressure is typically 80 psi
• Minimum acceptable is usually 60/80 (25% max loss) per manufacturer data
• Low readings require checking rings, valves, and head gasket via borescope

Memory trick: '60 is the floor' — below 60/80, the cylinder falls through

A mechanical device in the starter drive train that engages to crank the engine but automatically freewheels once the engine exceeds starter speed, protecting the starter from damage.

• Prevents engine from over-driving the starter after start
• Allows one-way torque transfer only
• Located in the starter adapter/gear reduction housing
• Failure can cause starter to remain engaged and be destroyed

Memory trick: Clutch lets go once the engine outruns it

A single electrical machine mounted on the accessory gearbox that cranks the turbine engine during start and automatically switches to generate electrical power once the engine reaches self-sustaining speed.

• Saves weight versus separate starter and generator units
• Switch-over is typically automatic via a start control unit
• Common on many turboprop and turbojet/turbofan engines

Memory trick: Starter-generator = 'Two jobs, one motor' — cranks then charges

A fuel system arrangement on multiengine aircraft that allows any engine to draw fuel from any tank, most commonly used during single-engine operation.

• Balances fuel usage after an engine failure
• Prevents stranding usable fuel in the inoperative engine's tank
• Distinct from firewall shutoff valves used to isolate a failed/fire-affected engine

Memory trick: Crossfeed lets the healthy engine 'borrow' fuel from its sick twin's tank.

Impulse blades redirect gas flow at constant pressure using energy from the stationary nozzle; reaction blades have converging passages that continue to accelerate and drop pressure within the rotating blade.

• Most engines use a combined impulse-reaction blade
• Reaction blades act like small nozzles
• Impulse blades rely on nozzle guide vanes for pressure drop

Memory trick: 'Reaction blades React by narrowing the path' — converging shape keeps accelerating gas.