Aircraft Engine Power, Operation, and Components

Posted on Jan 22, 2025 in Technology

Aircraft Engine Power and Performance

Theoretical Power (1) – Energy released from fuel combustion, representing total fuel energy.
Indicated Power (2) – Power developed by gases acting on the piston.
Effective Power (3) – Power delivered to the engine’s propeller shaft.
Maximum Power – The maximum effective power the engine can provide for a short time.
Nominal Power – The maximum effective power the engine is designed to provide for an extended period.
Friction Power (5) – Power lost due to friction within the engine’s internal parts.
Useful Power (4) – Power available for traction or propulsion, such as in a tractor or aircraft.
Required Power – Power needed to maintain level flight at a given speed.
Available Power – Maximum useful power the engine can provide to the aircraft.

Slow Motion – Rich mixture achieved by pulling the throttle back.
Takeoff – Maximum engine power, full throttle, rich mixture (10:1).
Ascent – Maximum continuous power, moderately rich mixture (12.5:1), gradually pulling the throttle.
Cruise – Reduced power and lean mixture (16:1), throttle adjusted to recommended RPM.
Acceleration – Emergency fuel injection for a richer mixture.
Stop – Achieved by cutting off the fuel mixture.

Thermal Efficiency – Ratio of mechanical power produced to thermal power released (25% to 30%).
Lightness – Ratio of mass to power, low for pistons.
Stroke – Movement from one dead center to another. 1 Cycle (720º) in 4-stroke engines has 6 phases.
2-Stroke Engine – 1 stroke (bottom to top – compression, ignition, combustion, intake), 2nd stroke (top to bottom – expansion and exhaust).
Piston – Compresses, transmits combustion force to the crankshaft.
Connecting Rod – Connects the piston to the crankshaft.
Crankshaft – Rotating part that transmits piston force via the crank.
Valve Control System – Opens with springs.
Engine Displacement – Volume displaced by the piston during its stroke, between dead centers.
Compression Ratio – Ratio of cylinder volume to combustion chamber volume.

Bearings – Support moving parts, minimizing friction. Supports the crankcase.
Compression Ring – Upper groove, seals the gap between the piston and cylinder.
Lubrication Ring – Lower groove, removes excess oil.
Induction System – Supports, filters, and heats the air.
Supercharging – Increases intake air pressure using centrifugal compressors.

Fuel Octane – 100 for octane, zero for isooctane, and normal for heptane.
Lubricant Oil – Lubricates moving parts and assists in engine cooling.
Viscosity – Resistance to oil flow; high viscosity (slow), low viscosity (fast).
Freezing Point – Temperature at which oil stops flowing; low freezing point is desirable.
Flash Point – Temperature at which oil ignites in contact with a flame; high flash point is desirable.
Fluidity – Oil should have high flow and be stable.
Neutrality – Oil should not be acidic.
Oil Radiator – Cools oil; viscosity increases at low temperatures and decreases at high temperatures.
Oil Pumps – Typically gear-type pumps.
Oil Filter – Removes impurities; should be cleaned and replaced.
Decanter – Some aircraft use gravity-based oil decanters.
Pressure Regulator – Prevents pressure from exceeding a set value.
One-Way Valve – Allows flow in one direction and prevents it in the other.
Bypass Valve – Opens under pressure, providing an alternative path.
Oil Pressure Gauge – Provides pressure readings.
Oil Thermometer – Measures oil temperature.