CAA NZ AME Piston Engines cheat sheet

Ideal Otto cycle efficiency: η = 1 − 1/r^(γ−1), where r is compression ratio and γ ≈ 1.4 for air; efficiency rises with compression ratio but is limited by detonation and fuel octane.

Four-stroke cycle: induction, compression, power (combustion/expansion), exhaust - two crankshaft revolutions per cycle; a four-cylinder four-stroke fires every 180° of crank rotation.

Brake mean effective pressure BMEP = (brake power × 60) / (n × swept volume × cycles per rev), with n in rpm; BMEP compares output independent of engine size.

Indicated power exceeds brake power by friction and pumping losses; mechanical efficiency = brake power / indicated power, typically 0.75–0.90 for aero piston engines.

Specific fuel consumption BSFC = fuel mass flow / brake power; best economy occurs lean of best power mixture, while best power is near 100–150 °F rich of peak EGT.

Detonation is uncontrolled explosive burning after normal ignition, driven by high MAP, high CHT, lean mixture, low octane or over-advanced timing; pre-ignition is ignition before the spark, usually from a hot spot.

Volumetric efficiency = actual air mass inducted / theoretical swept-volume air mass; it falls with throttle restriction and rises with tuned intake and exhaust ram effects.

Power is proportional to MAP × rpm × volumetric efficiency; at constant rpm, a change in manifold pressure of about 1 inHg alters power by roughly 3–4% at low boost.

Horizontally opposed (flat) four/six layouts dominate light aircraft: short crankshaft, low frontal area, good cooling, but wide nacelle and paired cylinders sharing a crankpin.

Radial engines use one connecting rod per crankpin (master rod) with articulated link rods; firing order alternates cylinders to smooth torque and cooling.

Crankshafts are forged or machined steel, dynamically balanced, and carry counterweights; runout limits and journal wear are checked against the maintenance manual.

Connecting rods: I-beam or H-beam section; big-end bearing is a shell or precision insert, small-end is a bushing or needle bearing; rod bolts are stretch- or torque-critical and are not reused out of limits.

Bearings: main bearings carry crank radial loads, thrust is taken by a flanged bearing or separate thrust washer; oil clearance is measured with plastigauge or micrometers.

Crankcase halves are split on the crankshaft centreline, line-bored for main bearings, and sealed with anaerobic sealant or gaskets; through-bolts and studs set bearing crush.

Firing order determines crankshaft throw layout: a flat-four typically fires 1-3-2-4 or 1-4-2-3 to alternate banks; incorrect order causes rough running and vibration.

Accessory drives (magnetos, oil pump, fuel pump, vacuum pump) are gear- or belt-driven from the crankcase; magneto drive ratio and timing marks must be re-established after reassembly.

Cylinder barrels are steel or chrome/nickel-plated; air-cooled aero cylinders use deep fins and a fin-to-baffle pressure cooling arrangement; bore and taper limits come from the manual.

Pistons are aluminium alloy with a cam-ground skirt, offset pin to reduce slap, and controlled expansion; ring grooves carry compression rings above the oil control ring.

Ring end gap and side clearance are measured in the bore; too little gap causes scuffing and breakage, too much causes blow-by and oil consumption.

Piston pin retention: full-floating pins with circlips or plugs, or pressed pins; circlip seating and pin-to-boss clearance are critical inspection points.

Valves: intake valves usually larger and may be sodium-cooled or stellite-faced; exhaust valves run hottest and need correct seat contact and stem-to-guide clearance.

Valve lash is set cold or hot per the manual; solid lifters need periodic adjustment while hydraulic lifters self-adjust within oil pressure limits.

Valve springs are checked for free length, squareness and installed pressure; weak springs cause valve float at high rpm and burnt valves.

Valve seats are ground to a specified contact width and angle; concentricity is checked with blue marking, and recession from burnt seats requires re-cutting or replacement.

Float-type carburettor metering: venturi depression draws fuel through the main jet; the float chamber maintains a constant head, and the mixture needle/air bleed trims the ratio.

Idle and off-idle circuits supply fuel at low airflow; accelerator pump enriches on rapid throttle opening to prevent lean stumble.

Mixture control valve leans the fuel-air ratio as altitude rises; best power is near 100–150 °F rich of peak EGT, best economy near peak EGT or lean of it within limits.

Carburettor icing occurs with temperature drop in the venturi plus moisture; apply carb heat when RPM drops or roughness appears, expect initial further RPM loss as melted ice enters the engine.

Fuel injection meters by airflow through a servo and air-fuel control unit; it gives more even distribution, no venturi icing, and allows precise lean-of-peak operation.

Fuel pressure and flow are checked against the manual; vapour lock risk rises with hot fuel lines, low pressure and volatile fuel grades.

Idle mixture is set by the idle mixture screw to give a specified RPM rise when the throttle is closed; too lean gives a stumble, too rich gives rough running and fouling.

Detonation margin depends on mixture, MAP and CHT; leaning above 75% power is restricted by most manufacturers to avoid detonation.

A magneto is a self-contained generator: rotating magnet induces EMF in the primary, points open to collapse the field, and the secondary coil produces the high voltage.

The condenser across the points suppresses arcing, speeds field collapse and protects the points; a failed condenser causes weak spark and point burning.

Timing is set at a specified advance before TDC (often 20–25°); internal magneto timing aligns the rotating magnet with the pole shoe, then the engine timing is set on number-one cylinder.

Impulse coupling provides a retarded, strong spark for starting and disengages above a set rpm; a failed impulse coupling can cause kickback and hard starting.

Two magnetos give redundancy and faster flame-front burn; the mag check shows RPM drop within limits per mag, with excessive drop indicating fouling or timing faults.

Ignition harness: shielded high-tension leads, a distributor rotor and terminal outlets; resistance and insulation tests detect arcing and radio noise.

Spark plugs: massive-electrode or fine-wire iridium; gap, reach and heat range must match the engine; fouling is cleaned and tested, and resistance is measured on resistor plugs.

Dead-cut check confirms the magneto switch grounds both mags; a live magneto is a serious hazard during prop handling.

Dry-sump lubrication: pressure pump feeds bearings and rocker boxes, scavenge pump returns oil to the tank; a wet-sump stores oil in the crankcase.

Oil pressure and temperature limits come from the manual; low pressure at idle can be normal, but low pressure at cruise indicates pump wear, blocked pickup or dilution.

Oil cooler is thermostatically or manually bypassed to hold oil temperature; a blocked cooler or low airflow raises temperature and thins the oil.

Straight mineral oil is used for break-in, then ashless dispersant oil; additive packages affect deposit control and seal compatibility.

Oil analysis and filter inspection detect metal, water and fuel dilution; rising iron or aluminium points to wear of specific components.

Air cooling: cylinder fins, baffles and cowl flaps control airflow; a pressure-plenum arrangement forces air through the fins rather than around them.

CHT and oil temperature limits protect the engine; high CHT with normal oil temperature suggests baffle leaks or a lean mixture, not an oil problem.

Cooling drag is managed with cowl flaps; closed flaps in climb raise CHT, open flaps in descent cause shock cooling and must be limited per the manual.

Exhaust systems route gases through stacks or a collector; cracks, leaks and loose clamps cause CO ingress into the cabin and must be inspected.

Turbocharging uses exhaust energy to drive a turbine coupled to a compressor; boost is controlled by a wastegate that bypasses exhaust around the turbine.

Supercharging is mechanically driven from the crankshaft; a gear-driven blower raises MAP without exhaust backpressure but consumes shaft power.

Wastegate and controller faults cause overboost or underboost; overboost protection and a manifold pressure limit protect the engine structure.

Turbocharged engines need a cool-down period before shutdown so the turbine and bearings do not soak in heat and coke the oil.

Intercooling lowers compressor outlet temperature, increasing density and detonation margin; aftercooling is the same function between compressor and throttle.

Critical altitude is the highest altitude at which rated MAP can be maintained; above it, power falls with density altitude.

Exhaust backpressure and turbine inlet temperature limits protect the turbine; high TIT with high MAP is a detonation and turbine damage risk.

Fixed-pitch props trade climb versus cruise by blade angle; a coarse pitch gives cruise speed but slower acceleration and lower static RPM.

Constant-speed propellers use a governor with flyweights and a speeder spring to control oil pressure to the hub, holding selected RPM by changing blade angle.

Governor operation: increasing RPM raises flyweight force, the pilot valve ports oil to increase blade angle; decreasing RPM does the reverse.

Oil pressure to the hub (or lack of it) determines pitch direction; loss of oil pressure drives the prop to fine pitch or feather depending on design.

Feathering rotates blades to the flight position to reduce drag on a failed engine; unfeathering uses accumulator or oil pressure to return to fine pitch.

Vibration sources: propeller balance, engine firing order, worn mounts and torsional resonance; a dynamic balance reduces vibration and bearing loads.

Propeller strike requires engine teardown inspection for crankshaft runout, counterweight and gear train damage.

RPM limits and manifold pressure limits are coupled: avoid overboost and overspeed combinations during rapid throttle movement.

Tachometer reads engine RPM; an electrical or mechanical drive, it is checked against a known reference for accuracy.

Manifold pressure gauge reads absolute pressure in the intake; at idle it reads low, and it is the primary power reference for a constant-speed prop.

CHT and EGT probes are thermocouples; EGT is used for mixture leaning, CHT for cooling and detonation monitoring.

Oil pressure and temperature gauges, fuel pressure/flow and fuel quantity indications are cross-checked during run-up and cruise.

Fire detection uses a thermocouple or continuous-loop sensor in the engine compartment, with a warning light and sometimes an audible alarm.

Fire suppression uses a fixed bottle with agent (Halon or clean agent) discharged to the engine compartment; the bottle pressure and squib circuit are inspected.

A fire warning requires shutting off fuel, mixture, ignition and electrical supply, then discharging the bottle and landing as soon as possible.

Instrument markings: green normal range, yellow caution, red limits; a gauge reading outside limits is treated as an engine malfunction until confirmed.

Compression check: differential test at a set pressure; leakage past rings (crankcase breather), intake valve (carburettor) or exhaust valve (exhaust stack) locates the fault.

Cylinder leakage limits and borescope inspection of valves, seats and piston crowns are part of routine inspection; burnt exhaust valves show as a wedge-shaped leak.

Run-up checks: magneto drop, carb heat drop, idle mixture, propeller cycle, oil pressure and vacuum; record values against limits.

Torque and safety: fasteners torqued to manual values and lockwired or tabbed; critical bolts are not reused if stretch limits are exceeded.

Troubleshooting follows symptom-cause logic: rough running at lean mixture points to induction leaks; high oil consumption to rings or guides; hard starting to ignition timing or impulse coupling.

Ground running requires chocks, fire extinguisher, prop clear area and monitoring of CHT, oil pressure and RPM; avoid prolonged ground running at high power.

Preservation: fogging oil into cylinders, sealing openings, dehydrating plugs and inhibiting fuel systems for storage; rotate or run per the manual.

Maintenance records must capture work performed, reference data, and sign-off by an appropriately authorised person; airworthiness depends on correct documentation.

Ideal Otto cycle efficiency: η = 1 − 1/r^(γ−1), where r is compression ratio and γ ≈ 1.4 for air; efficiency rises with compression ratio but is limited by detonation and fuel octane.

Four-stroke cycle: induction, compression, power (combustion/expansion), exhaust - two crankshaft revolutions per cycle; a four-cylinder four-stroke fires every 180° of crank rotation.

Brake mean effective pressure BMEP = (brake power × 60) / (n × swept volume × cycles per rev), with n in rpm; BMEP compares output independent of engine size.

Indicated power exceeds brake power by friction and pumping losses; mechanical efficiency = brake power / indicated power, typically 0.75–0.90 for aero piston engines.

Specific fuel consumption BSFC = fuel mass flow / brake power; best economy occurs lean of best power mixture, while best power is near 100–150 °F rich of peak EGT.

Detonation is uncontrolled explosive burning after normal ignition, driven by high MAP, high CHT, lean mixture, low octane or over-advanced timing; pre-ignition is ignition before the spark, usually from a hot spot.

Volumetric efficiency = actual air mass inducted / theoretical swept-volume air mass; it falls with throttle restriction and rises with tuned intake and exhaust ram effects.

Power is proportional to MAP × rpm × volumetric efficiency; at constant rpm, a change in manifold pressure of about 1 inHg alters power by roughly 3–4% at low boost.

Horizontally opposed (flat) four/six layouts dominate light aircraft: short crankshaft, low frontal area, good cooling, but wide nacelle and paired cylinders sharing a crankpin.

Radial engines use one connecting rod per crankpin (master rod) with articulated link rods; firing order alternates cylinders to smooth torque and cooling.

Crankshafts are forged or machined steel, dynamically balanced, and carry counterweights; runout limits and journal wear are checked against the maintenance manual.

Connecting rods: I-beam or H-beam section; big-end bearing is a shell or precision insert, small-end is a bushing or needle bearing; rod bolts are stretch- or torque-critical and are not reused out of limits.

Bearings: main bearings carry crank radial loads, thrust is taken by a flanged bearing or separate thrust washer; oil clearance is measured with plastigauge or micrometers.

Crankcase halves are split on the crankshaft centreline, line-bored for main bearings, and sealed with anaerobic sealant or gaskets; through-bolts and studs set bearing crush.

Firing order determines crankshaft throw layout: a flat-four typically fires 1-3-2-4 or 1-4-2-3 to alternate banks; incorrect order causes rough running and vibration.

Accessory drives (magnetos, oil pump, fuel pump, vacuum pump) are gear- or belt-driven from the crankcase; magneto drive ratio and timing marks must be re-established after reassembly.

Cylinder barrels are steel or chrome/nickel-plated; air-cooled aero cylinders use deep fins and a fin-to-baffle pressure cooling arrangement; bore and taper limits come from the manual.

Pistons are aluminium alloy with a cam-ground skirt, offset pin to reduce slap, and controlled expansion; ring grooves carry compression rings above the oil control ring.

Ring end gap and side clearance are measured in the bore; too little gap causes scuffing and breakage, too much causes blow-by and oil consumption.

Piston pin retention: full-floating pins with circlips or plugs, or pressed pins; circlip seating and pin-to-boss clearance are critical inspection points.

Valves: intake valves usually larger and may be sodium-cooled or stellite-faced; exhaust valves run hottest and need correct seat contact and stem-to-guide clearance.

Valve lash is set cold or hot per the manual; solid lifters need periodic adjustment while hydraulic lifters self-adjust within oil pressure limits.

Valve springs are checked for free length, squareness and installed pressure; weak springs cause valve float at high rpm and burnt valves.

Valve seats are ground to a specified contact width and angle; concentricity is checked with blue marking, and recession from burnt seats requires re-cutting or replacement.

Float-type carburettor metering: venturi depression draws fuel through the main jet; the float chamber maintains a constant head, and the mixture needle/air bleed trims the ratio.

Idle and off-idle circuits supply fuel at low airflow; accelerator pump enriches on rapid throttle opening to prevent lean stumble.

Mixture control valve leans the fuel-air ratio as altitude rises; best power is near 100–150 °F rich of peak EGT, best economy near peak EGT or lean of it within limits.

Carburettor icing occurs with temperature drop in the venturi plus moisture; apply carb heat when RPM drops or roughness appears, expect initial further RPM loss as melted ice enters the engine.

Fuel injection meters by airflow through a servo and air-fuel control unit; it gives more even distribution, no venturi icing, and allows precise lean-of-peak operation.

Fuel pressure and flow are checked against the manual; vapour lock risk rises with hot fuel lines, low pressure and volatile fuel grades.

Idle mixture is set by the idle mixture screw to give a specified RPM rise when the throttle is closed; too lean gives a stumble, too rich gives rough running and fouling.

Detonation margin depends on mixture, MAP and CHT; leaning above 75% power is restricted by most manufacturers to avoid detonation.

A magneto is a self-contained generator: rotating magnet induces EMF in the primary, points open to collapse the field, and the secondary coil produces the high voltage.

The condenser across the points suppresses arcing, speeds field collapse and protects the points; a failed condenser causes weak spark and point burning.

Timing is set at a specified advance before TDC (often 20–25°); internal magneto timing aligns the rotating magnet with the pole shoe, then the engine timing is set on number-one cylinder.

Impulse coupling provides a retarded, strong spark for starting and disengages above a set rpm; a failed impulse coupling can cause kickback and hard starting.

Two magnetos give redundancy and faster flame-front burn; the mag check shows RPM drop within limits per mag, with excessive drop indicating fouling or timing faults.

Ignition harness: shielded high-tension leads, a distributor rotor and terminal outlets; resistance and insulation tests detect arcing and radio noise.

Spark plugs: massive-electrode or fine-wire iridium; gap, reach and heat range must match the engine; fouling is cleaned and tested, and resistance is measured on resistor plugs.

Dead-cut check confirms the magneto switch grounds both mags; a live magneto is a serious hazard during prop handling.

Dry-sump lubrication: pressure pump feeds bearings and rocker boxes, scavenge pump returns oil to the tank; a wet-sump stores oil in the crankcase.

Oil pressure and temperature limits come from the manual; low pressure at idle can be normal, but low pressure at cruise indicates pump wear, blocked pickup or dilution.

Oil cooler is thermostatically or manually bypassed to hold oil temperature; a blocked cooler or low airflow raises temperature and thins the oil.

Straight mineral oil is used for break-in, then ashless dispersant oil; additive packages affect deposit control and seal compatibility.

Oil analysis and filter inspection detect metal, water and fuel dilution; rising iron or aluminium points to wear of specific components.

Air cooling: cylinder fins, baffles and cowl flaps control airflow; a pressure-plenum arrangement forces air through the fins rather than around them.

CHT and oil temperature limits protect the engine; high CHT with normal oil temperature suggests baffle leaks or a lean mixture, not an oil problem.

Cooling drag is managed with cowl flaps; closed flaps in climb raise CHT, open flaps in descent cause shock cooling and must be limited per the manual.

Exhaust systems route gases through stacks or a collector; cracks, leaks and loose clamps cause CO ingress into the cabin and must be inspected.

Turbocharging uses exhaust energy to drive a turbine coupled to a compressor; boost is controlled by a wastegate that bypasses exhaust around the turbine.

Supercharging is mechanically driven from the crankshaft; a gear-driven blower raises MAP without exhaust backpressure but consumes shaft power.

Wastegate and controller faults cause overboost or underboost; overboost protection and a manifold pressure limit protect the engine structure.

Turbocharged engines need a cool-down period before shutdown so the turbine and bearings do not soak in heat and coke the oil.

Intercooling lowers compressor outlet temperature, increasing density and detonation margin; aftercooling is the same function between compressor and throttle.

Critical altitude is the highest altitude at which rated MAP can be maintained; above it, power falls with density altitude.

Exhaust backpressure and turbine inlet temperature limits protect the turbine; high TIT with high MAP is a detonation and turbine damage risk.

Fixed-pitch props trade climb versus cruise by blade angle; a coarse pitch gives cruise speed but slower acceleration and lower static RPM.

Constant-speed propellers use a governor with flyweights and a speeder spring to control oil pressure to the hub, holding selected RPM by changing blade angle.

Governor operation: increasing RPM raises flyweight force, the pilot valve ports oil to increase blade angle; decreasing RPM does the reverse.

Oil pressure to the hub (or lack of it) determines pitch direction; loss of oil pressure drives the prop to fine pitch or feather depending on design.

Feathering rotates blades to the flight position to reduce drag on a failed engine; unfeathering uses accumulator or oil pressure to return to fine pitch.

Vibration sources: propeller balance, engine firing order, worn mounts and torsional resonance; a dynamic balance reduces vibration and bearing loads.

Propeller strike requires engine teardown inspection for crankshaft runout, counterweight and gear train damage.

RPM limits and manifold pressure limits are coupled: avoid overboost and overspeed combinations during rapid throttle movement.

Tachometer reads engine RPM; an electrical or mechanical drive, it is checked against a known reference for accuracy.

Manifold pressure gauge reads absolute pressure in the intake; at idle it reads low, and it is the primary power reference for a constant-speed prop.

CHT and EGT probes are thermocouples; EGT is used for mixture leaning, CHT for cooling and detonation monitoring.

Oil pressure and temperature gauges, fuel pressure/flow and fuel quantity indications are cross-checked during run-up and cruise.

Fire detection uses a thermocouple or continuous-loop sensor in the engine compartment, with a warning light and sometimes an audible alarm.

Fire suppression uses a fixed bottle with agent (Halon or clean agent) discharged to the engine compartment; the bottle pressure and squib circuit are inspected.

A fire warning requires shutting off fuel, mixture, ignition and electrical supply, then discharging the bottle and landing as soon as possible.

Instrument markings: green normal range, yellow caution, red limits; a gauge reading outside limits is treated as an engine malfunction until confirmed.

Compression check: differential test at a set pressure; leakage past rings (crankcase breather), intake valve (carburettor) or exhaust valve (exhaust stack) locates the fault.

Cylinder leakage limits and borescope inspection of valves, seats and piston crowns are part of routine inspection; burnt exhaust valves show as a wedge-shaped leak.

Run-up checks: magneto drop, carb heat drop, idle mixture, propeller cycle, oil pressure and vacuum; record values against limits.

Torque and safety: fasteners torqued to manual values and lockwired or tabbed; critical bolts are not reused if stretch limits are exceeded.

Troubleshooting follows symptom-cause logic: rough running at lean mixture points to induction leaks; high oil consumption to rings or guides; hard starting to ignition timing or impulse coupling.

Ground running requires chocks, fire extinguisher, prop clear area and monitoring of CHT, oil pressure and RPM; avoid prolonged ground running at high power.

Preservation: fogging oil into cylinders, sealing openings, dehydrating plugs and inhibiting fuel systems for storage; rotate or run per the manual.

Maintenance records must capture work performed, reference data, and sign-off by an appropriately authorised person; airworthiness depends on correct documentation.

Ideal Otto cycle efficiency: η = 1 − 1/r^(γ−1), where r is compression ratio and γ ≈ 1.4 for air; efficiency rises with compression ratio but is limited by detonation and fuel octane.

Four-stroke cycle: induction, compression, power (combustion/expansion), exhaust - two crankshaft revolutions per cycle; a four-cylinder four-stroke fires every 180° of crank rotation.

Brake mean effective pressure BMEP = (brake power × 60) / (n × swept volume × cycles per rev), with n in rpm; BMEP compares output independent of engine size.

Indicated power exceeds brake power by friction and pumping losses; mechanical efficiency = brake power / indicated power, typically 0.75–0.90 for aero piston engines.

Specific fuel consumption BSFC = fuel mass flow / brake power; best economy occurs lean of best power mixture, while best power is near 100–150 °F rich of peak EGT.

Detonation is uncontrolled explosive burning after normal ignition, driven by high MAP, high CHT, lean mixture, low octane or over-advanced timing; pre-ignition is ignition before the spark, usually from a hot spot.

Volumetric efficiency = actual air mass inducted / theoretical swept-volume air mass; it falls with throttle restriction and rises with tuned intake and exhaust ram effects.

Power is proportional to MAP × rpm × volumetric efficiency; at constant rpm, a change in manifold pressure of about 1 inHg alters power by roughly 3–4% at low boost.

Horizontally opposed (flat) four/six layouts dominate light aircraft: short crankshaft, low frontal area, good cooling, but wide nacelle and paired cylinders sharing a crankpin.

Radial engines use one connecting rod per crankpin (master rod) with articulated link rods; firing order alternates cylinders to smooth torque and cooling.

Crankshafts are forged or machined steel, dynamically balanced, and carry counterweights; runout limits and journal wear are checked against the maintenance manual.

Connecting rods: I-beam or H-beam section; big-end bearing is a shell or precision insert, small-end is a bushing or needle bearing; rod bolts are stretch- or torque-critical and are not reused out of limits.

Bearings: main bearings carry crank radial loads, thrust is taken by a flanged bearing or separate thrust washer; oil clearance is measured with plastigauge or micrometers.

Crankcase halves are split on the crankshaft centreline, line-bored for main bearings, and sealed with anaerobic sealant or gaskets; through-bolts and studs set bearing crush.

Firing order determines crankshaft throw layout: a flat-four typically fires 1-3-2-4 or 1-4-2-3 to alternate banks; incorrect order causes rough running and vibration.

Accessory drives (magnetos, oil pump, fuel pump, vacuum pump) are gear- or belt-driven from the crankcase; magneto drive ratio and timing marks must be re-established after reassembly.

Cylinder barrels are steel or chrome/nickel-plated; air-cooled aero cylinders use deep fins and a fin-to-baffle pressure cooling arrangement; bore and taper limits come from the manual.

Pistons are aluminium alloy with a cam-ground skirt, offset pin to reduce slap, and controlled expansion; ring grooves carry compression rings above the oil control ring.

Ring end gap and side clearance are measured in the bore; too little gap causes scuffing and breakage, too much causes blow-by and oil consumption.

Piston pin retention: full-floating pins with circlips or plugs, or pressed pins; circlip seating and pin-to-boss clearance are critical inspection points.

Valves: intake valves usually larger and may be sodium-cooled or stellite-faced; exhaust valves run hottest and need correct seat contact and stem-to-guide clearance.

Valve lash is set cold or hot per the manual; solid lifters need periodic adjustment while hydraulic lifters self-adjust within oil pressure limits.

Valve springs are checked for free length, squareness and installed pressure; weak springs cause valve float at high rpm and burnt valves.

Valve seats are ground to a specified contact width and angle; concentricity is checked with blue marking, and recession from burnt seats requires re-cutting or replacement.

Float-type carburettor metering: venturi depression draws fuel through the main jet; the float chamber maintains a constant head, and the mixture needle/air bleed trims the ratio.

Idle and off-idle circuits supply fuel at low airflow; accelerator pump enriches on rapid throttle opening to prevent lean stumble.

Mixture control valve leans the fuel-air ratio as altitude rises; best power is near 100–150 °F rich of peak EGT, best economy near peak EGT or lean of it within limits.

Carburettor icing occurs with temperature drop in the venturi plus moisture; apply carb heat when RPM drops or roughness appears, expect initial further RPM loss as melted ice enters the engine.

Fuel injection meters by airflow through a servo and air-fuel control unit; it gives more even distribution, no venturi icing, and allows precise lean-of-peak operation.

Fuel pressure and flow are checked against the manual; vapour lock risk rises with hot fuel lines, low pressure and volatile fuel grades.

Idle mixture is set by the idle mixture screw to give a specified RPM rise when the throttle is closed; too lean gives a stumble, too rich gives rough running and fouling.

Detonation margin depends on mixture, MAP and CHT; leaning above 75% power is restricted by most manufacturers to avoid detonation.

A magneto is a self-contained generator: rotating magnet induces EMF in the primary, points open to collapse the field, and the secondary coil produces the high voltage.

The condenser across the points suppresses arcing, speeds field collapse and protects the points; a failed condenser causes weak spark and point burning.

Timing is set at a specified advance before TDC (often 20–25°); internal magneto timing aligns the rotating magnet with the pole shoe, then the engine timing is set on number-one cylinder.

Impulse coupling provides a retarded, strong spark for starting and disengages above a set rpm; a failed impulse coupling can cause kickback and hard starting.

Two magnetos give redundancy and faster flame-front burn; the mag check shows RPM drop within limits per mag, with excessive drop indicating fouling or timing faults.

Ignition harness: shielded high-tension leads, a distributor rotor and terminal outlets; resistance and insulation tests detect arcing and radio noise.

Spark plugs: massive-electrode or fine-wire iridium; gap, reach and heat range must match the engine; fouling is cleaned and tested, and resistance is measured on resistor plugs.

Dead-cut check confirms the magneto switch grounds both mags; a live magneto is a serious hazard during prop handling.

Dry-sump lubrication: pressure pump feeds bearings and rocker boxes, scavenge pump returns oil to the tank; a wet-sump stores oil in the crankcase.

Oil pressure and temperature limits come from the manual; low pressure at idle can be normal, but low pressure at cruise indicates pump wear, blocked pickup or dilution.

Oil cooler is thermostatically or manually bypassed to hold oil temperature; a blocked cooler or low airflow raises temperature and thins the oil.

Straight mineral oil is used for break-in, then ashless dispersant oil; additive packages affect deposit control and seal compatibility.

Oil analysis and filter inspection detect metal, water and fuel dilution; rising iron or aluminium points to wear of specific components.

Air cooling: cylinder fins, baffles and cowl flaps control airflow; a pressure-plenum arrangement forces air through the fins rather than around them.

CHT and oil temperature limits protect the engine; high CHT with normal oil temperature suggests baffle leaks or a lean mixture, not an oil problem.

Cooling drag is managed with cowl flaps; closed flaps in climb raise CHT, open flaps in descent cause shock cooling and must be limited per the manual.

Exhaust systems route gases through stacks or a collector; cracks, leaks and loose clamps cause CO ingress into the cabin and must be inspected.

Turbocharging uses exhaust energy to drive a turbine coupled to a compressor; boost is controlled by a wastegate that bypasses exhaust around the turbine.

Supercharging is mechanically driven from the crankshaft; a gear-driven blower raises MAP without exhaust backpressure but consumes shaft power.

Wastegate and controller faults cause overboost or underboost; overboost protection and a manifold pressure limit protect the engine structure.

Turbocharged engines need a cool-down period before shutdown so the turbine and bearings do not soak in heat and coke the oil.

Intercooling lowers compressor outlet temperature, increasing density and detonation margin; aftercooling is the same function between compressor and throttle.

Critical altitude is the highest altitude at which rated MAP can be maintained; above it, power falls with density altitude.

Exhaust backpressure and turbine inlet temperature limits protect the turbine; high TIT with high MAP is a detonation and turbine damage risk.

Fixed-pitch props trade climb versus cruise by blade angle; a coarse pitch gives cruise speed but slower acceleration and lower static RPM.

Constant-speed propellers use a governor with flyweights and a speeder spring to control oil pressure to the hub, holding selected RPM by changing blade angle.

Governor operation: increasing RPM raises flyweight force, the pilot valve ports oil to increase blade angle; decreasing RPM does the reverse.

Oil pressure to the hub (or lack of it) determines pitch direction; loss of oil pressure drives the prop to fine pitch or feather depending on design.

Feathering rotates blades to the flight position to reduce drag on a failed engine; unfeathering uses accumulator or oil pressure to return to fine pitch.

Vibration sources: propeller balance, engine firing order, worn mounts and torsional resonance; a dynamic balance reduces vibration and bearing loads.

Propeller strike requires engine teardown inspection for crankshaft runout, counterweight and gear train damage.

RPM limits and manifold pressure limits are coupled: avoid overboost and overspeed combinations during rapid throttle movement.

Tachometer reads engine RPM; an electrical or mechanical drive, it is checked against a known reference for accuracy.

Manifold pressure gauge reads absolute pressure in the intake; at idle it reads low, and it is the primary power reference for a constant-speed prop.

CHT and EGT probes are thermocouples; EGT is used for mixture leaning, CHT for cooling and detonation monitoring.

Oil pressure and temperature gauges, fuel pressure/flow and fuel quantity indications are cross-checked during run-up and cruise.

Fire detection uses a thermocouple or continuous-loop sensor in the engine compartment, with a warning light and sometimes an audible alarm.

Fire suppression uses a fixed bottle with agent (Halon or clean agent) discharged to the engine compartment; the bottle pressure and squib circuit are inspected.

A fire warning requires shutting off fuel, mixture, ignition and electrical supply, then discharging the bottle and landing as soon as possible.

Instrument markings: green normal range, yellow caution, red limits; a gauge reading outside limits is treated as an engine malfunction until confirmed.

Compression check: differential test at a set pressure; leakage past rings (crankcase breather), intake valve (carburettor) or exhaust valve (exhaust stack) locates the fault.

Cylinder leakage limits and borescope inspection of valves, seats and piston crowns are part of routine inspection; burnt exhaust valves show as a wedge-shaped leak.

Run-up checks: magneto drop, carb heat drop, idle mixture, propeller cycle, oil pressure and vacuum; record values against limits.

Torque and safety: fasteners torqued to manual values and lockwired or tabbed; critical bolts are not reused if stretch limits are exceeded.

Troubleshooting follows symptom-cause logic: rough running at lean mixture points to induction leaks; high oil consumption to rings or guides; hard starting to ignition timing or impulse coupling.

Ground running requires chocks, fire extinguisher, prop clear area and monitoring of CHT, oil pressure and RPM; avoid prolonged ground running at high power.

Preservation: fogging oil into cylinders, sealing openings, dehydrating plugs and inhibiting fuel systems for storage; rotate or run per the manual.

Maintenance records must capture work performed, reference data, and sign-off by an appropriately authorised person; airworthiness depends on correct documentation.